chemical process equipment degradation vessel failure & design factors classifications of...

Chemical Process Equipment Degradation Vessel failure & Design Factors Classifications of Pressurized Vessels Codes and Standards of Pressurized Vessels Surface stress Flat Head Expanded Vessels Secondary stress Voids in Membranes

Vessels Reactors Mass transfer equipment Heat transfer equipment Solid-liquid separator Solid handling equipment Dryers Piping and piping system Fluid transfer equipment Fired unit Heat exchanger equipment

In-process vessels surge drums accumulators separators, etc. Pressurized tanks Spheres bullets Atmospheric, fixed roof storage tanks cone/dome roof Atmospheric, floating roof storage tanks

Storage Tank Autopolymerization Incident Production of GAA with a high water content (did not meet specification) Warm water (25 o C) was used to prevent the GAA from freezing (T = 13 o C) Water flows to the wagon was continuously supplied, the temperature was not monitored Approximately l5 l /2 hours after the tank wagon was filled, vapors started blowing out the loosened tank wagon lid and accumulating in the vicinity of the tank wagon. The steam-water mixer was shut off and approximately six minutes later the tank wagon exploded. The blast effect from the explosion destroyed an adjacent loading rack/pipe rack, and damaged other plant structures.

A combination of local overheating (hot surface) and local inhibitor deficiency was considered the most probable mechanism for initiation of polymerization. Contamination may have contributed to the violence of the polymerization once it was initiated. Water and iron were the two main candidates in contamination considerations. Screening experiments showed that water can reduce GAA stability at temperatures > 100 o C, and that soluble iron in the 1-100 ppm range can also reduce stability. This example illustrates the hazard of using temporary facilities for the storage of hazardous materials. Such facilities are often not subject to the same scrutiny as permanent facilities.

Batch reactors Semi-batch reactors Continuous-flow stirred tank reactors (CSTR) Plug flow tubular reactors (PFR) Packed-bed reactors (continuous) Packed-tube reactors (continuous) Fluid-bed reactors

Seveso Runaway Reaction An atmospheric reactor containing an uncompleted batch of 2,4,5-trichlorophenol (TCP) was left for the weekend. Its temperature was 1580C, well below the temperature at which a runaway reaction could start The reaction was carried out under vacuum, and the reactor was heated by steam in an external jacket, supplied by exhaust steam from a turbine at 190 o C and a pressure of 12 bar gauge The turbine was on reduced load, as various other plants were also shutting down for the weekend (as required by Italian law), and the temperature of the steam rose to about 300 o C. There was a temperature gradient through the walls of the reactor (300 o C on the outside and 160 o C on the inside) below the liquid level because the temperature of the liquid in the reactor could not exceed its boiling point. Above the liquid level, the walls were at a temperature of 300 o C throughout. When the steam was shut off and, 15 minutes later, the agitator was switched off, heat transferred from the hot wall above the liquid level to the top part of the liquid, which became hot enough for a runaway reaction to start. This resulted in a release of TCDD (dioxin), which killed a number of nearby animals, caused dermatitis (chloracne) in about 250 people, damaged vegetation near the site, and required the evacuation of about 600 people (Kletz 1994). The lesson learned from this incident is that provision should have been made to limit the vessel wall temperature from reaching the known onset temperature at which a runaway could occur.

Absorption Adsorption Extraction Distillation Scrubbing Stripping Washing

Ignition ofPyrophoric Materials in Gasoline Fractionator During a shutdown for maintenance, a gasoline fractionator in an olefins unit was readied for internal entry. After purging, the tower manways were removed and air ventilation begun. Shortly thereafter an exothermic process started in the packed section of the tower, resulting in severe overheating of the tower. The heat release rate grew so quickly that corrective action, such as applying cooling, was not effective in avoiding excessive temperature. The tower, which glowed a dull red during the incident, sustained extensive damage. Tower damage including buckled packing supports, fused packing, and visible distortion of the tower shell. The cause of the incident was determined to be the ignition of a pyrophoric material that accumulated during the fractionation process. This material was distributed over the large surface area of the tower packing, which promoted a high combustion rate upon contact with air. Such incidents have since been avoided by the performance of proper purging and washout procedures prior to opening the vessel. Note that spontaneous combustion can also occur with non-pyrophoric materials.

