fyp final thesis

FLARE DESIGN FOR EVALUATION OF AN EXISTING FLARE SYSTEM TO HANDLE

HIGHER LOADS THROUGH STEADY STATE SIMULATION

B.E CHEMICAL ENGINEERING

INTERNAL EXAMINER EXTERNAL EXAMINER

NAME ENGR. MUHAMMAD HANEEF MEMON NAME DR. SHAGUFTA ISHTEYAQUE

DESIGNATION ASSISTANT PROFESSOR DESIGNATION CHAIRPERSON K.U.

DEPARTMENT CHEMICAL DEPARTMENT DEPARTMENT CHEM. DEPARTMENT

SUBMITTED BY:-

NAME OF STUDENTS ROLL NO.

I. MUHAMMAD AHSAN KHAN D-12-CH-184

II. IBBAD AHMED MALIK D-12-CH-186

III. MUAHAMMAD ANAS KHAN D-12-CH-173

IV. TAHA NAREJO D-12-CH-143

V. OMAR KHAN D-12-CH-170

VI. MUHAMMAD WALLIULLAH D-12-CH-174

DEPARTMENT OF CHEMICAL ENGINEERING

DAWOOD UNIVERSITY OF ENGINEERING & TECHNOLOGY, KARACHI

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DEDICATION

THIS PROJECT IS DEDICATED TO OUR BELOVED

PARENTS AND TEACHERS WHOSE PRAYERS AND

AFFECTION ENABLED US TO BE WHAT WE ARE

TODAY.

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ACKNOWLEDGEMENT:-

All praises with our deepest gratitude for Almighty Allah, Whose Uniqueness, Oneness

and Wholeness is unchangeable. The following study is the effort undertaken by us under

the sublime guidance of Him, the most Beneficent and the Merciful, Who gave us the will

and courage to complete our work. May Allah always endow upon us, strength and courage

to pursue difficult tasks in the future.

We would like to thanks PARCO- Mid Country Refinery for giving the chance for doing

Final Year Project (FYP) in such a friendly and learning environment.

We would like to thanks the Mr. Tahir Rasheed our care taker who is an Ex-PARCO

Engineer and our project supervisor Mr. Haneef Memon Lecturer DUET, through which

we have got this opportunity to visit PARCO, We would also thanks Technical Service

Department (TSD) of PARCO who helped us at every phase of my FYP. Without their

co-operation, we would not be able to learn and complete this project.

We would also like to thanks my mentor Mr. Muhammad Ahmed Latif, Trainer Mr.

Muhammad Arif & Sir Qasim for their immense support and guide regarding our project.

Our special thanks for our families and friends for their help and support which they offered

us in every regard.

We are thankful to the library staff for their cooperation as well.

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SUMMARY

As the time surpassed the use of Petroleum products is increasing with the increase in

population. To fulfill this current requirement of petroleum , in coming future the PARCO

refinery is looking ahead to increase its production capacity, to achieve such a load it’s

mandatory to see whether the existing safety equipment is capable of sustaining that load

or not.

In this project we had crafted the method for checking that by taking the base unit as Crude

Distillation unit of the refinery. This project report comprises of the general information

regarding the data material and sheets required to design Flare system equipment for the

selected Pressure Safety Valves of Crude Distillation Unit including the details of the

designing of the equipment’s used.

TableofContents

1. CHAPTER01: INTRODUCTION………………………………………………………...……01

1.1ThephenomenaofFlaring…………………………………………………………………………………………02

1.2.1.TypesofFlare……………………………………………………………………………………...…….02

1.2.2.Vertical………………………………………………………………………………………………..……02

1.2.3.HorizontalFlare………………………………………………………………………………..……….04

1.2.4.SmokelessandNon‐smokelessflares……………………………………………...…………..04

1.3.MajorComponentsforaflaresystem……………………………………………………………...…………05

1.4.REFINERYCOMMONFLARESYSTEM………………………………………………………………....……..06

1.4.1.Mainflaresystem………………………………………………………………………………..……..06

2. CHAPTER2: RELIEFVALVE…………………………………………………………………08

2.1. Introduction…………………………………………………………………………………………………...………09

2.2.FunctionofReliefValves……………………………………………………………………………………..……09

2.3Sizingandsetpressure………………………………………………………………………………………….…..09

2.4TypesofReliefValves………………………………………………………………………………………………..10

2.4.1.Conventionalreliefvalves…………………………………………………………………..………10

2.4.2.BalancedBellowReliefValves…………………………………………………….………………11

2.4.3.PilotOperatedReliefvalves……………………………………………………………………....12

2.4.4.Rupturedisk.…………………………………………………………………………………………..…13

2.4.4.1Rupturediskincombinationwithpressurereliefdevices………………..13

2.5.SizeandLengthofInletPipingtoPressure‐ReliefValves…………………………………………….13

2.6.Potentialsforoverpressure………………………………………………………………………………..……..14

2.6.1.General………………………………………………………………………………………………………14

2.6.2.OverpressureScenarios………………………………………………………………………….….15

TableofContents

2.6.2.1.Fire………………………………………………………………………………………….…15

2.6.2.2.BlockedDischarge…………………………………………………………………….…15

2.6.2.3.Hydraulicexpansion………………………………………………...……………….…16

2.6.2.4.ControlValveFailure…………………………………………………………….……..17

2.6.2.5.GasBlowBy………………………………………………………………………...………17

2.6.2.6.TubeRupture…………………………………………………………………………...…18

2.6.2.7.UtilityFailure………………………………………………………………………………18

2.6.2.6.1.Lossofcoolingwater…………………………………………….……….18

2.6.2.6.1.Lossofinstrumentair…………………………………………..………..19

2.6.2.8.Pressuresurges………………………………………………………………….……….19

2.6.3.Determinationofindividualrelievingrates………………………………………………..……………21

2.6.3.1.Principalsourcesofoverpressure………………………………………………...……………..21

2.6.3.2.Effectsofpressure,temperature,andcomposition………………………………………24

2.6.3.3.Effectofoperatorresponse…………………………………………………………………………25

2.6.3.4.Outletcontroldevices……………………………………………………………………………...…26

2.6.3.5.Specialcapacityconsiderations……………………………………………………………..……26

2.6.3.6.Pipingdesignconsiderationsforgasbreakthrough………………………………………27

2.6.3.7.Sizingandsetpressure…………………………………………………………………………….…27

2.7.Firereliefloads………………………………………………………………………………………………………..28

2.7.1.General…………………………………………………………………………………………….……28

2.8.Fluidstoberelieved…………………………………………………………………………………………..……..29

2.8.1.General………………………………………………………………………………….…………..…..29

2.8.2.Vapour…………………………………………………………………………………………………30

2.8.3.Liquid……………………………………………………………………………………………...…….31

2.8.4.Mixedphase………………………………………………………………………………………….………………32

TableofContents

3.CHAPTER03: METHODOLGOY………………………………………………………………………34

3.1.Sizingmethodology..................................................................................................................................…...35

3.2CalculationProcedure……………………………………………………………………………………………….36

3.3FLARELOADSREVIEWASPERDESIGN100%LOADS…………………………………………………38

3.3.1.Objective…………………………………………………………….…………………………………38

3.5.PRESSURESAFETYVALVES(PSV)LOADREVIEWASPERDESIGN100%BASIS…………..39

3.5.1Objective……………………………………………………………………………………………….39

4.CHAPTER04:CALCULTIONS…………………………………………………………………………..………41

4.1.CalculationofRequiredCapacityfor100‐PSV‐011A/B…………………………….……..42

4.2CalculationofRequiredCapacityfor100‐PSV‐013…………………………………….…….46

4.3.CalculationofRequiredCapacityfor100‐PSV‐015A/B…………………………..………50

4.4.CalculationofRequiredCapacityfor100‐PSV‐016………………………………………….54

4.5.CalculationofRequiredCapacityfor100‐PSV‐017….……………………….…………….58

4.6.CalculationofRequiredCapacityfor100‐PSV‐018……………………………..…………..62

4.7.KnockoutDrumSizing…………………………………………………………………………………66

4.8.FlareSizingMethodology…………………………………………………………………………….68

5.CHAPTER05: DATASHEETS………………………………………………..………………………..70

6.CHAPTER06: PROCESSFLOWDIAGRAMOFSIMULATION……………………………91

7.CONCLUSION……………………………………………………………………..…………………………………..92

8.RECOMMENDATION……………………………………………………...……………………………..………..93

9.APPENDIX……………………………………………………………………….…………………………………….94

10.REFRENCES…………………………………………………………………………………………………………96

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CHAPTER NO: 01

INTRODUCTION

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1.1 The phenomena of Flaring:

Flaring equipment is provided in the refinery or petrochemical plant to ensure the safe

and efficient disposal of relieved gases or liquids. The disposals fluids are collected in

flare header and routed to the flare. It is extremely important in the event of a plant

emergency such as a fire or power failure. A properly operating flare system is the

critical component to prevent plant disruption from turning into disaster.

Flare is expected to operate 24/7. Flare must be in service for several years without a

need to shut it down. It always is available for flaring whenever a plant disruption

occurs.

The flaring system must be designed to do the following:

1. Reduce ground level concentration of hazardous materials

2. Provide the safe disposal of flammable materials.

1.2.1. Types of Flare:

1. Vertical

a. Self-Supported

b. Guyed supported

c. Derrick supported

2. Horizontal

3. Smokeless and Non-smokeless flares

1.2.2. Vertical:-

Vertical fares are generally oriented to be upward. The discharge point is in an elevated

position relative to the surrounding grade and/or nearby equipment. There are several

types of support methods for vertical fares. These include:

Self-Supported:-

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This is the simplest and most economical design for applications requiring short-stack

heights (up to 100 ft. overall height); however, as the flare height and/or wind loading

increases, the diameter and wall thickness required become very large and expensive.

Guyed supported:-

An elevated fare with the riser supported by cables. Cables are attached to the fare

riser at one or more elevations to limit the defection of the structure. The cables

(guy-wires) are typically positioned in a triangular plan to provide strong support.

Derrick supported:-

This is the most feasible design for stack heights above 350 ft. They use a single-

diameter riser supported by a bolted framework of supports. Derrick supports can be

fabricated from pipe (most common), angle iron, solid rods, or a combination of these

materials. They sometimes are chosen over guy-wire-supported stacks when a limited

footprint is desired.

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1.2.3. Horizontal Flare:-

The fared liquids and gases are piped to a horizontal fare burner that discharges into

a pit or excavation.

1.2.4. Smokeless and Non-smokeless flares:-

Smokeless fares eliminate any noticeable smoke over a specified range of flows.

Smokeless combustion is achieved by utilizing air, steam, pressure energy, or other

means to create turbulence and entrain air within the fared gas stream. Smokeless

fares can be provided with a steam-assist or air-assist system to improve combustion.

