API STD 622 2011 pdf 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 Terms and Definitions For the purposes of this standard, the following definitions shall apply. 3.1 active inhibitor A type of galvanic corrosion inhibitor, applied as a surface coating to packing or added to packing material during the die-forming process, providing a sacrificial anode material corroding in preference to the surrounding metal. See also corrosion inhibitor, galvanic corrosion, passive inhibitor, and pitting. 3.2 actuate To cause movement of a valve stem either by raising, lowering or turning it. 3.3 anti-extrusion ring A ring of packing used at one or both ends of a packing set to prevent extrusion of packing material into clearances. 3.4 ambient temperature Temperature of testing facility that is between 15 °C (60 °F) to 40 °C (110 °F). 3.5 axial In the direction of a shaft or stem axis. 3.6 braided packing Packing typically constructed of intertwining strands of synthetic or natural fibers. Strands may consist of yarn or filaments, and may also include metallic materials. Two primary braid configurations are square and interbraided or interlocking. 3.7 bolt torque The amount of twisting or turning effort (expressed as Nm, lbf-ft or lbf-in.) required to turn the nuts on a gland flange, commonly used to describe the load that a gland flange exerts on a valve packing set. 3.8 bore diameter The inside diameter into which packing is inserted; also called the stuffing box bore. 3.9 bushing Cylindrical spacer used to take up excess space in a stuffing box. 3.10 corrosion inhibitor An ingredient added to packing that decreases the potential for galvanic corrosion in the stuffing box. Corrosion inhibitors may be classified as either passive or active. See also, active inhibitor, galvanic corrosion, passive inhibitor, and pitting.
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.