Line Blockage Packing/Tray Blockage Hazards with Adsorbers

Shell and tube exchangers Air cooled exchangers Direct contact exchangers Others types including helical, spiral, plate and frame, and carbon block exchangers

Brittle Fracture of a Heat Exchanger An olefin plant was being restarted after repair work had been completed. A leak developed on the inlet flange of one of the heat exchangers in the acetylene conversion preheat system. To eliminate the leak, the control valve supplying feed to the conversion system was shut off and the acetylene conversion preheat system was depressured. Despite the fact that the feed control valve was given a signal to close, the valve allowed a small flow. High liquid level in an upstream drum may have allowed liquid carryover which resulted in extremely low temperature upon depressurization to atmospheric pressure. The heat exchanger that developed the leak was equipped with bypass and block valves to isolate the exchanger. After the leaking heat exchanger was bypassed, the acetylene conversion system was repressured and placed back in service. Shortly thereafter, the first exchanger in the feed stream to the acetylene converter system failed in a brittle manner, releasing a large volume of flammable gas. The subsequent fire and explosion resulted in two fatalities, seven serious burn cases, and major damage to the olefins unit. The acetylene converter pre-heater failed as a result of inadequate low temperature resistance during the low temperature excursion caused by depressuring the acetylene converter system. The heat exchanger that failed was fabricated from ASTM A515 grade 70 carbon steel. After the accident, all process equipment in the plant which could potentially operate at less than 20 o F was reviewed for suitable low-temperature toughness (Price 1989).

Leak/Rupture of the Heat Transfer Surface corrosion, thermal stresses, or mechanical stresses of heat exchanger internals Fouling, or Accumulation ofNoncondensable Gases External Fire

Failures are governed by: elastic failure, governed by the theory of elasticity (not applicable to thick wall); Beyond this, excessive plastic deformation or rupture will occur plastic failure, governed by the theory of plasticity Relevant properties: Yield strength Ultimate strength Multiaxial stress (combination of all)

typical spherical

spherical or cylindrical, with domed ends in shape cylindrical vessels are generally simpler to manufacture and save space Examples are: Boiler drums, heat exchangers, chemical reactors, and so on. Spherical vessels requires thinner walls for a given pressure and diameter than the equivalent cylinder. Typically used for large gas or liquid containers, gas- cooled nuclear reactors, containment buildings for nuclear plant, and so on. Containment vessels for liquids at very low pressures are sometimes in the form of lobed spheroids or in the shape of a drop

consists of a cylindrical main shell, with hemispherical headers several nozzle connections The geometries can be divided into plate- and shell-type configurations

Lower range: 0.25 kilopascals (kPa) Higher range 2000 megapascals (MPa). The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section VIII, Division 1,1 specifies a range of internal pressures from 0.1 MPa to 30 MPa.

Stress element Cylindrical pressure vessels, hydraulic cylinders, shafts with components mounted on (gears, pulleys, and bearings), gun barrels, pipes carrying fluids at high pressure,.. develop tangential, longitudinal, and radial stresses. Wall thickness t Radial stress rr Longitudinal stress ll (closed ends) A pressurized cylinder is considered a thin-walled vessel if the wall thickness is less than one-twentieth of the radius. < 1/20 t r Thin-walled pressure vessel Tangential stress Hoop stress

In a thin-walled pressurized cylinder the radial stress is much smaller than the tangential stress and can be neglected. Longitudinal stress, l ( l ) / 4 [ ( d o ) 2 ( d i ) 2 ] = ( p ) / 4 ( d i ) 2 Internal pressure, p F y = 0 Longitudinal stress ( l ) [ ( d i + 2 t ) 2 ( d i ) 2 ] = ( p ) ( d i ) 2 4t 2 is very small, ( l ) (4 d i t ) = ( p ) ( d i ) 2 l =l = p didi 2 t2 t l =l = p (d i + t) 4 t Max. longitudinal stress Pressure area

Projected area Hoop stress Tangential (hoop) stress 2 ( ) t ( length ) = ( p ) ( d i ) (length) F x = 0 = = p didi 2 t2 t Max. Hoop stress l =

