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PROCEDURES FOR PRESSURE SAFETY VALVES
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CONTENTS Page
1.0 Introduction 3
1.1 Scope 3
1.2 Definitions of Terms 3
1.3 Inspection And Recalibration Plan 5
2.0 Pressure Testing Requirements 5
2.1 Repair/Overhaul Requirements 6
2.2 Safety Requirements 6
2.3 Cleanliness 6
2.4 Personnel Qualification 7
3.0 PSV Testing and Recalibration Procedures 7
3.1 Introduction 7
3.2 As-Received, “Pre-pop” Test 7
3.3 Dismantling, Inspection and Overhauling of PSVs 8
3.4 Conventional (Spring Loaded) Safety Relief Valves 8
3.4.1 Cold Set Pressure Test 8
3.4.2 Seat Tightness Test 9
3.4.3 Body Leak Test 9
4.0 Pilot Operated Valves 10
4.1 Inspection Testing Repair and Setting of Pilot – Operated Valves 10
4.2 Types of Pilot Operated Valves 10
4.3 Definition of Terms for Pilot Operated Valves 10
4.4 Test Procedures 11
4.4.1 Introduction 11
4.4.2 Test Procedure Set Up 11
4.4.3 Set Pressure Adjustment 11
4.4.4 Reseat Adjustment 11
4.4.5 Performance Check – Relieving Pressure 11
4.4.6 Performance Check – Dome Pressure 11
4.5 Leakage Test 12
4.5.1 Leak Test Procedure – Complete Valve Assembly 12
4.5.2 Low Pressure Leakage Check 12
4.5.3 Pressure Leakage Check 12
4.5.4 Main Valve Function Check 13
5.0 Inspection and Replacement of Rupture Disks 13
6.0 Inspection and Testing of Pressure and/or Vacuum Vent Valves 14
7.0 Location Security 15
8.0 Reporting and Certification 15
8.1 Reporting 15
8.2 Certification 15
Appendix A: Annotated Schematic Drawing of Pressure Safety Devices
Appendix B: API 527 Maximum Seat Leakage Rates for Metal – Seated PSVs
Appendix C: Example of Pilot Valve Performance Requirements (Gas or Liquid Service) Appendix D: Example of Pilot Valve Performance Requirements (Snap Action)
Appendix E: Example of Pilot Valve Performance Requirements (Modulating Action) Appendix F: Pressure Safety Valve Overhaul Report Format
Appendix G: Pressure Safety Valves Test Certificate and Calibration Report Format Appendix H: Movements Report for Pressure Safety Valves
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1.0 Introduction
Pressure Safety Valves are safety critical components and are covered by national legislation (MOSR, 1997) and company general specification GS EXP 211- Plant Integrity Minimum Inspection Requirements (Section 3.8) for periodic in - service inspection and calibration. The service conditions of pressure safety valves vary widely and so exist in different areas of the process criticality matrix. However, unless a formal Risked Based Inspection approach is adopted, (which decision may be taken in the future by Head of Asset Integrity), all pressure safety valves are inspected and recalibrated after not more than 30months in service ( per MOSR, 1997) or after any lifting and /or passing during normal service conditions.
1.1 Scope
This procedure specifies EPNL’s general requirements for inspection, testing, overhauling, repairs and recalibration of PSVs at Test Room/Workshops. However, it shall be supplemented by a number of work instructions (WIs).
Coverage is limited to conventional spring loaded; balanced bellows; pilot operated devices; rupture or busting disk; thermal expansion relief valves and vacuum breakers which forms majority of protective devices used in EPNL.
(Hydraulic spill valves, integral to pumps, are not considered to be PSV’s. These shall be
maintained along with their associated equipment)
1.2 Definitions of Terms
Relief Valve:
A relief valve is a spring-loaded pressure relief valve actuated by the static pressure upstream of the valve. The valve opens normally in proportion to the pressure increase over the opening pressure. A relief valve is primarily used for liquid service.
Safety Valve:
A safety valve is a spring-loaded pressure relief valve actuated by the static pressure upstream of the valve and characterized by rapid opening or pop action. A safety valve is normally used for gas or vapour service.
Safety Relief Valve:
A safety relief valve is a spring-loaded pressure relief valve that may be used as either a safety or relief valve depending on the application.
Pressure Relief Device:
A pressure relief device is actuated by inlet static pressure and designed to open during an emergency or abnormal conditions to prevent a rise of internal fluid pressure in excess of a specified value.
Conventional Pressure Relief Valve:
A conventional pressure relief valve is a spring- loaded pressure relief valve whose performance characteristics are directly affected by changes in the back pressure on the valve.
4 Of 28 Balanced Pressure Relief Valve:
A balanced pressure relief valve is a spring loaded pressure relief valve that incorporates a means for minimizing the effect of back pressure on the performance characteristics.
Pilot Operated Pressure Relief Valves:
A pilot operated pressure relief valve is a pressure relief valve in which the main valve is combined with and controlled by an auxiliary pressure relief valve.
Cold Differential Test Pressure:
Cold differential test pressure is the inlet static pressure at which a pressure relief valve is adjusted to open on the test stand. This test pressure includes corrections for service conditions of back pressure and/or temperature.
Popping Pressure:
Popping pressure is the value of increasing inlet static pressure at which the disc moves in the opening direction at a faster rate as compared with corresponding movement at higher or lower pressures. It applies only to safety or safety relief valves on gas or vapour service. Overpressure:
Overpressure is a pressure increase over the set pressure of a pressure relief valve, usually expressed as a percentage of set pressure.
