Pressure Safety Manual
APPENDIX J – PRESSURE-RELIEF VALVE TEST PROCEDURES AND POLICIES
Subject Matter Experts: Shane Page, and David Paoletta
Contributor: Pressure Safety Committee
MN471000, Issue S
Revision Date: March 31, 2008; Replaces Document Dated: October 8, 2007
Administrative Changes: June 8, 2010, and May 26, 2011, and January 19, 2012
Pressure relief valves (PRVs) are an important component for safe operation of a pressure system. Periodic evaluations are required to confirm proper operation of these devices.
Line organizations are responsible for the proper application and maintenance of PRVs. These responsibilities include:
This appendix describes accepted policy on the testing of PRVs in use at SNL, and sets forth the procedures to be used by line organizations that have PRV testing capabilities at SNL.
- Identification and tracking.
- Visual inspections.
- Operational checks.
- Determining replacement intervals.
For PRV tests conducted at SNL, Members of the Workforce shall:
Members of the Workforce should refer PRV testing to the Onsite Calibration & Maintenance Department.
They will perform tests and supply the data needed by the line to assess whether the PRVs are suitable for use.
Members of the Workforce shall:
Pressure Installers shall:
- Be responsible for identifying, documenting and tracking relief valves for re-test. Note: Test tags applied by valve vendors signify that the valve meets manufacturer's specifications.
- When using new valves for special applications, confirm that the manufacturer's testing properly addresses the relevant parameters of valve performance (e.g., valves on toxic gas systems). Testing of only the routine parameters of cracking and re-seating pressures is not adequate; a stringent leak check should also be performed.
- Ensure that valves not subjected to adequate manufacturer's or vendor's testing procedures are adequately tested at SNL before being placed into service.
Members of the Workforce in line organizations that test their own PRVs shall use an authorized test station and follow the approved test procedures.
See SF 2001-PRV, Sandia Designated Pressure Relief Valve Test Station (Word file/Acrobat file), for the necessary approvals and validations required for test stations and operators.
Note: A manufacturer's original specifications and testing data or alternate test procedures and schedules may be acceptable documentation in applications where the normal test intervals and procedures could adversely affect continued valve performance or the overall safety and operation of the system. For complete details on special applications, see Special Cases - Nonroutine Testing Procedures.
The line Pressure Advisor and Safety Engineering shall inspect and approve all SNL-authorized PRV test stations. See SF 2001-PRV Sandia Designated Pressure Relief Valve Test Station (Word file/Acrobat file).
As a minimum, the following requirements shall be met.
Sources for pressure gauge calibration are acceptable if the source meets the requirements of CPR100.3.1, Standards and Calibration. The range, accuracy, and precision of the pressure indicator used for testing shall be commensurate with the valve's set pressure and its tolerances for acceptance or rejection. Follow the guidelines on assembling pressure hardware in Chapter 5, “Selecting and Assembling Pressure Hardware.”
A properly configured safety manifold system shall be provided for all test stations. Attention should be given to the proper use of relief valves to protect system components (gauges, etc.) from overpressure, and the vent valves should be located properly to receive pressure from system components after testing. Follow the guidelines described in Chapter 5, “Selecting and Assembling Pressure Hardware,” on assembling pressure hardware.
SNL test stations shall be capable of performing these functions, and the operators must be able to meet these requirements:
- Visually inspect valves for evidence of external leakage, corrosion, or other types of damage or evidence of usage conditions that may cause the valve to malfunction.
- Perform the actual testing of the valve according to the procedures in the following section, PRV Testing Procedures.
- Set the pressure for adjustable relief valves following guidelines in the following section, PRV Testing Procedures.
Note: PRV testing consists of making repetitive excursions through the cracking and re-seating pressures and recording those pressure values.
Members of the Workforce shall:
- Perform valve testing at room temperature.
- Use only clean, inert fluids to test valves.
- Test valves when discharging to atmosphere, with no appreciable backpressure.
- Consider the performance characteristic effects of temperature and backpressure for proper application of the PRV.
