fmds0732 factory mutual data sheet 7-32

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January 2010 of 50

FLAMMABLE LIQUID OPERATIONS

Table of Contents Page

1.0 SCOPE ............... ............... ............... ............... ............... ................ ............... ............... ............... ........... 31.1 Changes ............................................................................................................................................ 3

2.0 LOSS PREVENTION RECOMMENDATIONS ............... ............... ............... ............... ............... ............ 32.1 General Flammable and Combustible Liquid Occupancies ............................................................ 3

2.1.1 Construction and Location .................................................................................................... 32.1.2 Equipment and Processes .................................................................................................... 52.1.3 Occupancy ............................................................................................................................. 82.1.4 Ignition Source Control .......................................................................................................... 92.1.5 Operation and Maintenance ................................................................................................ 142.1.6 Training ................................................................................................................................ 152.1.7 Human Element ................................................................................................................... 152.1.8 Protection ............................................................................................................................ 16

2.2 Piping Systems .............................................................................................................................. 192.2.1 Construction and Location .................................................................................................. 192.2.2 Equipment and Processes .................................................................................................. 242.2.3 Operation and Maintenance ................................................................................................ 28

2.3 Flammable and Combustible Liquid Transfer Systems ................................................................. 292.3.1 Equipment and Processes .................................................................................................. 29

3.0 SUPPORT FOR RECOMMENDATIONS ............... ............... ............... ............... ............... ............... ... 363.1 Application of Recommendations .................................................................................................. 36

3.1.1 General ................................................................................................................................ 363.1.2 Fire Hazard .......................................................................................................................... 373.1.3 Piping Systems/Transfer Systems ...................................................................................... 373.1.4 Room Explosion Hazard ..................................................................................................... 373.1.5 Equipment Explosion Hazard .............................................................................................. 39

4.0 REFERENCES .............. ............... ............... ............... ............... ............... ............... ............... .............. 404.1 FM Global ...................................................................................................................................... 404.2 NFPA Standards ............................................................................................................................ 404.3 Others ............................................................................................................................................ 40

APPENDIX A GLOSSARY OF TERMS ............... ............... ............... ................ ............... ............... .......... 41APPENDIX B DOCUMENT REVISION HISTORY ..................................................................................... 43APPENDIX C CHARACTERISTICS OF FLAMMABLE AND COMBUSTIBLE LIQUID FIRES

AND EXPLOSIONS ............................................................................................................. 43C.1 Characteristics and Types of Flammable and Combustible Liquid Fires ..................................... 43

C.1.1 Pool Fires ............................................................................................................................ 43C.1.2 Unconfined Spill Fires ......................................................................................................... 43C.1.3 Spray Fires .......................................................................................................................... 44

C.2 Fire Control and Extinguishment .................................................................................................. 44C.3 Characteristics of Flammable/Combustible Liquid Vapor-Air Explosions ..................................... 45C.4 Explosion Control and Protection ................................................................................................. 45C.5 Equipment Explosion (Deflagration) Venting Design .................................................................... 46

C.5.1 Vent Sizing for a P red Greater Than 1.5 psig (0.1 bar g) (High Strength Equipment) ....... 46C.5.2 Vent Sizing for a P r of 1.5 psig (0.1 bar g) or Less (Low Strength Equipment) .............. 47C.5.3 Venting of Gases/Vapors Other Than Those Specified and Mists ..................................... 47C.5.4 Vent Mass and Location ..................................................................................................... 48C.5.5 Vent Discharge Arrangement .............................................................................................. 48

FM GlobalProperty Loss Prevention Data Sheets 7-32

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C.5.6 Effect of Turbulence ............................................................................................................ 48C.5.7 Effect of High Initial Pressures ........................................................................................... 49

C.6 Sight Glasses ................................................................................................................................ 49C.6.1 Properties of Glass ............................................................................................................. 49C.6.2 Types of Glass .................................................................................................................... 50

C.6.3 Sight Glass Design ............................................................................................................. 50

List of FiguresFig. 1. Preferred locations for processes containing flammable or combustible liquids. (Table 1) ............... 4Fig. 2a. Location of hazardous area rated electrical equipment for up to 70 gal (265 l) of

flammable/combustible liquid in open equipment. .......................................................................... 10Fig. 2b. Location of hazardous area rated electrical equipment for up to 70 gal (265 l) of

flammable/combustible liquid in closed equipment. ....................................................................... 11Fig. 3a. Location of hazardous area rated electrical equipment for more than 70 gal (265 l) of

flammable/combustible liquid in open equipment. .......................................................................... 12Fig. 3b. Location of hazardous area rated electrical equipment for more than 70 gal (265 l) of

flammable/combustible liquid in closed equipment. ....................................................................... 13Fig. 4. Buried-pipe entrance into building. ................................................................................................... 20

Fig. 5. Preferred arrangement for above grade pipe entrance into building. .............................................. 21Fig. 6. Welding neck type flange. ................................................................................................................ 23Fig. 7. Slip-on type flange. ........................................................................................................................... 23Fig. 8. Compressed inert-gas transfer method. ........................................................................................... 31Fig. 9. Hydraulic transfer method. ................................................................................................................ 33Fig. 10. Railcar loading/unloading station-bonding arrangement to prevent sparks due to stray currents. . 36Fig. 11. Sprinklered vs. Unsprinklered Flammable/Combustible Liquid Fires. ............................................ 45Fig. 12. Maximum Pressure Developed During Venting of Gases, With and Without Vent Ducts. ............ 49

List of TablesTable 1. Construction For Flammable and Combustible Liquid Occupancies (notes 1 & 2). ...................... 4Table 2. Sprinkler Protection for Occupancies Utilizing Flammable/Combustible Liquids. .......... .............. 17Table 3. Space Separation for Flammable/Combustible Liquid Loading/Unloading Stations. ................... 34Table 4. The volume of a stoichiometric vapor-air mixture that may be produced from either 1 gallon or

1 liter of some common flammable liquids. (Note: these values are based on completevaporization of the liquid.) ............................................................................................................. 39

Table 5. Heat of Combustion for Representative Materials. ....................................................................... 43Table 6. Explosion Venting Constants. .............. ............... ................ ............... ............... ............... ............. 46Table 7. Venting Constants for Other Vapors and Gases. ............... ............... ............... ................ ............ 48

7-32 Flammable Liquid Operations FM Global Property Loss Prevention Data Sheets

©2010 Factory Mutual Insurance Company. All rights reserved.



1.0 SCOPE

This loss prevention data sheet provides recommendations for the prevention of and protection against firesand explosions in occupancies handling, processing, or transferring flammable or combustible liquids. Datasheets covering specific occupancies may supersede this data sheet. Additional recommendations may be

needed to provide adequate prevention and protection features for a chemical process plant with the potentialfor hazardous chemical reactions, three dimensional fires, or operating pressures in excess of 100 psig (7bar g). Refer to Section 3.1 for guidelines on applying recommendations.

International standards may be applied when required, instead of referenced United States standards (i.e.,ASTM, ASME, etc.).

NFPA 30, Flammable and Combustible Liquids Code, also covers this material.

1.1 Changes

January 2010. Minor editorial changes were made. Added references to Data Sheet 4-12, Foam-Water Sprinkler Systems .

2.0 LOSS PREVENTION RECOMMENDATIONS

2.1 General Flammable and Combustible Liquid Occupancies

2.1.1 Construction and Location

Isolate flammable and combustible liquids by distance or construction so that they do not expose importantbuildings or facilities, and in turn are protected from fires originating elsewhere. The extent of isolationdepends on such factors as the quantity of flammable or combustible liquid, the consequences of failure ofsafeguards, and whether the hazard is one of fire only or of both fire and explosion.

2.1.1.1 Flammable and combustible liquid operations that create a fire and/or an explosion hazard shouldbe located as follows to reduce the exposure to important buildings or facilities, and to limit exposure to theflammable/combustible liquid operations from fires originating elsewhere (listed in order of preference; seeFigure 1, Table 1):

a) Detached outside location at least 75 ft (23 m) away from an important building or facility.A 50 ft (15 m)

separation is acceptable when only a fire hazard exists or an explosion hazard exists with less than1500 gal (6000 l) of liquid. (Fig. 1, Location 1)

b) Along an exterior wall of an important building (preferably at a corner to limit exposure and increaseavailable vent area). (Fig. 1, Location 2)

c) Inside an important building on the first floor, either at an exterior corner or along an exterior wall. Avoidlocations in basements, below-grade spaces or on upper floors of multistory buildings. If such locationsare unavoidable, the floor of the room should be completely cut off (i.e., no openings in the floor to the flooror space below, to prevent liquid or vapor escape) and liquid tight. An acceptable alternative for roomswith small spaces below is to completely fill in the space with a noncombustible material (e.g., fiberglass,mineral wool, earth). (Fig. 1, Locations 3 and 4)

2.1.1.2 Avoid below grade locations for equipment and piping containing flammable and combustible liquidsto help ensure adequate access for manual fire fighting efforts.

2.1.1.3 To limit the potential fire and explosion hazards created by flammable/combustible liquid occupancies,apply the construction features listed in Table 1 to both the exposing building/room and exposed importantbuildings. Table 1 applies if both the exposing building/room and the exposed building are adequatelysprinklered and adequate damage limiting construction, designed in accordance with Data Sheet 1-44,Damage-Limiting Construction, is provided when an explosion hazard exists.

Flammable Liquid Operations 7-32FM Global Property Loss Prevention Data Sheets




Table 1. Construction For Flammable and Combustible Liquid Occupancies (notes 1 & 2).

Location

Hazard Type

refer to Section 3.1

for definitions

Quantity of Flammable Liquid gal

(1)

Distance x

ft (m)

Cutoff Room/Building Construction

(note 3)Construction of Main Building’s

Exposed Wall C

A B Roof

(note 4)

1(note 5)

Explosion

> 1500 (6)> 75 (23) PV PV PV

Any

10-75(3-23)

PR PV LW

< 1500 (6)> 50 (15) PV PV PV

10-50(3-15)

PR PV LW

Fire

> 1500 (6) > 50 (15) LW

LW LW< 50 (15) FR

< 1500 (6) > 25 (8) LW

< 25 (8) FR

2(note 6) Explosion Any Abutting DNA PV

PV

Vertical ExposureProtection:

PR and 1 hour firerated for 10 ft (3 m)

above exposure.

HorizontalExposure

Protection:PR for length of

exposing wall ‘‘A’’plus 10 ft

(3 m) beyondPR Vertical Exposure

Protection: Any

3 & 4 Explosion

Any Inside PV PR PR

DNAFire NC FR FR

1. This table assumes adequate sprinkler protection is provided in the Main Building and the exposure. Table also assumes damage limitingconstruction is designed in accordance with Data Sheet 1-44, Damage-Limiting Construction.

2. If sprinkler protection is not provided in the exposing building (i.e., low value building), use Data Sheet 1-20, Protection Against Exterior Fire Exposure, (applies to Location 1 only). Use the following exposure rating in Data Sheet 1-20: Exposure ‘‘A’’ for quantities greaterthan 1500 gal (6000 l). Exposure ‘‘B’’ for quantities less than 1500 gal (6000 l). Construction features for the exposing building still apply

when an explosion hazard exists.3. The types of construction are defined as follows:

LW—light weight/noncombustible;NC—noncombustible;

FR—1 hour fire rated;PV—pressure venting;

PR—pressure resistant.

4. Pressure resistant construction should also be provided for floors that have spaces below. Roof construction should meet the requirementslisted in Data Sheet 1-44, Damage-Limiting Construction.

5. For × < 10 ft (3 m) with an explosion hazard, use Location 2, Explosion Hazard.6. For abutting structures with a fire hazard only, use Location 1, Fire Hazard, < 50 ft/ < 25 ft (15 m/8 m). Sprinklered and adequate damage

limiting construction, designed in accordance with Data Sheet 1-44, Damage-limiting Construction, is provided when an explosion hazardexists.

Fig. 1. Preferred locations for processes containing flammable or combustible liquids. (Table 1)





If the exposing building is not sprinklered (low value building, Location 1 only) and the quantity of flammableor combustible liquid in the building is more than 1500 gal (6000 l), apply spacing and constructionrecommendations listed in Data Sheet 1-20, Protection Against Exterior Fire Exposure, using exposure ‘‘A’’(Tables 2 through 7). Construction features shown in Table 1 still apply to the exposing building when anexplosion hazard exists.

If the exposing building is not sprinklered (low value building, Location 1 only) and quantity of flammable orcombustible liquid in the building is less than 1500 gal (6000 l), apply spacing and constructionrecommendations listed in Data Sheet 1-20, using exposure ‘‘B’’. Construction features shown in Table 1still apply to the exposing building when an explosion hazard exists.

2.1.1.4 For interior locations with flammable/combustible liquids having a flash point below 200 °F (93 °C),provide at least a one hour fire-rated partition to cut off the flammable liquid occupancy from surroundingoccupancies (Table 1). Other recommendations may exist for specific occupancies (covered by occupancyspecific data sheets).

If unheated combustible liquids with flash points above 200 °F (93 °C) are in use, the water supply is adequate,and no high-value occupancies are exposed, a curb surrounding the combustible liquid operation isacceptable in lieu of a fire rated partition. The curbing should be designed for a spill from largest vessel orcontainer plus a 2 in. (51 mm) freeboard in accordance with Data Sheet 7-83, Drainage Systems For

Flammable Liquids, (criteria for areas with containment but no drainage).2.1.1.5 When a flammable/combustible liquid occupancy creates a room explosion hazard (see Section 3.1.4),provide damage limiting construction as recommended in Table 1 and Data Sheet 1-44, Damage-Limiting Construction. If a mist explosion hazard exists, refer to Data Sheet 1-44, to design the explosion venting.When damage limiting construction is not possible for small rooms that create a severe exposure to high valueadjoining occupancies, consider an explosion suppression system. Install the system in accordance withData Sheet 7-17, Explosion Protection Systems.

2.1.1.6 Provide emergency drainage and/or containment for all flammable/combustible liquid areas protectedby water fire suppression systems. Determine the need for drainage and/or containment using Data Sheet7-83, Drainage Systems For Flammable Liquids. The design of the drainage/containment system or a possiblealternative to adequate drainage should be in accordance with Data Sheet 7-83. Curbs and floors inflammable/combustible liquid areas should be watertight. The surface grade around flammable/combustibleliquid areas should direct possible liquid releases away from important buildings.

Arrange drainage systems to prevent flammable vapors from backing up into buildings or rooms that aretied into those systems. One method of accomplishing this is the use of trapped drains. Provide thisarrangement for all buildings/rooms with drains that are tied into a drainage system that can handleflammable/combustible liquids regardless of the occupancy in that room/building.

2.1.2 Equipment and Processes

Equipment that handles flammable and/or combustible liquids should be designed to: 1) Confine the liquidsand vapors within the equipment, 2) Keep escaping material to a minimum and prevent its spread, and 3)Drain escaping liquids to a safe location.

2.1.2.1 Equipment and tanks should be closed or have a minimum of exposed flammable/combustible liquidsurface area and quantity.

2.1.2.2 Equipment should be constructed of materials that are compatible with the liquids in use andsurrounding environmental conditions, resistant to physical damage (e.g., impact), and are resistant to highexposing temperatures (e.g., flammable liquid fire).Avoid glass and plastic equipment (e.g., tanks or vessels).Metal equipment with a glass or plastic lining is acceptable. The equipment should be designed for themaximum hydrostatic head plus the usual corrosion and wear factors. The equipment should also bedesigned for use with flammable/combustible liquids.

2.1.2.3 Equipment containing flammable and combustible liquids should utilize indirect measurement orobservation instruments (e.g., thermocouple to measure temperature, sensor to measure pressure or liquidlevel, etc.) to reduce or eliminate leakage in the event of instrument failure. When direct measurement orobservation instruments (e.g., gauges, meters, liquid level indicators —glass type, sight glasses [see AppendixC, Section C.6], rotameters, sample tubes, etc.) are used the following safeguards should be applied:





a) Direct measurement instruments that use glass for containment (e.g., sight glasses, liquid levelindicator —glass type, rotameter) should be used only as a last resort and avoided entirely on processesthat contain flammable gases or flammable/combustible liquids above their normal atmospheric boilingpoint. Locate sight glasses above liquid level. Sight glasses and liquid level indicators should be FactoryMutual Research Approved (see Appendix A for definition). Follow the manufacturer ’s recommendations

for mounting and maintenance.

b) The instruments ’ materials of construction should be compatible with the materials being handled. Rateglass for the temperature, pressure and chemical service conditions under which it will operate.

c) The instruments ’ strength should be equal to or greater than the equipment to which they are attached.

d) Use restricted orifices in piping connecting the instruments to the equipment. Provide self-closingfaucets on draw-off/sample lines (sample tubes).

e) Avoid sudden temperature changes (e.g., addition of a very high or low temperature liquid to the insideor outside of a vessel) on instruments with glass components (e.g., sight glasses).

f) Inspect all instruments on a regular schedule. Determine inspection frequency by the severity of localconditions.

g) Inspect sight glasses at least once a week. Record sight glass inspections. When surface damage isdetected, replace the glass immediately. If sight glasses are exposed to frequent changes in temperatureand pressure, replace at regular intervals as determined by processing conditions.

h) Rotameters should be armored and arranged so only a sample of the flow is directed through the glassreading chamber instead of the entire stream. Vents on air releases used in conjunction with somemetering devices should be piped to outdoor locations to prevent the release of flammable or combustibleliquids in the event of meter failure.

i) Conduct instrument maintenance, including tightening bolts and replacement, only when the associatedequipment or piping has been shut down and depressurized. Equipment containing flammable liquidsor gases should be emptied and purged.