In case of thick-walled pressurized cylinders, the radial stress, r, cannot be neglected. Assumption longitudinal elongation is constant around the plane of cross section, there is very little warping of the cross section, l = constant dr r + d r rr 2 ( )(dr)(l) + r ( 2r l ) ( r + d r ) [ 2 ( r + dr ) l ] = 0 l = length of cylinder F = 0 ( d r ) ( dr ) is very small compared to other terms 0 r r dr drdr = 0 (1)

l = l = E rr E Deformation in the longitudinal direction + r = 2 C 1 = ll E constant (2) Consider, d ( r r 2 ) dr = r 2 drdr dr + 2 r r Subtract equation (1) from (2), r + r + r dr drdr = 2 C 1 r r dr drdr = 0 (1) 2rr + r22rr + r2 dr drdr = 2 r C 1 Multiply the above equation by r d ( r r 2 ) dr = 2rC12rC1 r r 2 = r 2 C 1 + C 2 rr = C1= C1 C2C2 r2r2 + = C1= C1 C2C2 r2r2

Boundary conditions rr = - p i at r = r i rr = - p o at r = r o = p i r i 2 - p o r o 2 r i 2 r o 2 ( p o p i ) / r 2 r o 2 - r i 2 Hoop stress rr = p i r i 2 - p o r o 2 + r i 2 r o 2 ( p o p i ) / r 2 r o 2 - r i 2 Radial stress p i r i 2 - p o r o 2 ll = r o 2 - r i 2 Longitudinal stress

Special case, p o (external pressure) = 0 = p i r i 2 r o 2 - r i 2 (1 + ro2ro2 r2r2 ) rr = r o 2 - r i 2 (1 - ro2ro2 r2r2 ) p i r i 2 Hoop stress distribution, maximum at the inner surface Radial stress distribution, maximum at the inner surface

Two basic theories of failure are used in the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section I, Section IV, Section III Division 1 (Subsections NC, ND, and NE), and Section VIII Division 1 use the maximum principal stress theory. The maximum principal stress theory (sometimes called Rankine theory) is appropriate for materials such as cast iron at room temperature, and for mild steels at temperatures below the nil ductility transition (NDT) temperature Section III Division 1 (Subsection NB and the optional part of NC) and Section VIII Division 2 use the maximum shear stress theory or the Tresca criterion.

1. select the necessary relevant information, establishing in this way a body of design requirements 2. Select the suitable materials by referring to the specified design code, i.e. allowable design or nominal stress that is used to dimension the main pressure vessel thickness 3. Conduct the design of various vessel components such as nozzles, flanges, and so on. 4. Arrange, finalize and analyze these various components for failure 5. ensure the adequacy of stress distribution 6. Check against different types of postulated failure modes 7. Iterate the proposed design until the most economical and reliable product is obtained. 8. The functional requirements should also cover the geometrical design parameters such as size and shape, location of the penetrations, and so on.

Excessive elastic deformation including elastic instability Excessive plastic deformation Brittle fracture Stress rupture or creep deformation (inelastic) - high temperatures Plastic instability and incremental collapse High strain and low cycle fatigue Stress corrosion due to environmental considerations as well as mode of operation Corrosion fatigue

Corrosion is the deterioration of materials by chemical interaction with their environment. The term corrosion is sometimes also applied to the degradation of plastics, concrete and wood, but generally refers to metals.

It involves direct attack of dry gases (Air and Oxygen) on the metal through chemical reactions. As a result an oxide layer is formed over the surface. This type corrosion is not common. Dry corrosion It involves direct attack of aqueous media (strong or dilute, acidic or alkaline) on metal through electrochemical reactions. The moisture and oxygen are also responsible. This type of corrosion is quite common. Wet corrosion

Corrosion specifically refers to any process involving the deterioration or degradation of metal components. The best known case is that of the rusting of steel. Corrosion processes are usually electrochemical in nature. When metal atoms are exposed to an environment containing water molecules they can give up electrons, becoming themselves positively charged ions, provided an electrical circuit can be completed.

Solution pH. Oxidizing agent. Temperature. Velocity. Surface Films. Other Factors.