An air-assist system utilizes fans to provide mixing energy at the tip.

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1.3 Major Components for a flare system:-

1.3.1. Air seal:

A device used to minimize or eliminate the air back into the riser from the exit.

1.3.2. Blow off:

The loss of a stable fame where the fame is lifted above the burner. This occurs if the

fuel velocity exceeds the fame velocity.

1.3.3. Burn back:

Internal burning within the tip. This might result from air backing down the flare burner

at purge or low flaring rates.

1.3.4. Burn-pit flare:

An open excavation normally equipped with a horizontal flare burner that can handle

liquid as well as vapor hydrocarbons.

1.3.5. Design flares capacity:

The maximum design flow to the flare normally expressed in kilograms per hour

(pounds per hour) of a specific composition, temperature, and pressure.

1.3.6. Direct ignition:

Ignition of a pilot by a spark at the pilot rather than by a flame front generator.

1.3.7. Flare header:

The piping system that collects and delivers the relief gases to the flare.

1.3.8. Pilot:

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A small continuously operating burner that provides ignition energy to light the flared

gases. The flare pilot must reliably ignite the flare. If the pilot fails, unburned

hydrocarbons and/or toxic gases could be released to the atmosphere, potentially

resulting in a vapor cloud explosion, odor problems or adverse health effects. In most

elevated flare applications, the pilot cannot be accessed for service or replacement

while the flare is in operation. The pilot system must be reliable enough to operate for

years without maintenance.

1.3.9. Mach number:

The ratio of the fluids velocity divided by the speed at which sound waves propagate

through the fluid.

1.3.10. Liquid seal:

A device that directs the flow of relief gases through a liquid (normally water) on their

path to the flare burner. It can be used to protect the flare header from air flashback,

to divert flow, or to create backpressure for the flare header.

1.3.11. Knockout drum:

A vessel in the flare header designed to remove and store condensed and entrained

liquids from the relief gases.

1.3.12. Relief gas:

Gas or vapor vented or relieved into flare header for conveyance to a flare.

Sometimes called waste gas, flared gas or waste vapor.

1.3.13. Flame Detection:

The flame detection system confirms that the pilots are lit. This is often confused with

simple confirmation that a flame exists. While these two statements are usually

7

synonymous, there is an important difference. If the pilots are lit and a volume of inert

gas is released, the flare flame will be extinguished only while the inert gas is being

discharged. If the Pilots are not lit, but the flare is, and a volume of inert gas is released,

the flare flame will remain extinguished after the inert gas release and until a pilot can

be ignited. If the pilots are not lit because they have failed, the flare may remain unlit

for an extended period of time. Consequently, it is important to confirm both the

presence of a flame and also the presence of a pilot flame.

1.4 REFINERY COMMON FLARE SYSTEM (U-915)

The flare system is designed to collect, to knockout liquid, to prevent flashback and to

dispose of relieving vapor. An elevated main flare is provided to combust relief valve

discharges.

1.4.1 Main flare system

Relieving vapor and liquid from the following units are collected to main flare system:

1. Crude Distillation Unit

2. Vacuum Distillation Unit

3. Gas Concentration Process Unit

4. Visbreaking Process Unit

5. DieselMax Process Unit

6. Plat forming Process Unit

7. Plat forming Process Unit CCR Section

8. Naphtha Hydro treating Process Unit

9. Kerosene Merox Process Unit

10. LPG Merox Process Unit

11. Fuel Gas System

12. LPG Sphere Tanks

13. Boiler Section in Utility Facilities

8

CHAPTER 2

Relief Valve

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2.1 Introduction

Pressure relief valves or other relieving devices are used to protect piping, valves,

fittings, and equipment’s against excessive pressures higher than their design

pressures. Proper selection, use, location, and maintenance of relief devices are

essential to protect personnel and equipment as well as to comply with codes and

laws.

Relief Valves are essential because safety switches do fail or can be bypassed for

technical or operational reasons. Also, even when safety switches operate correctly,

shutdown valves take time to operate, and there may be pressure stored in upstream

vessels that can overpressure downstream equipment while the system is shutting

down. Thus, Relief valves are essential elements in the facility safety system.

2.2 Function of Relief Valves

The function of the relief valve is:

i. To open and relieve excess pressure

ii. To reclose and prevent flow of fluid after normal conditions have been restored.

2.3 Sizing and set pressure

The required relieving rate is not easy to determine. Since every application is for a

relieving liquid, the required relieving rate is small; specifying an oversized device is,

therefore, reasonable. 1) Relief valve is commonly used. If there is reason to believe

that this size is not adequate, the procedure can be applied. If the liquid being relieved

is expected to flash or form solids while it passes through the relieving device, the

procedure in is recommended.

Proper selection of the set pressure for these relieving devices should include a study

of the design rating of all items included in the blocked- in system. The thermal-relief

pressure setting should never be above the maximum pressure permitted by the

weakest component in the system being protected. However, the pressure-relieving

10

device should be set high enough to open only under hydraulic expansion conditions.

If thermal-relief valves discharge into a closed system, the effects of back pressure

should be considered.

2.4 Types of Relief Valves

i. Conventional relief valves.

ii. Balance bellows relief valves.

iii. Pilot Operated Relief valves.

iv. Rupture disk.

v. Rupture disk in combination with pressure relief devices.

2.4.1. Conventional relief valves:

Conventional pressure relief valve is characteristics are directly affected by changes

in backpressure on the valve. These valves are normally used when the back pressure

is less than 10% of the set pressure.

Bonnets on conventional pressure-relief valves can either be opened or closed type

bonnets and do not have any special venting requirements. Open bonnets are often

used in steam service and are directly exposed to the atmosphere. Valves with closed

bonnets are internally vented to the pressure relief valve discharge. The bonnet

normally has a tapped vent that is closed off with a threaded plug.

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2.4.2. Balanced Bellow Relief Valves:

It is a spring loaded pressure relief valve that contains a bellow arrangement to

minimize the effect of back of pressure on operational characteristics. These valves

are normally used when the back pressure is between 10-50% of set pressure.

Balanced bellows pressure-relief valves are utilized in applications where it is

necessary to minimize the effect of back pressure on the set pressure and relieving

capacity of the valve. This is done by balancing the effect of the back pressure on the

top and bottom surfaces of the disc. This requires the bonnet to operate at atmospheric

pressure. The bonnets of balanced bellows pressure-relief valves must always be

vented to ensure proper functioning of the valve. The

12

Bonnet vent may also provide a visual indication in the event of a bellows failure. The

vent must be designed to avoid plugging caused by ice, insects, or other obstructions.

When the fluid is flammable, toxic, or corrosive, the bonnet vent may need to be piped

to a safe location.

2.4.3. Pilot Operated Relief valves:

It is a pressure relief valve in which major relieving device or main valve is combined

with and controlled by a self-operated auxiliary pressure relief valve (Pilot). These

13

valves are normally used when the back pressure is greater than 50% of set pressure

and the margin between operating pressure and set pressure is less than 10%.

The pilot is often vented to the atmosphere under operating conditions, since the

discharge during operation is small. When vent discharge to the atmosphere is not

permissible, the pilot should be vented either to the discharge piping or through a

supplementary piping system to a safe location. When vent piping is designed, avoid

the possibility of back pressure on the pilot unless the pilot is a balanced design.

2.4.4. Rupture disk:

Rupture disk device is a non-reclosing pressure relief actuated by static differential

pressure between the inlet and outlet of the device and designed to function by the

bursting of a rupture disk. A rupture disk device includes a rupture disk and rupture

disk holder.

2.4.4.1. Rupture disk in combination with pressure relief devices:

A rupture disk can be installed either upstream or downstream of a pressure relief

valve to protect them from corrosion and leakage.

2.5. Size and Length of Inlet Piping to Pressure-Relief Valves

When a pressure-relief valve is installed on a line directly connected to a vessel, the

total non-recoverable pressure loss between the protected equipment and the

pressure-relief valve should not exceed 3 percent of the set pressure of the valve for

pilot-operated pressure relief valves. When a pressure-relief valve is installed on a

process line, the 3 percent limit should be applied to the sum of the loss in the normally

non-flowing pressure-relief valve inlet pipe and the incremental pressure loss in the

process line caused by the flow through the pressure-relief valve. The pressure loss

should be calculated using the rated capacity of the pressure-relief valve.

14

Pressure losses can be reduced by rounding the entrance to the inlet piping, by

reducing the inlet line length, or by enlarging the inlet piping. The nominal size of the

inlet piping must

Be the same as or larger than the nominal size of the pressure relief valve inlet

connection. Keeping the pressure loss below 3 percent becomes progressively more

difficult at low pressures as the orifice size of pressure-relief valve increases. An

engineering analysis of the valve performance at higher inlet losses may permit

increasing the allowable pressure loss above 3 percent. When a rupture disk device is

used in combination with a pressure-relief valve, the pressure-drop calculation must

include the additional pressure drop developed by the disk.

2.6. Potentials for overpressure

2.6.1. General

Pressure vessels, heat exchangers, operating equipment and piping are designed to

contain the system pressure. The design is based on the normal operating pressure at

operating temperatures; the effect of any combination of process upsets that are likely

to occur; the differential between the operating, and set pressures of the pressure-

relieving device; the effect of any combination of supplemental loadings such as

earthquake and wind.

The process-systems designer shall define the minimum pressure- relief capacity

required to prevent the pressure in any piece of equipment from exceeding the

maximum allowable accumulated pressure.

2.6.2. Overpressure Scenarios

In the design of any production facility, the most common relieving conditions are:

i. Fire

ii. Blocked discharge

iii. Thermal or Hydraulic Expansion

15

iv. Control Valve Failure

v. Gas blow by

vi. Heat exchanger tube rupture

vii. Utility failure

viii. Pressure surges

2.6.2.1. Fire:

In a plant, fire occurs mainly due to hydrocarbon oil leakage and spillage. If fire can

occur on plant-wide basis, this condition may dictate the sizing of the entire relief

system; however, since equipment may be dispersed geographically, the effect of fore

exposure on the relief system may be limited to a specific plot area. Vapor generation

will be higher in any area which contains a large number of un-insulated vessels.

Various empirical equations have been developed to determine relief loads from

vessels exposed to fire. Fire conditions may overpressure vapor filled, liquid filled or

mixed phase systems.

In case of vapor filled or mixed-phase systems, the un-wetted surface are a containing

the gas, vapor or supercritical fluid of effective increasing the pressure of the system

due to gas or vapour expansion when the area is exposed to fire.

In case of liquid filled or mixed phase systems, the surface area wetted by vessel

internal liquid content is effective generating vapors when the area is exposed to fire

to determine vapour generation, only that portion of the vessel that is wetted by its

internal liquid that is equal to or less than above the source of flame usually refers to

ground grade but could be at any level at which a substantial spill or pool fire could be

sustained.

