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.

Table of Contents

1. CHAPTER 01: INTRODUCTION………………………………………………………...……01
1.1 The phenomena of Flaring…………………………………………………………………………………………02
1.2.1. Types of Flare……………………………………………………………………………………...…….02
1.2.2. Vertical………………………………………………………………………………………………..……02
1.2.3. Horizontal Flare………………………………………………………………………………..……….04
1.2.4. Smokeless and Non‐smokeless flares……………………………………………...…………..04
1.3. Major Components for a flare system……………………………………………………………...…………05
1.4. REFINERY COMMON FLARE SYSTEM………………………………………………………………....……..06
1.4.1. Main flare system………………………………………………………………………………..……..06
2. CHAPTER 2: RELIEF VALVE…………………………………………………………………08
2.1. Introduction…………………………………………………………………………………………………...………09
2.2. Function of Relief Valves……………………………………………………………………………………..……09
2.3 Sizing and set pressure………………………………………………………………………………………….…..09
2.4 Types of Relief Valves………………………………………………………………………………………………..10
2.4.1. Conventional relief valves…………………………………………………………………..………10
2.4.2. Balanced Bellow Relief Valves…………………………………………………….………………11
2.4.3. Pilot Operated Relief valves……………………………………………………………………....12
2.4.4. Rupture disk.…………………………………………………………………………………………..…13
2.4.4.1Rupture disk in combination with pressure relief devices………………..13
2.5. Size and Length of Inlet Piping to Pressure‐Relief Valves…………………………………………….13
2.6. Potentials for overpressure………………………………………………………………………………..……..14
2.6.1. General………………………………………………………………………………………………………14
2.6.2. Overpressure Scenarios………………………………………………………………………….….15

Table of Contents

2.6.2.1. Fire………………………………………………………………………………………….…15
2.6.2.2. Blocked Discharge…………………………………………………………………….…15
2.6.2.3. Hydraulic expansion………………………………………………...……………….…16
2.6.2.4. Control Valve Failure…………………………………………………………….……..17
2.6.2.5. Gas Blow By………………………………………………………………………...………17
2.6.2.6. Tube Rupture…………………………………………………………………………...…18
2.6.2.7. Utility Failure………………………………………………………………………………18
2.6.2.6.1. Loss of cooling water…………………………………………….……….18
2.6.2.6.1. Loss of instrument air…………………………………………..………..19
2.6.2.8. Pressure surges………………………………………………………………….……….19
2.6.3. Determination of individual relieving rates………………………………………………..……………21
2.6.3.1. Principal sources of overpressure………………………………………………...……………..21
2.6.3.2. Effects of pressure, temperature, and composition………………………………………24
2.6.3.3. Effect of operator response…………………………………………………………………………25
2.6.3.4. Outlet control devices……………………………………………………………………………...…26
2.6.3.5. Special capacity considerations……………………………………………………………..……26
2.6.3.6. Piping design considerations for gas breakthrough………………………………………27
2.6.3.7. Sizing and set pressure…………………………………………………………………………….…27
2.7. Fire relief loads………………………………………………………………………………………………………..28
2.7.1. General…………………………………………………………………………………………….……28
2.8. Fluids to be relieved…………………………………………………………………………………………..……..29
2.8.1. General………………………………………………………………………………….…………..…..29
2.8.2. Vapour…………………………………………………………………………………………………30
2.8.3. Liquid……………………………………………………………………………………………...…….31
2.8.4. Mixed phase………………………………………………………………………………………….………………32

Table of Contents

3. CHAPTER 03: METHODOLGOY………………………………………………………………………34
3.1. Sizing methodology..................................................................................................................................…...35
3.2 Calculation Procedure……………………………………………………………………………………………….36
3.3 FLARE LOADS REVIEW AS PER DESIGN 100% LOADS…………………………………………………38
3.3.1. Objective…………………………………………………………….…………………………………38
3.5. PRESSURE SAFETY VALVES (PSV) LOAD REVIEW AS PER DESIGN 100% BASIS…………..39
3.5.1 Objective……………………………………………………………………………………………….39