Four Type of corrosion 1. Fluid corrosion, General 2. Fluid corrosion, Localized 3. Fluid corrosion, Structural 4. Fluid corrosion, Biological.

The effect of this type is swelling, crazing, cracking, softening etc. e.g. corrosion of plastic & non metal Physicochemical corrosion This type of corrosion occur at discrete point of metallic surface. Metallic surface gets divided in to anodic and cathodic portion Electrochemical corrosion

It is most commonly observed on diff location. Four type 1. Specific site corrosion 2. Stress induced corrosion 3. Liquid flow related corrosion 4. Chemical reaction related corrosion

Mechanically weak spots or dead spots in a reaction vessel cause sp site corrosion. Three type 1. Inter-granular corrosion 2. Pitting corrosion 3. Crevice corrosion

Selective corrosion that occurs in the grain boundaries in a metal/alloy is called as inter-granular corrosion. When it is severe it causes loss of strength and ductility. E.g. Austenitic S.S + HNO3 grain boundary ppt. S.S is stabilized by adding niobium/titanium (less than 0.03 %).

In this type pits and cavity develops. They range from deep cavities of small diameter to shallow depression. E.g. allow of Al/S.S + Aq. Solution Cavities. Pitting occur when there is break in protective oxide layer and imperfections on the underlying metal. Chloride

Here, corrosion take place in crevices bcz solutions retained at this place and takes longer time to dry out. When this occurs, the severity of attack is more severe at crevices. Crevices are formed bcz of the metal contact with another piece of the same or other metal or with a nonmetallic material. Corrosion in crevice is due to deficiency of O2, Acidity changes, Depletion of inhibitor.

Residual internal stress in metal external applied stress accelerate the corrosion. Residual internal force is produced by: Deformation during fabrication Unequal rate of cooling from high temp. Internal stress rearrangement involving volume changes Stress induced by rivets, bolts and shrink fits. Eliminating high stress areas prevent this type of corrosion.

At the surface, if the tensile stress is equal to or more than yield stress, the surface Develops crack is known as stress Corrosion cracking. E.g. cold formed brass develops crack in the environment of ammonia. Embrittlement of cracking of steel is observed in caustic solution.

Corrosion fatigue is the ability of metal surface to withstand repeated cycle of corrosion. The metal surface is stressed and simultaneously attacked by the corrosive media. Pits indicating corrosion are formed initially, which further develops in to cracks. The protective surface oxide film reduces corrosion. Under cycling or repeated stress conditions, rupture of protective oxide films takes place at a higher rate than at which new protective films can be formed. So the rate of corrosion is enhanced.

Fretting corrosion occurs when metals slide over each other and cause mechanical damage to one or both. During relative movement of metals, two process may occur, (i) frictional heat is generated, which oxidize the metal to form oxide films. (ii) removal of the protective films resulting in exposure of fresh surface to corrosion attack. This can be avoided by using harder materials, minimizing friction by lubrication or by proper designing of the equipment.

Liq. Metals can cause corrosion. The driving force is the tendency of the liq. To dissolve solids or penetrating the metal along the grain boundaries at place of wetting. E.g. mercury attack on Al alloy Molten Zinc on S.S.

Also referred as erosion corrosion or velocity accelerated corrosion. It is accelerated by removal of corrosive products, which would otherwise tend to stifle the corrosion reaction.

Erosion is the destruction of metal by abrasion and attrition caused by the flow of liq./gas. Factors that influence erosion 1. Alloy content of the steel (e.g. Cr, Cu, Mn) 2. Pipe system design and component geometry. 3. Water and steam composition (especially pH and oxygen content). The use of harder metals and changes in velocity or environment are used to prevent erosion.

Formation of transient voids or vacuum bubbles in a liq stream passing over a surface is known as cavitation. The bubble may collapse on the metal surface thereby causing severe impact or explosive effect. So considerable damage and corrosion is observed. Cavitation corrosion is also observed around propellers, rudder in pumps etc.

Corrosion involves chemical reactions such as oxidation and reduction. Galvanic corrosion Oxygen conc cell Hydrogen embrittlement

It is associated with the flow of current to a less active metal from a more active metal in the same environment. Coupling of two metals, which are widely separated in the electrochemical series, generally produces an accelerated attack on the more active metal, zinc.