2.1.2.4 Flammable or combustible liquid handling and processing equipment that, under normal operatingconditions, have the potential for a vapor-air explosion or mist explosion within the equipment (i.e., equipmentexplosion hazard —see Section 3.1.5) should be protected by one of the following methods (listed in orderof preference):

a) Provide explosion venting designed to limit the pressure developed by an explosion to approximately133% of the equipment ’s yield strength (stress). If damage to the equipment creates a significant exposure(i.e., high value equipment or difficult to replace), design the explosion venting to limit the pressuredevelopment to approximately two thirds ( 2 ⁄ 3) of the equipment’s yield strength (stress) to preventpermanent equipment deformation. Equipment explosion venting calculations are presented in theAppendix C, Section C.5. The initial pressure of the equipment must be considered when calculating theneeded vent size.

b) Design the equipment to contain the maximum expected pressure due to a vapor-air explosion. Themaximum pressure should not exceed 133% of the equipment’s yield strength (stress). To preventpermanent equipment damage, the maximum pressure should not exceed two thirds ( 2 ⁄ 3) of theequipment’s yield strength (stress). Most vapor-air explosions will produce a maximum pressure ofapproximately nine times the initial absolute pressure in the equipment (this applies to equipment operatingat atmospheric or at elevated initial pressures).

c) Provide a gas inerting system designed in accordance with Data Sheet 7-59, Inerting and Purging of Tanks, Process Vessels, and Equipment, that is arranged to prevent the creation of a flammable vapor-airmixture. The inerting system should have a reliable inert gas supply. Equipment operators should be welltrained on the importance and function of the inerting system.

d) An explosion suppression system, designed in accordance with Data Sheet 7-17, Explosion Protection Systems, should be provided on high value equipment, equipment that exposes high value processes,or equipment with frequent explosions, when either explosion venting, containment, or inerting cannot beprovided.





2.1.2.5 Provide purging or ventilation systems for equipment with a vapor-air explosion hazard to reducethe risk of creating a vapor-air mixture in the flammable (explosive) range (not needed on inerted equipment).Design purging systems in accordance with Data Sheet 7-59, Inerting and Purging of Tanks, Process Vessels,and Equipment. Ventilation systems should be designed in accordance with Data Sheet 6-9, Industrial Ovens and Dryers. Utilize purging to avoid passing through the flammable (explosive) range of the flammable vapor

during start-up or shutdown operations. Design ventilation systems to limit flammable vapor concentrationsto less than 25% of the lower flammable (explosive) limit (these systems are normally found in ovens anddryers).

2.1.2.6 Supports for important equipment or equipment containing flammable/combustible liquids(e.g., mixing tanks, storage tanks) that are blocked from ceiling sprinkler discharge (i.e., equipment that iswider than 3 ft (0.9 m) or 10 ft 2 (0.9 m 2 ) in area) should be protected against potential failure due to the hightemperatures created by pool fires. Use automatic water spray or sprinklers, arranged to protect the supports,in rooms without a room explosion hazard. Use reinforced concrete or protected steel supports when a roomexplosion hazard exists or as an alternative to water spray or sprinklers.

2.1.2.7 Tanks, mixers and other equipment to which flammable or combustible liquids are transferred shouldbe arranged to prevent accidental overflow. One or a combination of the following methods or equivalentshould be used (listed in order of preference):

a) Provide a trapped overflow drain leading back to the source of supply or to a point of safe discharge.The capacity of the overflow drain should be at least equal to that of the fill pipe.

b) A liquid level-limit switch arranged to stop the liquid flow by closing a valve or stopping the pump shouldbe provided. An audible alarm may be used as a first warning that is followed by shutdown of the liquidflow. The liquid level-limit switch should be Approved. This arrangement is acceptable if the equipmentnormally operates under pressure so that an overflow drain is not practical but overflow is possible duringfilling because of open manholes or sampling connections. This may also be used in conjunction with anoverflow drain (provide an alarm to prevent overflow).

The use of weigh tanks, measuring tanks, and dispensing meters to accurately provide a measured quantityof liquid to a tank will assist in the prevention of overflows. Arrange weigh tanks and measuring tanks toprevent overflow (using either ‘‘a ’’or ‘‘b’’). The use of a dispensing meter does not eliminate the need to followrecommendations a and b above.

2.1.2.8 Provide overflow protection and emergency bottom drains for open top tanks to prevent overflowdue to sprinkler discharge and hose streams, and to remove the exposed flammable/combustible liquid froma fire area. The overflow protection and emergency bottom drains should be designed in accordance withData Sheet 7-9, Dip Tanks, Flow/Roll Coaters, and Oil Cookers. Sprinkler discharge overflow protection maybe omitted if the exposure created by spilling flammable/combustible liquids is limited, and one of thefollowing is provided:

a) The tank or equipment is equipped with automatic closing covers or normally closed covers.

b) The liquid in the tank has a flash point above 200 °F (93 °C).

c) The tank has a capacity of less than 100 gal (380 l) and there is less than 20 ft 2 (1.9 m 2 ) of exposedsurface.

Provide at least 6 in. (150 mm) of freeboard on tanks without overflow protection.

2.1.2.8.1 Emergency bottom drains may be omitted if the exposure created by burning flammable/combustibleliquids is limited, and one of the following exists:

a) The liquid has a flash point greater than 200 °F (93 °C).

b) The tank has a capacity of less than 500 gal (1900 l) and is located on the first floor.

c) The tank has a capacity of less than 150 gal (600 l) and is located on an upper floor.

2.1.2.9 Equipment heating should be provided by steam, hot water, organic heat transfer fluid (see DataSheet 7-99/12-19, Heat Transfer By Organic and Synthetic Fluids) or other means not requiring an open flame.Arrange heating equipment for automatic control. Provide a high temperature interlock arranged to providean audible alarm and shut down the heating equipment. Equipment and process temperatures should becontinuously monitored by the operator. Maximum equipment temperatures should be below the liquid ’sautoignition or autodecomposition temperature.





2.1.2.10 Flammable/combustible liquid storage should be cut off from points of use (e.g., manufacturing area).The quantity of flammable/combustible liquids in areas where they are used should be limited to one shift ’sneeds (approximately 100 gal (400 l) or as specified by other specific data sheets).

2.1.2.11 Use drum pumps (preferred, easy control of liquid discharge) or self-closing faucets (gravity driven,

less control with failure of faucet), where permitted, for drums arranged for dispensing flammable andcombustible liquids. Use drip cans below faucets with on-side dispensing operations of Class I flammableliquids (in areas where the ambient temperature can approach 100 °F (38 °C) include Class II combustibleliquids). A shallow metal drip pan is acceptable for use with Class II and III combustible liquids except as notedabove. The drum pumps, self-closing faucets, and drip cans should be Approved.

2.1.2.12 Provide safety bungs on drums of Class I liquids arranged for upright dispensing with a drum pumpthat is not equipped with pressure and vacuum relief vents. If ambient temperatures can approach 100 °F(38 °C), safety bung use should include Class II liquids. Also provide safety bungs on drums of Class I, II andIII liquids arranged for on-side dispensing. Safety bung use for Class III liquids is intended to prevent possiblespillage during on-side dispensing. Safety bungs prevent the creation of vacuum during dispensing, preventthe release of flammable/combustible liquids and their vapors, allow the release of excess internal pressurethat can be created when the drum is exposed to a fire (i.e., prevent a BLEVE), and prevent the flashbackof released vapor. Attach safety bungs only to the 2 in. (51 mm) drum opening to ensure its proper operation.

Provide safety bungs on intermittent drum storage of flammable or combustible liquids located in a dispensingarea if the stored drums will be exposed to a spill from the dispensing drum and sprinkler protection in thearea is not adequate for drum storage (Data Sheet 7-29, Flammable Liquid Storage in Portable Containers)or sprinkler operation may be delayed (e.g., locations under 20 ft [6 m] high ceilings). Store the drums onthe floor, upright and a maximum of one high. If the dispensing area is adequately curbed and drained so aspill will not expose the stored drums, safety bungs are not needed on the stored drums. Drums stored inadequately protected dedicated storage areas do not need safety bungs.

2.1.2.13 Use Approved safety cans for handling small quantities of Class I, II, and IIIA liquids. Class IIIBliquids can be handled in nonrated containers.

2.1.2.14 Use Approved flammable liquid storage cabinets for storing small quantities (type, quantity andcontainer size is limited by Approval Standard) of Class I, II, and IIIA liquids in manufacturing areas or areasthat are not designed for flammable or combustible liquid use. Provide mechanical ventilation in cabinetswhere flammable vapors may be present (e.g., open containers, dispensing in cabinet). To maintain cabinet

integrity, the ventilation ducts should have a fire resistance similar to the cabinet. If ventilation is not needed,keep the two ventilation openings closed to ensure the cabinet ’s fire rating is maintained.

2.1.2.15 Flammable/combustible liquids should be transferred in closed systems. Arrange liquid pumpingand piping systems in accordance with recommendations listed in Sections 2.2 and 2.3.

2.1.3 Occupancy

2.1.3.1 Ventilation

Ventilation systems are designed to confine, dilute and remove the maximum normal amount of flammablevapor released from equipment and handling of flammable and combustible liquids during normal operations.Adequately designed low level ventilation will reduce the chances of a flammable vapor-air mixtureaccumulating in the process area. Excessive vapor release caused by equipment failure (pipe break, releasefrom a relief valve), accidental discharge of heated flammable/combustible liquids (drum or tank spill), oran uncontrolled chemical reaction (venting a reactor) cannot be adequately safeguarded by the ventilationrates provided below. Designing a ventilation system to remove a large vapor release is outside the scope ofthis document.

2.1.3.1.1 Continuous low level mechanical ventilation designed to provide 1 cfm/ft 2 (0.3 m 3 /min/m 2 ) of floorarea should be provided in rooms or buildings where Class I liquids or liquids with a flash point up to 300 °F(149 °C) that are heated above their flash point are used.

2.1.3.1.2 In addition to providing the design in Recommendation No. 2.1.3.1.1, the exhaust ventilation shouldconfine flammable vapor concentrations exceeding 25% of the lower explosive limit to within 2 ft (0.6 m)of points of release (e.g., open mixing or dip tanks, dispensing stations).





2.1.3.1.3 Exhaust air should be removed through a system of blowers, fans and ductwork terminating outof doors away from air inlets, doorways and other openings. Exhaust ducts should be constructed ofnoncombustible materials. Run the ducts as directly as possible to the outdoors with a minimum of bends.Protect long runs of ventilation ducts with the potential for accumulation of combustible deposits inaccordance with Data Sheet 7-78, Industrial Exhaust Systems. Exhaust systems for small rooms may consist

of a fan installed at floor level arranged to exhaust out of doors (i.e., installed in exterior wall).

The ventilation system should take suction within 12 in. (0.3 m) of the floor. Locate intake openings at opentank lips, near equipment or dispensing, and in any pits located within the cutoff room or within 25 ft (8 m)of the operations that produce vapors.

Ventilation systems that are arranged to recirculate air into the room should be provided with an Approvedcombustible gas detector arranged to stop recirculation, and return to full exhaust when the vaporconcentration reaches 25% of its lower explosive limit (LEL).

2.1.3.1.4 At a minimum, interlock exhaust fans with equipment power supplies. However, if flammable orcombustible liquids are kept in the room or building during idle periods, the exhaust ventilation should operatecontinuously and be monitored (provide visual or audible ventilation failure alarm at occupied locations).

2.1.3.1.5 Provide make-up air inlets in exterior walls. Air inlets should be remote from exhaust outlets so thatair will sweep through the hazardous area. If gas or oil make-up air heaters are provided, they should beindirect-fired and properly safeguarded.

If make-up air is taken from other plant areas, those areas should be free of flammable or combustible liquids.Install automatic closing fire dampers or doors at make-up air inlet openings in interior fire walls or partitions.The dampers or doors should have a fire rating equal to that of the walls.

2.1.3.1.6 For unheated liquids with a flash point greater than 100 °F (38 °C) and heated liquids with a flashpoint greater than 300 °F (149 °C), provide natural draft ventilation arranged to provide 1 ft 2 (0.1 m 2 ) of freeinlet and outlet opening per 500 ft 2 (47 m 2 ) of floor area.

2.1.4 Ignition Source Control

A basic design goal for occupancies that contain flammable and combustible liquids is the elimination andcareful control of all potential ignition sources. Prevention measures should prevent contact of an ignitionsource with any flammable vapor-air mixture.

2.1.4.1 Provide hazardous location rated electrical equipment in accordance with Data Sheet 5-1, Electrical Equipment in Hazardous (Classified) Locations, and the NFPA National Electric Code, Article 500, whenhandling: a) Class I liquids, or b) Class II or III liquids heated above their flash point (including possible ambienttemperatures). Electrical equipment should be Approved. Class I Division 1 and Class I Division 2 areasshould be defined as follows:

a) Areas with less than 5 gal (19 l) of flammable/combustible liquid in a single container or piece ofequipment generally do not require rated electrical equipment (limited exposure).

b) Areas with 5 gal to 70 gal (19 l to 265 l) of flammable/combustible liquids in a single container or pieceof equipment should use either Figure 2a or 2b.

c) Areas with more than 70 gal (265 l) of flammable/combustible liquids, in a single container or pieceof equipment, with low pressures (less than 100 psig [7 bar g]) should use either Figure 3a or 3b. Electricalequipment with contacts (e.g., make-and-break or sliding contacts: motors, switches, breakers, etc.)should be avoided directly above and 10 ft (3 m) beyond the Class I Division 1 area. Provide light fixtureswith lenses to enclose bulb Protect all equipment against physical damage. If electric equipment withcontacts is located above a Class I Division 1 area, the contacts should be fully enclosed in a metalhousing.

d) Buildings or rooms where an explosion hazard has been determined to exist should use Figure 3a todefine Class I Division 1 areas. The remainder of the room or building should be defined as a Class IDivision 2 area (floor to ceiling).

Processes using flammable/combustible liquids at high pressures are not covered by this recommendation.These occupancies require a full review of processing conditions to determine areas requiring hazardousarea rated electrical equipment.





The use of all nonrated equipment (including maintenance equipment, battery operated equipment, etc.)unless it is recognized as being intrinsically safe, should be strictly prohibited in rated areas unless the areahas been purged of all flammable and combustible liquids as well as their vapors. An alternative is to providea pressurized or purged enclosure for the electric equipment designed in accordance with Data Sheet 5-1,Electrical Equipment in Hazardous (Classified) Locations.

Standard electrical equipment is acceptable in: a) areas handling unheated Class II or III liquids, or b)above-grade areas with flammable liquid piping (no associated equipment such as pumps, valves, connectand disconnect points, filters, tanks, etc.).

2.1.4.2 Equipment handling Class I liquids or Class II and III liquids heated above their flash points shouldbe electrically bonded and grounded in accordance with Data Sheet 5-8, Static Electricity, Data Sheet 5-10,Protective Grounding for Electric Power Systems and Equipment, and NFPA National Electric Code, Articles250 and 500. Proper grounding and bonding of equipment reduces the potential for buildup of electric chargeon separated pieces of equipment due to static accumulations or stray electric currents.

2.1.4.3 Prohibit smoking or the use of open flames in all rooms or buildings requiring hazardous locationrated electrical equipment (i.e., Class I Division 1 or 2). Post signs to define hazardous areas and staterestrictions for the area.

1. Class I, Division 1 within 5 ft (1.5 m) of Flammable Vapor Release

2. Class I, Division 2

Separation Between Pit and Point of Vapor Liberation

Is Ventilation Provided in Pit?

Electrical Equipment Needed in Pit

0 – 5 ft (0 – 1.5 m) Yes/No Class IDivision 1

5 – 20 ft(1.5 – 6 m)

No Class IDivision 1

Yes Class I

Division 2> 20 ft (6 m) Yes/No Ordinary

4. Ordinary Electric Equipment

3.

Fig. 2a. Location of hazardous area rated electrical equipment for up to 70 gal (265 l) of flammable/combustible liquid in open equipment.





2.1.4.4 When heating rooms or buildings containing a flammable or combustible liquid occupancy, use asystem that does not introduce an ignition source (e.g., steam or hot water, organic heat transfer oil, orhazardous location rated electric heating). Direct natural gas/fuel oil-fired make-up air heaters are acceptableif the heating unit is located outside the room or building and there is no air recirculation. Heating equipmenttemperatures should be below the auto-ignition point of the liquids present in the room. If Class I liquidsare present, the heaters should be at least 4 ft (1.2 m) above the floor level.

2.1.4.5 Arrange all equipment that may produce sparks (electrical, static, mechanical, or friction), open flames,or hot surfaces to prevent or strictly limit contact with flammable/combustible liquids or their vapors.Equipment that, over time, may produce sparks or hot spots due to wear (e.g., rotating equipment such as

motors, agitators, pumps, etc.) should be maintained on a strict schedule.Equipment or piping that create hot surfaces (e.g., steam pipe) should be avoided in areas with piping systemscontaining unusually low ignition temperature liquids, such as carbon disulfide.

2.1.4.6 Industrial trucks should be properly rated and Approved for use in areas requiring Class I Division1 or 2 electrical equipment. Refer to Data Sheet 7-39, Industrial Trucks, to select the appropriate truck rating.

2.1.4.7 Avoid hot work of any kind in areas handling, processing or storing flammable liquids. Hot Workprovides an ignition source in an area where fuel is available in significant quantities and in a readily ignitableform. Ideally, relocate any hot work to a nonhazardous location. When relocation is not possible, adocumented Hot Work Permit System is needed.





0 – 15 ft(0 – 5 m)


Yes Class IDivision 2

> 15 ft (5 m) Yes/No Ordinary


2.

Fig. 2b. Location of hazardous area rated electrical equipment for up to 70 gal (265 l) of flammable/combustible liquid in closed equipment.





Use a documented permit system to strictly control all hot work operations. The permit is issued only aftera complete review of all proposed work, the hazards in the area, and all precautions needed to prevent a fireor explosion. If all of the requirements cannot be met, then the permit should not be issued and the workshould not be allowed.