4. CHAPTER 04: CALCULTIONS…………………………………………………………………………..………41
4.1. Calculation of Required Capacity for 100‐PSV‐011A/B…………………………….……..42
4.2 Calculation of Required Capacity for 100‐PSV‐013…………………………………….…….46
4.3. Calculation of Required Capacity for 100‐PSV‐015A/B…………………………..………50
4.4. Calculation of Required Capacity for 100‐PSV‐016………………………………………….54
4.5. Calculation of Required Capacity for 100‐PSV‐017….……………………….…………….58
4.6. Calculation of Required Capacity for 100‐PSV‐018……………………………..…………..62
4.7. Knock out Drum Sizing…………………………………………………………………………………66
4.8. Flare Sizing Methodology…………………………………………………………………………….68
5. CHAPTER 05: DATA SHEETS………………………………………………..………………………..70
6. CHAPTER 06: PROCESS FLOW DIAGRAM OF SIMULATION……………………………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

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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

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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

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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

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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

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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.

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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

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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

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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

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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

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(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:-

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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

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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 .
0.1406
320.030 ∗ 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 ∗ 320.03
4913 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/cm2
G
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
66796.4
320.030 ∗ 0.975 ∗ 1.0 ∗ 1.0 ∗ 444.053
1159.8 ∗ 1.0
164.2
A 1.32 inch2
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 .
0.1406
320.030 ∗ 1.0
1560 1159.8 .
1159.8 .
0.008183

47

′
2.233 440.619 .
0.008183
5720.367 2
0.1406√233 ∗ 440.619
5720.367 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/cm2
G
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

136833
320.030 ∗ 0.975 ∗ 1.0 ∗ 1.0 ∗ 425.919
1159.8 ∗ 1.0
233
A 2.29 inch2
to cm2
:
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 .
0.1406
320.030 ∗ 1.0
1560 1260.6 .
1260.6 .
0.005269
′
2.396 440.619 .
0.005269

51

9517.42 2
0.1406√233 ∗ 440.619
3517.42 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)
G
4.3.3.2. Solution
∗
1 24.8 ∗ 0.21 24.8
1 30.008 / 2
1 425.919 / 2.

53

140850
320.030 ∗ 0.975 ∗ 1.0 ∗ 1.0 ∗ 425.919
1260 ∗ 1.0
233
A 2.46 inch2
to cm2
:
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 .
0.1406
320.030 ∗ 1.0
1560 1159.8 .
1159.8 .
0.008183

55

′
1.908 444.053 .
0.008183
4913 2
0.1406√164.2 ∗ 320.03
4913 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/cm2
G
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

66796.4
320.030 ∗ 0.975 ∗ 1.0 ∗ 1.0 ∗ 444.053
1159.8 ∗ 1.0
164.2
A 1.32 inch2
to cm2
:
8.54 2 .

58

load:
. √
.
.
4.5.1. Data:
W=Relieving load=?
4.5.2. Solution:
∗ ′
′
1 /
′
0.1406
∗
1 .
1 .
0.1406
320.030 ∗ 1.0
1560 1159.8 .
1159.8 .
0.008183
′
2.233 440.619 .
0.008183

59

5720.367 2
0.1406√233 ∗ 440.619
5720.367 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)
G
4.5.3.2. Solution
∗
1 24.8 ∗ 0.21 24.8
1 30.008 / 2
1 425.919 / 2.

61

136833
320.030 ∗ 0.975 ∗ 1.0 ∗ 1.0 ∗ 425.919
1159.8 ∗ 1.0
233
A 2.29 inch2
to cm2
:
14.82 2 .

62

load:
. √
.
.
4.6.1. Data:
W=Relieving load=?
4.6.2. Solution:
∗ ′
′
1 /
′
0.1406
∗
1 .
1 .
0.1406
320.030 ∗ 1.0
1560 1260.6 .
1260.6 .
0.005269
′
2.396 440.619 .
0.005269

63

9517.42 2
0.1406√233 ∗ 440.619
3517.42 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)
G
4.6.3.2. Solution
∗
1 24.8 ∗ 0.21 24.8
1 30.008 / 2
1 425.919 / 2.