Set Pressure:
Set pressure is the value of increasing inlet static pressure at which a pressure relief valve displays one of the operational characteristics as defined under "opening pressure”, “popping pressure”, or “start-to-discharge pressure” depending on service or as designated by the applicable code or regulation. It is one value of pressure stamped on the pressure relief valve. Reseating Pressure:
Reseating pressure is the value of decreasing inlet static pressure at which the valve disc re-establishes contact with the seat or at which lift becomes zero.
Lift:
Lift is the actual travel of the disc away from closed position when a valve is relieving. Blow-down:
Blow-down is the difference between the set pressure of a pressure relief valve and actual reseating pressure expressed as a percentage of the set pressure.
Back Pressure:
Back pressure is the static pressure existing at the outlet of a pressure relief device due to pressure in the discharge system.
Thermal Expansion Relief Valve:
A Thermal expansion relief valve is a device releasing hydrocarbon trapped inside a capacity (usually a pipeline section) submitted to heat input in order to maintain pressure below design pressure. The acronym TSV is used.
Bursting or Rupture Disk:
Rupture disk or bursting disk it is a type of sacrificial blind spade designed to burst at a certain level of pressure contained in the sensitive element to protect.
5 Of 28 Vacuum Relief Valve:
A Vacuum Relief Valve is a Pressure Relief Device designed to admit fluid to prevent an excessive internal vacuum; it is designed to re-close and prevent further flow of fluid after normal conditions have been restored.
EPNL Serialisation Numbers:
This is a six digit number generated by UNISUP (SAP) to track PSV’s movement since they are not treated as a functional location, but as equipment. For PSVs not bearing this number, it has to be requested for the Asset Integrity Section’s Technical Clerk and hard stamped on the flange of the PSV before overhaul or recalibration.
1.3 Inspection And Re-calibration Plan
A “general” Inspection and recalibration programme of all PSVs due for inspection and
recertification shall be issued by the Asset Integrity Section from SAP to the General Maintenance Contractors (GMC). This shall be defined for a rolling twelve months on a monthly basis.
A “detailed” rolling twelve months’ Inspection and recalibration programme of all PSVs must
be provided by the relevant GMC monthly for EPNL approvals by Maintenance and Asset Integrity.
The plan shall be sent to:
DGM’s JV Onshore/Offshore
Field Operation Managers, Onshore/Offshore Methods Managers, Onshore /Offshore Respective Site Managers (RSES)
Head of Process / Treatment Onshore/Offshore Head of Maintenance Onshore/Offshore
Head of Asset Integrity
Senior Integrity Methods Engineer
2.0 Inspection and Testing Requirements
2.1 Selection of Sub-Contractors and Personnel
Testing, calibration, and certification of EPNL’s PSVs shall only be carried out (in shop or on site) by a Contractor who has the “Special Category” Permit to operate as an Oil Industry Service Company, awarded by the Department of Petroleum Resources (DPR) and who has been approved by EPNL after an audit visit (by Total HSE and Integrity Sections) to check for compliance of facilities and Procedures to TOTAL’s Standards.
The respective site GMCs shall make available to EPNL a list of proposed Valve Technicians from each Contractor for approval.
In addition to excellent safety orientation, personnel shall have acquired adequate technical knowledge and practical experience in the related duties. He/she should be able to carry out calibration, overhauls and testing of valves according to approved procedures and manufacturer’s recommendations.
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2.2 Safety Requirements
Adequate measures shall be taken to protect personnel against possible hazards. These must include, but not be limited to:
Barriers/shielding must be considered, particularly for high pressure gas tests
Using properly inspected, calibrated and certified testing components, e.g. pumps, compressors, pressure control devices, piping system, pressure hoses, and pressure gauges etc.
Positioning the valve discharge nozzle to prevent exposure of personnel to a sudden blast of air, water, or other projectiles from the valve.
Utilisation of personal protective equipment e.g. ear defenders, eye goggles, safety boots, etc.
Not attempting to test valves at pressures above that for which the test bench is designed.
2.2 Testing, Overhaul and Re-certification Equipment
The following minimum provisions shall be mandatory for carrying out pressure test on valves: The test room shall be equipped with pneumatic facilities capable of providing a supply of air or nitrogen at a pressure above the pressure required for the range of valves to be tested at the valve test bench.
There shall be hydraulic facilities for the hydraulic testing of valves. Quick change adaptors for different sizes of valves.
All necessary fixtures, fittings and tools required for the test set up.
Calibrated and fully certified pressure gauges adequate for the working range pressure (Gauge range should be maximum of three times the test pressure).
The frequency of calibration shall not exceed one year and the calibration certificates shall be available at all times for sighting.
In addition, the testing facility shall be equipped with the equipment and tools listed below as a minimum for overhaul and repairs of metal seated and soft-seated valves.
A Standard test bench fitted with all necessary accessories Lapping machine and accessories.
Lapping stones. Surface plates. Grinding kit.
General hand tools.
An optimum stock of repair kits for replacement of spare / soft goods i.e. soft seats, seals, gaskets, etc which should be available before removal of the valve from situ Test fluid to be employed should be filtered.
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3.0 PSV Testing and Recalibration Procedures 3.1 Introduction
It is mandatory that an EPNL representative and DPR personnel must be afforded the opportunity to witness the dirty inspection / pre-pop and overhaul of PSVs.
For a valve in Gas service, the test medium must be Nitrogen or dive-quality air (or other gas as specified). A valve in liquid service can be tested by liquid or gas.