Precautions are listed on the FM Global Hot Work Permit itself. Some of the minimum requirements include:

a) Automatic sprinkler protection should be in service. Charged small hose or fire extinguishers shouldbe available at work area.

b) Remove flammable and combustible liquid storage from the area. All combustibles within 35 ft (11 m)of the work should be removed or covered with a fire-resistive tarpaulin (see Data Sheet 1-0, Safeguards During Construction, Alteration and Demolition).

c) Drain all equipment or piping in the area of flammable and combustible liquids. Equipment or pipe tobe worked on should be steam cleaned or provided with an inert atmosphere to prevent creation of aflammable atmosphere (see Data Sheet 7-59, Inerting and Purging of Tanks, Process Vessels, and

1. Class I,, Division 1 within 5 ft (1.5 m) of Flammable Vapor Release





0 – 5 ft(0 – 1.5 m)

Yes (alwaysneeded)

Class IDivision 1

5 – 25 ft(1.5 – 8 m)



≥ 25 ft(8 m)


Yes Ordinary

4. No Equipment With Make-and-Break or Sliding Contacts(e.g., motors, switches, receptacles, cutouts, etc.)Equipment Protected Against Physical DamageLighting Equipment Provided With a Lens to Enclose the Bulb

3.

Fig. 3a. Location of hazardous area rated electrical equipment for more than 70 gal (265 l) of flammable/combustible liquid in open equipment.





Equipment). Piping supplying the area with flammable and combustible liquids should be shut off at thesource (valve should be locked shut to prevent unexpected opening). If the piping is to be worked on, itshould be blanked off. Check equipment or piping with an Approved portable oxygen analyzer (see DataSheet 5-49, Gas and Vapor Detectors and Analysis Systems) before and during the hot work. This is toensure that sufficient oxygen to support combustion is not present inside the equipment or piping.

d) All permanent storage tanks or piping that cannot be moved or drained must be protected againstphysical contact and heat from hot work equipment. Preferably all equipment that is within reach of thehot work equipment (grinder, welding rod holder, cutting torch, etc.) will be drained, purged and inerted. Ifthis is not possible due to the quantities of flammable liquids involved, physical protection can be provided

by placing welding curtains and temporary barriers between the equipment and the hot work. A carefulreview of the area is required to ensure that no vents or other openings are near the hot work that couldallow fumes and sparks from the hot work to meet.

e) Keep mechanical ventilation in the room/building in operation. Use a portable combustible gas analyzerbefore and during the work. If any detectable readings are obtained, then work cannot begin or continueuntil the source is found and suitably mitigated such that the concentration is maintained below 10% ofthe LEL.

f) Provide a continuous fire watch both during and at least 60 minutes after work. Check the area at leasthourly for up to three hours after the end of hot work operations.






0 – 25 ft(0 – 8 m)



> 25 ft (8 m) Yes/No Ordinary

3.

Fig. 3b. Location of hazardous area rated electrical equipment for more than 70 gal (265 l) of flammable/combustible liquid in closed equipment.





Avoid the use of nonrated electrical equipment in areas containing flammable liquids. If such equipment mustbe temporarily introduced, view this as hot work and follow the permit precautions. As with other hot work,if the precautions cannot be taken, the permit should not be issued and the nonrated electrical equipmentshould not be used.

For situations where the above steps are not applicable or unusual circumstances are present, consult aspecialist in flammable/combustible liquid handling before any hot work is performed.

2.1.5 Operation and Maintenance

Thorough operator training and a complete maintenance program are fundamental components of anyprocess that utilizes flammable/combustible liquids. Both items will contribute to reducing the potential for afire or explosion as well as reduce the frequency and severity of such occurrences. As the complexity offlammable/combustible liquid processes increase, the need for high levels of operator training and strictequipment maintenance programs becomes essential to the proper operation of the process. Tailor trainingprograms and maintenance schedules to meet each location ’s specific needs.

2.1.5.1 A series of routine checkpoints with normal condition limits should be inspected by the operator forprompt detection of abnormal conditions. Determine the frequency of the checks by the process conditionsand severity of the consequences due to a process upset. Check all safety devices and process control

features at the beginning of each shift2.1.5.2 All emergency shutoff valves for piping systems containing flammable and combustible liquids shouldbe clearly labeled with a sign indicating what is controlled.

2.1.5.3 Equipment (tanks, drums, etc.) containing flammable and combustible liquids should be clearly labeledindicating the content of the equipment and the type of hazard they present (e.g., flammable, combustible).

Piping containing flammable and combustible liquids should be labeled and color coded. Piping containingspecific flammable and combustible liquids should indicate the liquid name and direction of flow. Identificationis particularly important where piping passes through walls, at valves and fittings, and at points of use. Anacceptable piping identification system is described in ANSI A13.1, Scheme for Identifications of Piping Systems. Pipe labeling and coding will reduce mix-ups during liquid transfer, prevent mistakes duringmaintenance operations, and reduce confusion during emergency responses.

2.1.5.4 Provide a raw materials inspection program to ensure delivery of expected materials and prevent

the introduction of foreign or incompatible materials into a storage or distribution system.2.1.5.5 Management should strictly control all changes or new installations in processes or areas containingflammable and combustible liquids. Conduct a full review of all planned changes by qualified loss preventionconsultants as well as other authorities having jurisdiction before the project begins.

2.1.5.6 Establish a complete preventive maintenance program designed to ensure that equipment is operatingas it has been engineered to operate. Refer to Data Sheet 9-0/17-0, Maintenance, to evaluate existingprograms or as a guide to develop new programs. This program should also include regular documentedtesting of safety devices and process control features in accordance with the manufacturer ’srecommendations.

Preventive maintenance programs for equipment and areas containing flammable or combustible liquidsshould include: mechanical and electrical equipment, piping systems (e.g., connect/disconnect points, pumps,flanged fittings, flexible pressure hoses, swing joints, etc.), system control devices (e.g., valves, computer

controllers, etc.), and emergency control or relief devices (e.g., emergency shutoff valves, float valves,pressure relief devices, etc.). Follow preventive maintenance schedules closely to prevent the creation of anignition source (e.g., equipment breakdown and overheating, improperly sealed hazardous area rated electricequipment) or the release of flammable or combustible liquid (e.g., pipe joint failure).

Conduct frequent inspections to detect and repair leakage. Use a flammable-vapor detector to locate smallleaks (detector should be Approved). Prohibit the use of open flames or spark-producing devices.

2.1.5.7 Perform maintenance or repair operations only on equipment that has been depressurized, shut downand drained of any flammable/combustible liquids. This includes tightening or loosening bolts or flanges,packing glands, or making new connections. Piping should be depressurized, drained, flushed, purged andinerted before it is opened or tapped. Bolts for flanges or for connections to flanged fittings should betightened with a torque wrench to ensure proper tightness without overstressing. Prohibit the use of power





tools unless the precautions listed in Recommendation No. 2.1.4.7 are strictly followed. Use Approved safetytools in areas where a flammable atmosphere may exist.

2.1.5.8 Relocate equipment needing repair or maintenance that requires use of a cutting torch or other hotwork operation preferably to a nonhazardous location. Regardless of where the work is done, the equipment

should be drained, flushed, purged, and inerted as necessary to eliminate all flammable and combustibleliquids and their vapors. Use anApproved combustible vapor analyzer (see Data Sheet 5-49, Gas and Vapor Detectors and Analysis Systems) before and during work to make certain equipment that is not inerted hasbeen fully purged and remains purged of any flammable vapors. Check equipment that is inerted beforeand during work with an Approved oxygen analyzer to ensure a flammable atmosphere is not present. FollowRecommendation No. 2.1.4.7 and Data Sheet 7-59, Inerting and Purging of Tanks, Process Vessels, and Equipment, to ensure all flammable vapors and potential ignition sources have been eliminated.

2.1.5.9 Use an equipment isolation procedure to supervise valves controlling flammable and combustibleliquids that are shut off for repair or other maintenance procedures. Equipment isolation procedures shouldbe strictly controlled to ensure equipment repairs/maintenance are complete before flammable/combustibleliquids are introduced.

2.1.5.10 Remove unused piping or tanks. Cap open end pipes promptly. Unused equipment that is notremoved should be completely drained and purged of all flammable/combustible liquids and their vapors.

The equipment should also be disconnected from any surrounding active equipment and clearly labeled asshutdown to reduce the chances of accidental use.

2.1.5.11 Protect flammable and combustible liquid handling and transfer equipment against external corrosion.Protective coatings for buried tanks and piping should be carefully applied and inspected before they arecovered. Conduct regular inspections of the equipment to investigate external corrosion. Increase theinspection frequency of equipment located in corrosive atmospheres.

2.1.6 Training

2.1.6.1 Create a training program for all employees (including operators, emergency organization members,and security personnel) who have access to or work in areas containing or processing flammable/combustibleliquids. Design and supervise the training programs to address the complexity of process operations andthe hazard level present at a facility. The training should include proper handling, equipment operation, andemergency procedures as well as the consequences of failing to follow the procedure. Provide training for

all new employees. Refresher programs should also be provided, as needed, for current employees. Theprogram should at least include:

a) The hazards created by the materials in use.

b) The proper operation or shutdown of the equipment under normal and emergency conditions. Criticalprocedures should be printed and posted for convenient reference.

c) Proper material handling procedures (i.e., bonding/grounding, self-closing faucets, safety bungs, etc.).

d) Flammable/combustible liquid piping system operation and shutdown including the location of all localand remote shutoff valves.

e) Proper flammable/combustible liquid transfer procedures.

f) The location, proper type and proper use of fire extinguishers for the hazard present.

g) Fixed extinguishing systems operation and function.

2.1.7 Human Element

2.1.7.1 Establish an emergency response plan at locations handling or processing flammable/combustibleliquids. Design the plan to control the extent of damage due to fires or explosions by at least ensuring promptfire department notification, shutdown of fuel supply, and availability of provided fire protection features. Theplan should also include spill response procedures aimed at limiting spill size (e.g., prompt shutdown of liquidflow), containing released liquid (e.g., use of sand bags), and elimination of all ignition sources that may beexposed by the spill, or flammable vapors, until the spill is cleaned up. The actual extent of the emergencyresponse plan, including spill response procedures, will depend on the hazards present, facility size,availability of emergency response personnel from surrounding communities (e.g., fire department, spillresponse teams, etc.), and local, state or federal regulations.





The facility ’s emergency organization members and the local fire department should be familiar with thelocation of flammable/combustible liquid processes as well as the emergency response plan. Use emergencyresponse drills to reinforce the employee training programs (including emergency organization) and assistthe fire department in pre-fire planning.

2.1.7.2 Arrange security rounds to include areas handling flammable and combustible liquids during idleperiods. Train security personnel to ensure all equipment and valves that contain or control flammable andcombustible liquids are shut down (including pumps, emergency shutoff valves, mixers, etc.).

2.1.7.3 Establish excellent housekeeping standards for areas storing or handling flammable and combustibleliquids. Clean up spills promptly. Keep waste materials in Approved oily waste cans. Remove waste daily.Maintain adequate aisles to permit unobstructed movement of personnel and access for fire fighting.

2.1.8 Protection

2.1.8.1 Provide automatic sprinkler protection over all areas storing, processing, or transferring flammableand/or combustible liquids. Extend the sprinkler protection to the physical limits of the area. The physical limitsare defined by at least one hour rated fire walls and curbs. Sprinkler systems over areas defined by curbsonly (see Recommendation No. 2.1.1.4) should extend over and 20 ft (6 m) beyond the curbed area. Thesprinkler system should be either a standard closed head, preaction or deluge type. Preaction systems are

preferred over dry systems for unheated locations. Install the sprinkler system in accordance with Data Sheet2-8N, Installation of Sprinkler Systems (NFPA).

2.1.8.2 Provide sprinkler protection under any obstruction to water distribution that exceeds 3 ft (0.9 m) inwidth or diameter and 10 ft 2 (0.9 m 2 ) in area (e.g., under large tanks or pieces of equipment, below gratedmezzanines) to ensure adequate cooling for steel structures. Spacing below mezzanines should be 100 ft 2

(9 m 2 ) per head.

2.1.8.3 Automatic sprinkler protection may be omitted in building areas that contain no combustibles (includingcombustible construction) other than flammable or combustible liquid piping if all of the following exist:

a) The piping is welded with no flanged joints or has threaded joints that meet the criteria listed inRecommendation No. 2.2.1.3.6. Evaluate fire protection requirements for external pipe racks inaccordance with Data Sheet 7-14, Fire & Explosion Protection for Flammable Liquid, Flammable Gas, &Liquefied Flammable Gas Processing Equipment & Supporting Structures.

b) There are no valves, pumps, or other accessories that are known to be potential leakage points.c) The piping system consists solely of ferrous piping installed as recommended in Section 2.2 of thisdocument.

Automatic sprinkler protection may also be omitted in low value buildings (including pump houses, etc.) withflammable and combustible liquid processes that have adequate space separation (see Section 2.1.1) fromimportant buildings and structures.

2.1.8.4 Sprinkler spacing should be a maximum of 100 ft 2 (9 m 2 ) when protecting liquids with a flash pointless than 200 °F (93 °C) or greater than 200 °F (93 °C) and heated to its flash point. A maximum spacing of130 ft 2 (12 m 2 ) when protecting liquids with a flash point greater than or equal to 200 °F (93 °C).

2.1.8.5 Automatic sprinkler systems (i.e., wet, preaction, or deluge) should be hydraulically designed asindicated in Table 2. If a dry sprinkler system is provided, increase the sprinkler operating areas by 50%.These tables apply to ordinary manufacturing occupancies that use flammable and/or combustible liquids (noliquid quantity limitations) with no potential for a three dimensional fire. Refer to Data Sheet 7-14, Fire &Explosion Protection for Flammable Liquids, Flammable Gas, & Liquefied Flammable Gas Processing Equipment & Supporting Structures, for plants or buildings that are dedicated to flammable/combustible liquid processing (i.e., plants with processes that involve chemical reactions, chemical plants, etc.), any processthat creates the potential for three dimensional flammable/combustible liquid fires, or processes that operateat high pressures (pressures approximately 100 psig [7 bar g] or greater). Sprinkler protectionrecommendations provided in other data sheets that address specific occupancies that use flammable/ combustible liquids supersede the recommendations in this document.





Table 2. Sprinkler Protection for Occupancies Utilizing Flammable/Combustible Liquids.

Liquid Flash Point,

o

F ( o

C)

Liquid Heated

To/Above

Flash Point

Room/ Equipment Explosion

Hazard

(note 1)

Sprinkler Temperature

Rating o

F ( o

C)

Density gpm/sq ft

(mm/min)

Area of Demand,

ft 2

(m 2

)

Hose Streams (note 2),

gpm

(1/hr)

Duration (note 3),

min Any liquid with an associated room/ equipment explosion hazard ornitrocellulose lacquer

286 (141)0.30 (12)

6000 (560)1000 (3800) 120

165 (74) 8000 (740)

< 100 (38) DNA No 286 (141)

0.30 (12) 4000 (370)

500 (1900) 60

165 (74) 6000 (560)

100 – 200(38-93)

Yes No 286 (141)

0.30 (12) 4000 (370)

165 (74) 6000 (560)

No No 286 (141)

0.25 (10) 4000 (370)

165 (74) 6000 (560)

> 200 (93)Yes No

286 (141)0.25 (10)

4000 (370)165 (74) 6000 (560)

No No 286 (141)

0.20 (8) 3000 (280)

165 (74) 4000 (370)

1. See Sections 3.1.4 and 3.1.5 for definition of room/equipment explosion hazard.2. Hose stream demands may need to be increased if shielded areas exist.3. Water supply durations may need to be increased when local conditions delay fire fighting efforts (e.g., lack of drainage, inaccessible

areas, etc.).

Sprinkler protection for flammable/combustible liquid processes and transfer systems may be designed forthe surrounding occupancy when one of the following applies:

a) The aggregate area of an open tank and its drainboard is less than 20 ft 2 (2 m 2 ).

b) The total liquid surface area of an open tank does not exceed 10 ft 2 (1 m 2 ).

c) The aggregate liquid capacity within the fire area is less than 70 gal (265 l). The flammable orcombustible liquid should be kept in flammable liquid storage cabinets.

d) The area contains properly arranged ferrous piping (no valves, manifolds, pumps, or other accessories).2.1.8.6 Sprinklers provided below open grate mezzanines (no flammable or combustible liquids locatedabove the mezzanine) should be hydraulically designed to provide the same density as recommended for theceiling over half the recommended area (or the entire mezzanine area; whichever is smaller). Thesesprinklers should be balanced with the ceiling demand at the point of connection. If flammable liquids arelocated above the mezzanine, a three dimensional fire potential exists and Data Sheet 7-14, Fire & Explosion Protection for Flammable Liquid, Flammable Gas, & Liquefied Flammable Gas Processing Equipment &Supporting Structures, should be used for system design.

2.1.8.7 Spacing of detectors for interior deluge systems (either pilot head, electric, or pneumatic) shouldbe in accordance with Data Sheet 2-8N, Installation of Sprinkler Systems (NFPA), (pilot heads —same spacingas sprinklers, electric or pneumatic devices under smooth ceilings —follow spacing requirements listed inthe Approval Guide for the particular model) or as recommended in data sheets that cover the specificoccupancy. Exterior deluge system design should be in accordance with Data Sheet 7-14.

Detector spacing for preaction systems (either pilot head, electric, or pneumatic) should be as follows:

a) Pilot head spacing should be the same as the sprinkler spacing. Preaction sprinkler systems that usepilot heads should be considered dry systems for design purposes regardless of detector spacing.

b) Electric or pneumatic detector spacing should be the greater of one-half the listed linear detectorspacing or the full sprinkler spacing. Preaction systems with this detector spacing may be considered wetsystems for design purposes. Preaction systems with a detector spacing greater than the above spacingshould be considered dry systems for design purposes. The spacing should never exceed the devices ’listed spacing (e.g., Approval Guide , a publication of FM Approvals, listing).





2.1.8.8 Sprinkler piping, valves, and fittings exposed by occupancies that create an explosion hazard shouldbe protected in accordance with Data Sheet 2-8N, Installation of Sprinkler Systems (NFPA), and Data Sheet7-14, Fire & Explosion Protection for Flammable Liquid, Flammable Gas, & Liquefied Flammable Gas Processing Equipment & Supporting Structures.