2.6.2.2. Blocked Discharge:

In this over pressure scenario, it is assumed that all outlets of vessel, pump,

compressor, fired heater or other equipment item are shut in (blocked) due to

16

mechanical failure or human error, and the total inlet flow stream (gas, liquids or both)

to the equipment must flow out through the relief valve. The Capacity of the relief

devices must be at least as great as the capacity of the source of overpressure.

For example, blocked discharge could occur, if the equipment has been shut

in and isolated and the operator opens the inlet before opening the outlet

Valves.

2.6.2.3. Hydraulic expansion:

Hydraulic expansion is the increase in liquid volume caused by an increase in

temperature. It can result from several causes, the most common of which are the

following:

1. Piping or vessels are blocked in while they are filled with cold liquid and are

subsequently heated by heat tracing, coils, ambient heat gain or fire.

2. An exchanger is blocked in on the cold side with flow in the hot side.

3. Piping or vessels are blocked in while they are filled with liquid at near-ambient

temperatures and are heated by direct solar radiation.

In certain installations, such as cooling circuits, the processing scheme, equipment

arrangements and methods, and operation procedures make feasible the elimination

of the hydraulic-expansion relieving device, which is normally required on the cooler,

fluid side of a shell-and-tube exchanger. Typical of such conditions are multiple-shell

units with at least one cold-fluid block valve of the locked-open design on each shell

and a single-shell unit in a given service where the shell can reasonably be expected

to remain in service, except on shutdown. In this instance, closing the cold-fluid block

valves on the exchanger unit should be controlled by administrative procedures and

possibly the addition of signs stipulating the proper venting and draining.

Procedures when shutting down and blocking in. Such cases are acceptable and do

not compromise the safety of personnel or equipment, but the designer is cautioned

17

to review each case carefully before deciding that a relieving device based on

hydraulic expansion is not warranted.

2.6.2.4. Control Valve Failure:

To protect a vessel or system from overpressure when all outlets on the vessel or

system are blocked, the capacity of the relief device must be at least as great as the

capacity of the sources of pressure. If all outlets are not blocked, the capacity of the

unblocked outlets may properly be considered. The sources of overpressure include

pumps, compressors, high pressure supply headers, stripped gases from rich

absorbent, and process heat. In the case of heat exchangers, a closed outlet can

cause thermal expansion or possibly vapor generation.

The quantity of material to be relieved should be determined at conditions that

correspond to the set pressure plus overpressure instead of at normal operating

conditions. The required valve capacity is often reduced appreciably when this

difference in conditions is considered. The effect of friction drop in the connecting line

between the source of over-pressure and the system being protected should also be

considered in determining the capacity requirement.

2.6.2.5. Gas Blow By:

It is the most critical and sometimes overlooked condition in the production of the

facility design. It assumes that there is a failure of an upstream control valve feeding

the pressure vessel and that the relief valve must handle the maximum gas flow rate

into the system during this upset condition.

For example, if the liquid control valve on a high-pressure separate were fail to open,

all the liquid would dump to the downstream lower-pressure vessel. Then the gas from

the high pressure separator would start to flow to the downstream vessel. The lower

pressure vessels relief valve must be sized to handle the total gas flow rate that will

flow through the liquid dump valve in a full open position. We normally assume

18

(Conservatively) that the upstream vessel pressure is at its maximum operating

pressure and the downstream low pressure vessel is at its PSV set point. Most

accidents involving over pressuring of low pressure separators are a result of relief

valves not being adequately sized to handle the gas blow by condition.

2.6.2.6. Tube Rupture:

In this common for a shell and tube exchanger to have a high pressure fluid ion the

tubes and a lower pressure rated shell. If there is a break in one of the tubes, the higher

pressure fluid will leak to the completely split with choked flow from both sides of the

break. The relieving rate through the relief valve provided on the low pressure shell

side of the heat exchanger is dependent on the diameter of the tube and the phase of

the fluid present in both shell side and tube side.

In shell-and-tube heat exchangers, the tubes are subject to failure from a number of

causes, including thermal shock, vibration and corrosion. Whatever the cause, the

result is the possibility that the high-pressure stream overpressures equipment on the

low-pressure side of the exchanger. The ability of the low-pressure system to absorb

this release should be determined. The possible pressure rise shall be ascertained to

determine whether additional pressure relief is required if flow from the tube rupture

discharges into the lower-pressure stream.

2.6.2.7. Utility Failure:

Possible relieving situations caused by a utility failure must be carefully considered.

Typically causes are:

Loss of cooling

Loss of instrument air

2.6.2.7.1. Loss of cooling water:-

19

Loss of the cooling water may occur on an area wide or plant wide basis. Affected are

fractionating columns and other equipment’s utilizing water cooling. Cooling water

failure is often the governing case in sizing flare systems.

2.6.2.7.2. Loss of instrument air

The loss of instrument air drives all air-operated valves to their specified fail position.

This action of many valves can result in overpressure if the specified failure positions

of the valves are not selected to prevent overpressure. Likewise, failure of electric

instrument power can drive control systems and electrically operated valves to their

specified failure positions. Consideration should be given to the effect on flare- or blow

down-system loading of valves failing open or closed due to instrument-air failure or

power failure.

Electric Power Failure, similar to cooling water failure, may occur on an area wide or

plant wide basis and may have a variety of affects. Since electric pumps and air coolers

are fan drives are often employed in process units, a power failure may cause the

immediate loss of reflux to fractionators. Motor driven compressors will also shut down.

Power failures may result in major relief loads.

Instrument air system failure whether related to electric power failure or not, must be

considered in sizing of the flare system since pneumatic control loops will be

interrupted. Also control valves will be interrupted. Also control valves will assume the

position as specified on “loss of air” and the resulting effect on the flare system must

be considered. Loss of instrument air can result in overpressure. If the specified failure

positions of the valves are not selected to prevent overpressure.

2.6.2.8. Pressure surges

2.6.2.8.1. Water hammer

The probability of hydraulic shock waves, known as water hammer, occurring in any

liquid-filled system should be carefully evaluated. Water hammer is a type of

20

overpressure that cannot be controlled by typical pressure-relief valves, since the

response time of the valves can be too slow. The oscillating peak pressures, measured

in milliseconds, can raise the normal operating pressure by many times. These

pressure waves damage the pressure vessels and piping where proper safeguards

have not been incorporated. Water hammer is frequently avoided by limiting the speed

at which valves can be closed in long pipelines. Where water hammer can occur, the

use of pulsation dampeners or special bladder-type surge valves should be

considered, contingent on proper analysis.

2.6.2.8.2. Steam hammer

An oscillating peak-pressure surge, called steam hammer, can occur in piping that

contains compressible fluids. The most common occurrence is generally initiated by

rapid valve closure. This oscillating pressure surge occurs in milliseconds, with a

possible pressure rise in the normal operating pressure by many times, resulting in

vibration and violent movement of piping and possible rupture of equipment. Pressure-

relief valves cannot effectively be used as a protective device because of their slow

response time. Avoiding the use of quick-closing valves can prevent steam hammer.

2.6.2.8.3. Plant fires

A provision for initiating a controlled shutdown or installation of a depressuring system

for the units can minimize overpressure that results from exposure to external fire.

To limit vapor generation and the possible spread of fire, facilities should also allow for

the removal of liquids from the systems. Normally operating product withdrawal

systems are considered superior and more effective for removing liquids from a unit,

compared with separate liquid pulldown systems. Liquid hold-up required for normal

plant operations, including refrigerants or solvents, can be effective in keeping the

vessel wall cool and does not necessarily require systems for its removal. Provisions

21

may be made either to insulate the vessel's vapor space and apply external water for

cooling or to depressure the vessel using a vapor depressuring system.

Area design should include adequate surface drainage facilities and a means for

preventing the spread of flammable liquids from one operating area to another. Easy

access to each area and to the process equipment shall be provided for firefighting

personnel and their equipment. Fire hydrants, firefighting equipment and fire monitors

should be placed in readily accessible locations.

2.6.3 Determination of individual relieving rates

2.6.3.1. Principal sources of overpressure

The basis for determining individual relieving rates that result from various causes of

overpressure in the form of general considerations and specific guidelines. Good

engineering judgment, rather than blind adherence to these guidelines, should be

followed in each case. The results achieved should be economically, operationally and

mechanically feasible, but in no instance should the safety of a plant or its personnel

be compromised.

Table 2 lists some common occurrences that can require overpressure protection. This

table is not intended to be all- inclusive or complete in suggesting maximum required

relieving rates; it is merely recommended as a guide...

Table 2 — Guidance for required relieving rates under selected conditions

Item

No. Condition

Liquid-relief

guidance Vapour-relief guidance

1 Closed outlets

on vessels

Maximum

liquid pump-in

Rate

Total incoming steam and vapour plus

that generated therein at relieving

conditions

22

2

Cooling-water

failure to

Condenser

— Total vapour to condenser at

relieving Conditions

3 Top-tower reflux

failure —

Total incoming steam and vapour plus

that generated therein at relieving

conditions less vapour condensed by

side stream reflux

4 Side stream

reflux failure —

Difference between vapour entering

and leaving equipment at relieving

conditions

5 Lean-oil failure to

absorber — None, normally

6 Accumulation of

non-condensable —

Same effect in towers as found for

Item 2; in other vessels, same effect

as found for Item 1

7

Entrance of

highly volatile

Material Water

into hot oil

— —

Water into hot oil — For towers, usually not predictable

Light

hydrocarbons

into hot oil

—

For heat exchangers, assume an area

twice the internal cross-sectional area

of one tube to provide for the vapour

generated by the entrance of the

volatile fluid due to tube rupture

entrance of the volatile fluid due to tube

23

rupture entrance of the volatile fluid

due to tube rupture

8

Overfilling

storage or surge

vessel

Maximum

liquid pump-in

rate

—

9

Failure of

automatic

controls

— Analyze on a case-by-case basis

10 Abnormal heat or

vapour input —

Estimated maximum vapour

generation including non-

condensables from overheating

11 Split exchanger

tube

Liquid

entering from

twice the

cross-

sectional area

of one tube

Steam or vapour entering from

twice the cross-sectional area of one

tube; also same cross-sectional area

of one tube; also same cross-sectional

area of one tube; also same effects

found in Item 7 for exchangers

12 Internal

explosions —

Not controlled by conventional relief

devices but by avoidance of

circumstances

13 Chemical

reaction —

Estimated vapour generation from both

normal and uncontrolled conditions;

consider two- phase effects.