Prior to testing, the test equipment should be blown out with dry, high pressure air to remove any dust or particles which may have accumulated. The final testing shall be witnessed by personnel from EPNL’s Integrity Section and DPR
Note: Currently, DPR require 14 days’ notice, in writing, for planned PSV re-certification. 3.2 As-Received, “Pre-pop” Test
The valve shall be “pre-popped” to determine how it would have performed in service.
If heavy fouling of the valve is observed, it should be considered whether a pre-pop would damage the valve, in which case the pre-pop can be waived, but such a decision must not be taken lightly as it is very important to know how the valve would have performed in service. The nature of the fouling must be investigated (initiated by the Site Integrity Engineer) and measures taken to prevent future re-occurrences
The inlet side of the valve to be tested should be carefully cleaned to ensure that there is no dirt, dust or loose particles adhering to the inside of the nozzle or the underside of the disc. A satisfactory test is one were the valve lifts within -10% and +5% of the CDTP. This test is done by mounting the PSV on the bench test block and slowly increasing the pressure on the valve. The relieving pressure is determined by watching a pressure gauge and noting the point at which the valve pops or relieves.
However, if the valve does not pop before reaching an inlet pressure of 120% of the CDTP, the test shall be aborted and the valve considered as stuck shut (failed to lift).
This failure to lift shall be directed to the Head of Asset Integrity for further investigation on a case-by-case basis.
Notes:
1) Valve Previously in Service: - If, initially, the valve opens at between 105% and 120% of the CDTP, it shall be popped for a second time to assess how it could have performed in service. If the second test falls between 90% and 105% of the CDTP, then both readings are recorded and the test is deemed to be acceptable
2) New Valve: - To be pre-popped 3 times.
1st Test; - For alignment (can rectify any out-of-alignment from transporting)
2nd and 3RD Tests:- to prove repeatability. The 3rd value is recorded as the value set for service
The “As-received” tests results shall be recorded on testing report form, Appendices F and G. An acceptable pre-pop is one where the final lift falls within the limits set pressure tolerances specified in 3.4.1 below.
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3.3 Dismantling, Inspection, and Overhauling of PSVs
The valve shall be carefully dismantled in accordance with manufacturer’s manuals and recommendations. At each stage in the dismantling process, the various parts of the valve shall be visually inspected for evidence of wear, deformation and corrosion.
After dismantling, each part shall be cleaned and examined for wear, corrosion or damage. Seating surfaces on the disk and nozzle shall be inspected for roughness or damage which might result in valve leakage. The spring should be checked for evidence of cracking or deformation. The fit between the guide and the disk or disk holder should be checked for proper clearance and visually inspected for evidence of scoring. The bellows in balanced-type valves should be checked for cracks or other failures that may affect performance. The details of this inspection, including general internal and external condition, shall be recorded in the PSVs Overhaul Report Sheet and the test certificate and report. See Appendices F and G.
Parts that are worn or damaged must be replaced or reconditioned. Damaged springs or damaged bellows must be replaced. Replacement parts shall be obtained from the original manufacturer of the Pressure Relief Valve. The seating surface of the disc and nozzles may be machined or lapped if evidence of wear or damage is found. Seats lapping shall be carried out according to the manufacturer’s recommendations and procedures by using proper lapping blocks and correct lapping compound grades.
After the valve has been inspected and re-conditioned, it must be re-assembled in accordance with the manufacturer’s instructions. Once the re-assembly is completed, the Pressure Relief Valve is ready to be tested according to the procedures described hereafter.
Note for Valves Which Have Been Passing in Service: Where possible a repair kit should be
used for a valve which has been passing in service. If a new kit is used the next recertification date is from the date of fitting; if a new kit is not used and / or the passing valve has not been overhauled, the next date of inspection runs from the previous full recertification
3.4 Conventional (Spring Loaded) Safety Relief Valves 3.4.1 Cold Set Pressure Test
The valve shall be mounted on the test bench in the vertical position and air pressure slowly applied to the valve inlet for cold set pressure taking into consideration correction factors for temperature and back pressure based on the manufacturer recommendations. Valve upper and lower blow-down rings, where fitted, shall be adjusted as recommended by the valve manufacturer. This procedure shall be repeated until the required cold set pressure is obtained.
When the correct cold set pressure is obtained, the valve pops (lifts) and this should be within the set pressure tolerances specified by below. It is mandatory to verify that the obtained cold set pressure has remained unchanged by repeating the test – first for alignment, second and third for repeatability. The value of the third lift shall be recorded in the test report.
±2 Psi (±0.13 Bars) for pressure up to and including 70Psi (4.8 Bars) ±3% of set pressure for pressure above 70Psi (4.8 Bars)
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The cold set pressure and spring adjustment shall be recorded and entered on the Test Certificate (See Appendix G). It is recommended that spring adjustment is measured with reference to the top face of the bonnet and not the top surface of the lock nut.
3.4.2 Seat Tightness Test
Following a successful cold set pressure test, the valve shall be fitted with a suitable flange at its outlet orifice to test for tightness. This flange has a hole in the centre to take a “bubble test pot” built to API Standard 527 (see figure 6).
With the valve on the test bench in the vertical position, test pressure is adjusted to 95percent of the cold set pressure for valves whose cold set pressure is greater than 1015 Psi (70 Bars) and the leakage rate in bubbles per minute (BPM) determined.
For valve set between 1015 Psi (70 Bars) and 50 Psi (3.45 Bars), the test pressure shall be adjusted to 90percent of the cold set pressure and the leakage rate in bubbles per minute (BPM) determined.