It is due to the presence of oxygen electrolytic cell. i.e. diff in the amt of oxygen in solution at one point exists when compared to another. Corrosion is accelerated when the O2 is least, for example, under gasket, stuffing boxes etc.

hydrogen can penetrate carbon steel and react with carbon to form methane. The removal of carbon result in decreased strength. Corrosion is possible at high temp as significant hydrogen partial pressure is generated. This cause a loss of ductility, and failure by cracking of the steel. Resistance to this type of attack is improved by allowing with chromium / molybdenum.

Hydrogen damage can also result from H2 generated by electrochemical corrosion reaction. The result is failure by embrittlement, cracking, and blistering. This is observed in solution of sp weak acids such as hydrogen sulphide and HCN.

Here, the strength is reduced on account of corrosion. This may occur when one component of the alloy is removed or released into solution. The corrosion pdt may retain in the plant. E.g. Graphite corrosion Dezincification

Graphite is allotropy of carbon. Graphite corrosion may occur in gray cast iron. Metallic iron is converted in to corrosive pdts leaving a residue of intact graphite mixed with iron corrosive pdts and other insoluble constituent of cast iron. When the layer of corrosion is impervious corrosion will cease. If layer is porous corrosion will be greater.

When carbon steel is heated for prolonged periods at temp greater than 455 C, carbon may segregated, which is then transformed in to graphite. So the structural strength of the steel is affected. Employing killed steels of Cr and Molybdenum or Cr and Ni can prevent this type of corrosion.

It is seen in brass containing more than 15 % zinc. In brass the principle pdt of corrosion is metallic copper, which may redeposit on the plant. Another mechanism involves the formation of zinc corrosion pdts. Corrosion may occur as a plug filling pits or as a continuous layer surrounding the unaffected core of brass. It can be reduced by addition of small amt of arsenic, antimony or phosphorus to the alloy.

The metabolic action of M.O. can either directly or indirectly cause deterioration of a metal. Such a process is called as a biological corrosion. The cause of biological corrosion are: 1. Producing corrosive environment or altering environment composition. 2. Creating electrolyte conc cells on the metal surface. 3. Altering resistance to surface films. 4. Influencing the rate of cathodic/ anodic reaction.

The role of biological corrosion may be explained by sulphate reducing bacteria in slightly acidic or alkaline soils. Sulphat e Hydrogen Sulphite Calcium Sulphite Iron Sulphide Corrosion pdt Reducing bacteria Anaerobic On Iron in Soil

The corrosion may be prevented or controlled by following ways: 1. Selection of proper material 2. Proper design of equipment 3. Coating and lining 4. Altering environment 5. Inhibitors 6. Cathodic protection 7. Anodic protection

Corrosion should not be permitted in fine wire screen, orifice and other items in which the dimensions are critical and change is not permitted. In some cases, non metallic materials will be more economic and have good performance. It should be considered if their strength, temp and design is satisfactory. The corrosion characteristics of chemicals and limitation of construction material can be considered. The processing conditions should also be considered.

In the design of equipment, the number of fittings like, baffles, valves and pumps should be considered. Corrosion can be minimized if the equipment design facilitates Elimination of crevices Complete drainage of liquids Ease of cleaning Ease of inspection and maintenance A direct contact between two metal is avoided, if they are seperated widely in elecrochemical series. Or they should be insulated.

Nonmetallic coatings and linings can be applied on steel and other materials of construction in order to combat corrosion. Coating methods: electroplating, cladding, organic coating. The thickness of lining is important. Effective linings can be obtained by bonding directly to substrate metal or building multiple layers. Organic coatings can be used in tanks, piping and pumping lines.

A thin non-reinforced paint like coating of less than 0.75 mm thickness should not be used in services for which full protection is required. The cladding of steel with an alloy is another approach to this problem. Sp glass can be bonded to steel so that the liner is 1.5 mm thick which is impervious. Piping and equipment lined in this manner are used in severely corrosive acid services.