2.1.8.9 Automatic sprinkler protection may be supplemented with a fixed special protection system (local ortotal flooding —gaseous, dry chemical, water spray) to limit the exposure created by a potential flammable/ combustible liquid fire. A special protection system should be provided to:

a) Limit fire damage and downtime for high value processes.

b) Limit exposure to high value surrounding occupancies that are susceptible to smoke and water damage.

c) Provide local protection for open tanks that are not accessible to fire fighting with portable extinguishers.

d) Limit the exposure created by inadequate space separation between important buildings or processesand flammable/combustible liquid operations (e.g., loading and unloading stations, piping systems, etc.).

The special protection system should beApproved and designed in accordance with the applicable data sheet.

2.1.8.10 When an open (deluge) or closed-head AFFF (aqueous film forming foam) sprinkler system isprovided as an alternative to a standard sprinkler or deluge system, the following design criteria should be

used (not acceptable in areas with a three dimensional fire potential or warehouse/storage areas):a) Closed or open-head AFFF sprinkler systems should be hydraulically designed to provide either thedensity listed in Table 2 or the minimum required density provided in the Approval Listing, whichever islarger. The AFFF concentrate injection percentage should be in accordance with the Approval Listing.The closed-head systems should be designed to deliver this density over the demand area listed in Table 2.This protection is acceptable with or without adequate drainage (except when superseded by a specificoccupancy data sheet).

b) Exterior hose stream demand and water supply duration should be as recommended in Table 2.

c) Areas with adequate drainage in accordance with Data Sheet 7-83, Drainage Systems for Flammable Liquids, should have at least a 10-minute supply of AFFF concentrate provided. Areas without adequatedrainage should have at least a 20-minute supply of AFFF concentrate provided. The supply should bebased on the sprinkler system design requirements, hose stream design requirements and the required

concentrate injection percentage provided in parts (a) and (b) above.d) Adequate containment designed in accordance with Data Sheet 7-83, should be provided whenadequate drainage is available. If adequate drainage is not available, containment should be designedto hold sprinkler and hose stream discharge for the full 20-minute foam concentrate duration.

e) The AFFF concentrate should be compatible and Approved for the flammable or combustible liquidbeing protected. The AFFF delivery system (proportioning equipment, sprinklers) should be Approved.

f) The AFFF system should be installed in accordance with Data Sheet 4-12, Foam-Water Sprinkler Systems.

2.1.8.11 Portable extinguishers should be provided for areas (interior and exterior) utilizing or handlingflammable and combustible liquids. Extinguishers should be either carbon dioxide, dry chemical, or AFFFtype. Refer to Data Sheet 4-5, Portable Extinguishers, to determine effective sizes and locations for theextinguishers. Extinguishers should be Approved. Protect extinguishers located outside against freezing.

2.1.8.12 Provide small hose (1- 1 ⁄ 2 in. [38 mm]) stations with combination spray/solid stream nozzles in areasutilizing or handling flammable and combustible liquids. Space hose stations to allow full coverage of thearea being protected. Add a water demand of 50 gpm (11 m 3 /h) to the sprinkler demand for a single hosestation (100 gpm [23 m 3 /h] should be added for more than one hose station).

2.1.8.13 Manual protection consisting of yard hydrants should be located within 200 ft (60 m) of all outsideflammable and combustible liquid handling and process areas (e.g., pump houses, loading and unloadingstations, valve-manifold houses, process structures, etc.). Provide manual foam protection for critical processor handling areas containing liquids with flash points below 200 °F (93 °C). Manual foam protection can beprovided by a fixed water spray system, fixed monitor nozzles, or mobile monitor and hose nozzles. Designthe system in accordance with Data Sheet 4-7N, Low Expansion Foam Systems .





2.2 Piping Systems

2.2.1 Construction and Location

2.2.1.1 Location and Arrangement

2.2.1.1.1 Locate flammable and combustible liquid piping systems outside (above or below ground) ofimportant buildings and structures. Arrange points of entry to buildings or structures to minimize inside pipingand to ensure a direct route to the point of use. Avoid piping flammable and combustible liquids throughor under buildings or process structures that do not use the liquids (e.g., reduce pipe length by taking a shortcut through a building).

2.2.1.1.2 Pipe routes should prevent or limit fire exposure to piping systems created by other plantoccupancies.

2.2.1.1.3 Protect piping against mechanical damage. Do the following to prevent or limit mechanical damageto piping:

a) Provide adequate clearance for aboveground pipe that passes over roadways or railroad sidings. Theamount of clearance provided should be posted on signs at each crossing point.

b) Locate buried piping at least 1 ft (0.3 m) from building foundations, railroad tracks or other facilitiessubject to vibration and settling. Enclose piping that passes below building footings or railroad tracks ina larger pipe.

c) Mark buried piping routes to permit visual determination of their location.

d) Interior pipe risers within 6 ft (1.8 m) of the floor that are exposed to vehicles or mobile equipmentshould be installed inside reinforced concrete columns, between flanges of steel columns, in a securelyanchored larger pipe, or provided with some other type of guard that will prevent contact with the mobileequipment. Locate pipe risers in areas not exposed to mobile equipment or vehicles as close as possibleto walls or columns.

2.2.1.1.4 Protect interior and exterior piping (above or below ground) against external corrosion. Cover buriedpipe with noncorrosive backfill, or for ease of replacement and maintenance, place in covered masonrytrenches or split-tile ducts. Evaluate environmental conditions for aboveground installations to ensure

adequate precautions have been taken to prevent corrosion (e.g., exposure to weather conditions or corrosiveatmospheres).

2.2.1.1.5 Support exterior aboveground piping on noncombustible structures that are adequately protectedagainst vehicle impact damage. Piping may also be located on noncombustible building walls and abovenoncombustible roofs. Place piping supported by a wall below window level. Piping runs above roofs shouldhave welded joints and avoid having known leakage points (e.g., flanged fittings, valves, meters, etc.).

Roofs supporting piping that contains known leakage points should be arranged to promptly direct any liquidrelease to a properly arranged collection point through a dedicated collection and removal system (e.g., metalcollection pan below leakage points attached to a metal trough which directs a spill to a collection tank;enclose entire piping system in a sealed metal duct arranged to direct spills to a containment tank). The liquidcollection and removal system should prevent damage to the roof covering due to liquid contact and preventthe released liquid, or its vapors, from entering the building.

2.2.1.1.6 Avoid passing exterior pipe routes through service tunnels, sewer manholes, or other undergroundpits.

2.2.1.1.7 Locate interior pipe routes either overhead or in covered (removable steel plates) trenches in thefloor. Avoid basement areas, vacant spaces below grade, and concealed or other inaccessible locationswithin plant buildings. Place overhead piping as close as possible to ceilings and beams or along walls atleast 6 ft (2 m) above floor level. If a floor trench is used, do the following to prevent the collection of flammablevapor or flammable/combustible liquid in the trench:

a) Provide drainage in accordance with Data Sheet 7-83, Drainage Systems for Flammable Liquids. Thetrench may be used to direct the liquid to a collection point that does not expose the building (e.g., pitchthe trench to an exterior collection point so a spill that collects in the trench will be directed out of thebuilding).





b) Provide positive exhaust ventilation throughout the trench when the piping system is transporting liquidswith a flash point below 100 °F. Alternatives to providing ventilation are filling the trench with sand (thiswill eliminate the need for drainage as well).

c) If the trench passes below a cutoff wall (e.g., enters a flammable liquid room from an adjacent area),

cut the trench off at the wall with a liquid tight noncombustible barrier. The section of trench outside thearea using the flammable/combustible liquids does not require drainage or ventilation if it is welded pipingonly (no leakage points —valves, flanged joints, etc.). Protect the section of trench inside the room ortrench areas containing potential leakage points as stated in parts (a) and (b) above.

2.2.1.1.8 If piping is located inside a building and is below grade (e.g., basement areas) or is inaccessible(e.g., vacant below grade spaces) provide one of the following:

a) Enclose the pipe in a larger pipe throughout its entire length (Fig. 4). Weld the larger pipe at joints.Provide a means of checking for leaks (e.g., provide a low point drain that is accessible for inspection atregular intervals).

b) Enclose the pipe in sealed ductwork throughout its entire length. Arrange the ductwork to permitinspection for leaks and allow drainage of potential leaks to a collection location (e.g., tank or flammable/ combustible liquid drainage system).

c) Basements or below grade spaces containing flammable or combustible liquid piping should beprovided with automatic sprinkler protection (Table 3), adequate drainage (per Data Sheet 7-83, Drainage Systems for Flammable Liquids), and a low level continuous mechanical exhaust ventilation system forthe entire space. Design the ventilation system to provide 0.5 cfm/ft 2 (0.15 m 3 /min/m 2 ). Natural ventilationis acceptable for pipe containing liquids with a flash point greater than 100 °F (38 °C).

Fig. 4. Buried-pipe entrance into building.





2.2.1.1.9 Piping should enter buildings above grade. Buried piping should be brought above grade beforeentering a building as shown in Figure 5. The piping should be adequately protected against damage due tobuilding settlement. Where flammable or combustible liquid piping enters a building below grade, seal allother nearby openings in the foundation.

2.2.1.1.10 Enclose piping in a pipe sleeve where the piping passes through exterior walls and foundations.Seal the opening between the sleeve and the pipe. Extend the sleeve to the exterior of the wall or foundationat least 2 in. (51 mm) or 18 in. (460 mm) respectively. (Figs. 4 & 5)

2.2.1.1.11 Arrange piping system to permit drainage of its content during maintenance operations (repairs,cutting and welding, etc.). This can be accomplished by pitching pipe back toward the supply, providing lowpoint drains, and providing flanged connections at various locations to permit disconnection and blankingof the pipe.

2.2.1.2 Pipe Materials

2.2.1.2.1 Choose flammable and combustible liquid pipe materials using The American Society of MechanicalEngineers (ASME) Standard B31.3-1990 or latest edition, Chemical Plant and Petroleum Refinery Piping,as a basic guideline. Consider the following factors when choosing a pipe material:

a) Chemical compatibility with the liquid to be handled.

Fig. 5. Preferred arrangement for above grade pipe entrance into building.





b) Operating environment.

c) Operating strength (i.e., design for maximum expected pressure and temperature).

d) Resistance to mechanical shock (e.g., impact damage).

e) Resistance to thermal shock (e.g., quick cooling or heating due to expected and unexpected processconditions).

f) Resistance to high exposure temperatures (e.g., high melting point or noncombustible material thatwill resist softening or decomposition when heated by an exposure fire).

2.2.1.2.2 Avoid materials such as cast irons, high silicon irons, plastics (thermoplastic, thermoset), glass,and aluminum in flammable and combustible liquid piping systems due to their potential for failure (low impactstrength, low pressure ratings, low resistance to thermal shock, and low melting point). Seamless copperor brass pipe and tubing is acceptable for use with flammable and combustible liquids in sprinklered locationssubject to the design conditions provided in ASME B31.3-1990 or latest edition.

2.2.1.2.3 Underground pipe should meet the above requirements (i.e., compatible with liquid in use, adequatestrength for maximum expected operating conditions, high impact strength, and high resistance to thermalshock) but may be a low melting point material (e.g., plastic —thermoplastic, thermoset) since there is nopotential for a fire exposure.

2.2.1.2.4 Consider seamless steel pipe for interior piping systems that operate under severe cyclic conditions(i.e., pressure cycles, thermal cycles —for example a hydraulic system) and create a significant exposureto the facility.

2.2.1.2.5 Use stainless steel, nickel alloy, lined (glass, rubber, lead, plastic, etc.) steel pipe, or other similarmaterial when process conditions require high purity levels or create severely corrosive conditions. Thesematerials provide a high resistance to heat and mechanical damage. Lined pipe may fail internally with impactor thermal shock, but the steel pipe shell will still contain the pipe contents.

2.2.1.2.6 Provide flexible all-metal seamless hose in piping systems exposed to vibration, settling or thermalchange. The installation should be in accordance with Section 2.2.2.1.

2.2.1.3 Pipe Joints

2.2.1.3.1 Piping systems containing flammable and combustible liquids should have welded joints. Providea limited number of flanged joints to permit pipe system dismantling for equipment maintenance or removal.Welded joints connecting pipe lengths and fittings should be butt welded in accordance with ANSI/ASMEB16.25, Butt Welding Ends, and ASME B31.3, Chemical Plant and Petroleum Refinery Piping, Chapter 5.Welding should be done by qualified welders under close supervision, with all hot work safeguards observed.The flanged joints should be provided at connections to system accessories (e.g., pumps, valves, tanks,etc.) and at various points in-line (e.g., entrance to a room or building).

2.2.1.3.2 Design flanged joints in accordance with ANSI/ASME B16.5, Pipe Flanges and Flanged Fittings,and ASME B31.3. Provide the following for flanged joints:

a) Flanges should be constructed of forged or cast steel. Do not use cast iron flanges. Bronze flangesare acceptable in sizes of 2 in. (50 mm) or less in sprinklered areas.

b) Flanges should be welding-neck type (flange is butt welded to pipe end —see Fig. 6). A double weldedslip-on type flange (flange slips over pipe end and is welded outside and inside —see Fig. 7) is acceptablefor use in systems that are noncyclic and have operating pressures less than 100 psig (7 bar g).

c) Design flanges on lined pipe (i.e., plastic, glass, etc., in steel pipe) to prevent leakage in the event oflining failure (e.g., fire exposure to pipe melts plastic lining).

d) Consider high integrity or protected flanges (i.e., flanges designed or protected to prevent leakage orfull failure) when the exposure created by leakage (fire or explosion) is significant (e.g., spray fire exposureto high value occupancies, flange failure would create explosion potential).

2.2.1.3.3 Bolting materials for flanges should be alloy steel conforming to ASTM A193, Alloy Steel Bolting Materials for High Temperature Service, Grade B-7 or equivalent. Nuts should be alloy steel conforming toASTM A194, Carbon and Alloy Steel Nuts for Bolts for High Pressure and High Temperature Service. Bolt andnut dimensions and threads should conform to nationally recognized codes. Existing installations with carbon





steel and wrought iron bolts are acceptable in sprinklered areas or in outside areas with limited exposures.Make the effort to replace the bolts during maintenance of the joints or if the bolts are corroded.

2.2.1.3.4 Gaskets for use with flanged joints should be compatible with the flange type being used. Considerthe following factors when choosing a gasket material:

a) Chemical compatibility with the liquid in use.

b) Strength and temperature limitations (adequate for maximum possible system pressure andtemperature as well as system pressures when exposed by external fire).

c) Resistance to leakage or total failure.

d) Resistance to cold flow.

e) Resistance to decomposition or melting with an external fire exposure (e.g., noncombustible, highmelting point —greater than 1200 °F [650 °C]).

2.2.1.3.4.1 Use one of the following types of gasket for flammable and combustible liquid service:

a) Spiral-wound stainless steel, Monel, copper, Inconel 600, or equivalent metallic gasket with graphite,ceramic, or equivalent filler.

b) Metal ring-joint gasket consisting of dead-soft aluminum, Monel, copper, or equivalent.

c) Graphite gasket without organic fillers or resins.

2.2.1.3.4.2 Other gasket materials consisting of fiber-sheet, paper, vegetable fiber, plastic, cork, lead, rubber,Teflon, or equivalent are tolerable in existing systems located in sprinklered areas if all of the following aretrue:

a) The operating pressure is less than 100 psig (7 bar g).

b) The system is noncylic.

Fig. 6. Welding neck type flange.

Fig. 7. Slip-on type flange.





c) The potential exposure created by a gasket failure is limited.

d) The joints are outside and either underground or aboveground with limited exposure.

2.2.1.3.5 Join nonferrous metallic piping with flanged, brazed or flared connections. Brazing alloys shouldhave a minimum melting point of 1000 °F (535 °C). Do not use fillet-brazed joints or soldered joints.

2.2.1.3.6 Avoid threaded joints. New systems containing liquids with flash points of 200 °F (93 °C) and aboveor existing systems (any flash point) with threaded joints can be considered tolerable when all of the followingare true:

a) The exposure created by leakage is minimal.

b) The piping system has an operating pressure less than 100 psig (7 bar g).

c) The piping system has limited leakage (constant repairs for leakage would indicate that a change in joint type is needed).

d) Operating conditions are not cyclic.

e) Operating conditions do not create corrosion problems.

If the piping creates a significant exposure, severe cyclic conditions exist or corrosion problems exist, replace

the threaded connections with butt welded joints. Piping systems with high pressures (greater than 100 psig[7 bar g]) or leakage problems should have the threaded joints seal welded. A combination of leakageproblems and high system pressures in a piping system should have threaded joints replaced with butt welded joints.


2.2.2.1 Flexibility and Support of Piping Systems

2.2.2.1.1 Design flammable and combustible liquid piping systems to provide adequate expansion andflexibility to handle thermal expansion and contraction due to internal operating conditions (e.g., systemtemperature changes) and external conditions (e.g., environmental effects) or other movements (e.g., fluidhammer effects, settlement, vibration). Provide system flexibility to prevent: a) failure of piping or supportsfrom overstress or fatigue b) leakage at joints and c) creation of damaging stresses in piping, valves or other

connected equipment.2.2.2.1.2 Evaluate piping system flexibility in accordance with ASME B31.3, Section 319. Provide systemflexibility by the use of pipe bends, welding elbows, pipe hangers, flexible hose connectors and other flexibledesigns. Do not use expansion slip joints.

2.2.2.1.3 Provide pipe hangers to support and secure piping systems in accordance with the rules listed inData Sheet 2-8N, Installation of Sprinkler Systems (NFPA), or ASME B31.3, Section 321. Consider thefollowing when designing and installing hangers:

a) Design pipe hangers to support the full weight of the system including all live loads (e.g., content, snow),dead loads (e.g., pipe, valves, insulation), and test loads (e.g., test liquid weight).

b) Design pipe hangers for expected dynamic effects (e.g., hydraulic shock, wind loads, vibration) andpotential thermal expansion and contraction loads.

c) Arrange pipe hangers to prevent excessive vibration and strain on connecting equipment.

d) Limit horizontal pipe spans to reduce stress on pipe walls. Long horizontal spans should be supportedfrom cables or trusses.

e) Arrange hangers to prevent stress on joints and pipe sagging.

f) Hangers and anchoring devices should consist of high melting point, noncombustible materials, or beinsulated against possible exposure fires.

g) Follow closely manufacturer ’s recommendations for supporting specialty piping.