For valves set at 50psi or less, the test pressure shall be held at 5psi below the cold set pressure immediately after popping and leakage rates in bubbles per minute determined. Seat tightness test for Metal Seated valves are considered acceptable if leakage rates fall within limits specified by API Standard 527. See Appendix B.
Notes:
1. The valve Technician must be able to determine the orifice size to apply the relevant acceptable BPM
2. It is permissible to release the pressure and then increase to 90% cold differential set pressure (CDSP)
3.4.3 Body Leak Test
With the valve remaining on the test bench an appropriate flange is fitted to its outlet and static test pressure is applied through the outlet flange. This pressure is equal to the valve outlet flange rating or allowable back pressure whichever, is less.
With pressure being maintained a soapy solution is applied to all the body and bonnet joints to check for leaks. Test duration between 2-3 minutes.
For bellows fitted valves, the bellows tightness is tested by applying a low pressure (1 bar) through the valve outlet flange. A check for leaks using a soapy solution is then carried out to the bonnet vent hole, the blow-down ring adjustment screw connections and the bonnet flange joint. On satisfactory completion of the above tests the valve upper and lower blow down rings, where fitted, are to be checked with reference to their initial setting. If any difference is observed readjustment is to be made as advised by the manufacturer.
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4.0 Pilot Operated Valves
This section establishes the general procedure for assembly, functional testing and normal performance requirements of pilot operated safety-relief valves. However, because of the many types of pilot operated valves available, the valve manufacturer’s recommendations for inspection, repair and testing for the specific valve should be consulted and followed.
(Refer Appendices C, D & E for examples illustrating some of the numerous differences between pilot operated valves).
4.1 Inspection, Testing, Repair and Setting of Pilot – Operated Valves
Inspection, testing, maintenance, and setting of the pilot mechanism may be handled separately from the main valve.
The pilot gets tested and re-certified. As a minimum the pilot valve shall be pre-popped,
stripped, examined, cleaned, re-built, calibrated and recertified following valve manufacturer’s recommendations for inspection, repair, and testing.
The main valve gets inspected:- As a minimum, the integrity engineer carries out a visual
inspection of the main valve inlet and outlet (bearing in mind the specific service) and a visual of the tie-in piping for cleanliness, fouling, corrosion, etc.
If no problems are observed, the valve can be re-installed, using new gaskets.
Many of the considerations that apply to other pressure relief valves also apply to pilot operated valves. The following is a list of additional considerations that apply:
Inspect soft goods (O – rings, diaphragms, gaskets) Check for plugging in pilot assembly and external tubing Check for material trapped in valve dome area
Check all tubing fittings for leakage
Inspect the pressure pick-up device and its orientation
4.2 Types of Pilot Operated Valves
There are two different types of pilot operated valves • Snap Action (Rapid full Opening and Closing)
• Modulating Action ( Opens proportionally to the over pressure)
4.3 Definition of Terms for Pilot Operated Valves
Set pressure is that pressure at which the pilot valve relieves on increasing inlet pressure to reduce the dome pressure to 70% or less of supply. On snap action pilots the dome pressure will decrease very rapidly. For modulating action pilots, the dome pressure will decrease in proportion to the rate of increase in supply pressure.
Cracking pressure is that inlet pressure at which first leak occurs at the pilot exhaust port on increasing pressure.
Reseat pressure is that pressure where the dome pressure increases to 75% or more of supply. For "pop" action pilots this pressure is usually 90% to 92% of set pressure. On modulating action pilots, it will be 96% to 100% of set pressure.
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Reseat leakage is the leakage across the pilot valve seat at reseat pressure. For snap action pilots this leakage should be zero at reseat. On modulating action pilots, leakage will occur until the supply pressure has decreased to the amount specified in the performance requirements, usually 90% to 95% of set pressure.
Dome pressure is the pressure at the dome connection of the pilot valve.
4.4 Pilot Operated Valves: Test Procedures 4.4.1 Introduction
The test medium shall be shop air or nitrogen at ambient conditions for all main valves and all gas service pilots, unless otherwise specified. Pilots for liquid service may be set on water. Full scale of the gauge used shall not be greater than three times set pressure.
All pilot valve assemblies shall be tested to make sure the correct dome pressure is obtained to operate the main valve. The pilot supply pressure and dome pressure shall be recorded on the test certificate and report (See Appendix G).
4.4.2 Test Procedure Set Up - Pilot
The following procedures shall be used to test the pilot valve, using air or nitrogen at ambient temperature as the pressure medium for gas service pilots and water for liquid service pilots, unless otherwise specified.
Install the pilot valve on a test drum per Figure 4 and 5. The "dome" connection is a blind connection with a pressure gauge to indicate dome pressure reduction at set pressure.
4.4.3 Set Pressure Adjustment
Adjust the spring adjusting screw to obtain the correct set pressure. Clockwise rotation increases the set pressure. Tighten the locknut after adjustment is completed.
4.4.4 Reseat Adjustment
On all pilots except modulating pilots, adjust the blow down adjustment screw to obtain the desired reseat pressure. Tighten the locknut after adjustment is completed.
Note: The reseat value of the main valve with internal pressure pickup for the pilot will be
approximately 3% to 4% less than the reseat value of the pilot only on snap action pilots due to the pressure loss in the dipper tube.
4.4.5 Performance Check - Relieving Pressure
Cycle the pilot a minimum of three times to make sure it is relieving and reseating at consistent pressures. Increase the pressure very slowly in order to obtain an accurate reading of the relieving pressure and to detect any erratic performance.