65

140850
320.030 ∗ 0.975 ∗ 1.0 ∗ 1.0 ∗ 425.919
1260 ∗ 1.0
233
A 2.46 inch2
to cm2
:
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
TAG No. 100‐PSV‐011A/B
Service 100‐V12
KEROSCENE COLECER
Full Semi Nozzle Full
Safety Or Relief Safety
Type ConveNtional
Bonnet Type Close
Size in out 4" 6"
Rating or Screwed 300#RF 150#RF
Facing SMOOTH
Material
Body & Bonnet CARBON STEEL
Seat & Disc 316S.S
Resillent Seat Seal
Guide & Rings MTR STD
Springs MTR STD
Bellows 316LS.S
OPTION
Cap: Screwed or Bolted BOLT
Lever: Plained Or Oacked PACKED
YES
BASIS Code ASME
Case FIRE
Fluid H.C
Mol. Wt. 73.4
Sp, Gr. ‐
Ope.Press kg/cm2G 0.4
Des. Temp degC 137
Des. Press kg/cm2G 3.9/FV
Set press kg/cm2G 2.67
Relieving Temp T1 degC 137 738.6 deg R
Vessel Wall Temp TW degC 593.333 1560 deg R
Back Pressure CONST. kg/cm2G 0.07
Variable kg/cm2G 0.31
Total kg/cm2G 0.38
Coficent Discharge K
Over Press. % 21
Over Press. Factor
Comp. Factor 0.97
Cp/Cv 1.06
Visocsity cP 0.02
Baromtoric Pressure kg/cm2A 1.03
Discharge to FL Header
Releiving Pressure P1 kg/cm2
3.2307 60.5550051 psia
Environmental Factor F' 0.02629062
Exposed Surface Area A' m2
125.662596 1352.66519 ft2
Relieving Load W kg/hr 12690.4679 27919.0293 lb/hr
Orifice Cal. cm2 29.7827561 4.61633643 inches2
Sel. cm2 41.161
Dessign Orifice letter P
Line No. IN OUT FL‐1403 FL‐1401
Line Class A1A1 A1A1
Line Shchedule
P & ID No D‐XXX‐1225‐XXX 100‐134
See NOTE( Sheet NO. XXX) A, B,V
O
P
E
R
A
T
I
N
G

C
O
N
D
I
T
I
O
N
S
O
T
H
E
R
S
REMARKS
C
O
N
S
T
R
U
C
T
I
O
N
Test Gag
DAWOOD UNIVERSITY OF ENGINEENRING & TECHNOLOGY
Department Of Chemical Engineering
FINAL YEAR PROJECT SPECIFICATION
SAFETY RELIEF VALVES (CDU)
G
E
N
E
R
A
L
71

No 18
Quanttiy 1
TAG No. 100‐PSV‐013
Service 100‐V14
BLOWCASE OVERHEAD
LINE
Type ConveNtional
Bonnet Type Close
Size in out 1‐1/2" 3"
Facing SMOOTH
Material
Seat & Disc 316S.S
Resillent Seat Seal
Springs MTR STD
Bellows ‐
OPTION
YES
BASIS Code ASME
Case FIRE
Fluid H.C
Mol. Wt. 85.6
Sp, Gr. ‐
Des. Temp degC 171
Total kg/cm2G 0.51
Over Press. % 21
Over Press. Factor
Comp. Factor 0.97
Cp/Cv 1.09
Visocsity cP 0.02
Releiving Pressure P1 psig 10.043 157.245521 psia
16.0906813 173.204319 ft2
Sel. cm2 3.245
Dessign Orifice letter G
Line No. IN OUT PG‐3503 FL‐3503
Line Shchedule
P & ID No D‐XXX‐1225‐XXX 100‐135
See NOTE( Sheet NO. XXX) A
G
E
N
E
R
A
L
O
T
H
E
R
S
O
P
E
R
A
T
I
N
G