2.2.2.1.4 Provide flexible hose connectors in piping systems to prevent dangerous stresses due to vibration,settling, or thermal change. Provide the following material and installation features to ensure adequate hosestrength/durability and protection against physical damage:





a) Flexible hose should be constructed of high strength, noncombustible material that is resistant todecomposition or melting when exposed to an exposure fire, and compatible with the liquid in use. All-metalconstruction consisting of materials such as steel, Monel, stainless steel, brass, bronze, or an equivalentmaterial are preferred. Reinforced rubber hose with a synthetic liner and a metal-braid covering isacceptable when needed to meet operational requirements. Do not use soft rubber, plastic, or other

unreinforced or unprotected combustible tubing.

b) The hose should be bent only in one plane without subjecting it to tensile, torsional, or excessivebending stresses.

c) Protect the hose against mechanical damage.

d) Hose joints should comply with all rigid pipe joint recommendations (Section 2.2.1.3).

e) Hose and fittings should have a bursting strength that is greater than the maximum expected workingpressure with a safety factor of at least 4.

2.2.2.1.5 Arrange piping systems located in areas exposed by earthquakes in accordance with Data Sheet1-2, Earthquakes.

2.2.2.2 Heating and Insulating Piping Systems

2.2.2.2.1 Arrange pipe heating systems to prevent: 1) local overheating, 2) the creation of an ignition sourcefor the pipe content or surrounding combustibles, and 3) overpressurization of piping sections that may beisolated between valves. Operate heating systems at the minimum temperature needed to meet processrequirements. Heated pipe sections that may be isolated between valves while the heating system is activeshould have a pressure relief device provided to prevent overpressurization. Liquid trapped in an isolatedsection of heated pipe can produce significant pressures due to liquid expansion and/or vapor liberation.Relief valves should be piped to a location that does not create an exposure to important plant facilities orbuildings.

2.2.2.2.2 Provide pipe heating by one of the following methods or an equivalent: a) steam-tracing, b) electricheating cable, or c) impedance heating (i.e., pass a low voltage alternating current through the pipe). Donot use open flames. Data Sheet 9-18/17-18, Prevention of Freeze-ups, should be used to develop freeze-upprevention plans.

2.2.2.2.3 Steam-tracing should be arranged as follows:a) Provide the minimum steam pressure needed to make the liquid fluid.

b) Provide a steam regulator.

c) Install a pressure relief valve downstream of the regulator. Set the relief valve to open at a pressure just above the regulator.

d) Enclose the pipe and steam-tracing in insulation.

2.2.2.2.4 An electric heating cable system should be arranged as follows:

a) Heating cable should be fastened along the pipe or spirally wound around the pipe. Enclose the pipeand cable in insulation.

b) Heating cable should be continuous (no splices). Electrical connections should be visible for inspection.

c) Provide individual thermostat controls for each cable section. Fuses or fused disconnect switches ofas low a rating as practical should also be provided.

d) Electrical equipment (thermostats, plug assemblies, and switches) exposed to various weatherconditions should be enclosed in weatherproof housings. All sparking equipment (i.e., equipment withmake-and-break contacts) should be well separated from the pipeline and locations requiring hazardousarea rated electrical equipment.

e) All electric heating cable equipment should be Approved.

2.2.2.2.5 An impedance heating system should be arranged as follows:





a) Systems should be installed and tested as complete units by the manufacturer or other qualifiedinstaller. The installation should conform to the requirements of the authority having jurisdiction and Article427 —Fixed Electric Heating Equipment For Pipelines and Vessels, of the National Electric Code (1990or current edition).

b) Piping sections that are heated should be insulated from unheated sections with electricallynonconductive fittings to confine the current paths and to eliminate any current leakage at hazardouslocations.

c) Provide an automatic high-temperature-limit cutoff switch in each circuit of each system to preventoverheating of liquid in event of failure of the operating temperature control thermostat.

d) Enclose all parts of the piping and fittings in electrical and thermal insulating material to preventaccidental grounding of the system. Provide a ground fault interrupt (GFI) device for the power supplyof all impedance heating systems.

e) Locate all sparking equipment (e.g., switches, transformers, contacts) well away from the pipeline andareas requiring electrical equipment rated for hazardous locations.

f) Test the heating system periodically to ensure its continued proper operation. All maintenance on thesystem should be conducted by trained employees or contractors.

2.2.2.2.6 Insulation provided on the piping system should be noncombustible. Provide nonabsorbentinsulation (e.g., closed cell cellular glass) near flanged fittings or other potential leakage points (e.g., valves,pumps). Any type of insulation (e.g., calcium silicate, glass fiber batts, mineral wool, etc.) is acceptable overwelded pipe.

2.2.2.3 Piping System Control Valves and Safety/Emergency Shutoff Valves

2.2.2.3.1 Flammable and combustible liquid piping systems should be provided with adequate valving toensure proper system control, regulation, isolation, and ability to shut down all fluid flow in the event of afire.

2.2.2.3.2 Select control valves and safety/emergency shutoff valves using the following criteria:

a) The valve should be compatible with the liquid in use (including the packing and lubricants).

b) Valve bodies should be cast steel construction. Bronze is acceptable for valves 2 in. (50 mm) or smallerinstalled in sprinklered areas. Use stainless steel, Monel, lined-steel, or an equivalent when processconditions require the use of special materials. Cast iron bodies and yokes are not acceptable.

c) Rate the valve for the maximum expected system pressures and temperatures.

2.2.2.3.3 Consider the following for the selection and arrangement of process control valves:

a) Valve should provide positive indication of its status (i.e., open or closed, direction of flow).

b) Valves may be either manually operated at point of use or remotely operated depending on complexityof the system. Remotely operated valves should fail in a safe position.

c) Arrange valves to ensure adequate control of liquid direction and flow rate. The valve arrangementshould also minimize the potential for improper system operation (e.g., allowing liquid flow to the wrongtank, permitting too high a liquid flow rate, etc.). Proper valve operation can be accomplished through theuse of check lists for manual system operation and through process control systems for remote operation.Thorough employee training is needed for either approach.

d) Arrange control valves to isolate important equipment to permit maintenance operations orreplacement.

e) Control valves that may be exposed to severe fire conditions (e.g., valves located in a flammable liquidroom) where loss of their function could significantly increase the exposure (e.g., valve controllingflammable liquid flow from the bottom of a tank where valve failure would release the tank contents) shouldbe a Approved firesafe shutoff valve.





2.2.2.3.4 Safety/emergency shutoff valves should be either diaphragm, solenoid, or fusible-element (weightor spring operated) type. Positive displacement pumps may also be used as a safety/emergency shutoff.The valves should be Approved. Valves that may be exposed to a flammable/combustible liquid fire shouldbe Approved fire safe shutoff valves.

2.2.2.3.5 Arrange safety/emergency shutoff valves to permit complete shutdown of liquid flow during a fireand to limit the quantity of liquid released in the event of accidental escape. In general this can beaccomplished by isolating the liquid supply and shutting off liquid at the various points of use. The actualnumber and location of safety/emergency shutoff valves will vary depending on the piping system size,complexity and potential exposure created by a release. All piping systems containing flammable/combustibleliquids should at least have safety/emergency shutoff valves in the following locations:

a) On discharge lines of interior or exterior tanks (aboveground or underground), arranged for transferby gravity, centrifugal pump, inert gas pressure, or other means that provide continuous pressure on thesystem.

b) On bottom-discharge lines of exterior aboveground tanks feeding a positive displacement pump whenmultiple tanks are located in the same area (e.g., two or more tanks in a diked area or a single tank ina diked area that is not accessible during a fire) to permit supply shutdown in the event of a leak at thepump. A single exterior tank (e.g., single tank in a diked area that is accessible) feeding a positive

displacement pump may have a manually operated valve on the bottom-discharge line.c) On bottom-discharge lines of interior tanks feeding positive displacement pumps to permit supplyshutdown in the event of a leak at the pump.

d) At points of use such as dispensing operations or delivery lines to equipment. Valves may be locatedon each feed pipe to a piece of equipment/dispensing operation or on the supply pipe to a manifold feedingequipment/dispensing operation. A single valve located at the entrance point to a building or cutoff roomis also acceptable.

2.2.2.3.6 Safety/emergency shutoff valves or positive displacement pumps should be arranged for automaticand manual operation. In locations that are constantly attended and where leakage will be quickly discovered,manual operation is acceptable. Arrange both automatic and manual valve operation to shut down allflammable/combustible liquid flow in and to the area affected (i.e., shutdown valves at supply tank and atpoints of use).

2.2.2.3.7 Automatic operation of safety/emergency shutoff valves and/or positive displacement pumps shouldbe accomplished by one of the following methods:

a) Thermal actuation by use of heat detectors (e.g., HADs) located above the points of use (includingpotential leak points, such as pumps, that create a significant exposure), fusible link operated valves, oruse of thermoplastic tubing for air supply to a pneumatic valve (loss of air supply will cause valve to close,thermoplastic tubing will melt when exposed to a fire). Fusible link operated valve placement should ensureit will be exposed to a fire caused by a flammable/combustible liquid release. If the valve ’s placementlimits its exposure to a potential fire, the valve should either be arranged to ensure its operation (e.g., inaddition to link at valve, provide a second link over expected leak points with a cable attached to the valvehandle which is arranged to close when the cable releases) or be replaced with a valve that can be remotelyoperated.

b) Actuation by operation of a fire protection system such as automatic sprinklers and special protectionsystems (water spray, gaseous extinguishing system, etc.). Safety/emergency shutoff valves may be tiedinto pressure switches, waterflow alarms, or fire detection systems. Arrangements should be made topermit protection system alarm testing without unwanted production shutdown.

c) Release of a dead-man type control or self-closing valve. These types of controls require constantattendance by the operator and will close automatically when the operator leaves. Provide self-closingvalves at dispensing operations upstream of any flexible hose.

d) Actuation by abnormal system conditions such as high/low pressure and excess flow. Use thisarrangement to reduce a flammable/combustible liquid release before ignition when the expected fire orexplosion exposure is excessive. Provide this type of actuation system in addition to a method listedabove (a – c).





2.2.2.3.8 Manual operation of safety/emergency shutoff valves and/or positive displacement pumps shouldbe accomplished by providing one or more stop buttons or switches located within the flammable/combustibleliquid operation area (arranged for easy access by the operators and at points of egress from the buildingor structure) and at accessible remote locations (e.g., control room, security station, etc.).

2.2.2.3.9 Provide check valves in piping arranged to feed tanks, receivers, or other vessels when: a) theliquid flow is in one direction only and b) the vessel can supply a leak in the feed pipe by reverse flow. Installthe check valve as close to the vessel as possible. Check valves used on systems with materials that mayimpair their proper operation (e.g., paint, printing ink) should be physically checked regularly.

2.2.2.3.10 Provide hydraulic accumulators or safety relief valves on pipelines that can be valved off withliquid trapped between valves to prevent damage or overpressure from thermal expansion of the liquid. Pipethe relief valve discharge to a properly arranged collection point.

2.2.3 Operation and Maintenance

2.2.3.1 Piping systems should be inspected and tested in accordance with ASME B31.3, Chapter VI.Inspections should include all pipe joints (welded and flanged) and pipe supports. Conduct all testing beforepainting, insulating, or burying of the pipe system.

2.2.3.2 Conduct pressure testing on all piping systems before introduction of flammable/combustible liquids.Hydrostatic testing should be conducted, using water as a test liquid, for systems that will not be adverselyaffected by water and with design pressures greater than 1 psig (0.07 bar g). Systems that are incompatiblewith water or that have a design pressure less than 1 psig (0.07 bar g) should be pneumatically tested usingcompressed air or inert gas (generally, pneumatic testing should be avoided when possible due to the highrelease energy potential created by compressed gas).

2.2.3.3 The following should be provided to conduct a hydrostatic leak test on the piping system:

a) Vent the piping to permit removal of air within the system.

b) Relief valves, rupture disks, pumps, vessels of appreciable volume, and other portions of the systemrated below the test pressure should be blanked off or removed.

c) Reinforce piping supports if the test liquid is heavier than the liquid the system was designed to contain.

d) Pressurize the test liquid to 1.5 times the system ’s design pressure. Consider normal operatingtemperatures when picking a test pressure.

e) Hold the test pressure for at least 30 minutes.

f) While pressurized, the system should be visually inspected for leaks.

g) All leaks should be repaired and the system retested until the test pressure can be held for the statedtime period.

2.2.3.4 Provide the following to conduct a pneumatic leak test on the piping system. Conduct pneumatictests with caution due to the high release energy potential present in compressed gases.

a) Relief valves, rupture disks, pumps, tanks, and other portions of the piping system rated below thetest pressure should be blanked off or removed.

b) A pressure relief device set for the test pressure plus the lesser of 50 psig (3 bar g) or 10% of testpressure should be provided on the piping system.

c) Provide a test pressure of 110% of the design pressure or a minimum of 3 psig (0.2 bar g). The systemshould be raised to the test pressure in small increments, to locate large leaks at low pressures.

d) Hold the test pressure for 30 minutes.

e) After the test period, reduce the pressure to the design pressure and inspect for leaks using a solutionof soap and water.

f) All leaks should be repaired and the system retested until the test pressure can be held for the statedtime period.





2.3 Flammable and Combustible Liquid Transfer Systems


2.3.1.1 Transfer by Pumping

2.3.1.1.1 Arrange pumping systems to pressurize the piping system only when there is a demand for liquidat the point of use. Avoid piping systems that are pressurized when not in use.

2.3.1.1.2 Arrange pumps to shut down when safety/emergency shutoff valves are actuated.

2.3.1.1.3 Arrange pumping systems to provide the minimum pressure required for system operation.

2.3.1.1.4 Use a positive displacement pump when possible to permit complete shutoff of liquid flow. Acentrifugal pump is acceptable but can only be arranged to shut off pumping. Liquid flow may continue bysiphoning or gravity flow.

2.3.1.1.5 Consider the following factors when choosing pump construction features:

a) Pumps should be cast steel construction. The pump, packing, and trim should be compatible with theliquid being handled.

b) Studs used to attach packing glands to pumps should have the nuts on the outside ends to indicatethe amount of thread engaged. Avoid cap screws.

c) The pump casing, impeller, and other moving parts should be constructed of nonsparking materials ifthe pump is to operate dry at frequent intervals.

d) Provide pumps with high integrity seals (dual seals) or use seal-less type pumps when the exposurecreated by a leak at the pump is significant or the frequency of leakage is high.

2.3.1.1.6 Install a pressure relief valve downstream of positive displacement pumps. It should have adequatecapacity to prevent excessive pressure build-up in the system. Pipe the relief valve discharge back to thesupply source or to the suction side of the pump. Systems containing liquids with a closed-cup flash point of0°F (-18 °C) or less should have relief valves discharge back to the supply source to prevent possibleoverheating due to the churning action of the pump.

2.3.1.1.7 Arrange submerged or vertical-shaft centrifugal pumps to prevent dry operation of rotating partsin the vapor space of a tank. Using the pumped liquid to cool the pump and bearings is acceptable.

2.3.1.1.8 Pumps should be located as follows (listed in order of preference):

a) Outdoor locations.

b) Noncombustible pump house.

c) Cutoff room in a main building.

Pumps located near outdoor storage tanks should be placed outside of containment dikes to limit the exposureto the tank from the pump.

2.3.1.1.9 Pumps located on open pads or in pump houses, without water spray protection should be spacedto limit exposure to important buildings as follows:

a) High pressure (approx. > 100 psig [7 bar g]) or high flow rate (approx. > 100 gpm [23 m 3 /h]) pumpsshould be spaced in accordance with Data Sheet 1-20, Protection Against Exterior Fire Exposure , (usingExposure B in Tables 2 through 7).

b) Low pressure (approx. < 100 psig [7 bar g]) or low flow rate (approx. < 100 gpm [23 m 3 /h]) pumps shouldbe spaced in accordance with Data Sheet 1-20 (using Exposure C in Tables 2 through 7).

2.3.1.1.10 Pumps located on open pads protected with a water spray system should be spaced to limitexposure to important buildings as follows:

a) High pressure or high flow rate pumps should be 50 ft (15 m) away from a building. Within 50 ft (15 m)the exposed wall should be at least one hour fire rated.

b) Low pressure or low flow rate pumps should be 25 ft (8 m) away from a building. Within 25 ft (8 m)the exposed wall should be at least one hour fire rated.





2.3.1.1.11 Pumps located in pump houses protected with a water spray system should be spaced to limitthe exposure to important buildings using Table 1, Construction for Flammable or Combustible LiquidOccupancies, (for high pressure or high flow rate pumps use the > 1500 gal [6000 l] section; for low pressureor low flow rate pumps use the < 1500 gal [6000 l] section).

2.3.1.1.12 Protect pumps located in pump houses or cutoff rooms in accordance with Sections 2.1.1 (Locationand Construction), 2.1.3.1 (Ventilation), 2.1.4 (Ignition Source Control), 2.1.5 (Operations and Maintenance),2.1.6 (Training), 2.1.7 (Human Element), and 2.1.8 (Protection). Evaluate pump rooms or pump houses fora room explosion hazard based on the material being pumped.

2.3.1.2 Gravity Transfer

2.3.1.2.1 Use gravity transfer operations for flammable and combustible liquid transfer when other methodsare not compatible with the liquids in use (e.g., some volatile liquids may cause vapor lock when pumped)or for small systems (limited exposure).

2.3.1.2.2 Arrange gravity transfer operations to permit isolation of the supply in the event of a leak or fire.Gravity transfer does not allow easy fluid flow control since the driving force is gravity, rather than a pump.

2.3.1.2.3 Use safety/emergency shutoff valves to isolate the liquid supply. Locate the valves as close to thesource as possible.