14 Hydraulic

expansion:

Cold-fluid shut in —

24

Lines outside

process area

shut In

—

15

Power failure

(steam, electric,

or other)

—

Study the installation to determine the

effect of power failure; size the relief

valve for the worst condition that can

occur

16 Fractionators — Loss of all pumps, with the result that

reflux and cooling water would fail

17 Reactors —

Consider failure of agitation or stirring,

quench, size the valves for vapour

generation from a runaway reaction

18 Air-cooled

exchangers —

Fan failure; size valves for the

difference between normal and

emergency duty

19 Surge vessels — Maximum liquid inlet rate

2.6.3.2. Effects of pressure, temperature, and composition

Pressure and temperature should be considered to determine individual relieving

rates, since they affect the volumetric and compositional behavior of liquids and

vapours. Vapour is generated when heat is added to a liquid. The rate at which vapour

is generated changes with equilibrium conditions because of the increased pressure

in a confined space and the heat content of streams that continue to flow into and out

of the equipment. In many instances, a volume of liquid can be a mixture of

components with different boiling points. Heat introduced into fluids that do not reach

their critical temperature under pressure-relieving conditions produces a vapour that is

rich in low-boiling components. As heat input is continued, successively heavier

25

components are generated in the vapour. Finally, if the heat input is sufficient, the

heaviest components are vaporized.

During pressure-relieving, the changes in vapour rates and relative molecular masses

at various time intervals should be investigated to determine the peak relieving rate

and the composition of the vapour. The composition of inflowing streams can also be

affected by variations in time intervals and, therefore, requires study.

Relieving pressure can sometimes exceed the critical pressure (or pseudo-critical

pressure) of the components in the system. In such cases, reference shall be made to

compressibility correlations to compute the density — temperature — enthalpy

relationships for the system fluid. If the overpressure is the result of an inflow of excess

material, then the excess mass quantity shall be relieved at a temperature determined

by equating the incoming enthalpy with the outgoing enthalpy.

In a system that has no other inflow or outflow, if the overpressure is the result of an

extraneous excess heat input, the quantity to be relieved is the difference between the

initial contents and the calculated remaining contents at any later time. The cumulative

extraneous enthalpy input is equal to the total gain in enthalpy by the original contents,

whether they remain in the container or are vented. By calculating or plotting the

cumulative vent quantity versus time, the maximum instantaneous relieving rate can

be determined. This maximum usually occurs near the critical temperature. In such

cases, the assumption of an ideal gas can be too conservative,) oversize’s the

pressure-relief valve. This equation should be used only when physical properties for

the fluid are not available.

2.6.3.3. Effect of operator response

The decision to take credit for operator response in determining maximum relieving

conditions requires consideration of those who are responsible for operation and an

understanding of the consequences of an incorrect action. A commonly accepted time

26

range for the response is between 10 min and 30 min, depending on the complexity of

the plant. The effectiveness of this response depends on the process dynamics.

2.6.3.4. Outlet control devices

Each outlet control valve should be considered in both the fully opened and the fully

closed positions for the purposes of relief-load determination. This is regardless of the

control-valve failure position because failure can be caused by instrument-system

failure. If one or more of the inlet valves are opened by the same failure that caused

the outlet valve to close, pressure-relieving devices can be required to prevent

overpressure. The required relieving rate is the difference between the maximum inlet

and maximum outlet flows. All flows should be calculated at relieving conditions. Also,

one should consider the effects of inadvertent closure of control devices by operator

action.

For applications involving single outlets with control devices that fail in the closed

position, pressure-relieving devices can be required to prevent overpressure. The

required relieving rate is equal to the maximum expected inlet flow at relieving

conditions.

For applications involving more than one outlet and a control device that fails in the

closed position on an individual outlet, the required relieving rate is the difference

between the maximum expected inlet flow and the design flow (adjusted for relieving

conditions and considering unit turndown) through the remaining outlets, assuming

that the other valves in the system remain in their normal operating position. For

applications involving more than one outlet, each with control devices that fail in the

closed position because of the same failure, the required relieving rate is equal to the

maximum expected inlet flow at relieving conditions.

2.6.3.5. Special capacity considerations

27

Although control devices, such as diaphragm-operated control valves, are specified

and sized for normal design operating conditions, they are also expected to operate

during upset conditions, including periods when pressure-relieving devices are

relieving. Valve design and valve operator capability should be selected to position

the valve plug properly in accordance with control signals during abnormal conditions.

Because the control-valve capacities at pressure-relieving conditions are not the same

as those at normal conditions, the control-valve capacities should be calculated for

the relieving conditions of temperature and pressure in determining the required

relieving rates. In extreme cases, the state of the controlled fluid can change (e.g.

from liquid to gas or from gas to liquid). The wide-open capacity of a control valve

selected to handle a liquid can, for example, differ greatly when it handles a gas. This

becomes a matter of particular concern where loss of liquid level can occur, causing

the valve to pass high-pressure gas to a system sized to handle only the vapour

flashed from the normal liquid entry.

2.6.3.6. Piping design considerations for gas breakthrough

Gas breakthrough across a control valve can result in slug- flow high liquid velocities.

The resultant transient loads on the piping shall be taken into account, including the

mechanical design and pipe supports.

NOTE: Locating the relief device closer to the upstream control valve can reduce the

amount of pipe support required and can also reduce the size of the relief device.

2.6.3.7. Sizing and set pressure

The required relieving rate is not easy to determine. Since every application is for a

relieving liquid, the required relieving rate is small; specifying an oversized device is,

therefore, reasonable. 1) Relief valve is commonly used. If there is reason to believe

that this size is not adequate, the procedure in can be applied. If the liquid being

28

relieved is expected to flash or form solids while it passes through the relieving device,

the procedure in is recommended.

Proper selection of the set pressure for these relieving devices should include a study

of the design rating of all items included in the blocked- in system. The thermal-relief

pressure setting should never be above the maximum pressure permitted by the

weakest component in the system being protected. However, the pressure-relieving

device should be set high enough to open only under hydraulic expansion conditions.

If thermal-relief valves discharge into a closed system, the effects of back pressure

should be considered.

2.7. Fire relief loads

2.7.1. General

The appropriate fire sizing equation applies to the equipment being evaluated should

be used. The fire-sizing equation is applied to process vessels and storage vessels,

including those designed to the pressure-design code. These equations were re-

evaluated by the API Pressure Relief Subcommittee and found to be appropriate for

the specific equipment covered by this International Standard. The fire-sizing

equations assume typical in-plant conditions for facilities within the scope of this

International Standard but can be understated for vessels in partially enclosed or

enclosed areas, such as those in buildings or on-offshore platforms these documents

provide an alternative approach based on analytical methods and can be used to

model fire-heat input for all

Types and sizes of fire. To use these methods for fire-relief calculations, it is necessary

to specify the average fire temperature, rather than the instantaneous peak

temperature. For a wetted area of 10 m2 (approx. 100 ft2) and an average fire

temperature of 750 °C (approx. 1 400 °F)...

It is typically assumed that the vessel is isolated during a fire in order to simplify the

analysis, although a more detailed analysis can be warranted in certain cases.

29

Crediting for alternative relief paths that remain open during an overpressure event is

generally an acceptable practice. However, it should be recognized that operators

and/or emergency responders attempt to isolate certain lines and vessels during a fire

condition in order to limit the fire spread and to safely shutdown the unit. There can

also be actuated valves that fail in the closed condition when exposed to a fire. It can

be difficult to establish with a degree of certainty whether a particular line will indeed

remain open under all fire conditions. Further, unless the line is open to atmosphere,

consideration should be given to the potential that the fire-relief flow in the alternative

relief path will overpressure other equipment. Hence, it can be necessary to add the

fire-relief load elsewhere. Ultimately, the user shall decide whether a scenario is

credible or not.

The heat absorption equations for vessels containing liquids and heat absorption

equations for vessels containing only gases/vapors.

Either the vapor thermal-expansion relief load or the boiling-liquid vaporization relief

load, but not both, should be used. It is a practice that has been used for many years.

There are no known experimental studies where separate contributions of vapor

thermal expansion versus boiling-liquid vaporization have been determined.

2.8. Fluids to be relieved

2.8.1. General

A vessel can contain liquids or vapors or fluids of both phases. The liquid phase can

be subcritical at operating temperature and pressure and can pass into the critical or

supercritical range during the duration of a fire as the temperature and pressure in the

vessel increase.

The quantity and composition of the fluid to be relieved during a fire depend on the

total heat-input rate to the vessel under this contingency and on the duration of the

fire.

30

The total heat input rate to the vessel may be computed by means of one of the

formulas in using the appropriate values for wetted or exposed surfaces and for the

environment factor.

Once the total heat-input rate to the vessel is known, the quantity and composition of

the fluid to be relieved can be calculated, providing that enough information is available

on the composition of the fluid contained in the vessel.

If the fluid contained in the vessel is not completely specified, assumptions should be

made to obtain a realistic relief flow rate for the relief device. These assumptions may

include the following:

estimation of the latent heat of the boiling liquid and the appropriate relative

molecular mass of the fraction vaporized;

Estimation of the thermal-expansion coefficient if the relieving fluid is a liquid, a

gas or a supercritical fluid where a phase change does not occur.

2.8.2. Vapour

For pressure and temperature conditions below the critical point, the rate of vapour

formation (a measure of the rate of vapour relief required) is equal to the total rate of

heat absorption divided by the latent heat of vaporization. The vapour to be relieved is

the vapour that is in equilibrium with the liquid under conditions that exist when the

pressure-relief device is relieving at its accumulated pressure.

The latent heat and relative molecular mass values used in calculating the rate of

vaporization should pertain to the conditions that are capable of generating the

maximum vapour rate.

The vapour and liquid composition can change as vapours are released from the

system. As a result, temperature and latent-heat values can change, affecting the

required size of the pressure-relief device. On occasion, a multicomponent liquid can

be heated at a pressure and temperature that exceed the critical temperature or

pressure for one or more of the individual components. For example, vapours that are

31

physically or chemically bound in solution can be liberated from the liquid upon

heating. This is not a standard latent-heating effect but is more properly termed

degassing or dissolution. Vapour generation is determined by the rate of change in

equilibrium caused by increasing temperature.

For these and other multicomponent mixtures that have a wide boiling range, it might

be necessary to develop a time-dependent model where the total heat input to the

vessel not only causes vaporization but also raises the temperature of the remaining

liquid, keeping it at its boiling point.

An example of a time-dependent model used to calculate relief requirements for a

vessel that is exposed to fire and that contains fluids near or above the critical range.

The recommended practice of finding a relief vapor flow rate from the heat input to the

vessel and from the latent heat of liquid contained in the vessel becomes invalid near

the critical point of the fluid, where the latent heat approaches zero and the sensible

heat dominates.

If no accurate latent heat value is available for these hydrocarbons near the critical

point, a minimum value of 115 kJ/kg (50 Btu/lb.) is sometimes acceptable as an

approximation.

