California Code of Regulations
Title 8 - Industrial Relations
Division 1 - Department of Industrial Relations
Chapter 4 - Division of Industrial Safety
Subchapter 1 - Unfired Pressure Vessel Safety Orders
Article 7 - Compressed and Liquefied Natural Gas System
Section 536 - Piping Standards

(1) All pipe, tubing, fittings and other piping components between the tank and the first shutoff valve shall be designed for the full range of pressures, temperatures and loadings to which they may be subjected with a factor of safety of at least 8 based on the minimum specified tensile strength at room temperature. All other pipe, tubing, fittings and other piping components shall be suitable for the full range of pressures, temperatures and loadings to which they may be subjected with a factor of safety of at least 4. In no case may underground piping be less than Schedule 80 for piping systems having a working pressure exceeding 100 psi. Any material used, including gaskets and packing, shall be compatible with natural gas and its service conditions.

(2) All piping and tubing shall be run as directly as practical with adequate provisions for expansion, contraction, jarring, vibration and settling. Exterior piping may be either buried or installed aboveground and shall be well supported and protected against mechanical damage.

Underground piping shall be buried not less than 18 inches below the surface of the ground unless otherwise protected. All underground piping shall be protected from corrosion by coating in compliance with Section 533 (b) or equivalent. Zinc coatings (galvanizing) shall not be considered adequate protection for piping below ground.

(3) All welded piping shall be fabricated and tested in accordance with the ANSI Code for Pressure Piping, Petroleum Refinery Piping, B31.3, 1966 Edition or equivalent.

(4) All valves shall be suitable for the full range of pressure and temperature to which they may be subjected. The manufacturer shall stamp or otherwise permanently mark the valve body to indicate the service ratings. Other piping components such as strainers, snubbers and expansion joints shall also be permanently marked by the manufacturer to indicate the service ratings. All materials such as valve seats, packing, gaskets, diaphragms, etc. shall be resistant to the action of natural gas under the conditions to which they are subjected.

(5) Use of the following is prohibited:

(1) Flanged joints or threaded joints which have not been seal welded on liquid lines between the tank and the first shutoff valve are prohibited.

(2) All LNG piping over 2-inch pipe size shall be welded, flanged or silver brazed with a material having a melting point exceeding 1,000 degrees Fahrenheit. Compression type couplings and threaded joints shall not be used except that seal welded threaded joints may be used.

(3) Piping 2-inch or smaller may be threaded, welded or flanged except as prohibited in 536 (c) (1).

(4) Threaded nipples and pipe shall be at least Schedule 80.

(5) Plugs shall be solid or else they shall be bull plugs of at least Schedule 80 seamless pipe.

(6) For service temperatures of minus 20 degrees Fahrenheit or above, threaded piping and tubing with compression type couplings may be used except as prohibited in 536 (c) (2).

(7) Pipe supports for piping having a service temperature below minus 20 degrees Fahrenheit shall be designed to minimize heat transfer so that support steel embrittlement and piping restraints caused by ice formation will be prevented.

(8) Bellows type expansion joints in low temperature service shall be provided with external insulation that will prevent ice from forming on the bellows.