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

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§540. LNG Vaporizer Installation.

(a) Vaporizers in excess of 1-gallon capacity shall be provided with suitable automatic means to prevent liquid from passing into the vapor system. This is not applicable to vaporizers discharging back to the vessel only.

(b) Vaporizers in excess of 1-gallon capacity shall be provided with one or more safety relief valves suitable for use with natural gas and set to open at not less than the maximum working pressure and not more than 110 percent of the maximum working pressure of the vaporizer.

(c) The minimum relieving capacity of the safety relief valves shall be at least equal to the capacity marking on the vaporizer nameplate as required in Section 525 (c)(5). This marking shall be determined for exposure to external fire and shall be sufficient to prevent pressure in the vaporizer from exceeding 120 percent of the maximum working pressure. When determined by calculation, the applicable formula in Appendix A shall be used.

The safety relief valve discharge shall be led outside of the vaporizer building, if any, and be discharged at a safe place.

(d) No coil or other device carrying artificial heat for vaporization shall be located inside of any LNG vessel not constructed for vaporizing only.

(e) Vaporizers shall not be installed inside of buildings unless the building is specifically designed for housing LNG vaporizers; in which case the building shall be constructed of non-combustible material and be adequately ventilated at both the floor line and ceiling. Ventilation shall be designed to prevent gasses lighter than air from being trapped at ceiling level.

NOTE: Ventilation is considered adequate when no mixture of flammable gases is permitted in concentrations exceeding 1/5 of the lower flammability limit for such mixture.

(f) Surge tanks, containing vapor only at 20 psi or less, shall be located at least 10 feet from important buildings and property lines. Such tanks operating at pressures exceeding 20 psi shall be located with respect to important buildings and property lines in accordance with Order 531(a).

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