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4.4.6 Performance Check - Dome Pressure
Flow the pilot valve except at the set pressure to obtain the dome pressure reading. If sufficient gas capacity is not available to flow the pilot at the set pressure, read the lowest dome pressure at the time of reseat. This method is not applicable for modulating pilots. For the no-flow modulating pilot, increase the supply pressure to 110% of nameplate set. The dome pressure must decrease to less than 40% of the supply.
4.5 Leakage Test
For gas service pilots, leakage shall be detected using a bubble tube tester of the type shown in Figure 6. For liquid service pilots, leakage shall be detected visually.
Slowly increase the pressure at the inlet port until leakage is detected at the pilot exhaust port. This pressure shall be recorded as the cracking pressure.
Further increase the pressure at the inlet port until the pilot actuates or "pops". This pressure shall be recorded as the set pressure. For the no-flow modulating pilot, no leakage at the pilot exhaust should occur with inlet supply pressure held constant and the dome pressure has stabilized.
Shut off the inlet pressure to the test accumulator and allow the pilot to reseat. This pressure shall be recorded as the reseat pressure. For modulating pilots, reduce the inlet pressure of the test accumulator in accordance with the specified reseat pressure. Check the valve for leakage at the exhaust port.
Repeat the steps above a minimum of three times. The cracking pressure, set pressure and reseat pressure shall be within the limits for three consecutive cycles. The valve action shall be consistent.
Slowly increase the inlet pressure until the leakage test pressure is reached. Maintain this pressure for one minute and check for leakage at the exhaust port and at the blow down adjustment. No leakage shall occur.
4.5.1 Leak Test Procedure - Complete Valve Assembly
Completely assemble the pilot on the main valve. Connect the main valve inlet to a pressure source as shown in Figure 3. Shop air at ambient temperature shall be used as the test medium unless otherwise specified. For liquid service valves, a leakage at the pilot exhaust not to exceed 60 bubbles/minute is acceptable if no leakage occurred when tested on water.
4.4.2 Low Pressure Leakage Check
Slowly increase the inlet pressure to 30% of the set pressure. Check for main valve nozzle, seat, and piston seal leakage at the main valve outlet. No visible leakage shall occur in 15 seconds. To help in seating the valve seat and piston seal, the valve may be actuated several times.
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4.4.3 Pressure Leakage Check
Apply pressure to the inlet equal to 90% of the set pressure. Check for leakage at the main valve outlet. Using a suitable gas and air leak detector solution, check for leakage at the cap seal and other pressure connections. No leakage shall occur at the valve outlet and no visible leakage shall be detected at the cap seal or other pressure connections in one minute. Where superimposed back pressure is specified, the downstream or exhaust connections which are exposed to the back pressure shall be tested at 1.5 times the specified back pressure and all mechanical connections so pressurized will be checked for leaks. No visible leakage shall occur in one minute using a suitable gas and air leak detector solution.
4.4.4 Main Valve Function Check
Caution: This test must be performed at a slow rate of pressure increase to insure that the
main valve does not go into full lift. The pressure applied to the inlet is not to exceed 105% of nameplate set pressure.
After completing the high pressure leakage check, verify main valve opening as follows. Remove the bubble tube leakage tester from the outlet flange and slowly increase the inlet pressure above 90% of set pressure. Continue increasing inlet pressure until an audible discharge at the valve outlet verifies main valve opening.
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5.0 Inspection and Replacement of Rupture Disks
Rupture disks are used in services where a large relieving capacity is required to give a rapid drop in pressure. The disks are made from a wide variety of metallic and non-metallic material. Rupture disks may be inspected visually.
Rupture Disks should be thoroughly inspected after removal from their operational location. Inspection should include a check of flanges for leakage and a check of the disk for fatigue, corrosion, failure, and build up of coke or other foreign material that could adversely affect the disk’s performance. They should be renewed as required, based on their reliability and condition.
Because they cannot be tested, Rupture Disks should be replaced on a regular schedule based on their application, the manufacturer’s recommendations, and past experience. This recommendations and schedule must be provided by the Maintenance Department.
If a block valve is located ahead of the disk, the block valve should be locked open during operation. If replacement of the disk is necessary, the block valve should be locked closed until disk installation has been accomplished. Normally in this case, a rupture disk cannot be inspected without being removed. Therefore, inspection of the disk should be part of the routine developed for inspection of the Pressure Relief Valves.
A rupture disk installed upstream of the relief valve to prevent valve corrosion is normally set to burst either at the set pressure of the Pressure Relief Valves it is protecting or at a pressure 3 % – 5 % less than the set pressure.
Caution: The relief valve must be designed so that it will not fail to open at its proper pressure
setting regardless of any backpressure accumulated between the valve disk and the rupture disk. If backpressure builds up between an ordinary spring-loaded safety relief valve and a rupture disk, the valve will not open at its set pressure. In this case, the valve should be replaced by a specially designed valve such as a diaphragm valve equipped with a bellows above the disk.
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6.0 Inspection and Testing Of Pressure and/or Vacuum Vent Valves
The relieving devices on tanks may be separated into pressure and/or vacuum relief devices on atmospheric tanks and PSVs on pressure storage vessels. The inspection, testing, maintenance, and setting of relieving devices on pressure storage tanks are similar to those of PSVs on process equipment. Pressure and/or vacuum vent valves on atmospheric tanks are designed to vent air and vapour from the tank during filling operation and to admit air when the tank is drawn down. Because pressure and/or vacuum vent valves are in continuous service, they are prone to failure by sticking unless examined periodically.