2.3.1.3 Inert-Gas Transfer

2.3.1.3.1 Gas transfer systems should use inert gas (e.g., nitrogen, carbon dioxide) to avoid the potentialfor more violent vapor-air explosions and increased flammable liquid explosive limits that would occur withthe use of air. Do not use air.

2.3.1.3.2 Tanks for inert gas transfer systems should be constructed, installed, and tested in accordancewith ASME or other recognized codes for unfired pressure vessels.

2.3.1.3.3 The gas pressure should be the minimum needed to force the liquid through the transfer systemat a rate to meet the operating demands.

2.3.1.3.4 Provide the following minimum equipment on an inert gas transfer system (Fig. 8):

a) Provide an accessible manual shutoff valve on the gas supply line.

b) Provide a pressure regulator in the gas supply line set at the minimum needed pressure.

c) Provide a check valve on the gas supply line and the tank fill line to prevent the backflow of liquid.

d) A two-way, three port power operated directional control valve (e.g., solenoid valve; energized valvepermits gas flow to pressurize tank, de-energized valve permits release of tank pressure to vent) orequivalent should be provided on the gas supply line downstream of the check valve.

e) A pressure relief valve set at a slightly higher pressure than the regulator should be provideddownstream of the regulator or on the tank.

f) Provide the process supply line with a safety/emergency shutoff valve.

g) Provide the tank fill line with a power operated control valve (e.g., solenoid, motor, air operated).

h) Provide a liquid level control on the tank to prevent overflow.

i) Vent lines for the storage tank (pressure relief line, directional valve vent line) should be provided withflame arresters for liquids with a flash point below 100 °F (38 °C).





2.3.1.3.5 The inert gas transfer system should be interlocked to operate as follows:

a) During normal operation the safety/emergency shutoff valve should be open, the fill line control valveshould be shut, and the directional valve on the gas supply line should be arranged to allow gas flowinto the storage tank.

b) During filling operations the safety/emergency shutoff valve should be closed, the fill line control valveshould be open, and the directional valve on the gas supply line should be arranged to vent the tankpressure.

c) During fire or leakage conditions the safety/emergency shutoff valve should be closed, the fill line controlvalve should be closed, and the directional valve on the gas supply line should be arranged to vent thetank pressure.

Arrange the inert gas transfer system to prevent valve operation before confirmation of proper valve position(e.g., interlock valves on large systems electrically or provide clear procedures for manual valve operationon small systems). Arrange the control valves to operate automatically (i.e., interlock with safety/emergencyshutoff valve) in the event of a fire or leakage.

2.3.1.4 Hydraulic Transfer

2.3.1.4.1 Liquids that are not miscible in water and present hazards that may not be controlled with otherliquid transfer arrangements should be hydraulically transferred (e.g., carbon disulfide, which has a very lowflash point and ignition temperature). Liquids may be either heavier or lighter than water.

2.3.1.4.2 Tanks for hydraulic transfer systems should be constructed, installed, and tested in accordancewith ASME or other recognized code for unfired pressure vessels.

2.3.1.4.3 Use a double tank arrangement (water tank and flammable liquid tank) to permit recovery and re-useof the water. A single tank arrangement is acceptable when other water recovery equipment is available (e.g.,water treatment plant). (Fig. 9)

2.3.1.4.4 Arrange the hydraulic transfer system to operate on demand instead of continuous operation.

2.3.1.4.5 Supply the following minimum equipment for a double tank hydraulic transfer system (Fig. 9):

a) Provide a positive displacement pump to deliver water to the flammable/combustible liquid storage tank.Place a foot valve on the suction supply line for the pump.

b) Provide a check valve on the water delivery line and the flammable/combustible liquid tank fill line.

Fig. 8. Compressed inert-gas transfer method.





c) A pressure relief valve set just above the system operating pressure should be provided downstreamof the pump or on the tank. The pressure relief valve should be piped back to the water tank.

d) A power operated control valve (e.g., solenoid, motor, air operated) should be provided on the processsupply line and the flammable/combustible liquid tank fill line.

e) Provide the water storage tank with a vent line. The vent line should be supplied with a flame arresterfor liquids with a flash point below 100 °F (38 °C).

f) A second water line with a control valve should be provided between the two tanks to permit water toreturn to the storage tank when the flammable/combustible liquid tank is being filled.

g) Provide a liquid level control on the flammable/combustible liquid storage tank to prevent overflow.

2.3.1.4.6 Supply the following minimum equipment for a single tank hydraulic transfer system (Fig. 9):

a) Provide an accessible manual control valve on the water supply line.

b) Provide a pressure regulator on the water supply line.

c) Provide a check valve on the tank fill line and the water delivery line (upstream of the two way valve).

d) Provide a two-way, three port power operated valve on the water supply line (valve permits water

delivery to tank or water removal from tank).e) A pressure relief valve set just above the operating pressure should be provided downstream of theregulator or on the tank.





Fig. 9. Hydraulic transfer method.





f) Provide a power operated control valve on the fill line and the process supply line.

g) Provide a liquid level control on the tank to prevent overflow.

2.3.1.4.7 The double and single tank hydraulic transfer systems should be interlocked to operate as follows:

a) During normal operation, the control valve on the process supply line is open and the control valveon the tank fill line is closed. For the single tank system, the two-way valve is arranged to permit waterflow when needed. For the double tank system, the valve on the water return line is closed and the pumpis arranged to operate when flow is needed.

b) During flammable/combustible liquid tank filling operations, the control valve on the process supplyline is closed and the control valve on the fill line is open. For the single tank system, the two-way valveon the water supply line allows water flow out of the tank. For the double tank system, the pump is offand the control valve on the water return line is open.

c) During a fire or leak, the control valves on the process supply line and the fill line are closed. For thesingle tank system, the two-way valve is in the same position as described in part (b). For the doubletank system, the pump is off.

Arrange the hydraulic transfer system to prevent valve or pump operation before confirmation of proper valveposition (e.g., interlock the control valves and the pump). The valves and pump should operate automaticallyin the event of leakage or fire (i.e., interlock with safety/emergency shutoff valve at the point of liquid use).

2.3.1.4.8 Arrange hydraulic transfer systems to prevent water flow into the process supply line. Double tanksystems should use the same size tanks (limits water quantity). Single tank systems should use float operatedcontrol valves on the discharge lines (float will close when tank is full of water).

2.3.1.4.9 For flammable or combustible liquids that are lighter than water, the water supply line should beextended to the bottom of the liquid supply tank and the discharge and fill lines should be at the top of theliquid supply tank. For flammable or combustible liquids that are heavier than water, the water supply lineshould be at the top of the supply tank and the discharge and fill lines should extend to the bottom of thesupply tank.

2.3.1.5 Loading and Unloading Stations

2.3.1.5.1 Rail cars and trucks used for flammable and combustible liquids should meet Department ofTransportation (DOT) or equivalent specifications.

2.3.1.5.2 Separate loading and unloading stations from important buildings and facilities to limit the potentialexposure from a liquid spill and fire. When possible provide at least 50 ft (15 m) separation or the minimumdistances listed in Table 3.

Table 3. Space Separation for Flammable/Combustible Liquid Loading/Unloading Stations.

Exposed Wall Construction

Space Separation Flash Point

100 o F (38 o C)and Below

Flash Point Greater Than 100 o F (38 o C)

Combustible or With UnprotectedOpenings

50 ft (15 m) 25 ft (8 m)

Noncombustible, Blank or WithProtected Openings 25 ft (8 m) 15 ft (5 m)

2.3.1.5.3 An automatic water spray special protection system, designed in accordance with Data Sheet 4-1N,Water Spray Fixed Systems (NFPA), should be provided for loading/unloading stations when the stationexposes high value plant facilities (i.e., inadequate separation) or if the station is vital to plant production.

2.3.1.5.4 Supply loading and unloading stations with either curbing, drainage, grading, or a combination todirect a potential liquid spill to a collection location that is accessible to fire fighting and liquid recoveryoperations, but does not expose important buildings or facilities.

2.3.1.5.5 Supply loading and unloading stations with adequate control and safety/emergency shutoff valvesto permit control of normal operations as well as isolation of the rail car or truck and plant piping systems





in the event of a leak or fire. Provide safety/emergency shutoff valves on all bottom discharge lines of railcars or trucks and on the plant side of flexible piping. Arrange the valves for automatic operation in the eventof a fire as well as remote manual operation and protection from physical damage (e.g., internal tank valvewith a shear fitting downstream).

2.3.1.5.6 Use top loading and unloading of rail cars and trucks when possible. Bottom loading and unloadingis tolerable when:

a) Space separation is provided as recommended.

b) A liquid spill will not expose important buildings or facilities.

c) Safety/emergency shutoff valves are provided on discharge lines of the rail car or truck.

2.3.1.5.7 Use positive displacement pumps for top unloading operations to prevent siphoning. Place the pumpon a noncombustible platform above the liquid level and arrange it to shut down automatically or manually(from a remote location) in the event of a fire or leak.

2.3.1.5.8 Provide overflow protection for the rail car/truck or the storage tank. Arrange liquid level controlsto automatically shut down filling operations when the tank is full. This control system may be used alone orin conjunction with meters, scales or manual observation.

2.3.1.5.9 Use steel pipe and swing joints or metal type flexible hose when needed for connections to railcars, tank trucks or barges. Metal reinforced rubber hose is acceptable if required by process conditions andif resistant to the materials being handled and rated for system pressure.

2.3.1.5.10 Provide the following at tank truck loading and unloading stations:

a) Conduct all loading and unloading operations on level surfaces.

b) Provide bonding and grounding in accordance with Data Sheet 5-8, Static Electricity. Connect bondingwires before opening tank domes.

c) Set the truck ’s hand brake and block the wheels before connecting to fixed piping.

d) Post warning signs indicating the tank truck is connected to the piping system.

2.3.1.5.11 Provide the following at rail car loading and unloading stations (Fig. 10):

a) Conduct all loading and unloading operations on level tracks in a private siding on plant property orequivalent location with permanent piping to storage tanks.

b) Provide stray current protection by bonding the fill pipe (or pipes) to at least one rail and to the rackstructure (if metallic). In areas with excessive stray currents, provide all pipes entering the rack area withinsulating flanges to electrically isolate the rack piping from the pipelines (Fig. 10).

c) Accurately align rail cars with loading/unloading connection points to avoid excessive stress on theconnections.

d) Protect rail cars against other moving railcars by providing derailers at least one car length away atthe open end of the siding. The use of existing railroad switches is acceptable if they can be locked in theclosed position.

e) Set the brakes and block the wheels before connecting to the fixed piping system.

f) Warning signs indicating the rail car is connected to the fixed piping system should be posted untilthe rail car is disconnected.

2.3.1.5.12 Vents on rail cars and trucks should be provided with flame arresters for liquids with flash pointsbelow 100 °F (38 °C).

2.3.1.5.13 Protect loading and unloading stations against uncontrolled ignition sources in accordance withSection 2.1.4.

2.3.1.5.14 Label all piping clearly to avoid intermixing materials.

2.3.1.5.15 All loading and unloading operations should be constantly attended.

2.3.1.5.16 Liquids that require heating for transfer purposes should be delivered in rail cars or trucks thatare equipped with heating coils. Use the minimum steam pressure necessary to bring the liquid to a fluid state.





Control the steam with a regulator set to the minimum pressure needed. Install a pressure relief valvedownstream of the regulator set to a slightly higher pressure.

3.0 SUPPORT FOR RECOMMENDATIONS

3.1 Application of Recommendations

3.1.1 General

A flammable or combustible liquid is defined as any material that in its normal state is a liquid and will burn.The ability of a liquid to burn is generally tied to the existence of a flash point (closed cup or open cup).

However, a flash point alone will not always indicate if a liquid is capable of sustaining combustion. Someliquid solutions (e.g., 15% ethyl alcohol in water) may have a closed cup flash point but do not have a fire point(i.e., the liquid solution cannot produce enough flammable vapor to permit sustained combustion —the vapormixture produced has a very low heat of combustion and slow heat release rate).

The recommendations in this data sheet (general, piping system, transfer system) are not intended for liquidsor liquid solutions that do not have a fire point ( Note: These liquid solutions may be labeled as a flammableor combustible liquid in accordance with state or federal regulations). Materials that are unstable or veryreactive may not be adequately protected by the recommendations in this data sheet.

Flammable liquids are easily ignited (vapors can be present at room temperature) and difficult to extinguish.Combustible liquids require heating for ignition and are easier to extinguish by cooling the liquid below itsfire point with sprinkler discharge. Flammable and combustible liquids have a high heat of combustion, and

Fig. 10. Railcar loading/unloading station-bonding arrangement to prevent sparks due to stray currents.





once ignited will produce a high heat release rate (i.e., fires will produce high temperatures in a short periodof time). They are fluid and can spread rapidly when a leak or rupture involves a tank or piping system.

Vapors from flammable and combustible liquids can form explosive mixtures with air. Some liquids areunstable or very reactive (e.g., burn when exposed to air without an ignition source, susceptible to

spontaneous heating, react violently with other materials including water). These characteristics combine tocreate a significant fire and/or explosion hazard.

The actual hazard associated with a particular process containing or using flammable or combustible liquids,in addition to the characteristics of the particular liquid, also depends on conditions such as:

a) Quantity of liquid.

b) The confinement of the liquid (open or closed containers, piping systems).

c) The potential for leakage or overflow.

d) Separation from important structures or buildings.

e) Control of ignition sources.

f) Available fire protection.

Each process or occupancy should be evaluated separately to determine the actual exposure created bythe flammable or combustible liquid.

3.1.2 Fire Hazard

A flammable or combustible liquid will always create a fire hazard. However, the exposure created by thehazard is considered limited for occupancies with all the following qualities:

a) Quantities of flammable or combustible liquids less than approximately 70 gal (265 l) in one fire area.

b) A low susceptibility to water damage.

c) No vapor-air explosion hazard.

Recommendations covering location, construction and mechanical ventilation for flammable and combustibleliquid processes generally do not need to be applied to occupancies that meet the above conditions.

Automatic sprinkler protection, proper equipment, proper handling procedures, and control of ignition sourcesshould be provided in any area handling flammable and combustible liquids regardless of quantity.

3.1.3 Piping Systems/Transfer Systems

Piping system recommendations should be applied to all piping systems containing flammable or combustibleliquids based on the potential exposure created by the system. For additional recommendations concerningcutting oils and hydraulic fluids refer to Data Sheet 7-37, Cutting Oils, and Data Sheet 7-98, Hydraulic Fluids,respectively.

3.1.4 Room Explosion Hazard

The potential for a vapor-air explosion hazard exists in a room containing flammable or combustible liquidswhen their release into the room will produce sufficient flammable vapor to create a vapor-air mixture abovethe lower explosive limit. The ability of a liquid to produce enough vapor to create an explosion hazard

depends on many variables, such as the physical characteristics of the liquid (e.g., vapor pressure), theoperating temperature and pressure of the process containing the liquid, and the ventilation systemarrangement within the room.

Liquids with high vapor pressures at room temperature (i.e., low atmospheric boiling points) have a highvaporization rate without heating, while liquids with lower vapor pressures require heating to produce similarvaporization rates. The ventilation system must be arranged to sweep across the floor to prevent theaccumulation of flammable vapor-air mixtures. Improperly designed, high level ventilation may actuallyfacilitate the formation of a flammable vapor-air mixture within the room.

The severity of a vapor-air explosion within a room depends on several items, such as: 1) the material ’sphysical characteristics such as reactivity (K g ) and fundamental burning velocity, 2) the percent of the room ’svolume occupied by the vapor and 3) the vapor ’s concentration. The largest pressure increase during an





explosion is normally produced by vapor-air mixtures, with concentrations just above stoichiometric. Atpresent, there is no methodology to quantify the relationship between explosion severity and either the fractionof the room ’s volume occupied by the vapor-air mixture, or the vapor concentration if other than worst case.In general, explosions involving vapor-air mixtures occupying less than the full room volume or lean vapor-airmixtures produce lower pressure increases than explosions involving full room volumes or vapor-air mixtures

of worst case concentrations.

At present, there is no simple method for predicting the potential for creating an explosion hazard or predictingthe severity of an explosion hazard. However, various materials and process conditions can be divided intotwo general categories, those that may create a severe explosion hazard and those that may create a weakexplosion hazard. A severe explosion hazard exists if there is a potential for creating a large quantity offlammable vapor in a relatively short time frame. A weak explosion hazard exists when there is a potentialfor creating a limited quantity of flammable vapor due either to low vaporization rates or limited liquidquantities.

Severe Explosion Hazards

The following materials and/or process conditions may produce a severe room explosion hazard inoccupancies where flammable/combustible liquids are handled/processed:

1. Flammable liquids with atmospheric boiling points below 100 °F (38 °C) (i.e., liquids with high vaporpressures —Class 1A liquids).

2. Liquids with closed cup flash points up to 300 °F (149 °C) that are handled or can be heated, due toimproperly arranged heating system (e.g., electric heating system without a high temperature shutoff), to orabove their atmospheric boiling points.

3. A significant fraction (10% or more) of the room ’s volume occupied by a single piece of equipment thatpresents an equipment explosion hazard. This includes equipment that is not properly designed to vent orcontain an explosion, equipment designed to vent an explosion into the room or equipment without ventingthat is provided with an inert gas system. Equipment that is adequately designed to vent an explosion to anarea outside the room or to contain an explosion does not create a room explosion hazard.

In either of the first two cases, there must be enough liquid/vapor released to fill a significant portion of theroom ’s volume with a stoichiometric vapor-air mixture. Research indicates that this level be at least 10%of the room ’s volume. The size of a liquid/vapor release should be limited to a single credible event (i.e., either

base release amount on the largest container or a justifiable release scenario). Rooms containing thesematerials or process conditions would need damage limiting construction designed in accordance with DataSheet 1-44, Damage-Limiting Construction, to prevent excessive damage to the building, equipment andstock. If the potential liquid/vapor release amount cannot reach this limit, ignition of the vapor-air mixture willlikely produce a weak explosion as described in Weak Explosion Hazards.