Corrosion can be reduced by employing following conditions: 1. Removing air from boiler feed water prevents the influence of water on steel 2. Reducing the temp 3. Eliminating moisture 4. Reducing the velocity of turbulence 5. Shortening the time of exposure 6. Pumping the inert gas into solutions 7. Reducing aeration.

The corrosion inhibitors are added to the environment to decrease corrosion of metals. This form protective films. 1. Adsorption type, e.g. adsorbed on metal 2. Scavenger phase type, e.g. remove corrosion agent 3. Vapor phase type, e.g. sublime and condense on metal surface. Inhibitors are generally used in quantities less than 0.1 % by weight.

e.g. of inhibitors 1. Chromate, Phosphates & Silicates protect iron and Steel in aq solution. 2. Organic sulphide and Amines protect iron and Steel in acidic solution. 3. Copper sulphate protects S.S in hot diluted solution of H2SO4.

It is based on the galvanic action between the metals of the anode and cathode suspended in the solution. The metals to be protected is made a cathode. Electrons are supplied, there by dissolution of metal is suppressed. It can be achieved by: 1. Sacrificial anode method 2. Impressed emf method

In this method, anodes are kept in electrical contact with the metal to be protected. The anodes are sacrificed, since it goes into solution. E.g. for the protection of iron and steel tanks, the metals such as Zinc, Al, Mg and their alloy are used as sacrificial anodes. This are used in limited pH range. Anode metal is selected from electrochemical series. The anodes should not be poisonous and not detrimental to the pdts.

It is also known as applied current system, i.e., external voltage is impressed between tank and electrodes. The negative terminal of power is connected to the material to be protected. So the natural galvanic effect is avoided and the anode is maintained positive. Since anode is not consumed, metal or non corrodable material can be used.

This method is used for large tanks to store mild corrosive liquors. In these cases, mild steel is used with negligible corrosion. Cathodic protection method is simple and the most effective. It is inexpensive. It enables the use of cheaper material for plant construction. Dis-advantage: Corrosion can not be reduced to zero.

In this method, a predetermined potential is applied to the metal specimen and the corresponding current changes are observed. During the initial stage, the current increases indicating the dissolution of the metal. When the current reaches a critical point, passivisation occur, i.e., the oxide layers set in suitable oxidizing environment. The potential at the critical point is called passivating potential. Above this passivating potential, the current flows decreases to a very small value called passivating current.

The passivating current is defined as the minimum protective current density required to maintain passivisation. At this stage, an increase in potential will not be corrode the metal since the later is in highly passive state. E.g. in case of S.S. titanium becomes easily passive and can not offer cathodic protection.

Advantages : The anodic protection method is utilized in the transportation of conc H2SO4. Dia-advantages: Corrosion can not be reduced to zero. This method cannot be applied for metals, which do not passivate.

Dies & punches In the compression of tablets the dies and punches should be free from rust & corrosion Chromium plated dies and punches avoid this problem. Milling equipment Here a perfect fit between the moving part should be obtained for effective size reduction. Corrosion does not affect the mill performance but the surface imperfection do not facilitate proper cleaning

Solutions that come in contact with the reactor surface leads to corrosion. Chemical processing reactors Glass, glass lined and S.S. materials are used for the construction of the fermentors. During fermentation the release of trace metals from the fermentors may have deleterious effects on enzyme and metabolic pathway of organism. Maintenance of hygiene, need for sterility and prevention of contamination are imp consideration in the construction of fermenrors. Fermentors Prolonged storage of reactive chemicals leads to corrosion of the containers. Storage containers

Cost of Corrosions Equipment Structure replacement Loss of product Maintenance & repair Need for excess capacity or redundant of equipment Corrosion control Designated technical supports Design Insurance Parts Equipment inventories Cause financial losses Has major impacts on economy

Historical analysis Initial Study by Uhlig, 1949: emphasized on the economic importance of corrosion 1970s UK, US & Japan started the study 1970s T.J.Hoar chaired the UK national study which was mainly conducted via survey and interview 1977 Japans national study that follows Uhlig methodology - Battelle-NBS estimated the total direct cost of corrosion using economic input/output framework 1983 Australia adopted the input/output framework 1995 Kuwait adopted the input/output framework Major conclusions: the total annual cost of corrosion ranged from 1 5% of each countrys GDP