The inspection of each vent valve in place should include the checking of the discharge opening for obstructions. The top of the valve should be removed and the pallets checked for freedom of movement. Seats should be checked to ensure that there is no sticking or leakage, since the forces actuating the valve are small. If the valve has a flame arrester on the inlet nozzle, it should be inspected for excessive fouling or plugging. If necessary, it should be removed for cleaning.
Caution: Inspection of the flame arrester in service is important because any malfunction may
result in the loss of expensive equipment. Inspection, testing, maintenance, and setting of pressure and/or vacuum vent valves should include the following special steps:
• Sticking should be corrected and prevented. The disks (pallets) of the devices should be checked for sticking. If the disks are stuck, the product’s effect on the seal material and on the disk material should be investigated. If necessary the seal material and the disk material should be changed.
• The disk should be checked and maintained. Once a disk is removed, it should be cleaned, and its mass should be determined. Check the mass against the mass required for the correct relieving pressure of the device. [The setting of a pressure-vacuum device depends on the mass of the disk compared to the area of the opening covered by the disk. Set pressure is usually a standard ½ ounce per square inch (0.43 kPa), but may go as high as 24 ounce per square inch (10.43 kPa)] If the mass is not correct, mass must be added or removed until the correct mass has been achieved. Disk condition and serviceability should be checked, and unusable disks should be replaced.
• The seats and pallets of the disk seating areas must be checked and cleaned. • The gaskets at the disk seating areas must be checked and, if necessary, replaced. • The protective screens must be checked for serviceability and, if necessary, renewed.
• Hinges and hinge pins must be checked for operability and, as necessary, serviced, lubricated, and replaced.
• Any special coating used internally or externally on the body should be checked and, if unserviceable, replaced.
• The hood should be inspected and, if unserviceable, replaced. • The bolts should be checked and, as required, replaced.
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7.0 Location Security
Every adjustable part of the valve shall be double-checked for correct location and positioning after testing. On completion of all works, on any type of valve, the spring adjustment must be secured by copper wire and a crimped lead seal
8.0 Reporting and Certification 8.1 Reporting
Reporting is to provide all related information for the tested valve as contained in appendices B and C i.e. the as-received conditions; details of overhaul work performed, test results, etc. Minimum information required should include:
EPNL Number
The "as-received" condition of the valve, and the pre-pop pressure. Details of the inspection and repair/overhaul work performed. Condition of the valve following overhaul and/or re-setting.
Final pressure test results in figures i.e. cold set pressure, bubbles/minute, and spring adjustment (MM) position of blow down ring(s) etc.
A statement that the valve has satisfactorily passed the required tests.
Other related Valve's information e.g. name plate data, trim details, duty etc. shall be recorded only once, for registration and inspection purposes. Such information should be amended, whenever necessary, to indicate any related changes, or modifications.
8.2 Certification
Final tests of valves performed by approved contractors shall be signed off by Valve Technician and personnel from DPR and EPNL’s Asset Integrity Section who witnessed the test. The signed off Test Certificate and Calibration Reports shall be in quadruple copies. These copies shall be distributed as follows: Asset Integrity Office Copy, Field Copy, Contractor’s Copy and DPR’s Copy
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Appendix A
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Appendix A (contd)
Figure 4 – Bubble test for Pilot Valves
Figure 5 – Set Up for Testing of Pilot Valves
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Appendix C
PILOT OPERATED SAFETY RELIEF VALVE STANDARD PERFORMANCE REQUIREMENTS
(GAS OR LIQUID SERVICE) SET PRESSURE
The set pressure is where the dome pressure equals 70% + 2% of the supply pressure. The indicator must operate at nameplate set +3%.
Set Pressure ASME Performance Tolerance
Above 70 psig + 3% of the specified set pressure (1) [Above 483 KPAG]
70 psig & below + 2 psig [13.8 kPa] (2) [483 KPAG & below]
CRACKING PRESSURE
Set Pressure Cracking Pressure (Min.)
15 - 3705 psig 94% of the specified set pressure [103-25545 KPAG]
RESEAT PRESSURE
The reseat pressure is where the dome pressure equals 75% + 2% of the supply pressure. Set Pressure Reseat Pressure
15 - 70 psig 3 psig [20.7 KPAG] below specified set [103-276 KPAG] pressure
71 - 3705 psig 96% to 100% of the specified set [283-25545 KPAG] pressure
LEAKAGE TEST PRESSURE
No leakage shall occur for one minute at pressures between 30% of specified set pressure and the cracking pressure when checked with the supply pressure held constant. At pressures below 30% of set, the leakage rate for gas service pilots shall not exceed 20 bubbles/minute. For liquid service pilots there shall be no leakage. Pilots shall seal bubble tight at 5.0 psig [34.5 KPAG] for gas service pilots. For liquid service pilots there shall be no visible leakage.
DOME PRESSURE TEST
Set Pressure Dome Pressure
15-3705 psig Less than 40% of Supply at 110% of [103-25545 KPAG] specified set pressure
NOTES: EPNL Recommended Setting Tolerance (1) Adjust set pressure 0% to 2% above nameplate. (2) Adjust set pressure 1/2 psig [3.45 KPAG] to 1 1/2 psig [10.34 KPAG] above nameplate.
(3) For ISO-DOME pilots, adjust regulator for Dome supply to 92% + 2% of nameplate set.