The volume of a stoichiometric vapor-air mixture that can be produced by completely vaporizing one gallonof flammable/combustible liquid, V s (ft3 /gal), can be calculated using the following equation:

English Units:

Vs (cu ft/gal) = 8.33 × S.G. 1000.075 × V.D. C st

×

where: 8.33 is the weight of 1 gal of water (lb/gal)0.075 is the weight of 1 cu ft of air (lb/cu ft)S.G. is the specific gravity of the liquid (water=1)V.D. is the vapor density of the liquid, (air=1)C st is the liquid ’s stoichiometric vapor concentration (vol. %)

To calculate the volume of a stoichiometric vapor-air mixture that can be produced from one liter offlammable/combustible liquid, V s (m 3 /l), multiply the answer to the above equation by 0.00748. ( Note: thisconversion factor has the following units —[gal/l] [m3 /ft3 ].)

This calculation has been done for some common flammable liquids. The results are provided in Table 4. Ifa liquid being evaluated is not in the table, the above equation should be used to determine how much vaporwill be created.





Table 4. The volume of a stoichiometric vapor-air mixture that may be produced from either 1 gallon or 1 liter of some common flammable liquids. (Note: these values are based on complete vaporization of the liquid.)

Material C st (% by Volume) V s (cu ft/gal) V s (cu m/l)Acetone 5.0 890 6.7Benzene 2.7 1325 9.9

Ethyl Acetate 4.0 835 6.3Ethyl Alcohol 7.1 785 5.9Ethyl Ether 3.4 880 6.6Heptane 1.9 1170 8.8Isopropyl Alcohol 4.5 945 7.1Methyl Alcohol 12.0 675 5.1Methyl Butyl Ketone 2.4 1060 7.9Methyl Ethyl Ketone 3.7 965 7.2Pentane 2.6 1025 7.7Toluene 2.3 1405 10.5Vinyl Acetate 4.5 745 5.6Xylene 2.0 1355 10.1

Loss history has also shown that a severe room explosion hazard can be created with liquids having flashpoints between 300 °F (149 °C) and 425 °F (218 °C) that are heated to their atmospheric boiling point andpressurized. These materials have the potential for creating an aerosol mist that can explode. Data Sheet7-99/12-19, Heat Transfer by Organic and Synthetic Fluids, provides further discussion about these types ofmaterials and mist explosions in general.

Weak Explosion Hazards

The following material properties and/or process conditions may produce a weak explosion hazard inoccupancies where flammable/combustible liquids are handled/processed:

1. Liquid with a closed-cup flash point of 20 °F (-7°C) or less.

2. Liquid with a closed-cup flash point of 100 °F (38 °C) or less (Class 1B and 1C liquids) which is handledat or can be heated to more than 60 °F (33 °C) above its flash point. Heat sources may include chemical

reactions or poorly controlled heating systems (e.g., electric heater without high temperature shutoff).3. A small fraction (less than 10%) of the room ’s volume occupied by a single piece of equipment that presentsan equipment explosion hazard. This includes equipment that is not properly designed to vent or containan explosion, equipment designed to vent an explosion into the room or equipment without venting that isprovided with an inert gas system. Equipment that is adequately designed to vent an explosion to an areaoutside the room or to contain an explosion does not create a room explosion hazard.

While the above conditions should be expected to cause explosive vapor-air concentrations in the proximityof the released liquid, they generally will produce vapor-air mixtures with most of the volume near the leanlimit of the explosive range. Only a small percentage (less than 10%) of the room ’s volume may contain astoichiometric mixture. These conditions generally produce easily controlled pressure increases that maynot need damage limiting construction designed in accordance with Data Sheet 1-44, Damage-Limiting Construction. However, fully enclosed rooms (i.e., no venting-windows or vent panels) and rooms withload-bearing walls can still experience significant damage (i.e., wall collapse).

3.1.5 Equipment Explosion Hazard

The potential for a vapor-air explosion within a piece of equipment exists whenever the containedflammable/combustible liquid is handled at or can be heated to a temperature above its closed-cup flashpoint. The potential for a mist explosion within a piece of equipment exists whenever the contained flammable/ combustible liquid is present as an aerosol mist (e.g., spray washers used to clean metal parts). A mist maybe created in equipment whenever the liquid is sprayed depending on the type of spray nozzle and operatingpressure. The liquid does not have to be heated to form a mist. Depending on the operating temperature andpressure, the material, and the nature of the operation, the hazard (vapor-air or mist explosion) can becontinuous or intermittent.





Equipment containing liquids that can undergo violent chemical reactions should be evaluated using DataSheet 7-49/12-65, Emergency Venting of Vessels. Equipment protection against a vapor-air/mist explosionhazard should always be considered since improperly designed or protected equipment will be significantlydamaged by an internal vapor-air explosion.

4.0 REFERENCES

4.1 FM Global

Data Sheet 1-0, Safeguards During Construction, Alteration and Demolition.Data Sheet 1-2, Earthquakes.Data Sheet 1-20, Protection Against Exterior Fire Exposure.Data Sheet 1-44, Image-Limiting Construction.Data Sheet 2-8N, Installation of Sprinkler Systems (NFPA).Data Sheet 3-10, Installation/Maintenance of Private Fire Service Mains and their Appurtenances.Data Sheet 4-1N, Fixed Water Spray Systems for Fire Protection.Data Sheet 4-5, Portable Extinguishers.Data Sheet 4-7N, Low Expansion Foam Systems.Data Sheet 4-12, Foam-Water Sprinkler Systems.

Data Sheet 5-1, Electrical Equipment in Hazardous (Classified) Locations .Data Sheet 5-8, Static Electricity.Data Sheet 5-10, Protective Grounding for Electric Power Systems and Equipment .Data Sheet 5-49, Gas and Vapor Detectors and Analysis Systems.Data Sheet 6-9, Industrial Ovens and Dryers .Data Sheet 7-9, Dip Tanks, Flow/Roll Coaters, and Oil Cookers.Data Sheet 7-14, Fire & Explosion Protection for Flammable Liquid, Flammable Gas, & Liquefied Flammable Gas Processing Equipment & Supporting Structures .Data Sheet 7-17, Explosion Protection Systems.Data Sheet 7-29, Flammable Liquid Storage in Portable Containers.Data Sheet 7-37, Cutting Oils.Data Sheet 7-39, Industrial Trucks.Data Sheet 7-49, Emergency Venting of Vessels.Data Sheet 7-59, Inerting and Purging of Tanks, Process Vessels, and Equipment.

Data Sheet 7-78, Industrial Exhaust Systems.Data Sheet 7-83, Drainage Systems for Flammable Liquids.Data Sheet 7-98, Hydraulic Fluids.Data Sheet 7-99, Heat Transfer By Organic and Synthetic Fluids.Data Sheet 9-0/17-0, Maintenance and Inspection.Data Sheet 9-18/17-18, Prevention of Freeze-ups.

4.2 NFPA Standards

NFPA 30, Flammable and Combustible Liquids Code, 1996.NFPA 68, Guide for Venting of Deflagrations, 1988.National Electric Code, Article 427, Fixed Electric Heating Equipment for Pipelines and Vessels.National Electric Code, Article 500.

4.3 Others

American Society of Mechanical Engineers (ASME) Standard B31.3-1990, Chemical Plant and Petroleum Refinery Piping.American Society of Mechanical Engineers (ASME) Standard B16.5, Pipe Flanges and Flanged Fittings.ANSI A13.1, Scheme for Identifications of Piping Systems.ANSI/ASME B16.25, Butt Welding Ends.ANSI/ASME B16.5, Pipe Flanges and Flanged Fittings.ASTM A193, Alloy Steel Bolting Materials for High Temperature Service.ASTM A194, Carbon and Alloy Steel Nuts for Bolts for High Pressure and High Temperature Service.





APPENDIX A GLOSSARY OF TERMS

Approved: references to ‘‘Approved ’’ in this data sheet means the product and services have satisfied thecriteria for Factory Mutual Research Approval. Refer to the Approval Guide for a complete listing of productsand services that are Factory Mutual Research Approved.

Flammable Liquids: are defined as liquids having closed-cup flash points below 100 °F (38 °C) and vaporpressures not exceeding 40 psia (3 bar a) at 100 °F (38 °C) (thus excluding liquefied petroleum gases, liquefiednatural gases and liquefied hydrogen). Flammable liquids are referred to as Class I liquids, and aresubdivided as follows:

• Class IA liquids —flash points below 73 °F (23 °C) and boiling points below 100 °F (38 °C). Examples areacetaldehyde, ethyl ether, ethyl chloride, isoprene, pentane and methyl formate. Class IA liquids are themost hazardous from the fire protection standpoint due to their low boiling points and high volatility.

• Class IB liquids —flash points below 73 °F (23 °C) and boiling points at or above 100 °F (38 °C). Examplesare acetone, carbon disulfide, benzene, cyclohexane, ethyl acetate, 100% ethyl alcohol, gasoline, heptane,octane, toluene and methyl alcohol.

• Class IC liquids —flash points at or above 73 °F (23 °C) and below 100 °F (38 °C). Examples are styrene,methyl isobutyl ketone, isobutyl alcohol and turpentine.

Combustible Liquids: liquids having closed-cup flash points at or above 100 °F (38 °C). They are referred toas either Class II or Class III liquids and are subdivided as follows:

• Class II liquids —flash points at or above 100 °F (38 °C) and below 140 °F (60 °C). Examples include Nos. 1-3fuel oils, kerosene, n-decane, hexyl alcohol, and stoddard solvent.

• Class IIIA liquids —flash points at or above 140 °F (60 °C) and below 200 °F (93 °C). Examples include aniline,benzaldehyde, butyl cellosolve, nitrobenzene and pine oil.

• Class IIIB liquids —flash points at or above 200 °F (93 °C). Examples include animal oils; ethylene glycol;glycerine; lubricating, quenching, and transformer oils; triethanolamine; benzyl alcohol; hydraulic fluidsand vegetable oils.

Flash Point: a liquid ’s flash point is the minimum temperature at which sufficient vapor is liberated to forma vapor-air mixture that will ignite and propagate a flame away from the ignition source (flash fire not

continuous combustion). Evaporation will take place below the flash point, but the quantity of vapor releasedis not sufficient to produce an ignitable vapor-air mixture. A flash point can be determined by using eithera closed or open cup test apparatus. The closed cup test will produce lower flash points than open cup testsbecause it provides greater vapor containment (i.e., increases vapor accumulation). The closed cup flashpoint is used to classify liquids because it is conservative (i.e., produces lowest flash point for liquid) and itrepresents the condition in which most liquids are handled (i.e., most liquids are contained in closedcontainers or equipment).

Vapor Pressure: a liquid ’s vapor pressure is a measure of the pressure created by its vapor at a specifictemperature. The vapor pressures for flammable or combustible liquids provide a basis for comparing thevolatility of the liquids at various temperatures (i.e., provides a measure of the tendency of the liquids tovaporize). Flammable or combustible liquids with a high vapor pressure at room temperature are morehazardous than liquids with lower vapor pressures because they will produce more flammable vapor withoutheating. Vapor pressure data is often not available.

Boiling Point: a liquid ’s boiling point is the temperature at which its vapor pressure is equal to the atmosphericpressure on the liquid. The boiling point is measured at an atmospheric pressure of 14.7 psia (approximately1 bar a). The boiling point of a flammable or combustible liquid permits the comparison of liquid volatilitywithout knowing the vapor pressures. Liquids with low boiling points are very volatile.

Fire Point: a liquid ’s fire point is the lowest temperature at which a liquid in an open container will give offenough vapor to ignite and continue to burn. Fire points are generally slightly higher than the open cup flashpoint for a particular liquid. Liquids can have flash points without having fire points. A liquid without a firepoint will not burn (e.g., 15% ethanol-water solution: closed cup flash point 107 °F (42 °C), no fire point; 15%acetone-water solution: closed cup flash point 49 °F (9 °C), no fire point).





Flammable (Explosive) Limits/Flammable (Explosive) Range: the terms flammable and explosive are usedinterchangeably since unconfined vapors mixed in air will burn while confined vapors will produce anexplosion.

Flammable or combustible liquids do not burn, their vapors do. The flammable vapors produced by most

liquids require oxygen to burn. Combustion is an oxidation reaction between a fuel and an oxidizer —notalways oxygen. Combustion will occur only when an adequate concentration of fuel (flammable vapor) andan oxidizer are present. Combustion in air (approximately 21% oxygen) can take place over a range of vaporconcentrations (expressed in terms of percentage by volume of vapor in air). The minimum vaporconcentration in air that, when ignited, will propagate a flame is the lower flammable limit. The maximumvapor concentration in air that when ignited will propagate a flame is the upper flammable or explosive limit.The range of vapor concentrations between the lower and upper flammable limits is the flammable range.

The flammable range for a vapor can be altered by changes in oxygen concentration, pressure changes ortemperature changes. An increase in oxygen concentration or pressure will increase the upper flammablelimit and have a minimal effect on the lower limit. An increase in temperature will increase the upper limit andreduce the lower limit. Overall, an increase in oxygen concentration, pressure or temperature will increasethe hazard created by a flammable or combustible liquid by increasing its vapor ’s flammable range.

Vapor Density: is the weight of a volume of pure vapor or gas (with no air present) compared to the weight

of an equal volume of dry air at the same temperature and pressure. It is calculated as the ratio of themolecular weight of the gas to the average molecular weight of air, 29. A vapor density figure less than oneindicates the vapor is lighter than air. A figure greater than one indicates the vapor is heavier than air.

Flammable and combustible liquids produce vapors that are heavier than air. The vapors will collect at floorlevel and exhibit fluid properties (i.e., they will flow to low points and accumulate). Flammable vapor, if notremoved by ventilation, can flow to an ignition source and flash back to the vapor source.

Specific Gravity: the specific gravity of a substance is the ratio of the weight of the substance to the weightof the same volume of another substance. The specific gravity for flammable and combustible liquids isprovided using water as a basis. Specific gravities less than one indicate the liquid will float on water whilespecific gravities greater than one indicate the liquid will sink in water. This information permits a determinationof what effect water will have on a flammable or combustible liquid fire. Liquids heavier than water will sinkindicating water would extinguish a fire involving this liquid (cover liquid and smother fire). Liquids lighter thanwater will float indicating the fire would not be extinguished but could be spread by water if adequate drainage

is not provided.Water Soluble (Miscible) Flammable and Combustible Liquids: when water soluble (miscible) flammable orcombustible liquids are mixed with water a homogeneous solution is formed. The flash point, fire point, heatof combustion, and heat release rate of the solution will be different from the pure flammable or combustibleliquid. The flash point and fire point of the solution will increase as the water concentration increases. Ata certain water concentration (varies for different flammable or combustible liquids) the fire point will no longerexist and the solution will no longer present a fire hazard (e.g., 15% ethyl alcohol in water, 15% acetonein water).

However, the solution will still produce a closed cup flash point creating the potential for confusion in decidingthe hazard presented by the liquid (e.g., 15% ethyl alcohol in water has a closed cup flash point ofapproximately 107 °F [42 °C], 15% acetone in water has a closed cup flash point of approximately 44 °F [7 °C]).The heat of combustion and heat release rate for a solution will decrease as the water concentrationincreases showing a reduction in the overall fire hazard (i.e., a fire involving the solution will produce lessheat at a slower rate than pure flammable or combustible liquid).

The above factors indicate that fires involving water soluble flammable or combustible liquids can beextinguished by diluting the liquid with water (need approximately 4 gal [15 l] of water to dilute 1 gal [4 l] ofethyl alcohol to extinguishment). Also, solutions of water and a soluble flammable or combustible liquid maypresent a significantly reduced fire hazard (or no fire hazard) due to quicker fire extinguishment with water(e.g., need approximately 1- 1 ⁄ 2 gal [6 l] of water to dilute 1 gal [4 l] of a 50% ethyl alcohol/water solution toextinguishment) and reduced thermal damage potential (e.g., a 20% ethyl alcohol/water solution produces aheat of combustion that is much less than that produced by paper products, and the heat release rate willbe low indicating this solution presents an insignificant fire hazard).





APPENDIX B DOCUMENT REVISION HISTORY

January 2010. Minor editorial changes were made. Added references to Data Sheet 4-12, Foam-WaterSprinkler Systems.

May 2008. Minor editorial changes were made.

September 2000. This revision of the document has been reorganized to provide a consistent format.

May 1998. Reformatted.

November 1993. Minor Technical Revision.

July 1993. Minor Technical Revision.

March 1993. Major Technical Revision.

APPENDIX C CHARACTERISTICS OF FLAMMABLE AND COMBUSTIBLE LIQUID FIRES ANDEXPLOSIONS

C.1 Characteristics and Types of Flammable and Combustible Liquid Fires

A flammable or combustible liquid fire is the combination of flammable vapor and air with the evolution ofheat and light (i.e., an exothermic oxidation reaction) without significant pressure development. The firehazard created by flammable/combustible liquids is more severe than the hazard created by other combustiblematerials (e.g., wood, paper, etc.) due to their: a) high heats of combustion, b) high heat release rates andc) fluid properties. The following comparison of heats of combustion for flammable/combustible liquids andother combustible material (Table 5) illustrates one measure of fire hazard severity.

The severity of a fire is also dependent on the heat release rate. A heat release rate generally depends onthe heat of combustion, arrangement or geometry (e.g., exposed surface area), and combustion efficiencyof the material. The heat release rate for a flammable/combustible liquid fire is greater than that of othercombustibles because they have a high heat of combustion, favorable geometry, and a good combustionefficiency. The fluid properties of flammable/combustible liquids tend to create large surface areas when theliquids are released (e.g., unconfined liquid spill will spread over a large floor area; pressurized liquids canbe released in the form of small drops or a mist). These properties also influence fire spread since a fire willexpand over the full area of a spill or spray.