For fire contingencies with regard to vessels containing heavy ends (e.g. vacuum-

column bottoms), the vaporization temperature can be significantly above the

temperature at which the vessel fails. Hence, sizing should not be based on liquid

vaporization. In this case, the pressure-relief device may be sized for the products of

thermal cracking at a temperature at which the decomposition occurs.

If pressure-relieving conditions are above the critical point, the rate of vapour discharge

depends only on the rate at which the fluid expands as a result of the heat input

because a phase change does not occur.

2.8.3. Liquid

32

The hydraulic-expansion equations may be used to calculate the initial liquid relieving

rate in a liquid-filled system when the liquid is still below its boiling point. However, this

rate is valid for a very limited time, after which vapour generation becomes the

determining contributor in the sizing of the pressure-relief device.

There is an interim time period between the liquid-expansion and the boiling-vapor

relief during which it is necessary to relieve the mixtures of both phases

simultaneously, either as flashing, bubble, slug, froth or mist flow until sufficient vapor

space is available inside the vessel for phase separation. With the exception of foamy

fluids, reactive systems and narrow-flow passages (such as vessel jackets), this

mixed-phase condition.

Is usually neglected during sizing and selecting of the pressure- relief device...

Experience as well as recent work in this area] has shown

That the time required to heat a typical system from the relief-device set pressure to

the relieving conditions allows for the relief of any two-phase flow prior to reaching the

relieving conditions. As such, full disengagement of the vapour is realized at the

relieving conditions and the assumption of vapour-only venting is appropriate for relief

device sizing.

Experience has shown there is minimal impact on the discharge system for the two-

phase transition period. However, the user may consider the impact of transient two-

phase flow on the design of the downstream systems.

If a pressure-relief device is located below the liquid level of a vessel exposed to fire

conditions, the pressure-relief device should be able to pass a volume of fluid

equivalent to the volume of vapor generated by the fire.

Determination of the appropriate state of the fluid can be complicated. A typical

conservative assumption is to use bubble point liquid.

2.8.4. Mixed phase

33

Two-phase relief-device sizing is not normally required for the fire case, except for

unusually foamy materials.

In non-reactive systems subjected to an external fire, boiling occurs at or near the walls

of the vessel, commonly referred to as wall- heating. On the other hand, reactive

systems in which an external fire can result in an exothermic reaction are subject to

boiling throughout the volume of the vessel due to heat evolved from the reaction. This

is commonly referred to as volumetric heating, which results in more liquid-swell than

wall-heating and, thus, increases the potential for longer-duration two-phase relief.

Furthermore, significantly higher heat- generation rates associated with runaway

reactions result in higher vapor velocities and further potential for long-duration two-

phase flow. The Design Institute of Emergency Relief Systems concluded an intensive

research programmed to develop methods for the design of emergency relief systems

to handle runaway reactions.

Note: There are total many overpressure scenarios according to which the vendor

study to total workloads for one specific PSV. Therefore, for different PSV’s there are

different work load which is obtained from the formula according the scenario given

but we consider the most occurring scenario that is fire case.

34

CHAPTER 03

METHODOLOGY

35

3.1. Sizing Methodology

1. Calculate the relieving pressure and relieving temperatures.

2. Consider the Relieving rate required based on the governing overpressures

scenario. Relieving rates for each applicable over pressure scenario shall be

calculated. The overpressure scenario which gives the highest relieving rate is the

governing over pressure scenario.

Note: The vessel may be subjected to more than one over pressurizing condition under

different failure scenarios. For example: a low pressure separator may be subjected to

blocked discharge, gas blow by from the high pressure separator, and fire. Only one

of these failures is assumed to happen at any time. The relieving rate needs to be

calculated for each of these scenarios but relief valve size is determined for the

maximum relieving rate which will be governing overpressure scenario.

3. Identify the phase (Vapor Phase/ Liquid Phase/ Two Phase) of the relieving

fluid at relieving conditions.

4. Calculate the required orifice discharge area using equipment given in API RP

520.

5. Select orifice designation and size ( Refer API 526)

6. Calculate the actual relieving rate (rated Capacity) based on selected orifice

discharge area.

7. Calculate the relief valve upstream and downstream line sizes using the rated

capacity.

36

3.2. Calculation Procedure

3.2.2. Relieving pressure

Relieving Pressure= Set Pressure +Over Pressure

3.2.3. Determination of Over pressure:

Governing over pressure can be taken from the following chart and tables for different

cases given below.

3.2.4. Determination of type of flow:

Here in PARCO mostly subcritical flow has been noted. Sub-critical flow is flow in which

the downstream pressure (Back Pressure) ≥ Pcf

In this case the equation used to find the effective discharge area is given as:

735 ∗

Where,

A= required effective discharge area of the device, in2

W=required flow through the device, Lb/hr

KD=Effective Coefficient of discharge

Kb=0.975 when a pressure relief valve is installed with or without rupture disk in

combination.

Kb=0.62 when pressure relief valve is not installed and sizing is for a rupture disk.

Kc=Combination correction factor for Installation with a rupture disc upstream of the

pressure relief valve.

1.0, when rupture is not installed

0.9, when rupture disk is installed in combination with pressure relief valve

37

T=Relieving Temperature of the deviation of the actual gas from a perfect gas, a ratio

evaluated at inlet relieving conditions

M=Molecular weight of the gas or vapor at inlet relieving conditions.

3.2.5. Orifice Designation and size

From the table below standard orifice area and designation is selected, which should

be greater than the required orifice area.

Standard Orifice Area and Designations

Orifice Area (in2)

D

E

F

G

H

J

K

L

M

N

P

A

R

T

0.110

0.196

0.307

0.503

0.785

1.287

1.838

2.853

3.60

4.34

6.38

11.05

16.0

26.0

38

3.3. FLARE LOADS REVIEW AS PER DESIGN 100% LOADS

3.3.1. Objective:

The reason for doing flare load review is:

i. To study the method for designing flare system and its equipment by

establishing a basis.

ii. To prepare data sheet for the specification of parameters used in flare design.

To achieve this objective we have done the following things:

We selected Crude Distillation Unit U-100 for the reviewing of PSV load.

i. With the help of P&ID of each of the equipment present in CDU unit we listed

lines form sample point, PSV and other lines that were going to the common

header of the flare.

ii. With the help of engineering manual of Flare System U-915 we analyzed all

the required for the main flare system. Collected the specification of current

flare system, such as diameter, flare stack height, etc.

iii. We obtained the formula by studying Standard and Codes of American

Petroleum Institute (API) 521- Pressure-Relieving and Depressurizing System

iv. Then we calculated flare diameter, flare stack height, etc. for existing flare

system with the help of API 521 and then prepared our own data sheet for flare

which was previously not available in the engineering manuals.

v. Designing Parameters present in the engineering manual was prepared using

vendor’s method and therefore it has little difference from that we have

calculated.

39

3.4 KNOCKOUT DRUMAS PER 100% DESIGN LOAD:-

3.4.1. Objective:

The reason for doing Separation of a fluid:

iii. To study the method for separation the fluid for its component by establishing

a basis.

iv. To prepare data sheet for the specification of parameters used in knockout

drum.

To achieve this objective we have done the following things:

vi. We selected Crude Distillation Unit U-100 for the reviewing of PSV load.

vii. With the help of P&ID of each of the equipment present in CDU unit we listed



viii. After collection fluid in flare header we move the fluids in knockout drum to

separate gas and liquids after separation the gases components further move

into the flare system.

ix. We obtained the formula by studying Standard and Codes of American

Petroleum Institute (API) 521- Pressure-Relieving and Depressurizing System.

Then we calculated knockout drum diameter and length, and then prepared our

own data sheet for knockout drum which was previously not available in the

engineering manuals.

x. Designing Parameters present in the engineering manual was prepared using

vendor’s method and therefore it has little difference from that we have

calculated.

40

3.5. PRESSURE SAFETY VALVES (PSV) LOAD REVIEW AS PER DESIGN 100%

BASIS:-

3.5.1. Objective

The reason for doing the PSV load review is:

i. To verify the existing loads of the PSV.

ii. To calculate the loads and orifice area manually.

To achieve these objectives following steps were carried out:

i. We selected Crude Distillation Unit U-100 for the reviewing of PSV load.

ii. With the help of P&ID of each of the equipment present in CDU unit we listed



iii. With the help of engineering manuals of CDU U-100 we were able to find

different parameters required for the size of PSV.

iv. We studied all possible scenarios on which usually PSV’s workload is

designed.

v. Sizing of three PSV were done that were based on the scenario (FIRE) to find

the load.

vi. We obtained the formula by studying Standard and Codes of American

Petroleum Institute (API) 521- Pressure-Relieving and Depressurizing System

vii. With the help of these parameters we were able to design our own data sheet

of the existing PSV’s.

viii. Then manual calculations were carried out and parameters from the data sheet

of the engineering manual were verified and reviewed.

41

CHAPTER 04

CALCULATIONS

42

4.1. Calculation of Required Capacity for 100-PSV-011A/B

For different scenarios there is different formula for calculation of the load. Following

is calculation of load for fire scenario and respected formula has been used for PSV

load:

. √.

.

4.1.1. Data:

W=Relieving load=?

Molecular Weight=164.2

P1=Upstream relieving pressure=444.053

Tw= vessel wall temperature= 1560 degR

T1= Gas temperature at upstream relieving pressure=1159.8 degR

4.1.2. Solution:

Calculating A’ (discharge area)

∗ ′

′1 /

′

Now we have calculated F’ which is environmental factor from the following formula:

0.1406∗

1 .

1 .

0.1406320.030 ∗ 1.0

1560 1159.8 .

1159.8 .

0.008183

Placing this value in discharge area formula:

43

′1.908 444.053 .

0.008183

4913 2

Placing the above value of A’ in load formula:

0.1406√164.2 ∗ 320.034913 1560 1156 .

1156 .

66789.9098 /

Converting into kg/hr:

. /

44

4.1.3. PSV Orifice Area Calculation

Unit name: Crude Distillation Unit (U-100)

Tag: 100-PSV-011A/B

Formula Used:

4.1.3.1. Data:

W = Work load (Req. Capacity) = 30362 kg/hr = 66796.4 lb/hr

Kd= 0.975

Kc = Combination correction factor= 1.0

Kb = 1.0

Cp/Cv = 1.04

Compressibility Factor = Z= 1.0

Relieving Temperature = 371 degC = 1159.8 degR

P1= Upstream Relieving pressure (To be calculated)

C=320.030 (From API-520)

Set pressure = 25 kg/cm2G

Overpressure = 21% of Set pressure

Molecular weight = M = 164.2

4.1.3.2. Solution

Calculating Relieving Pressure (P1):

∗ %

1 25 0.21 25

1 30.25 / 2

Converting it into psia

1 444.053 / 2.

