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Subchapter 1. Unfired Pressure Vessel Safety Orders
Article 7. Compressed and Liquefied Natural Gas System

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§523. Design and Construction of Natural Gas Tanks.

(a) General. All new natural gas tanks shall be constructed, inspected, and stamped in compliance with the Code, unless the design, material, and construction of the tank are accepted by the Division as equivalent to code.

(b) Compressed Natural Gas. In addition to the stamping required by the Code, the stamping on all new CNG tanks shall include the following:

(1) Volumetric capacity in standard cubic feet of natural gas when filled to the limits provided by these regulations.

(2) The words “For CNG.”

(3) The head and shell thicknesses.

(c) Liquefied Natural Gas. The outer vessel of double wall cryogenic vessels shall be designed for the full range of pressure and/or vacuum to which it will be subjected and for adequate structural support of the inner tank and insulation under all imposed loadings. Equipment shall For Appendix A, refer to end of subchapter 1.

In addition to the stamping required by the Code, the stamping for all new LNG tanks shall include the following:

(1) Net volumetric capacity in U. S. gallons.

(2) The words “For LNG.”

(3) The head and shell thicknesses.

(4) Minimum safety relief valve capacity in cfm air. See 541 (c) (1) and (2).


Authority cited: Section 142.3, Labor Code. Reference: Section 142.3, Labor Code, and Chapter 855, Statutes of 1977.


1. Repealer of Article 7 (Section T8-550) and new Article 7 (Sections 523-544) filed 12-8-72 as an emergency; effective upon filing. Certificate of Compliance included (Register 72, No. 50).

2. Amendment of subsection (c) filed 8-6-76; effective thirtieth day thereafter (Register 76, No. 32).

3. Amendment of subsection (a) filed 4-1-77; effective thirtieth day thereafter (Register 77, No. 14).

4. Amendment filed 1-17-80; effective thirtieth day thereafter (Register 80, No. 3).

5. Amendment of article 7 headnote filed 9-25-2002 as an emergency; operative 9-25-2002 (Register 2002, No. 39). A Certificate of Compliance must be transmitted to OAL by 1-23-2003 or emergency language will be repealed by operation of law on the following day.

6. Certificate of Compliance as to 9-25-2002 order transmitted to OAL 1-17-2003 and filed 2-24-2003 (Register 2003, No. 9).

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