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

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§528. Transfer, Operation and Maintenance.

(a) General.

(1) No natural gas shall be vented to the atmosphere unless the vent is led to a safe point of discharge. Nothing in this Order shall prohibit the use of gaging devices which vent to the atmosphere through an opening not exceeding No. 54 drill size.

(2) No smoking or open flame shall be permitted within 10 feet of any vessel during the filling operation.

(3) All threaded filling connections shall be kept effectively capped when not in use. These caps or plugs shall be so designed that they will vent to the atmosphere while at least 3 full threads are engaged.

(4) No employer or employee shall charge natural gas into any tank or cylinder not specifically designed for the most severe pressure and temperature conditions to which the vessel may be subjected.

(5) During the transfer of natural gas at least one attendant familiar with the transfer operation shall be responsible for and be on the premises during the transfer operation. during the transfer of LNG the attendant shall remain in attendance at the controls necessary to stop the transfer operation. The attendant required by this Order may be considered familiar with the transfer operation and has performed the operation at least through 3 full cycles under supervision. When natural gas is being transferred to or from a motor vehicle, the engine shall be stopped unless the motor is used to operate a pump or compressor required to transfer the product. During such loading or unloading from transportation tanks, the hand or emergency brake of the vehicle shall be set and the wheels blocked. Transportation tanks shall be bonded during the transfer operation except that bonding is not required where the transfer systems are depressurized by bleeding before disconnecting, see Paragraph 537(a)(4), and providing also that closed connections are made before transfer begins.

(6) No natural gas shall be transferred with the point of delivery less than 10 feet from any important building or house trailer, or within 5 feet from a sidewalk or public highway, street or road unless the failure to transfer would create a hazard. At the discretion of the Division, the point of delivery may be located a lesser distance from important buildings constructed of concrete or masonry materials. Nothing in this Order shall be so construed as to prohibit the following:

(A) The fueling of machinery or vehicles used in road construction or maintenance.

(B) The filling of motor fuel tanks or cylinders of not more than 30-gallon capacity.

(7) Pumps and compressors shall be suitable for use with the product to be handled for the full range of pressure and temperature to which they may be subjected. Positive displacement transfer pumps shall be equipped with a pressure actuated bypass valve and/or a recirculating system which shall limit the pressure to the maximum design pressure of the pump or piping system whichever is lower.

(8) Control devices shall be designed for the pressure, temperature and service expected and shall be so installed that icing conditions will not cause malfunction.

(9) The owner and/or user shall maintain all pressure vessels and their appurtenances, piping systems, vaporizers, controls and devices in a safe condition.

(10) A portable fire extinguisher having a rate of not less than 20BC shall be provided at the transfer operation area.

(b) Compressed Natural Gas.

(1) The pressure to which a CNG tank is charged shall not exceed the maximum allowable working pressure of the tank being filled at normal temperature. DOT cylinders shall be charged in accordance with DOT pressure and temperature regulations.

(c) Liquefied Natural Gas.

(1) To provide for the expansion of LNG with temperature, the tanks shall not be filled beyond the level specified by the tank manufacturer and in no case more than 90 percent.

(2) Tank fuel loading and unloading areas shall be substantially level.

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