45

Substituting the values in the formula

66796.4320.030 ∗ 0.975 ∗ 1.0 ∗ 1.0 ∗ 444.053

1159.8 ∗ 1.0164.2

A 1.32inch2

Converting A from inch2 to cm2:

8.54 2 .

46

4.2. Calculation of Required Capacity for 100-PSV-013



load:

. √.

.

4.2.1. Data:

W=Relieving load=?


P1=Upstream relieving pressure=440.619 psia



4.2.2. Solution:


∗ ′

′1 /

′

Now we have calculated F’ which is environmental factor from the following

formula:

0.1406∗

1 .

1 .

0.1406320.030 ∗ 1.0

1560 1159.8 .

1159.8 .

0.008183


47

′2.233 440.619 .

0.008183

5720.367 2


0.1406√233 ∗ 440.6195720.367 1560 1159.8 .

1159.8 .

137431.2374 /

Converting it into Kilogram per hour

. /

48

4.2.3. PSV load Calculation


Tag: 100-PSV-013

Formula Used:

4.2.3.1. Data:


Kd= 0.975


Kb = 1.0

Cp/Cv = 1.04




C=320.030 (From API-520)

Set pressure = 24.8 kg/cm2G


Molecular weight = M = 233

4.2.3.2. Solution


∗

1 24.8 ∗ 0.21 24.8

1 30.008 / 2


1 425.919 / 2.

49


136833320.030 ∗ 0.975 ∗ 1.0 ∗ 1.0 ∗ 425.919

1159.8 ∗ 1.0233

A 2.29inch2


14.82 2 .

50

4.3. Calculation of Required Capacity for 100-PSV-015A/B



load:

. √.

.

4.3.1. Data:

W=Relieving load=?





4.3.2. Solution:


∗ ′

′1 /

′


0.1406∗

1 .

1 .

0.1406320.030 ∗ 1.0

1560 1260.6 .

1260.6 .

0.005269


′2.396 440.619 .

0.005269

51

9517.42 2


0.1406√233 ∗ 440.6193517.42 1560 1260.6 .

1260.6 .

144995.898 /


. /

52



Tag: 100-PSV-015A/B

Formula Used:

4.3.3.1 Data:


Kd= 0.975


Kb = 1.0

Cp/Cv = 1.04




C=320.030 (From API-520)




4.3.3.2. Solution


∗

1 24.8 ∗ 0.21 24.8

1 30.008 / 2


1 425.919 / 2.

53


140850320.030 ∗ 0.975 ∗ 1.0 ∗ 1.0 ∗ 425.919

1260 ∗ 1.0233

A 2.46inch2


15.9 2 .

54




load:

. √.

.

4.4.1. Data:

W=Relieving load=?


P1=Upstream relieving pressure=444.053



4.4.2. Solution:


∗ ′

′1 /

′


0.1406∗

1 .

1 .

0.1406320.030 ∗ 1.0

1560 1159.8 .

1159.8 .

0.008183


55

′1.908 444.053 .

0.008183

4913 2


0.1406√164.2 ∗ 320.034913 1560 1156 .

1156 .

66789.9098 /

Converting into kg/hr:

. /

56

4.4.2.3. PSV Orifice Area Calculation


Tag: 100-PSV-016

Formula Used:

4.4.2.3.1. Data:


Kd= 0.975


Kb = 1.0

Cp/Cv = 1.04




C=320.030 (From API-520)

Set pressure = 25 kg/cm2G


Molecular weight = M = 164.2

4.4.2.3.1. Solution


∗ %

1 25 0.21 25

1 30.25 / 2


1 444.053 / 2.

57


66796.4320.030 ∗ 0.975 ∗ 1.0 ∗ 1.0 ∗ 444.053

1159.8 ∗ 1.0164.2

A 1.32inch2


8.54 2 .

58




load:

. √.

.

4.5.1. Data:

W=Relieving load=?





4.5.2. Solution:


∗ ′

′1 /

′


0.1406∗

1 .

1 .

0.1406320.030 ∗ 1.0

1560 1159.8 .

1159.8 .

0.008183


′2.233 440.619 .

0.008183

59

5720.367 2


0.1406√233 ∗ 440.6195720.367 1560 1159.8 .

1159.8 .

137431.2374 /


. /

60



Tag: 100-PSV-017

Formula Used:

4.5.3.1. Data:


KD= 0.975


Kb = 1.0

Cp/Cv = 1.04




C=320.030 (From API-520)




4.5.3.2. Solution


∗

1 24.8 ∗ 0.21 24.8

1 30.008 / 2


1 425.919 / 2.

61


136833320.030 ∗ 0.975 ∗ 1.0 ∗ 1.0 ∗ 425.919

1159.8 ∗ 1.0233

A 2.29inch2


14.82 2 .

62




load:

. √.

.

4.6.1. Data:

W=Relieving load=?





4.6.2. Solution:


∗ ′

′1 /

′


0.1406∗

1 .

1 .

0.1406320.030 ∗ 1.0

1560 1260.6 .

1260.6 .

0.005269


′2.396 440.619 .

0.005269

63

9517.42 2


0.1406√233 ∗ 440.6193517.42 1560 1260.6 .

1260.6 .

144995.898 /


. /

64



Tag: 100-PSV-018

Formula Used:

4.6.3.1. Data:


Kd= 0.975


Kb = 1.0

Cp/Cv = 1.04




C=320.030 (From API-520)




4.6.3.2. Solution


∗

1 24.8 ∗ 0.21 24.8

1 30.008 / 2


1 425.919 / 2.

65


140850320.030 ∗ 0.975 ∗ 1.0 ∗ 1.0 ∗ 425.919

1260 ∗ 1.0233

A 2.46inch2


15.9 2 .

66

Knockout Drum Sizing Methodology

Step 1: Calculate the Reynold’s number

μ

Where,

D = Diameter of particle

ρv= Density of vapour

ρL=Density of liquid

µ= Viscosity of the gas

Step 2: Calculate Terminal Velocity

Where,

D = Diameter of the particle

ρL= Density of liquid

ρv = Density of vapour

C = Drag-coefficient

g = Acceleration due to gravity

67

Step 3: Calculate diameter and area of the vessel

Where,

A= Area of the Vessel

Q= Volumetric Flow Rate

Vt= Terminal Velocity

Where,

D= Diameter of the vessel

A= Area of the vessel

Step 4: Calculate the Length of the Drum

L/D = 3.25

Where,

L/D= Slenderness Ratio

L= Length of the Drum

D= Diameter of the Drum

Note: Slenderness ratio is taken between 2 to 5

68

FLARE SIZING METHODOLOGY

Step 1: Calculate Flare Diameter

. .

Where,

Ma= Mach number (0.2 to 0.5)

q= Mass Flow Rate kg/hr

T= Average Temperature (k)

M= Molecular weight

Z= Compressibility Factor

Step 2: Distance from the flare center to the boundary

Where,

F= Fraction of heat radiated

Q= Heat liberated (kW)

K= Maximum allowable radiation (kW/m2)

Τ= Fraction of K transmitted through the atmosphere

Step 3: Calculate Lower Explosive Limit Concentration

∞ ∞

69

Where,

Uj= Flare Tip Velocity (m/sec)

U∞=wind Velocity (m/sec)

Md=20

Mj=36

Step 4: Calculate the parameter for wind velocity (dj.R)

.∞

∞.

Where,

Dj=Flare Diameter m

Mj= Average Molecular weight

T∞=Temperature of Wind k

Tj=Average Temperature k

Step 5: Find out the Vertical Distance From the flare header to flare center XC from

the graph.

Step 6: Calculate the flare stack height

Where,

D= distance from the flare center.

70

CHAPTER 05

DATA SHEETS

No 15/16

Quanttiy 1

TAGNo. 100‐PSV‐011A/B

Service 100‐V12

KEROSCENECOLECER

FullSemiNozzle FullSafetyOrRelief SafetyType ConveNtionalBonnetType CloseSize in out 4" 6"RatingorScrewed 300#RF 150#RFFacing SMOOTHMaterialBody&Bonnet CARBONSTEELSeat&Disc 316S.SResillentSeatSealGuide&Rings MTRSTDSprings MTRSTDBellows 316LS.SOPTIONCap:ScrewedorBolted BOLTLever:PlainedOrOacked PACKED

YESBASIS Code ASME

Case FIREFluid H.CMol.Wt. 73.4Sp,Gr. ‐Ope.Press kg/cm2G 0.4Des.Temp degC 137Des.Press kg/cm2G 3.9/FVSetpress kg/cm2G 2.67RelievingTemp T1 degC 137 738.6 degR

VesselWallTemp TW degC 593.333 1560 degRBackPressure CONST. kg/cm2G 0.07

Variable kg/cm2G 0.31Total kg/cm2G 0.38

CoficentDischarge KOverPress. % 21OverPress. FactorComp.Factor 0.97Cp/Cv 1.06Visocsity cP 0.02BaromtoricPressure kg/cm2A 1.03Dischargeto FLHeaderReleivingPressure P1 kg/cm2 3.2307 60.5550051 psiaEnvironmentalFactor F' 0.02629062ExposedSurfaceArea A' m2 125.662596 1352.66519 ft2

RelievingLoad W kg/hr 12690.4679 27919.0293 lb/hr

Orifice Cal. cm2 29.7827561 4.61633643 inches2

Sel. cm2 41.161DessignOrificeletter P

LineNo. IN OUT FL‐1403 FL‐1401LineClass A1A1 A1A1

LineShchedule

P&IDNo D‐XXX‐1225‐XXX 100‐134

SeeNOTE(SheetNO.XXX) A,B,V

OPERATINGCONDITIONS

OTHERS

REMARKS

CONSTRUCTION

TestGag

DAWOODUNIVERSITYOFENGINEENRING&TECHNOLOGYDepartmentOfChemicalEngineeringFINALYEARPROJECTSPECIFICATION

SAFETYRELIEFVALVES(CDU)

GENERAL

71

No 18

Quanttiy 1

TAGNo. 100‐PSV‐013

Service 100‐V14

BLOWCASEOVERHEAD

LINEFullSemiNozzle FullSafetyOrRelief SafetyType ConveNtionalBonnetType CloseSize in out 1‐1/2" 3"RatingorScrewed 300#RF 150#RFFacing SMOOTHMaterialBody&Bonnet CARBONSTEELSeat&Disc 316S.SResillentSeatSealGuide&Rings MTRSTDSprings MTRSTDBellows ‐OPTIONCap:ScrewedorBolted BOLTLever:PlainedOrOacked PACKED

YESBASIS Code ASME




CoficentDischarge KOverPress. % 21OverPress. FactorComp.Factor 0.97Cp/Cv 1.09Visocsity cP 0.02BaromtoricPressure kg/cm2A 1.03Dischargeto FLHeaderReleivingPressure P1 psig 10.043 157.245521 psiaEnvironmentalFactor F' 0.02266078ExposedSurfaceArea A' m2 16.0906813 173.204319 ft2