C
O
N
D
I
T
I
O
N
S
REMARKS
C
O
N
S
T
R
U
C
T
I
O
N
Test Gag
72

No 21
Quanttiy 1
Service 100‐V15
FUEL GAS KO DRUM
OVERHEAD
Type ConveNtional
Bonnet Type Close
Size in out 1" 2"
Facing SMOOTH
Material
Seat & Disc 316S.S
Resillent Seat Seal
Springs MTR STD
Bellows ‐
OPTION
YES
BASIS Code ASME
Case FIRE
Fluid H.C
Mol. Wt. 19.3
Sp, Gr. ‐
Des. Temp degC 183
Des. Press kg/cm2G 8.3
Total kg/cm2G 0.32
Over Press. % 21
Over Press. Factor
Comp. Factor 1
Cp/Cv 1.3
Visocsity cP 0.02
10.043 157.245521 psia
4.17540503 44.9451564 ft2
Sel. cm2 0.709
Dessign Orifice letter D
Line No. IN OUT FG‐3708 FL‐3702
Line Shchedule
P & ID No D‐XXX‐1225‐XXX 100‐137
G
E
N
E
R
A
L
O
P
E
R
A
T
I
N
G

C
O
N
D
I
T
I
O
N
S
O
T
H
E
R
S
REMARKS
C
O
N
S
T
R
U
C
T
I
O
N
Test Gag
73

No 1
Quanttiy 1
Service 100‐V1
KEROSCENE COLECER
Type ConveNtional
Bonnet Type Close
Size in out 3" 4"
Facing SMOOTH
Material
Seat & Disc 316S.S
Resillent Seat Seal
Springs MTR STD
Bellows ‐
OPTION
YES
BASIS Code ASME
Case FIRE
Fluid H.C
Mol. Wt. 164.2
Sp, Gr. ‐
Des. Temp degC 371/40
Des. Press kg/cm2G 26/FV
Set press kg/cm2G 25
Total kg/cm2G 1.29
Over Press. % 21
Over Press. Factor
Comp. Factor 1
Cp/Cv 1.04
Visocsity cP 0.02
30.25 444.05398 psia
314.289151 3383.09097 ft2
Sel. cm2 11.858
Dessign Orifice letter K
Line Shchedule
P & ID No D‐XXX‐1225‐XXX 100‐114
See NOTE( Sheet NO. XXX) A, F, K, U
O
P
E
R
A
T
I
N
G

C
O
N
D
I
T
I
O
N
S
O
T
H
E
R
S
C
O
N
S
T
R
U
C
T
I
O
N
Test Gag
REMARKS
G
E
N
E
R
A
L
74

No 1
Quanttiy 1
Service 100‐V1
KEROSCENE COLECER
Type ConveNtional
Bonnet Type Close
Size in out 3" 4"
Facing SMOOTH
Material
Seat & Disc 316S.S
Resillent Seat Seal
Springs MTR STD
Bellows ‐
OPTION
YES
BASIS Code ASME
Case FIRE
Fluid H.C
Mol. Wt. 233
Sp, Gr. ‐
Total kg/cm2G 1.29
Over Press. % 21
Over Press. Factor
Comp. Factor 1
Cp/Cv 1.04
Visocsity cP 0.02
Releiving Pressure P1 Kg/cm2 30.008 440.619148 psia
Environmental Factor F 0.00797909
542.559079 5840.24842 ft2
Sel. cm2 11.858
Line Shchedule
P & ID No D‐XXX‐1225‐XXX 100‐114
G
E
N
E
R
A
L
O
P
E
R
A
T
I
N
G

C
O
N
D
I
T
I
O
N
S
C
O
N
S
T
R
U
C
T
I
O
N
Test Gag
O
T
H
E
R
S
REMARKS
75

No 1
Quanttiy 1
Service 100‐V1
KEROSCENE COLECER
Type ConveNtional
Bonnet Type Close
Size in out 3" 4"
Facing SMOOTH
Material
Seat & Disc 316S.S
Resillent Seat Seal
Springs MTR STD
Bellows ‐
OPTION
YES
BASIS Code ASME
Case FIRE
Fluid H.C
Mol. Wt. 233
Sp, Gr. ‐
Des. Temp degC 427
Total kg/cm2G 1.29
Over Press. % 21
Over Press. Factor
Comp. Factor 1
Cp/Cv 1.04
Visocsity cP 0.02
30.008 440.619148 psia
Environmntal Factor F' 0.00525864
882.57287 9500.24618 ft2
Sel. cm2 11.858
Line Shchedule
P & ID No D‐XXX‐1225‐XXX 100‐114
G
E
N
E
R
A
L
O
P
E
R
A
T
I
N
G