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Appendix D
PILOT OPERATED SAFETY RELIEF VALVE STANDARD PERFORMANCE REQUIREMENTS
(Snap Action) SET PRESSURE
Set Pressure ASME Performance Tolerance
Above 70 psig + 3% of the specified set pressure (1) [Above 483 KPAG]
70 psig & below + 2 psig [13.8 kPa] (2) [483 KPAG & below]
CRACKING PRESSURE
Set Pressure Cracking Pressure (Min.)
15 psig & above 95% of the specified set pressure [103 KPAG & above]
Below 15 psig 92 1/2 % of the specified set pressure [Below 103 KPAG]
RESEAT PRESSURE
Set Pressure Reseat Pressure (3)
15 psig & above 92 1/2% + 1% of the specified set pressure [103 KPAG & above]
Below 15 psig 92 1/2% + 1% of the specified set pressure [Below 103 KPAG]
LEAKAGE TEST PRESSURE
There shall be no leakage for one minute at pressures below the cracking pressure or at the reseat pressure.
DOME PRESSURE TEST
The dome pressure shall decrease rapidly, as with a snap and shall not exceed 20% of the inlet pressure while the pilot valve is venting at the specified set pressure.
NOTES: EPNL Recommended Setting Tolerance
(1) Adjust set pressure 0% to 1% above nameplate.
(2) Adjust set pressure 0 psig to 1 psig [0 to 6.89 KPAG] above nameplate. (3) To be checked with pilot flowing.
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Appendix E
PILOT OPERATED SAFETY RELIEF VALVE STANDARD PERFORMANCE REQUIREMENTS
(Modulating Action) (Gas or Liquid Service) Set Pressure
The set pressure is where the dome pressure equals 70% + 2% of the supply pressure. The indicator must operate at nameplate set +3%.
Set Pressure ASME Performance Tolerance
Above 70 psig + 3% of the specified set pressure (1) [Above 483 KPAG]
70 psig & below + 2 psig [13.8 KPAG] (2) [483 KPAG & below]
Cracking Pressure
Set Pressure Cracking Pressure (Min.) All 95% of the specified set pressure Reseat Pressure
The reseat pressure is where the dome pressure equals 76% + 2% of the supply pressure Set Pressure Reseat Pressure
All 99% to 100% of the specified set pressure Reseat Leakage Pressure (Pilot Seat)
Set Pressure Reseat Pressure (Min.)
All 95% + 1% of the specified set pressure Leakage Test Pressure
No leakage shall occur for one minute at pressures below the cracking pressure or at the reseat leakage pressure when checked per 7.2.6.
NOTES: EPNL Recommended Setting Tolerance (1) Adjust set pressure 0% to 1% above nameplate.
(2) Adjust set pressure 0 psig to 1 psig [0 to 6.89 KPAG] above nameplate. It is preferable that pilot valves are set separate from the main valve. However, the complete assembly, main valve and pilot valve, can still be tested on the test bench following the same procedure.
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Appendix F
Pressure Safety Valve - Overhaul Report
Note: This is the PSV workbook in Unisup
NAMES (Check data, nameplates, tag numbers etc) Tick Box
00ND 0-Inspection Not
Done/Not inspectable Inspection Not Done/Not inspectable
01NF 1-No finding
No finding - No action - Any data is correct and up to date; Name Plate is still in place and data in line with any documentation
02ED 2-Erroneous data
Minor defect - No action - Data discrepancies compared to equipment drawings, equipment data sheet, PID, FAME+ or SAP data base
02ID 2-Lack of
Identification/marking Minor defect - No action - Nameplate is missing; lack of identification, tag no., PK post, marker, SWL, etc 03ED 3-Erroneous data
Defective - Some action required - Data discrepancies compared to equipment drawings, equipment data sheet, PID, FAME+ or SAP data base
03ID 3-Lack of
Identification/marking Defective - Some action required -Nameplate is missing; lack of identification, tag no., PK post, marker, SWL, etc 04ED 4-Erroneous data
Action needed immediately - Data discrepancies compared to equipment drawings, equipment data sheet, PID, FAME+ or SAP data base
04ID 4-Lack of
Identification/marking Action needed immediately - Nameplate is missing; lack of identification, tag no., PK post, marker, SWL, etc
DIRTYS (Check internals for debris, scale, clogging etc) 00ND 0-Inspection Not
Done/Not inspectable Inspection Not Done/Not inspectable
01CL 1-Clean Good condition/As new - No action - No significant
Debris/Deposits, Corrosion products.
02CT 2-Clogged/Plugged
Minor defect - No action - Clogged/Plugged (Heat exchanger, Air cooler and Boiler tubes, or PSV nozzle.) ; not compromising process
02DD 2-Debris/Deposits
(sand, sludge, wax...) Minor defect - Minor Debris/Deposits quantity (Any type/size); not compromising process 02SC 2-Scales Minor defect - No action - Scale; not compromising process 03CT 3-Clogged/Plugged
Defective - Some action required - Clogged/Plugged (Heat exchanger, Air cooler and Boiler tubes, or PSV nozzle.); possibly compromising process
03DD 3-Debris/Deposits (sand, sludge, wax...)