Sel. cm2 3.245DessignOrificeletter G

LineNo. IN OUT PG‐3503 FL‐3503LineClass A1A1 A1A1

LineShchedule

P&IDNo D‐XXX‐1225‐XXX 100‐135SeeNOTE(SheetNO.XXX) A



GENERAL

OTHERS

OPERATINGCONDITIONS

REMARKS

CONSTRUCTION

TestGag

72

No 21

Quanttiy 1


Service 100‐V15

FUELGASKODRUM

OVERHEADFullSemiNozzle FullSafetyOrRelief SafetyType ConveNtionalBonnetType CloseSize in out 1" 2"RatingorScrewed 300#RF 150#RFFacing SMOOTHMaterialBody&Bonnet CARBONSTEELSeat&Disc 316S.SResillentSeatSealGuide&Rings MTRSTDSprings MTRSTDBellows ‐OPTIONCap:ScrewedorBolted BOLTLever:PlainedOrOacked PACKED

YESBASIS Code ASME

Case FIREFluid H.CMol.Wt. 19.3Sp,Gr. ‐Ope.Press kg/cm2G 5.7Des.Temp degC 183Des.Press kg/cm2G 8.3Setpress kg/cm2G 8.3RelievingTemp T1 degC 183 821.4 degRVesselWallTemp TW degC 593.333 1560 degRBackPressure CONST. kg/cm2G 0.07


CoficentDischarge KOverPress. % 21OverPress. FactorComp.Factor 1Cp/Cv 1.3Visocsity cP 0.02BaromtoricPressure kg/cm2A 1.03Dischargeto FLHeaderReleivingPressure P1 kg/cm2 10.043 157.245521 psiaEnvironmentalFactor F' 0.0214831ExposedSurfaceArea A' m2 4.17540503 44.9451564 ft2



Sel. cm2 0.709DessignOrificeletter D

LineNo. IN OUT FG‐3708 FL‐3702LineClass A1A1 A1A1LineShcheduleP&IDNo D‐XXX‐1225‐XXX 100‐137SeeNOTE(SheetNO.XXX) A



GENERAL

OPERATINGCONDITIONS

OTHERS

REMARKS

CONSTRUCTION

TestGag

73

No 1

Quanttiy 1


Service 100‐V1

KEROSCENECOLECER

FullSemiNozzle FullSafetyOrRelief SafetyType ConveNtionalBonnetType CloseSize in out 3" 4"RatingorScrewed 300#RF 150#RFFacing SMOOTHMaterialBody&Bonnet CARBONSTEELSeat&Disc 316S.SResillentSeatSealGuide&Rings MTRSTDSprings MTRSTDBellows ‐OPTIONCap:ScrewedorBolted BOLTLever:PlainedOrOacked PACKED

YESBASIS Code ASME

Case FIREFluid H.CMol.Wt. 164.2Sp,Gr. ‐Ope.Press kg/cm2G 14.4Des.Temp degC 371/40Des.Press kg/cm2G 26/FVSetpress kg/cm2G 25RelievingTemp T1 degC 371 1159.8 degR



CoficentDischarge KOverPress. % 21OverPress. FactorComp.Factor 1Cp/Cv 1.04Visocsity cP 0.02BaromtoricPressure kg/cm2A 1.03Dischargeto FLHeaderReleivingPressure P1 kg/cm2 30.25 444.05398 psiaEnvironmentalFactor F' 0.00797909ExposedSurfaceArea A' m2 314.289151 3383.09097 ft2RelievingLoad W kg/hr 31134.9327 68496.852 lb/hrOrifice Cal. cm2 8.47640985 1.31384615 inches2

Sel. cm2 11.858DessignOrificeletter K

LineNo. IN OUT FL‐1403 FL‐1401LineClass A2A1 A1A1LineShcheduleP&IDNo D‐XXX‐1225‐XXX 100‐114

SeeNOTE(SheetNO.XXX) A,F,K,U

OPERATINGCONDITIONS

OTHERS

CONSTRUCTION

TestGag

REMARKS



GENERAL

74

No 1

Quanttiy 1


Service 100‐V1

KEROSCENECOLECER


YESBASIS Code ASME

Case FIREFluid H.CMol.Wt. 233Sp,Gr. ‐Ope.Press kg/cm2G 7.5Des.Temp degC 371/50Des.Press kg/cm2G 26/FVSetpress kg/cm2G 24.8RelievingTemp T1 degC 371 1159.8 degR



CoficentDischarge KOverPress. % 21OverPress. FactorComp.Factor 1Cp/Cv 1.04Visocsity cP 0.02BaromtoricPressure kg/cm2A 1.03Dischargeto FLHeaderReleivingPressure P1 Kg/cm2 30.008 440.619148 psiaEnvironmentalFactor F 0.00797909ExposedSurfaceArea A' m2 542.559079 5840.24842 ft2





LineShchedule





GENERAL

OPERATINGCONDITIONS

CONSTRUCTION

TestGag

OTHERS

REMARKS

75

No 1

Quanttiy 1


Service 100‐V1

KEROSCENECOLECER


YESBASIS Code ASME

Case FIREFluid H.CMol.Wt. 233Sp,Gr. ‐Ope.Press kg/cm2G 14.4Des.Temp degC 427Des.Press kg/cm2G 26/FVSetpress kg/cm2G 24.8RelievingTemp T1 degC 427 1260.6 degR


Variable kg/cm2G 1.22

Total kg/cm2G 1.29CoficentDischarge KOverPress. % 21OverPress. FactorComp.Factor 1Cp/Cv 1.04Visocsity cP 0.02BaromtoricPressure kg/cm2A 1.03Dischargeto FLHeaderReleivingPressure P1 kg/cm2 30.008 440.619148 psia

EnvironmntalFactor F' 0.00525864ExposedSurfaceArea A' m2 882.57287 9500.24618 ft2





LineShchedule

P&IDNo D‐XXX‐1225‐XXX 100‐114SeeNOTE(SheetNO.XXX) A,F,K,U



GENERAL

OPERATINGCONDITIONS

OTHERS

CONSTRUCTION

TestGag

REMARKS

76

No 15/16

Quanttiy 1


Service 100‐V12

KEROSCENECOLECER

FullSemiNozzle FullSafetyOrRelief SafetyType ConveNtionalBonnetType CloseSize in out 4" 6"RatingorScrewed 300#RF 150#RFFacing SMOOTHMaterialBody&Bonnet CARBONSTEELSeat&Disc 316S.SResillentSeatSealGuide&Rings MTRSTDSprings MTRSTDBellows 316LS.SOPTIONCap:ScrewedorBolted BOLTLever:PlainedOrOacked PACKED

YESBASIS Code ASME





RelievingLoad W kg/hr 15228.5614 33502.8352 lb/hrOrifice Cal. cm2 35.7393073 5.53960371 inches2

Sel. cm2 41.161DessignOrificeletter P

LineNo. IN OUT FL‐1403 FL‐1401LineClass A1A1 A1A1LineShcheduleP&IDNo D‐XXX‐1225‐XXX 100‐134SeeNOTE(SheetNO.XXX) A,B,V



GENERAL

OPERATINGCONDITIONS

OTHERS

CONSTRUCTION

TestGag

REMARKS

77

No 18

Quanttiy 1


Service 100‐V14

BLOWCASEOVERHEAD

LINEFullSemiNozzle FullSafetyOrRelief SafetyType ConveNtionalBonnetType CloseSize in out 1‐1/2" 3"RatingorScrewed 300#RF 150#RFFacing SMOOTHMaterialBody&Bonnet CARBONSTEELSeat&Disc 316S.SResillentSeatSealGuide&Rings MTRSTDSprings MTRSTDBellows ‐OPTIONCap:ScrewedorBolted BOLTLever:PlainedOrOacked PACKED

YESBASIS Code ASME


VesselWallTemp TW degC 593.333 1560 degRBACKPRESSURE CONST. kg/cm2G 0.07





Sel. cm2 3.245DessignOrificeletter G

LineNo. IN OUT PG‐3503 FL‐3503LineClass A1A1 A1A1

LineShchedule

P&IDNo D‐XXX‐1225‐XXX 100‐135SeeNOTE(SheetNO.XXX) A

OPERATINGCONDITIONS

OTHERS

REMARKS

CONSTRUCTION

TestGag



GENERAL

78

No 21

Quanttiy 1


Service 100‐V15

FUELGASKODRUM

OVERHEADFullSemiNozzle FullSafetyOrRelief SafetyType ConveNtionalBonnetType CloseSize in out 1" 2"RatingorScrewed 300#RF 150#RFFacing SMOOTHMaterialBody&Bonnet CARBONSTEELSeat&Disc 316S.SResillentSeatSealGuide&Rings MTRSTDSprings MTRSTDBellows ‐OPTIONCap:ScrewedorBolted BOLTLever:PlainedOrOacked PACKED

YESBASIS Code ASME

Case FIREFluid H.CMol.Wt. 19.3Sp,Gr. ‐Ope.Press kg/cm2G 5.7Des.Temp degC 183Des.Press kg/cm2G 8.3Setpress kg/cm2G 8.3RelievingTemp T1 degC 183 821.4 degR



CoficentDischarge KOverPress. % 21OverPress. FactorComp.Factor 1Cp/Cv 1.3Visocsity cP 0.02BaromtoricPressure kg/cm2A 1.03Dischargeto FLHeaderReleivingPressure P1 kg/cm2 10.043 157.245521 psiaEnvironmentalFactor F' 0.0214831ExposedSurfaceArea A' m2 4.17540503 44.9451564 ft2



Sel. cm2 0.709DessignOrificeletter D

LineNo. IN OUT FG‐3708 FL‐3702LineClass A1A1 A1A1

LineShcheduleP&IDNo D‐XXX‐1225‐XXX 100‐137SeeNOTE(SheetNO.XXX) A

OPERATINGCONDITIONS

OTHERS

REMARKS

CONSTRUCTION

TestGag



GENERAL

79

No 1

Quanttiy 1TAGNo. 100‐PSV‐016

Service 100‐V1

KEROSCENECOLECER


YESBASIS Code ASME

Case FIREFluid H.CMol.Wt. 164.2Sp,Gr. ‐Ope.Press kg/cm2G 14.4Des.Temp degC 371/40Des.Press kg/cm2G 26/FVSetpress kg/cm2G 25RelievingTemp T1 degC 371 1159.8 degRVesselWallTemp TW degC 593.333 1560 degRBACKPRESSURE CONST. kg/cm2G 0.07