Caution: Members of the Workforce shall not allow system maximum allowable working pressure (MAWP) to be exceeded during in situ tests.
Note: Because of wide tolerances or first-pop effects, a PRV set at MAWP may need to exceed MAWP by some percentage before cracking open. In situ testing would not be allowed for these cases. The detrimental effects of fatigue caused by pressure cycling to MAWP should also be considered when choosing to test PRVs in place.
Members of the Workforce may test valves in-situ if the line Pressure Advisor approves the test setup and proposed procedures.
Members of the Workforce shall:
- Re-test and verify that a valve is suitable for use when there has been any adjustment of the set pressure of an adjustable PRV.
- Ensure that adjustable PRVs are adjusted to the desired pressure and locked in place.
- Ensure that the set pressure remains within the range specified in the manufacturer's data.
- Confirm cracking and re-seating pressures after all adjustments have been made and locked in.
Members of the Workforce should consult the Onsite
Calibration & Maintenance Department , or other designated test stations,
which can test valves for cracking, popping, and re-seat pressures using the
specific test procedures described in this section. Other valve parameters,
such as leakage, may need to be tested at other facilities by the user. Contact
the Pressure Advisor for assistance in testing these other parameters.
Members of the Workforce should be cognizant that:
- SNL does not provide ASME certification of PRVs or perform flow measurements.
- The flow characteristics of a properly operating, non-corroded valve are assumed to be the same as those originally specified by the manufacturer.
- The line organization determines if ASME certification is needed.
- Recertification must be performed at an ASME Code Shop to maintain ASME status.
Because the Onsite Calibration & Maintenance Department will not clean or repair valves, Members of the Workforce performing these functions shall:
- Use proper replacement parts and follow the manufacturer's repair and assembly procedures.
- Retest repaired valves to ensure proper operation.
Members of the Workforce shall not have burst disks tested by the Structural Mechanics Engineering Department; they are lot-tested by the manufacturer.
Members of the Workforce who use burst disks should specify inspection and replacement intervals for burst disks in the system Data Package.
Operators of PRV test stations shall follow this testing procedure:
- Steadily increase the pressure on the PRV, slowing the rate of increase as you approach the set pressure. A slow rate of increase is needed to accurately determine the cracking pressure. A metering valve may help control the rate of pressure increase.
- Record the initial cracking pressure. Measuring and recording popping pressures is optional. After reducing the pressure, record the initial re-seat pressure. Cracking, popping, and re-seat effects can be detected visually on the test gauge, by sound, or by monitoring flow. Record operator-observed valve leakage upon re-seat on the test data sheet.
- Record and report unusual first-pop effects to the user, as this may help determine the adequacy of the line's periodic inspections and may call for more frequent manual operations of the valve. Valves that will not settle in and give repeatable cracking or popping pressures (within 5% of previous readings) should be considered unreliable and therefore should be rejected. The user or line Pressure Advisor shall make this determination.
- Repeat this procedure to get at least two additional measurements of cracking, popping and re-seat pressures.
- Compute the average of the above measurements.
Note: If the first set of test pressures were significantly different than the repetitive values, do not include them in the average. Use an average of three or more readings taken when the valve has been exercised.
- Record and report to the user any other valve characteristics observed.
- Compare the average value determined in step 5 to the valve's nominal set pressure and refer to the tolerance charts in Table J-1 or the manufacturer's specifications.
- Note any operational conditions such as leakage or chatter upon re-seat in the comments section of the test data sheet.
- Document the operational test results and the application. The approval for use shall be made by the system's Pressure Installer or line Pressure Advisor
- Consult Table J-1, Tolerances Guidelines for PRV Testing, when determining operational characteristics and acceptance of a PRV.
Table J-1. Tolerance Guidelines for PRV Testing
|Nominal Cracking Pressures
|Non-ASME Code Valves
|ASME Code Valves
|0 to 5
5 to 10
10 to 25
25 to 500
500 to 2000
|Consult the applicable ASME Code
- In all cases, the application of a PRV influences the parameters tested, procedures required, and the acceptance/rejection criteria. The line organization shall make the above determinations under the guidance of the system Pressure Installer or Pressure Advisor.