Defective - Some action required - Medium Debris/Deposits quantity (Any type/size); possibly compromising process
03SC 3-Scales Defective - Some action required - Scale; possibly compromising process 04CT 4-Clogged/Plugged
Action needed immediately Clogged/Plugged (Heat exchanger, Air cooler and Boiler tubes, or PSV nozzle.); compromising process
04DD 4-Debris/Deposits
(sand, sludge, wax...) Action needed immediately - Major Debris/Deposits quantity (Any type/size); compromising process 04SC 4-Scales Action needed immediately - Scale; compromising process
24 Of 28 00ND 0-Inspection Not
Done/Not inspectable Inspection Not Done/Not inspectable
01BG 1-Body in good
condition Good condition/As new - No action - Body in good condition
02BE 2-Body externally
damaged/corroded Minor defect - No action - Body externally damaged/corroded
02BI 2-Body internally
damaged/corroded Minor defect - No action - Body internally damaged/corroded
03BE 3-Body externally
damaged/corroded Defective - Some action required - Body externally damaged/corroded 03BI 3-Body internally
damaged/corroded Defective - Some action required - Body internally damaged/corroded 04BE 4-Body externally
damaged/corroded Action needed immediately - Body externally damaged/corroded
04BI 4-Body internally
damaged/corroded Action needed immediately - Body internally damaged/corroded
PSDIS (Check the condition of the valve components) 00ND 0-Inspection Not
Done/Not inspectable Inspection Not Done/Not inspectable
01IG 1-Internals in good
condition Good condition/As new - No action - All internal parts in good condition 02DS 2-Disc
damaged/corroded Minor defect - No action - Disc damaged/corroded
02MI 2-Miscellaneous parts
condition Minor defect - No action - Miscellaneous internal parts damaged/corroded 02NO 2-Nozzle
damaged/corroded Minor defect - No action - Nozzle damaged/corroded
02SG 2-Spring
damaged/corroded Minor defect - No action - Spring damaged/corroded
03BU 3-Burst disc
damaged/corroded Defective - Some action required - Burst disc damaged/corroded (corrosion, buckling, pinholes.) 03BW 3-Bellow
damaged/corroded Defective - Some action required - Bellow damaged/corroded 03DS 3-Disc
damaged/corroded Defective - Some action required -Disc damaged/corroded 03MI 3-Miscellaneous parts
condition Defective - Some action required -Miscellaneous internal parts damaged/corroded 03NO 3-Nozzle
damaged/corroded Defective - Some action required - Nozzle damaged/corroded 03SG 3-Spring
damaged/corroded Defective - Some action required - Spring damaged/corroded 04BU 4-Burst disc
damaged/corroded Action needed immediately - Burst disc damaged/corroded (corrosion, buckling, pinholes.) 04BW 4-Bellow
damaged/corroded Action needed immediately - Bellow damaged/corroded
04DS 4-Disc
damaged/corroded Action needed immediately - Disc damaged/corroded
04MI 4-Miscellaneous parts
condition Action needed immediately - Miscellaneous internal parts damaged/corroded 04NO 4-Nozzle
damaged/corroded Action needed immediately - Nozzle damaged/corroded
04SG 4-Spring
damaged/corroded Action needed immediately - Spring damaged/corroded
Enter results below
STATUS Blow off pressure first lift Bar
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STATUS Post Overhaul Results - Leakage BPM Enter any comments below
26 Of 28
Appendix G
Test Certificate and Calibration Report of Pressure Safety Valves
Client: Date:
Work Order/P/Order No: Ref:
Valve Type (Conventional / Pilot / Bellows):
Location/Protecting Equipment:
VALVE DETAILS
Manufacturer: Cold Diff Set Pressure:
Type (Pilot): Inlet Size/Rating:
Type (Main Valve): Outlet Size/ Rating
Tag No: Orifice Size:
Serial No (Pilot) Temperature:
Serial No(Main Valve) Blow down (%Sp)
Set Pressure: EPNL Serial No:
PRE-POP REPORT
Test Medium:
Pre-Pop pres./Blow-off pres. first lift:
Subsequent Lifts Gauge No & Cal. Date:
Not pre-pop, why?
Carried out by: Sign: Date:
GENERAL CONDITION OF THE VALVE BODY
Body Material:
Body General Condition:
State specific defects& if any:
GENERAL CONDITION OF THE VALVE COMPONENTS
Bonnet:
Spring Material; Part number & Condition: Disc material; Part number & Condition: Nozzle material: Part number & Condition: Disc holder: O-Ring: Guide: Adjacent screw/nut: Diaphragm: Bellows Material: Burst disc:
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THICK AS APPLICABLE
Clean
Clogged/plugged
Debris/Deposits (Sand, Sludge, Wax.)
Scales
POST OVERHAUL RESULTS
Set Pressure:
CDSP:
Leakage Test (No. of Bubbles/Min)
CONCLUSION:
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Appendix H
Movements Report for Pressure Safety Valves
Where the original valve is reinstated in its original tag location only Section 1 should be completed.
In all other cases all three sections should be completed.
1. VALVE WAS REINSTATED AFTER RECERTIFICATION
TAG LOCATION MANUFACTURER'S SERIAL NUMBER EPNL SERIAL NUMBER
2. VALVE WAS NOT REINSTATED AFTER RECERTIFICATION
VALVE WAS MOVED TO: TAG LOCATION - (ENTER TAG NUMBER)
ON-SITE STORE - ( TICK IF TRUE)
EPNL WAREHOUSE - (TICK IF TRUE)
CONTRACTOR'S PREMISES -
(ENTER NAME OF CONTRACTOR)
VALVE WAS SCRAPPED: (TICK IF TRUE)
3. REPLACEMENT VALVE WAS INSTALLED
MANUFACTURER'S SERIAL NUMBER EPNL SERIAL NUMBER
VALVE ORIGINATED
FROM: TAG LOCATION - (ENTER TAG NUMBER)
ON-SITE STORE - ( TICK IF TRUE)
EPNL WAREHOUSE - (TICK IF TRUE)
CONTRACTOR'S PREMISES -
(ENTER NAME OF CONTRACTOR)