CoficentDischarge KOverPress. % 21OverPress. FactorComp.Factor 1Cp/Cv 1.04Visocsity cP 0.02BaromtoricPressure kg/cm2A 1.03Dischargeto FLHeaderReleivingPressure P1 psig 30.25 429.35398 psiaEnvironmentalFactor F 0.00797909

ExposedSurfaceArea A' m2 309.043244 3326.62264 ft2


Orifice Cal. cm2 12.2060302 1.89193846 inches2Sel. cm2 11.858DessignOrificeletter K


LineShchedule



OPERATINGCONDITIONS

OTHERS

REMARKS

CONSTRUCTION

TestGag

DAWOODUNIVERSITYOFENGINEENRING&TECHNOLOGY

DepartmentOfChemicalEngineeringFINALYEARPROJECTSPECIFICATION

SAFETYRELIEFVALVESFOR120%LOAD(CDU)

GENERAL

80

No 1

Quanttiy 1TAGNo. 100‐PSV‐017

Service 100‐V1

KEROSCENECOLECER


YESBASIS Code ASME

Case FIREFluid H.CMol.Wt. 233Sp,Gr. ‐Ope.Press kg/cm2G 7.5Des.Temp degC 371/50Des.Press kg/cm2G 26/FVSetpress kg/cm2G 24.8RelievingTemp T1 degC 371 1159.8 degR



CoficentDischarge KOverPress. % 21OverPress. FactorComp.Factor 1Cp/Cv 1.04Visocsity cP 0.02BaromtoricPressure kg/cm2A 1.03Dischargeto FLHeaderReleivingPressure P1 kg/cm2 30.008 440.619148 psiaEnvironmentalFactor F' 0.00797909

ExposedSurfaceArea A' m2 542.559079 5840.24842 ft2


Orifice Cal. cm2 17.6277563 2.73230769 inches2Sel. cm2 11.858DessignOrificeletter K


LineShcheduleP&IDNo D‐XXX‐1225‐XXX 100‐114SeeNOTE(SheetNO.XXX) A,F,K,U

DAWOODUNIVERSITYOFENGINEENRING&TECHNOLOGY

DepartmentOfChemicalEngineeringFINALYEARPROJECTSPECIFICATION

SAFETYRELIEFVALVES120%LOAD(CDU)

GENERAL

OPERATINGCONDITIONS

OTHERS

REMARKS

CONSTRUCTION

TestGag

81

No 1

Quanttiy 1


Service 100‐V1

KEROSCENECOLECER


YESBASIS Code ASME

Case FIREFluid H.CMol.Wt. 233Sp,Gr. ‐Ope.Press kg/cm2G 14.4Des.Temp degC 427Des.Press kg/cm2G 26/FVSetpress kg/cm2G 24.8RelievingTemp T1 degC 427 1260.6 degR


Variable kg/cm2G 1.22

Total kg/cm2G 1.29CoficentDischarge KOverPress. % 21OverPress. FactorComp.Factor 1Cp/Cv 1.04Visocsity cP 0.02BaromtoricPressure kg/cm2A 1.03Dischargeto FLHeaderReleivingPressure P1 kg/cm2 30.008 425.919148 psiaEnvironmentalFactor F' 0.00525864ExposedSurfaceArea A' m2 867.725724 9340.4276 ft2


Orifice Cal. cm2 18.8982252 2.92923077 in2



LineShcheduleP&IDNo D‐XXX‐1225‐XXX 100‐114SeeNOTE(SheetNO.XXX) A,F,K,U


SAFETYRELIEFVALVES120%LOAD(CDU)

GENERAL

OPERATINGCONDITIONS

OTHERS

REMARKS

CONSTRUCTION

TestGag

82

S.NoParamters Symbols Value Units

1 Calcuation for Dia & Length of KNockOut drum:

Volume of the vessel V 471.2 m3

Design Pressure Pd 3.5 kg/cm2G

Design Temperature Td 338 degC

Operating Pressure Po 0.5/0.1 kg/cm2G

Operating Temperature To 192/38 degC

Specific Gravity Sp.gr 0.9

2 Reynold Number

Diameter of the Particle D 0.0006 m

Density of the liquid ρl 900 kg/m3

Density of the vapor ρv 33 kg/m3

Viscosity of the gas µ 0.000012 kg/ms

Reynold Number C(Re)2 5.58E+11

3 Drop Out Velocity

Acceleration due to gravity g 9.8 m/sec2

Diameter of the Particle D 6.00E‐04 m



Drag‐Coefficient C 0.6 From C(Re)2

Drop Out Velocity Vt 0.585915 m/sec

4 Volumetric Flow Rate Conversion

Volumetric Flow Rate Q 51.26667 kg/sec

Q 2.712522 m3/sec

5 Dia & Area of the vessel

Volumetric Flow Rate Q 2.712522 m3/sec


Area of vessel A 4.629545 m2

Dimater of the vessel * D 2.427706 m 2427.71 mm

7 Length of the drum

Dimater of the vessel D 2.427706 m

Length of the drum L 7.890044 m 7890.04 mm


KNOCKOUT DRUM 100%

83

S.No Paramters Symbols Value Units








2 Reynold Number






3 Drop Out Velocity









Q 13.96238 m3/sec










KNOCKOUT DRUM 100%

84









2 Reynold Number






3 Drop Out Velocity









Q 3.255026 m3/sec










KNOCKOUT DRUM 120%

85









2 Reynold Number






3 Drop Out Velocity









Q 16.75485 m3/sec










KNOCKOUT DRUM 120%

86

S.No PARAMTERS SYMBOLS VALUE UNITS

1 Calculation OF flare Diameter

Mech No. Ma 0.48 ‐

Pressure P2 108 kPaCompressibility Factor Z 1 ‐Molecular Weight M 79.21 ‐Temperature T 482 KMass flow rate q 184560 kg/hrDiameter D 0.53 mHeat Liberated= Q 2.28E+06 kW

2 Calculation for flare stack hieghtFraction of heat liberated F 0.3 no unitHeat Liberated Q 2.28E+06 kWMax. Allowable Radiation K 9.46 kW/m2Fraction of K transmitted τ 1 no unitthrough the atmosphereDistance From the flame Center D 75.811097 mto the grade level boundary

3 Calcualtion of flare distortion caused by wind velociyMas Flow Rate q 184560 kg/hrTemperature T 482 KMol. Wt M 79.21 ‐

Vapor Volume fowrate qvap 25.60 m3/s4 Flare Tip Velocity

Temperature T 482 KMol. Wt M 36 ‐

Flare Tip Velocity Uj 160.18002 m/sec

5 Parameter for Jet Thrust and Wind Thrust (dj.R )

Flare Diameter dj 0.53 mMolecular Weight M 79.21 ‐Temperature T 482 degK


Wind Velocity Uά 8.94 m/sec

Temperature of wind Tά 289 degK

Jet Thrust and Wind Thrust (dj.R ) 65.764352 m

6 Lower Explosive limit Concentration Parameter for the Flare gas CLMolecular Weight of Wind Mw 29 ‐



Concentration Limit C' 0.021 ‐Molecular weight M 36 ‐

LEL Concentration Parameter CL 0.4670836 ‐

for the Flare gas7 Flare Stack Height

Distnace From the flare Center D 75.811097 m

Horizontal distnace from the Xc 50 m

flare stack to flame center.

Vertical Distance from the Yc 60 m

stack to the flare center.

Flare stack height Hf 15.811097 m


FLARE SYSTEM DATA SHEET 100% LOAD

87






4 Flare Tip VelocityTemperature T 482 KMol. Wt M 36 ‐





















88

S.No PARAMTERS SYMBOLS VALUE UNITS1 Calculation OF flare Diameter




4 Flare Tip VelocityTemperature T 482 KMol. Wt M 36 ‐




















FINAL SYSTEM DATA SHEET 120% LOAD


89






3 Calcualtion of flare distortion caused by wind velociyMas Flow Rate q 1140000 kg/hrTemperature T 482 KMol. Wt M 79.21 ‐

Vapor Volume fowrate qvap 158.11 m3/s4 Flare Tip Velocity

Temperature T 482 KMol. Wt M 36 ‐






















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PROCESS FLOW DIAGRAM OF FLARE

SYSTEM

SOFTWARE USED:

Name: ASPEN FlareNet

Version: 2006

Simulation Type: Steady State Simulation

PROJECT TITLE:

FLARE DESIGN FOR EVALUATION OF AN

EXISTING FLARE SYSTEM TO HANDLE HIGHER

LOADS THROUGH STEADY STATE SIMULATION

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CONCLUSION:

Flare is an important asset for the refinery to accomplish the global mission for

safer environment. The availability of a flare is absolutely necessary in oil and gas

production operations. It ensures that safe disposal of the hydrocarbon gas

inventory in the process installation is possible in emergency and shut down

situations.

If a refinery is looking forward to increase its production capacity or wanted to add

another unit to the process then it’s mandatory to go through current refinery safety

system and flaring system, so it can be assured which equipment can and cannot

handle the new load according to the changes made in the process.

By carrying out calculation we can conclude this if production capacity of refinery

is increased then the pressure safety valves of different units with in the premises

of the refinery needs to changed due to change in orifice area and there would be

increase in flare length also therefore revamping of most equipment of the plant

would be required.

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RECOMMENDATIONS

These are the following recommendation; we need to focus on it.

Steady state simulation modeling to support the relief valves sizing

calculations.

Modifications to existing relief valves (e.g. increasing orifice sizes), flare

stack height, knockout drum.

Changing the dia of tail pipe length for PSV’s.

APPENDIX

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APPENDIX

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APPENDIX

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References

Following are the names of the API, manuals and books used or considered for the

making of this report.

API Names:

i. API 520 Part 1 – Sizing, Selection and Installation of pressure Relieving

Devices in Refineries.

ii. API RP 521 – Pressure-Relieving and Depressurizing System.

iii. API 526 – Flanged Steel Relief Valves.

iv. API RP 14 E – Recommended Practice for Design and Installation of Offshore

Production Platform Piping Systems.

v. API 537 – General Flare Design, Sizing.

vi. API 12 – Specification for Oil and Gas Separators.

PARCO manuals:

vii. JCG Engineering Manual PARCO Refinery of Crude Distillation Unit (U-100).

viii. JCG Engineering Manual PARCO Refinery of Flare System (U-915).

ix. JCG Operating Manual PARCO Refinery of Crude Distillation Unit (U-100).

x. JCG Operating Manual PARCO Refinery of Flare System (U-915).

xi. PARCO Refinery Training & Internee Manuals by Process Department.

Chemical Engineering Books:

xii. Unit Operation of Chemical Engineering – By McCabe Smith.

xiii. Rules Of thumb for Chemical Engineering – By Hail

xiv. Chemical Engineering Calculation – By A Asokan

xv. Perry’s Chemical Engineer’s Handbook – By Perry’s & Green

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