|MN471000, Pressure Safety Manual
Sponsor: Michael W. Hazen, 4000
|Revision Date: October 8, 2007
Replaces Document Dated: August 29, 2007
This document is no longer a CPR. This document implements the requirements of Corporate Procedure ESH100.2.PS.1, Control Pressure Safety Hazards.
IMPORTANT NOTICE: A printed copy of this document may not be the document currently in effect. The official version is the online version located on the Sandia Restricted Network (SRN).
Subject Matter Experts: Shane Page, and David Paoletta
Contributor: Pressure Safety Committee
MN471000, Issue R (Q not used)
Revision Date: October 8, 2007; Replaces Document Dated: August 29, 2007
Administrative Change: November 21, 2007, December 19, 2007, June 8, 2010, and May 26, 2011, and January 19, 2012
This chapter identifies the Pressure Installer as the person responsible for servicing pressure vessels and components, providing guidance on what items need inspection, and providing guidance on how to maintain the equipment in a safe operating condition.
The overarching issue when developing a plan for servicing pressure systems is determining potential failure modes and the consequences resulting from such a failure. System specific factors such as pressure cycles, temperature, particulate contamination, embrittlement, corrosion, or other environmental factors are all potential mechanisms of degradation that should be considered when determining the frequency of inspection and repair/replacement. Performing inspections and tracking the maintenance history of vessels and components (over the service lifetime) provides an important baseline for the continued safe operation of pressure systems.
As part of the service and maintenance process, the Pressure Installer should evaluate the scope of work and the potential hazard it represents, the need for the Control of Hazardous Energy (COHE), and the use of Lockout/Tagout (LOTO) devices prior to performing maintenance activities. Common hazards presented by pressure systems include, but are not limited to, the creation of mechanical pinch points, hose whip, and the release of a toxic or pyrophoric gas. Follow current SNL policies on COHE procedures when applying locks and tags. Any specific procedure or system may need a COHE evaluation – when questions arise, contact your Division ES&H Team for assistance.
Note: Pressure installations are divided into the following two categories according to use:
The Pressure Installer of pressure, cryogenic and vacuum systems used in research and development shall be responsible for maintaining these systems.
The Facilities Mechanical Engineering and Controls Department shall be responsible for maintaining building pressure systems. Systems maintained and inspected by the Facilities Mechanical Engineering and Controls Department are identified via a Maintenance Number. Information about any Maintenance Numbered item may be obtained by contacting any maintenance planner.
Note: Building pressure systems may include, but are not limited to:
Pressure Installers who own cryogenic systems shall:
For Building Systems: Per (AP-502), Cryogenic Systems Ownership Responsibilities Administrative Procedure, the Facilities Mechanical Engineering and Controls Department shall:
Pressure Installers who own cryogenic systems shall:
Note: The inspection and maintenance of cryogenic systems should be provided through a Service Contract managed by the Facilities organization.
The Pressure Installer shall be responsible for determining, based upon the specific system application, the proper interval for re-testing or replacing system Pressure Relief Valves (PRVs). PRVs are subject to a “first pop” effect, which is an actual cracking of the PRV at a pressure higher than the original set pressure. Suggested time intervals are provided as guidance in Table 8-1 to assist the system owner in setting these re-test intervals. Additional factors to consider when specifying an interval may include the relationship between the system MAWP and the PRV set pressure, exercising the PRV, corrosive applications, and the past history of valve performance.
Pressure Installers shall be responsible for Pressure Relief Valve (PRV):
Note: Tags are commonly used for this purpose.
PRVs should be periodically inspected for evidence of leakage, corrosion, tampering, or other type of damage and for evidence of usage conditions that may cause the valve to malfunction. There should be a clear, unrestricted vent path on the outlet of the PRV. The Pressure Installer inspection process should include:
Note: Exercising the PRV could result in valve leakage. Do not cap, plug or restrict the flow on the outlet of a leaking PRV.