- The tolerances listed above represent general guidelines for acceptable test results as developed with time and experience in PRV testing. Test results outside the above tolerances may indicate unusual valve performance and may be cause for rejection of the valve. In these cases, consult the manufacturer's specifications for tolerances relevant to that particular valve and justify the acceptance or rejection of a valve's performance in the comments section of the "PRV Test Data Sheet" (Word file/Acrobat file) of SF 2001-PRV, Sandia Designated Pressure Relief Valve Test Station.
- In cases where valve leakage upon re-seat is noted, the application of the valve and the significance and safety implications of its leakage shall be considered by the line when determining acceptance or rejection.
Interpreting and Recording Test Data
The operators of PRV test stations shall provide a copy of the test data to the line.
The line representative (system Pressure Installer or Pressure Advisor) shall be responsible to:
- Interpret test results and determine the acceptance or rejection of the valve based on these test results and the valve's application.
- Include this information in the system data package and maintain it for the lifetime of the valve in order to analyze continued valve performance.
Test Data Sheet
The operators of PRV test stations shall:
- Complete a PRV test data sheet (see the Pressure Relief Valve (PRV) Test Data Sheet of SF 2001-PRV, Sandia Designated Pressure Relief Valve Test Station (Word file/Acrobat file). Alternate data sheet forms may be used at the discretion of the tester, provided that the alternate forms address all the data requirements.
- Retain a copy of the test data sheet at the testing station for a minimum of three years.
The operators of PRV test stations shall return rejected valves to the valve owner along with the test results.
The valve owner shall:
- Either repair a rejected valve according to manufacturer specifications and procedures and submit it for re-test, or dispose of it.
- Dispose of valves having corrosion from exposure to hazardous materials according to ES&H Corporate requirements.
SPECIAL CASES - NONROUTINE TESTING PROCEDURES
Note: In some cases, performance of the routine test procedures at stated intervals (see PRV Testing Procedures) would degrade valve performance or adversely affect the overall safe operation of a system. In such cases, special test procedures or intervals are then necessary.
Members of the Workforce shall:
- Document the safety and reliability of the PRV and the associated pressure system in the system data package that is then approved by the manager and reviewed by the line Pressure Advisor.
- For monitoring purposes, inform the safety engineering representative or the appropriate division ES&H team member, in writing, of these special cases of nonroutine testing.
For special cases, Members of the Workforce should consider the following topics of this section.
Document the reasons that the valve in question is not compatible with routine test procedures and/or intervals.
Alternate or redundant safety features of a system (excess flow valves, microprocessor control of interlocks, etc.) should be emphasized and included in the system data package. The acceptance or rejection criteria for the PRV may be influenced by these alternate safety features.
OEM specifications and testing from a known, reputable manufacturer are acceptable in lieu of in-house testing to place a valve into service for an initial interval. The manufacturer must, as a minimum, perform 100% testing of set and re-seat pressures. Other tests may also be required depending on the valve's application. Members of the Workforce should consult their Pressure Advisor, or the Safety Engineering SMEs for guidance on the acceptance of new PRVs.
- The user shall state, in the system Data Package, inspection and replacement or retest intervals for the valve and document any alternate tests or procedures that are performed.
Pressure Installers shall be responsible for monitoring test intervals of relief valves within their cognizance. See Chapter 8, "Servicing Pressure Vessels and Components," for a complete listing of the responsibilities concerning pressure relief valves.
Pressure Installers shall have replacement PRVs tested and ready for use before shutting down a system to replace valves due for re-test. The valve needing re-test may leak or for some reason fail its re-test. Without replacement valves, the system must then be shut down until a suitable replacement valve can be procured.
Note: Lockout/Tagout procedures may need to be followed where systems would be left unprotected.
Shane Page, email@example.com
Al Bendure, firstname.lastname@example.org
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