ASME B31-8a:2000 pdf download

ASME B31-8a:2000 pdf download ADDENDA to ASME B31.8-1999 GAS TRANSMISSION AND DISTRIBUTION PIPING SYSTEMS
(3) Mechanical Crack Arrestors. Mechanical crack arrestors consisting of sleeves, wire-rope wrap, heavy- wall pipe, or other suitable types have been shown to provide reliable methods of arresting ductile fracture. The mechanical crack arrestors shall be placed at intervals along the pipeline. CAUTION: The requirements specified in (2) above assume the pipeline is transporting essentially pure methane and the pipe is similar in fracture behavior to that used to develop the empirical equations above. The presence of heavier hydrocarbons can cause the gas to exhibit two-phase behavior on sudden decompression and thus requires a greater Charpy energy to arrest propagating pipe fracture. Likewise, pipe that has been control rolled or quench and tempered may not behave as indicated by the equations and may also require a greater Charpy energy to arrest a propagating fracture.
Calculations must be performed to determine if the decompression exhibits two-phase behavior, and an assessment must be made as to the applicability of the arrest equations where additional toughness is may be required. Otherwise, mechanical crack arrestors [see (3) above] should be installed, or the Charpy toughness requirements for arrest should be verified through experiments or additional calcu- lations. 841.111 Limitations on Design Pressure P in Para. 841.11. The design pressure obtained by the formula in para.
841.11 shall be reduced to conform to the following:
(a) P for furnace butt welded pipe shall not exceed the restrictions of para.841.11 or 60% of mill test pressure, whichever is the lesser.
(b) P shall not exceed 85% of the mill test pressure for all other pipes provided; however, that pipe, mill tested to a pressure less than 85% of the pressure required to produce a stress equal to the specified minimum yield, may be retested with a mill type hydrostatic test or tested in place after installation.
In the event the pipe is retested to a pressure in excess of the mill test pressure, then P shall not exceed 85% of the retest pressure rather than the initial mill test pressure. It is mandatory to use a liquid as the test medium in all tests in place after installation where the test pressure exceeds the mill test pressure. This paragraph is not to be construed to allow an operating pressure or design pressure in excess of that provided for by para. 841.11.
841.112 Limitations on Specified Minimum Yield Strength S in Para. 841.11
(a) If the pipe under consideration is not new pipe purchased under a specification approved and listed in this Code, the value of S may be determined in accord- ance with one of the following: (1) S value for new pipe qualified under para. 811.221 or 811.222 (2) S value for reuse of steel pipe qualified under one of the provisions of para. 817.1 (3) S value for pipe of unknown specification as determined by para. 817.13(h)
(b) When pipe that has been cold worked for meeting the specified minimum yield strength is subsequently heated to a temperature higher than 900°F for any period of time or over 600°F for more than 1 hr, the maximum allowable pressure at which it can be used shall not exceed 75% of the value obtained by use of the steel pipe design formula given in para. 841.11.
(c) In no case where the Code refers to the specified minimum value of a mechanical property shall the higher actual value of a property be substituted in the steel pipe design formula given in para. 841.11. If the actual value is less than the specified minimum value of a mechanical property, the actual value may be used where it is permitted by the Code, such as in para. 817.1 regarding the reuse of steel pipe.
841.113 Additional Requirements for Nominal Wall Thickness t in Para. 841.11
(a) The minimum wall thickness t required for pres- sure containment as determined by para. 841.11 may not be adequate for other forces to which the pipeline may be subjected. [See para. 840.1(a).] Consideration shall also be given to loading due to transportation or handling of the pipe during construction, weight of water during testing, and soil loading and other second- ary loads during operation. Consideration should also be given to welding or mechanical joining requirements. Standard wall thickness, as prescribed in ASME B36.10M, shall be the least nominal wall thickness used for threaded and grooved pipe.
(b) Transportation, installation, or repair of pipe shall not reduce the wall thickness at any point to a thickness less than 90% of the nominal wall thickness as determined by para. 841.11 for the design pressure to which the pipe is to be subjected. 841.114 Design Factors F and Location Classes. The design factor in Table 841.114A shall be used for the designated Location Class. All exceptions to basic design factors to be used in the design formula are given in Table 841.114B.