API STD 622 2011 pdf free download

API STD 622 2011 pdf free download.Type Testing of Process Valve Packing for Fugitive Emissions.
1 Scope This standard specifies the requirements for comparative testing of valve stem packing for process applications where fugitive emissions are a consideration. Packing(s) shall be suitable for use at service temperatures –29 °C to 538 °C (–20 °F to 1000 °F). Factors affecting fugitive emissions performance that are considered by this standard include temperature, pressure, thermal cycling, mechanical cycling, and corrosion. This standard is not intended to replace type testing of valve assemblies or valve production testing. This standard establishes requirements and parameters for the following tests: a) fugitive emissions, b) corrosion, and c) packing material composition and properties. Test methods apply to packing for use in on-off valves with the following stem motion(s): a) rising stem, and b) rotating stem. The test for fugitive emissions is based upon elements of EPA Method 21, providing comparative values of packing performance. 2 Reference Publications The following standards contain provisions that, through reference in this text, constitute provisions of this API standard. At the time of the publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. 3.11 die-formed packing A valve stem packing typically constructed from ribbons of graphite tape or braided packing that has been subjected to pre-compression with tooling of a specific geometry. This process changes the shape and density of the material from its original free shape and natural density to a defined shape and higher density. 3.12 EPA Method 21 A leak check method established by the Federal Government Environmental Protection Agency (EPA) for performing emissions measurements on equipment such as valves, pumps, and flanges. 3.13 eccentricity The distance that the central axis of a valve stem is offset from the central axis of the stuffing box through which it passes. 3.14 emissions Gaseous leak given off by a piece of equipment. Used in reference to volatile organic hydrocarbons (VOCs) and expressed in parts per million volumetric (ppmv or ppm). 3.15 galvanic corrosion An electro-chemical reaction that may occur between a metal and a material of a different chemical nobility, such as another metal, carbon, or graphite when both materials are exposed to an electrically conductive media. See also, active inhibitor, corrosion inhibitor, passive inhibitor, pitting. 3.16 gland A movable part which protrudes into a stuffing box to compress a packing set or packing ring. 3.17 gland load The amount of load applied to a packing set. 3.18 gland stud A threaded rod or eye-bolt, extending from a valve body against which the gland flange is tightened to compress a packing set. 3.19 leak Measurable amount of test fluid escaping from the test gland. 3.20 leak rate The quantity of test fluid passing through (or around) a seal in a given period of time. 3.21 mechanical cycle A motion of the stem simulating the movement of a valve obturator (such as disc or ball) from the fully closed position to the fully open position, and returning to the fully closed position. See also, stroke.
3.22 packing set A grouping of individual packing rings designed to fill the cavity of the valve stuffing box. 3.23 passive inhibitor A type of galvanic corrosion inhibitor blended into the raw graphite used in packing, providing a protective coating to prevent a galvanic reaction from occurring. See also, active inhibitor, corrosion inhibitor, passive inhibitor, pitting. 3.24 pitting Surface cavities that occur on a metal as a result of galvanic corrosion or mechanical erosion. See also, galvanic corrosion. 3.25 rising stem valve A valve in which the movement of the stem is in an axial direction, with no rotation. 3.26 rotating stem valve A valve that will fully open or close with a nominal 90° rotation of the stem. 3.27 spacer bushing See bushing. 3.28 stem A metal rod that connects the obturator (such as a disc or ball) of a valve to a handwheel, handle, or actuator. 3.29 stroke One half of a mechanical cycle starting from either a fully open or fully closed position. See also, mechanical cycle. 3.30 stuffing box A space into which a compression packing is inserted. Also known as a packing chamber. 3.31 surface finish A measure of the roughness of a surface typically expressed in micro-inches or micro-meters.