Direct costs additional or more expensive material $ of labor to manage $ of equipment Loss of revenue Loss of reliability Lost of capital Indirect costs Taxation Litigation Penalties Other payments

Total cost of corrosion control materials, method and services Control Methods: Organic and metallic protective coatings Corrosion-resistant alloys Corrosion inhibitor Polymers Anodic & cathodic protection Corrosion control & monitoring equipment Control service Corrosion R&D, education and training

Organic/metallic coatings Protect against corrosion for metallic substrate, e,g, carbon steel Effect of corrosion: reduction in service life of parts/components Typical cost of coating > USD 100 B Example of coatings: architectural coatings, OEM, special purpose, misc. paint products

Used when corrosion conditions prohibit the use of carbon steel Protective coatings could not provide the sufficient protection or economically not feasible Typical alloy used: stainless steel, titanium, and nickel-based Industry: Oil production & refinery & chemical processes or any other industry with high T or severe corrosive cdtns: nickel- based

30% of large property damage losses are caused by failures in tanks, process drums and marine vessels. Average Trended Loss was $40.5MM for tanks alone.

6486 accidents. 516 injuries. 90 deaths.

Power Boilers Water Boilers and Steel Tanks Cast Iron Boilers Pressure Vessels (poorest record)

1310 / 6486 accidents 437 / 516 injuries 73 / 90 deaths

Shell Head Attachements Piping Safety Valves Misc

Operator error or poor maintenance 149 / 933 Faulty Design 144 / 933 Corrosion or erosion 132 / 933 Pressure control failure 41 / 933 Other 420 / 933

Cracked 403 / 1087 Other - 298 / 1087 Leakage 163 / 1087 Rupture 158 / 1087 Explosion 22 / 1087 Collapsed Inward 15 / 1087

Search OSHA records On Internet - Google Extract records Create Excel Database Sort and Filter data Analyze Data

Normal mass balance. Start-up, shut down or upset. Recycle conditions. Off-loading situations unplanned.

Inventory logistics not well defined. Flammable or toxic inventories too high.

Dyke dimensions do not meet codes. Drainage does not follow NFPA 15. Catastrophic failure overwhelms dyke walls.

Not suitable for corrosive fluid at high temperature. Not suitable for low temperature excursions.

A-515-70 grade CS brittle failure of heat exchanger shell. Start-up, inlet flange leak, isolated exchanger and depressured to flare. 30 minutes to failure. Two fatalities, seven serious burns, major damage to ethylene plant.

Level control nozzles in wrong location. Nozzles too small creating impingement on far wall. PSV nozzles not suitable for thrust.

Chemical Emergency Preparedness and Prevention Office web site at www.epa.gov/ceppo/acc- his.html Check Rupture Hazard of Pressure Vessels. Check Catastrophic Failure of Storage Tanks.

Oil and Gas Journal, Dec 26, 1998 Pressure storage in spheres Removes bottom unloading lines. Converts to overhead siphon system. Excellent article on 4 process design options.

Impingement details not well designed. Pump-out sumps act as dirt trap. KO Pot internals not designed properly.

Design Pressure not suitable for upset conditions.

P&IDs must be examined for reactive chemical possibilities.

Very easy to bulge or suck-in resulting in loss of containment. PSV, pad de-pad settings very close. Floating roof explosion at Suncor in Sarnia. Roof hangs up on pump-out, air sucked into vapor phase, lightning ignites flammable vapor.

Pumping and temperature change breathing not allowed for in combination. High breathing losses a cost and an environmental problem - Benzene tank.

Not well understood. See BLOSS program for design options.

EO storage bunkers located 1 mile from ISBL. 3 independent means of checking quantity to prevent overfilling (dual LC, weigh scale & flow rate x time). Refrigeration to prevent polymerization, chart temperature. Dump contents to pond if runaway reaction takes place.

This short list is indicative of some of the problems caused by poor engineering discipline in vessel design. Recommend you obtain a copy of the Chemical Plant Design programs and follow the procedures built into the vessel design spreadsheets.

chemical process equipment degradation vessel failure & design factors classifications of...

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