New valves should be inspected for damage or contamination that may have occurred during packaging and shipment.
To help supply information for the retest process, the Onsite Calibration & Maintenance Department, or another approved PRV test station, can test and adjust PRVs in accordance with Appendix J and provide test results to the Pressure Installer.
PRV testing consists of applying pressure to a valve to determine the cracking, popping, and re-seat pressures. See Appendix J for complete details of PRV test procedures and policies.
Note: New PRVs purchased from qualified suppliers may be accepted for use at SNL for an initial interval without further testing.
Pressure Installers can use Table 8-1 as a tool to establish the testing intervals of pressure relief valves. Notation of the established PRV testing intervals should be documented within the system Pressure Safety Data Package. For further guidance, consult the pressure safety SMEs.
Inspection and Testing Intervals
Inert Applications (under 3000 psig) dry air, gases or liquids not reactive to valve materials, and non-glutinous fluids
High Pressure Applications (over 3000 psig)
Harsh Internal or External Environments, corrosives, glutinous or reactive fluids, otherwise damaging environments
Satisfactory test results do not alone validate the proper application of a PRV. Also consider such things as the relationship between the set pressure of the PRV and the MAWP of the system, flow capacity, correct placement, and ramifications of valve leakage in PRV applications.
Replace or repair in accordance with factory specifications, any damaged or defective valve.
Exercising the PRV could result in valve leakage. Do not cap, plug or restrict the flow on the outlet of a leaking PRV.
PRVs on pressure vessels manufactured under ASME Sections I and IV should be maintained in accordance with the recommendations of ASME and the National Board of Boiler and Pressure Vessel Inspectors in order to keep their ASME Code status current. Sandia will not attempt to provide flow capacity measurements or ASME approved repair functions, and can only perform an operational check to determine the cracking and re-seat pressures of ASME Code valves.The Facilities organization meets the need for testing by periodically exercising and inspecting pressure relief valves according to Maintenance Job Plans.
When determining the need to service pressure vessels and components, the Pressure Installer should consider utilizing the Sandia JIT procurement system as a means to obtain guidance information and to purchase quality components from known and reputable manufacturers. Sandia Pressure Safety SMEs can also serve as a point of contact for information on pressure, vacuum, and cryogenic systems.
Pressure Installers should consider servicing and maintaining the following types of components specific to the pressure system:
Bolts and Other Closure Hardware
Use the manufacturer’s recommendations to specify the correct torquing procedure, bolt lubrication, and torque limits for the specific sealing application.
Note: Repeated high torquing, fatigue, and corrosive environments can cause premature failure. Consult Pressure Safety Assistance Index to obtain assistance for hardware inspections involving Non-Destructive Evaluation (NDE).
Flexible Hoses, Fittings, and Tiedowns
Replace these items if they appear damaged or excessively worn, or if leakage is detected in the hose or fittings.
Note: Hoses, fittings, and tiedowns need frequent inspections.
Valves and Fittings
Replace valves and fittings periodically, depending on their condition and the corrosive effects of the pressurizing fluid.
Periodically check O-rings, gaskets, and packings for leaks. Replace as needed.
Establish a regular schedule to clean and change filter elements.
Regulators are pressure limiting devices and do not provide overpressure protection. When used in conjunction with properly sized pressure relief valves and, if applicable, flow restriction, pressure regulators may continue to be used indefinitely. Depending upon the application and the consequences of regulator failure, a preventative maintenance schedule may be appropriate.
Verify that the pressure regulator in service is appropriate for the current application. Do not change the CGA connection to place the regulator into a different gas service. Damaged or leaking CGA connections can be replaced for the current service.
Damaged or improperly operating regulators generally are replaced, rather than repaired; however, if the regulator is deemed repairable, the Pressure Installer should contact the manufacturer to perform the repair; or follow manufacturer specifications to perform onsite repair.
The Pressure Installer should periodically:
The Pressure Installer should consider the following special cautions when servicing Pressure Vessels and components:
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