C
O
N
D
I
T
I
O
N
S
O
T
H
E
R
S
C
O
N
S
T
R
U
C
T
I
O
N
Test Gag
REMARKS
76

No 15/16
Quanttiy 1
Service 100‐V12
KEROSCENE COLECER
Type ConveNtional
Bonnet Type Close
Size in out 4" 6"
Facing SMOOTH
Material
Seat & Disc 316S.S
Resillent Seat Seal
Springs MTR STD
Bellows 316LS.S
OPTION
YES
BASIS Code ASME
Case FIRE
Fluid H.C
Mol. Wt. 73.4
Sp, Gr. ‐
Des. Temp degC 137
Total kg/cm2G 0.38
Over Press. % 21
Over Press. Factor
Comp. Factor 0.97
Cp/Cv 1.06
Visocsity cP 0.02
3.2307 60.5550051 psia
125.666654 1352.66519 ft2
Sel. cm2 41.161
Dessign Orifice letter P
Line Shchedule
P & ID No D‐XXX‐1225‐XXX 100‐134
See NOTE( Sheet NO. XXX) A, B,V
G
E
N
E
R
A
L
O
P
E
R
A
T
I
N
G

C
O
N
D
I
T
I
O
N
S
O
T
H
E
R
S
C
O
N
S
T
R
U
C
T
I
O
N
Test Gag
REMARKS
77

No 18
Quanttiy 1
Service 100‐V14
BLOWCASE OVERHEAD
LINE
Type ConveNtional
Bonnet Type Close
Size in out 1‐1/2" 3"
Facing SMOOTH
Material
Seat & Disc 316S.S
Resillent Seat Seal
Springs MTR STD
Bellows ‐
OPTION
YES
BASIS Code ASME
Case FIRE
Fluid H.C
Mol. Wt. 85.6
Sp, Gr. ‐
Des. Temp degC 171
BACK PRESSURE CONST. kg/cm2G 0.07
Total kg/cm2G 0.51
Over Press. % 21
Over Press. Factor
Comp. Factor 0.97
Cp/Cv 1.09
Visocsity cP 0.02
10.043 157.245521 psia
16.0906813 173.204319 ft2
Sel. cm2 3.245
Dessign Orifice letter G
Line No. IN OUT PG‐3503 FL‐3503
Line Shchedule
P & ID No D‐XXX‐1225‐XXX 100‐135
O
P
E
R
A
T
I
N
G

C
O
N
D
I
T
I
O
N
S
O
T
H
E
R
S
REMARKS
C
O
N
S
T
R
U
C
T
I
O
N
Test Gag
G
E
N
E
R
A
L
78

No 21
Quanttiy 1
Service 100‐V15
FUEL GAS KO DRUM
OVERHEAD
Type ConveNtional
Bonnet Type Close
Size in out 1" 2"
Facing SMOOTH
Material
Seat & Disc 316S.S
Resillent Seat Seal
Springs MTR STD
Bellows ‐
OPTION
YES
BASIS Code ASME
Case FIRE
Fluid H.C
Mol. Wt. 19.3
Sp, Gr. ‐
Des. Temp degC 183
Des. Press kg/cm2G 8.3
Total kg/cm2G 0.32
Over Press. % 21
Over Press. Factor
Comp. Factor 1
Cp/Cv 1.3
Visocsity cP 0.02
10.043 157.245521 psia
4.17540503 44.9451564 ft2
Sel. cm2 0.709
Dessign Orifice letter D
Line No. IN OUT FG‐3708 FL‐3702
Line Shchedule
P & ID No D‐XXX‐1225‐XXX 100‐137
O
P
E
R
A
T
I
N
G