Table 5. Heat of Combustion for Representative Materials.Material Heat of Combustion Btu/lb (kcal/kg)

Petroleum-Based Flammable/Combustible Liquids > 20,000 (11,000)Pure Alcohols 13,000-14,000 (7,000-8,000)Distilled Whiskey (100 proof) 5,000 (3,000)Plastic Commodities > 10,000 (5,500)Polystyrene 17,000-18,000 (9,000-10,000)Class III Commodities 6,000-9,000 (3,000-5,000)

C.1.1 Pool Fires

Flammable or combustible liquids that are confined to open tanks or diked areas can create a pool fire. Theconfined liquid has a depth and controlled surface area. The heat release rate for this arrangement is limitedby the exposed surface area of the liquid. The length of time the fire can burn is controlled by the liquid depth.This type of fire can release up to 10,000 Btu/min/ft 2 (27,000 kcal/min/m 2 ) (assuming perfect combustionefficiency) of surface area. Approximately 1 gal (4 l) of liquid will be consumed each minute for each 12 ft 2

(1 m 2 ) of surface area and approximately 1 in. (25 mm) of liquid will be consumed every seven minutes.

C.1.2 Unconfined Spill Fires

A flammable or combustible liquid released on a level surface without confinement will spread out over thesurface and form a thin film. The area of the spill will depend on the amount of liquid released and the typeof surface it is released on. A fire involving this spill can release 10,000 Btu/min/ft 2 (27,000 kcal/min/m 2 ) ofsurface area. The fire duration depends on the quantity of liquid spilled.





C.1.3 Spray Fires

Flammable or combustible liquid spray fires result from leaks under pressure, as from hydraulic oil lines orliquid transfer piping. The spray (e.g., mist of small liquid droplets) is easily ignited, even at temperaturesbelow the flash point of the liquid, in the same manner as fuel-oil discharge from a domestic oil burner. The

liquid will burn nearly as fast as it is released producing heat release rates much greater than a pool or spillfire. A spray fire can produce approximately 120,000 Btu/gal (8,000 kcal/l). The duration of the fire dependson the fuel supply available and how quickly the fuel supply can be shut off.

C.2 Fire Control and Extinguishment

The damage from a flammable/combustible liquid fire, as from other burning materials, is primarily from heat.The heat released from this type of fire can affect large areas (e.g., spill or pool fire) or can affect a limitedarea with extreme temperatures (e.g., spray fire). The best heat absorbing medium known is water. The bestway to deliver water to a fire is the wet pipe automatic sprinkler system, which is considered the basicfire-control safeguard for flammable or combustible liquids. The purpose of special protection systems isto supplement the sprinkler system and reduce damage or downtime below that obtainable with sprinklerprotection alone.

The principal effect of sprinkler water on flammable/combustible fires is one of cooling. Each gallon (3.8 l)

of water, heated to its boiling point and converted to steam, will absorb 8000 Btu (2000 kcal). For maximumcooling, vaporization should occur close to the burning surface. Droplet size and velocity are critical becausethe spray must penetrate a zone of flame and rising heat waves. Sprinkler discharge can extinguish a poolfire involving unheated liquids with a flash point over 200 °F (93 °C) by cooling the liquid below its fire point.Sprinkler protection may not extinguish a fire involving liquids with a flash point below 200 °F (93 °C) but willhold temperatures at levels that will not cause major damage to buildings or equipment. (Fig. 11). Firesinvolving water soluble liquids or liquids heavier than water can be extinguished by sprinkler discharge (i.e.,dilute liquid to a concentration where it no longer has a fire point or smother fire by water floating on surfaceof liquid).

Sprinkler protection alone will not ensure control or extinguishment of a flammable or combustible liquid fire.The fire ’s size must be limited by providing curbing to stop fuel spread, which will limit the number of sprinklersthat will operate. In addition, the fuel supply must be controlled and drainage provided to limit the fireduration, which limits the needed water supply duration.

Special protection systems (e.g., water spray, foam, gaseous, and dry chemical) are designed to extinguisha fire or provide localized cooling of equipment and buildings.

Water spray protection systems deliver large amounts of water to a specific area that allows increased cooling(i.e., larger water droplets delivered at a higher velocity than available from ceiling sprinklers). These systemscan extinguish fires in liquids with flash points above 150 °F (66 °C), some viscous liquids with lower flashpoints, water soluble liquids and liquids heavier than water. These systems also are suitable for providingexposure protection for equipment, building or facilities.

Foam protection systems extinguish fires by blanketing the liquid and smothering the fire. The blanket persistsfor some time, reducing the likelihood of reflashing. The foam used must be compatible with the burningliquid. Foam may be delivered to a fire manually or automatically. Aqueous film forming foams (AFFF) maybe delivered with open or closed head sprinkler systems.

Gaseous protection systems extinguish flammable/combustible liquid fires by either reducing the oxygen

content over the liquid or by interfering with the combustion reaction. The gaseous agent can be deliveredby direct local application or by total flooding of the room or enclosure. No cleanup of the extinguishing agentis required after discharge.

Dry chemical protection systems extinguish flammable/combustible liquid fires by coating the liquid surfaceand smothering the fire. The dry chemical agent can be delivered by direct local application or by totalflooding of the room or enclosure.





C.3 Characteristics of Flammable/Combustible Liquid Vapor-Air Explosions

A vapor-air explosion is the rapid combustion of a flammable vapor and air (i.e., exothermic oxidation reaction)which produces heat, light and an increase in pressure. A vapor-air explosion can occur when flammablevapor and air are present, in a confined space, within the vapor ’s flammable (explosive) range and the mixturebecomes ignited. If unvented, the developed pressure may reach six to nine times the initial absolutepressure.

Boiling-liquid expanding-vapor explosions (BLEVE) occur when a confined liquid is heated above itsatmospheric boiling point by an exposure fire and suddenly released by rupture of the closed container. Partof the heated liquid immediately flashes to vapor and is ignited by the exposure fire, releasing heat at a lowerrate than the vapor-air explosion but for a longer period of time.

C.4 Explosion Control and Protection

Explosion damage is largely the result of pressure created by rapidly expanding gases in a confined space.Conditions under which explosive mixtures may accumulate should be eliminated or carefully controlled byprovision of adequate ventilation to dilute the vapors, by use of an inert atmosphere, or by other means.The effects of an explosion are reduced by explosion vents or damage-limiting building construction.

Fig. 11. Sprinklered vs. Unsprinklered Flammable/Combustible Liquid Fires.





Explosion-protection systems are available that detect an incipient explosion and, by suppressing and/orventing action, prevent the full impact of the explosion from developing. They are adaptable to vapor-airexplosion hazards in equipment and in small rooms.

Boiling-liquid expanding-vapor explosions can be prevented by reducing heat input to the closed container

or by bleeding off excess pressure from the container. Heat input rates can be reduced by insulation, byburying or mounding the vessel, or by automatic sprinklers or water spray. Excessive pressure can beprevented by atmospheric vent pipes, relief valves, bursting disks, or safety bungs.

C.5 Equipment Explosion (Deflagration) Venting Design

C.5.1 Vent Sizing for a P red Greater Than 1.5 psig (0.1 bar g) (High Strength Equipment)

The following vent sizing equation (1) (reprinted from NFPA 68, Guide for Venting of Deflagrations —1988edition) should be used to estimate the vent area needed for high strength equipment.

Av = dVf P hred e (gP stat )

(Note: the above equation must only be used with metric units)

With:

Av = Vent Area, m 2

P red = Reduced Explosion Pressure, bar gP stat = Static Venting Pressure, bar gV = Vessel Volume, m 3

e = 2.718 (base of natural logarithm)d,f,g,h = Constants as Defined in Table 6

• To convert m 2 to ft2 multiply by 10.76 ft 2 /m2

• To convert bar g to psig multiply by 14.5 psig/bar g• To convert m 3 to ft3 multiply by 35.31 ft 2 /m2

The constants, d, f, g and h, used in Equation (1) depend on the type of gas/vapor present. The data andequation were developed based on four gases: methane, propane, coke gas and hydrogen. The compositionlimits for the coke gas were:

45 – 55% Hydrogen6 – 10% Carbon Monoxide25 – 33% Methane4.6% Nitrogen0.1% Carbon Dioxide2 – 3% Unspecified Hydrocarbons

There are no available data to indicate whether the constants, determined for coke gas, vary significantlywithin these limits.

The table below, Table 6, indicates the constants to be used for each gas:

Table 6. Explosion Venting Constants.

Gas d f g h Methane 0.105 0.770 1.23 -0.823Propane 0.148 0.703 0.942 -0.671

Coke Gas 0.150 0.695 1.38 -0.707Hydrogen 0.279 0.680 0.755 -0.393





Equation (1) is valid only for vessels with a length to diameter ratios of 5 or less and for the following rangesof P red and vessel volume (V):

0.1 bar g ≤ P stat ≤ 0.5 bar gP stat +0.1 bar g ≤ P red ≤ 2 bar g

1 cu m ≤

V ≤

1000 cu mP red is the maximum pressure that will be developed during the vented explosion and is the highest pressurethat can be sustained by the equipment being protected. To prevent deformation of cylindrical equipment,P red should be based on two-thirds of the equipment ’s yield strength (stress). For rectangular or squareequipment, the above criteria may be used, however, some additional bracing may be needed to preventdeformation. If deformation is acceptable, but not rupture of the equipment, then P red should be based ontwo-thirds of the equipment ’s ultimate strength (stress). ( Note: the minimum listed ultimate strength for amaterial should always be used for this type of evaluation or design.)

Determination of P red based on the above criteria is best left to the equipment designer or a structuralengineer. Lacking any data, use of twice the normal vessel design pressure (such as ASME rating) wouldbe acceptable.

P stat is the set or relieving pressure of the deflagration vent. It should be at least 0.1 bar below the maximumdesired pressure during venting, P red .

C.5.2 Vent Sizing for a P r of 1.5 psig (0.1 bar g) or Less (Low Strength Equipment)

The design criteria provided in Data Sheet 1-44, Damage-Limiting Construction, should be used to estimatethe vent area needed for low strength equipment. The nomenclature listed in the data sheet represent thefollowing:

P r = Maximum Vented Explosion Pressure, psf (kPa) ( Note: this is equivalent to P red for high strengthequipment.)

P v = Vent Release Pressure, psf (kPa)Av = Vent Area, ft 2 (m 2 )As = Internal Surface Area, ft 2 (m 2 )

Limitations listed in Data Sheet 1-44 should be strictly followed.

P r is the maximum pressure that will be developed during the vented explosion and is the highest pressurethat can be sustained by the equipment being protected. To prevent deformation of cylindrical equipment,P r should be based on two-thirds of the equipment ’s yield strength (stress). For rectangular or squareequipment, the above criteria may be used, however, some additional bracing may be needed to preventdeformation. If deformation is acceptable, but not rupture of the equipment, then P r should be based ontwo-thirds of the equipment ’s ultimate strength (stress). ( Note: the minimum listed ultimate strength for amaterial should always be used for this type of evaluation or design.)

Determination of P r based on the above criteria is best left to the equipment designer or a structural engineer.Lacking any data, use of twice the vessel design pressure would be acceptable.

P v is the set or relieving pressure of the deflagration vent. It should be at least 50 psf (2.4 kPa) below themaximum desired pressure during venting, P r. Ideally P v should be 20 psf (0.96 kPa) or less.

Vent mass criteria listed in Data Sheet 1-44 are applicable for buildings and rooms only. The criteria listedin Appendix C, Section C.5.4 should be used for equipment design.

C.5.3 Venting of Gases/Vapors Other Than Those Specified and Mists

Deflagration testing is used to compare the relative reactivity or hazard of various gases or vapors. Whentested under similar conditions of turbulence, igniter strength and vessel size, the rate of pressure rise is agood measure of the ease of venting. Larger rates of pressure rise will require larger vent areas. A commonmeasure of this factor is K g (bar-m/sec) which is the rate of pressure rise normalized to vessel size.

If vent size calculations for high strength equipment are necessary for gases or vapors other than the standardgases listed above, an acceptable choice would be to use Equation (1) with the venting constants forhydrogen (i.e., worst case). Using Figure 10 and Table 5 in Data Sheet 1-44 would be the worst case forlow strength equipment). A second alternative would be to refer to Data Sheet 1-44, Table 1, which lists many





common gases and vapors. Based on the classification in Table 1, Equation (1) and Table 7 of this document,may be used with the venting constant for the comparable standard gas.

Table 7. Venting Constants for Other Vapors and Gases.

Data Sheet 1-44 Table Number Use Venting Constants For 3 Methane4 Propane5 Hydrogen

For high or low strength equipment containing gases or vapors that are not listed in Data Sheet 1-44, testsshould be conducted to determine the K g for the ‘‘new ’’ gas or vapor and compare it with K g for any of thestandard gases (conducted with the exact same vessel and conditions). Then either use Equation (1) and theventing constant for the comparable standard gas (high strength equipment) or the appropriate table in DataSheet 1-44 for the comparable standard gas (low strength equipment). For additional details of classifyinga particular gas/vapor refer to NFPA 68, Guideline for Venting of Deflagrations, Appendix A.

All mist explosion hazards should be evaluated as follows:For high strength equipment use Equation (1) and the constants for propane in Table 6.

For low strength equipment use Table 4 in Data Sheet 1-44.

C.5.4 Vent Mass and Location

The deflagration vent for low or high strength equipment should be of low mass per unit area. The vent shouldbe less than 2.5 lb/ft 2 (12.5 kg/m 2 ), to minimize inertia effects and delay in vent opening. The vent shouldopen reliably and should not present a missile hazard. Vents should be centrally located for equipment witha single vent (i.e., use largest side of equipment and avoid small ends) or symmetrically arranged for multiplevents (i.e., provide several equally sized vents spaced evenly on equipment).

C.5.5 Vent Discharge Arrangement

Vents should be arranged to discharge to a safe location, preferably outdoors. For equipment located insidebuildings or rooms, a vent pipe/duct may sometimes be used to direct discharge to a safe outdoor location.Vent pipes/ducts will, however, increase the vented explosive pressure experienced by the equipment dueto: 1) the force needed to overcome the inertia of the air column in the pipe/duct, 2) the back-flow ofcombustion products created by escaping unburned gases igniting in the pipe/duct, and 3) friction lossesdue to the gas flow through the pipe/duct (minimal effect). This increase in pressure will require a similarincrease in the strength of the equipment (P red or P r).

Vent pipe/ducts on high strength equipment should be as short and straight as possible; preferably limit lengthto less than 10 ft (3 m) and avoid elbows or direction changes. Use Figure 12 to determine the increasein P red to account for the effect of the vent pipe/duct. Failure to account for the vent pipe/duct effect may leadto equipment rupture during an explosion.

Vent pipe/ducts should not be provided on low strength equipment. The vent pipe/duct effect will increaseP r beyond the definition of low strength equipment (i.e., P r greater than 1.5 psig [0.1 bar g] so design for high

strength equipment). Vent pipe/ducts with a length to diameter ratio (L/D) of 1 or less can be used on anyequipment (high or low strength) without increasing P r or P red . Pipe/ducts with a diameter equal to or greaterthan its length will not generally produce an increase in the maximum pressure experienced by theequipment.

C.5.6 Effect of Turbulence

Equation (1) and the venting constants were based on quiescent mixtures in the test vessel. In some processequipment, the vapor space may be turbulent due to flow into and out of the vessel (e.g., gas injection intoa reactor). If such conditions are likely, limited test data indicates Equation (1) and venting constants forhydrogen will provide acceptable venting for gases other than high K g gases like hydrogen.





Sizing vents for turbulent conditions of high K g gases like hydrogen is not practical and other steps shouldbe taken to protect vessels containing these materials (e.g., inerting the vapor space).

The effect of ventilation induced turbulence within a piece of equipment may be disregarded when applyingEquation (1) or Data Sheet 1-44.

C.5.7 Effect of High Initial Pressures

The vent area equations are based on gases at initial pressures around atmospheric. Usually they areconsidered valid up to 1.2 bar a (17.4 psia) initial pressures. Initial pressures beyond 1.2 bar a (17.4 psia)cannot be handled by Equation (1) of this document, or Data Sheet 1-44.

C.6 Sight Glasses

C.6.1 Properties of Glass

All glass has a tensile strength of approximately 10,000 psi (70 MPa) and a compression strength ofapproximately 100,000 psi (700 MPa). The maximum allowable working tensile stress is approximately 1,000psi (7 MPa) for ordinary glass, and 2,000 to 4,000 psi (15 to 30 MPa) for high-strength glass. A lower factorof safety is possible with high-strength glass because of its superior resistance to fatigue and thermal shock.Surface scratches or chips will reduce the strength of glass to a small fraction of its original value. Thermalshock, either by a wide difference of temperature on either side of a piece of glass or by a rapid changeof temperature, can cause failure. Repetitive cycling of temperatures and pressures over extended periodsof time also appears to have a harmful effect on the strength of the glass.

Fig. 12. Maximum Pressure Developed During Venting of Gases, With and Without Vent Ducts.





C.6.2 Types of Glass

Glass for observation ports is specially manufactured in accordance with the intended application, as follows:

1. Ordinary heat-treated soda-lime glass is suitable only for operations at normal atmospheric pressuresand temperatures.

2. Specially heat-treated soda-lime glass is suitable for pressures of approximately 150 to 300 psig(10-20 bar g) and temperatures up to 400 °F (204 °C).

3. Annealed borosilicate glass is used at temperatures and pressures similar to those for ordinaryheat-treated soda-lime.

4. Tempered borosilicate glass is used for higher temperatures than the annealed glass, but is is more subjectto chemical deterioration.

5. High-silica glass is suitable for operations at high temperatures but only at low pressures.

C.6.3 Sight Glass Design

Glasses are usually circular. Older designs use a single glass mounted between two bolted flanges withgaskets to separate the glass from metal surfaces.

Newer Approved designs are available. One incorporates two tempered borosilicate glass pressure disksand an inside shield disk to protect against chemical deterioration, all sealed into one lens. The lens is bondedin a special holder to reduce lens pressures and stresses.

Another Approved design incorporates two tempered borosilicate glass pressure disks, with or without aninside shield disk, bonded into a lens assembly. A soft gasket fits around the glass circumferentially. A setscrew and metal-compression-ring arrangement presses against the gasket, which in turn holds the glass inplace by circumferential forces. This is intended to minimize tensile stress in the glass.


fmds0732 factory mutual data sheet 7-32

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