API RP 576-2017 pdf download.Inspection of Pressure-relieving Oevices.
1 Scope This recommended practice (RP) describes the inspection and repair practices for self-actuated pressure-relieving devices commonly used in the oil/gas and petrochemical industries. As a guide to the inspection and repair of these devices in the user’s plant , it is intended to ensure their proper pertormance. This pub lication covers self-actuated devices such as direct-acting spring-Ioaded valves , pilot-operated pressure-relief valves , rupture disks , pin-actuated devices , and weight-Ioaded pressure vacuum vents. The recommendations in this publication are not intended to supersede requirements established by regulatory bodies. This publication excludes tank weak seams and/or sections or tank thief hatches , explosion doors , fusible plugs , control valves , pressure-regulating devices , integral rotating equipment components , other devices that either depend on an external source of power for operation or are manually operated , or devices not designed to be inspected or recertified. Inspections and tests made at manufacturers’ plants , which are usually covered by codes or purchase specifications , are not covered by this publication. This publication does not cover training requirements for personnel involved in the inspection and repair of pressure-relieving devices. Those seeking these requirements should see API 51 0 and API 570 , which give the requirements for a quality control system and specify that the repair organization maintain and document a training program ensuring that personnel are qualified. 2 Normative References The following referenced documents are indispensable for the application of this documen t. For dated references , only the edition cited applies. For undated references , the latest edition of the referenced document (including any amendments) applies.
3 Terms and Definitions When used within this document , the following terms and definitions apply. 3.1 accumulation The pressure increase over the maximum allowable working pressure (MAWP) of the vessel or piping system , expressed in pressure units or as a percentage of MAWP or design pressure if a MAWP has not been established. Maximum allowable accumulations are established by applicable codes for emergency , operating , and fire contingencies. 3.2 backpressure The pressure that exists at the outlet of a pressure-relief device as a result of the pressure in the discharge system. Backpressure is the sum of the superimposed and built-up backpressures. 3.3 blowdown The difference between the set pressure and the closing pressure of a va lve , expressed as a percentage of the set pressure or in pressure units. 3.4 built-up backpressure The increase in pressure at the outlet of a pressure-relief device that deve lops as a result of flow after the pressure-relief device opens. 3.5 burst pressure The value of the upstream static pressure minus the value of the downstream static pressure just prior to when the disk bursts. When the downstream pressure is atmospheric , the burst pressure is the upstream static gauge pressure. 3.6 burst pressure tolerance The variation around the marked burst pressure at the specified disk temperature in wh ich a rupture disk will burs t. 3.7 car seal A device installed on a valve to secure it in a specified position (open or closed). When properly installed , the associated va lve cannot be operated unless the car seal is physically removed. 3.8 closing pressure The value of decreasing inlet static pressure at which the valve disc reestablishes contact with the seat or at which lift becomes zero , as determined by seeing , feeling , or hearing.
3.10 d es ign pr ess ur e The pressure , together with the design temperature , used to determine the minimum permissible thickness or physical characteristic of each vessel component as determined by the vessel design rules. The design pressure is selected by the user to provide a suitable margin above the most severe pressure expected during normal operation at a coincident temperature. It is the pressure specified on the purchase order. This pressure may be used in place of the MAWP in all cases where the MAWP has not been established. The design pressure is equal to or less than the MAWP. 3. 11 galling A condition whereby excessive friction between high spots results in localized welding with subsequent splitting and a further roughening of rubbing surfaces of one or both of two mating parts 3.12 huddling chamb er An annular chamber located downstream of the seat of a pressure-relief valve for the purpose of assisting the valve to achieve lif t. 3.13 lift The actual travel of the disc away from the closed position when a pressure-relief valve is relieving. 3.14 lifting lever A device on the relief valve that applies external force to the stem of the relief valve , which can be used to manually operate the valve. 3.15 manufacturing design range The pressure range at which the rupture disk shall be marked. Manufacturing design ranges are usually catalogued by the manufacturer as a percentage of the specified burst pressure. Catalogued manufacturing ranges may be modified by agreement between the user and the manufacturer.