C
O
N
D
I
T
I
O
N
S
O
T
H
E
R
S
REMARKS
C
O
N
S
T
R
U
C
T
I
O
N
Test Gag
G
E
N
E
R
A
L
79

No 1
Quanttiy 1
Service 100‐V1
KEROSCENE COLECER
Type ConveNtional
Bonnet Type Close
Size in out 3" 4"
Facing SMOOTH
Material
Seat & Disc 316S.S
Resillent Seat Seal
Springs MTR STD
Bellows ‐
OPTION
YES
BASIS Code ASME
Case FIRE
Fluid H.C
Mol. Wt. 164.2
Sp, Gr. ‐
Set press kg/cm2G 25
BACK PRESSURE CONST. kg/cm2G 0.07
Total kg/cm2G 1.29
Over Press. % 21
Over Press. Factor
Comp. Factor 1
Cp/Cv 1.04
Visocsity cP 0.02
Releiving Pressure P1 psig 30.25 429.35398 psia
Environmental Factor F 0.00797909
309.043244 3326.62264 ft2
Sel. cm2 11.858
Line Shchedule
P & ID No D‐XXX‐1225‐XXX 100‐114
O
P
E
R
A
T
I
N
G

C
O
N
D
I
T
I
O
N
S
O
T
H
E
R
S
REMARKS
C
O
N
S
T
R
U
C
T
I
O
N
Test Gag
SAFETY RELIEF VALVES FOR 120% LOAD (CDU)
G
E
N
E
R
A
L
80

No 1
Quanttiy 1
Service 100‐V1
KEROSCENE COLECER
Type ConveNtional
Bonnet Type Close
Size in out 3" 4"
Facing SMOOTH
Material
Seat & Disc 316S.S
Resillent Seat Seal
Springs MTR STD
Bellows ‐
OPTION
YES
BASIS Code ASME
Case FIRE
Fluid H.C
Mol. Wt. 233
Sp, Gr. ‐
Total kg/cm2G 1.29
Over Press. % 21
Over Press. Factor
Comp. Factor 1
Cp/Cv 1.04
Visocsity cP 0.02
30.008 440.619148 psia
542.559079 5840.24842 ft2
Sel. cm2 11.858
Line Shchedule
P & ID No D‐XXX‐1225‐XXX 100‐114
SAFETY RELIEF VALVES 120% LOAD (CDU)
G
E
N
E
R
A
L
O
P
E
R
A
T
I
N
G

C
O
N
D
I
T
I
O
N
S
O
T
H
E
R
S
REMARKS
C
O
N
S
T
R
U
C
T
I
O
N
Test Gag
81

No 1
Quanttiy 1
Service 100‐V1
KEROSCENE COLECER
Type ConveNtional
Bonnet Type Close
Size in out 3" 4"
Facing SMOOTH
Material
Seat & Disc 316S.S
Resillent Seat Seal
Springs MTR STD
Bellows ‐
OPTION
YES
BASIS Code ASME
Case FIRE
Fluid H.C
Mol. Wt. 233
Sp, Gr. ‐
Des. Temp degC 427
Total kg/cm2G 1.29
Over Press. % 21
Over Press. Factor
Comp. Factor 1
Cp/Cv 1.04
Visocsity cP 0.02
Releiving Pressure P1 kg/cm2 30.008 425.919148 psia
Exposed Surface Area A' m2 867.725724 9340.4276 ft2
Orifice Cal. cm2 18.8982252 2.92923077 in2
Sel. cm2 11.858
Line Shchedule
P & ID No D‐XXX‐1225‐XXX 100‐114
SAFETY RELIEF VALVES 120% LOAD (CDU)
G
E
N
E
R
A
L
O
P
E
R
A
T
I
N
G

C
O
N
D
I
T
I
O
N
S
O
T
H
E
R
S
REMARKS
C
O
N
S
T
R
U
C
T
I
O
N
Test Gag
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/cm2
G
Design Temperature Td 338 degC
Operating Pressure Po 0.5/0.1 kg/cm2
G
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
Density of the liquid ρl 900 kg/m3
Density of the vapor ρv 33 kg/m3
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
Drop Out Velocity Vt 0.585915 m/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

FYP Final Thesis

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