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NFPA 58, LP-Gas Code, sets out the minimum valve and fitting requirements for propane tanks used to supply dispensers. Selecting or verifying that dispenser tank valves and fittings are proper for a certain installation requires an examination of the application and operating requirements for the dispenser, and company operating procedures.
5.1.2Identifying Required Dispenser
Tank Valves and Fittings
In this module you will learn to:
1. Identify NFPA 58 code requirements for ASME tank valves & fittings
2. Verify proper specifications and protection measures for tank relief valves
3. Verify that proper components for the dispenser installation are provided
Identifying NFPA 58 code requirements for ASME tank valves and fittings
NFPA 582004
1.3.2 (11) Propane dispensers located at multiple fuel refueling stations shall comply with NFPA 30A, Code for Motor Fuel Dispensing Facilities and Repair Garages.
NFPA 58 definitions of propane dispensers are given in:3.3.21.1 Dispensing Station3.3.21.2 Vehicle Fuel Dispenser
5.2.1.8 Containers in dispensing stations not located in LP-Gas bulk plants, industrial plants, or industrial applications shall have an aggregate water capacity not greater than 30,000 gallons.
5.7.7.4 ASME containers over 4000 gallons water capacity shall also be equipped with the following appurtenances:
1) An internal spring-type, flush-type full internal, or external pressure relief valve (see Annex E)
2) A fixed maximum liquid level gauge
3) A float gauge, rotary gauge, slip tube gauge, or a combination of these gauges
6.7.2.4 Rain caps or other means shall be provided to minimize the possibility of the entrance of water or other extraneous matter into the relief device or any discharge piping. Provision shall be made for drainage where the accumulation of water is anticipated.
6.7.2.5 The rain cap or other protector shall be designed to remain in place, except during pressure relief device operation, and shall not restrict pressure relief device flow.
6.7.2.7 The pressure relief valve discharge on each aboveground container of more than 2000 gallon water capacity shall be piped vertically upward to a point at least 7 feet above the top of the container, and the discharge opening shall be unobstructed to the open air.
Dispenser supply tanks over 4,000 gallons water capacity or having a filling opening diameter 1½-inch or larger require a transfer bulkhead equipped with an emergency shutdown valve (ESV) for the vapor equalizing connection (if 1¼-inch or larger), and an ESV for the liquid fill connection. A backflow check valve may be used for the liquid line if flow of liquid is limited to one direction (into the dispenser supply tank).
Figure 6. Transfer Bulkhead and Emergency Shutdown Valves for Supply Tank with Filling Opening 1½ Inch (Liquid) or Larger
The dispenser supply tank liquid opening that connects to the propane transfer pump must be fitted with an internal excess-flow valve. For supply tanks not located in a bulk or industrial plant having water capacities of 4,000 gallons or less a positive shutoff valve must be provided in conjunction with the internal excess-flow in one of the two methods listed below:
1. A manual valve located in the piping immediately down-stream of the excess-flow
2. An internal valve which incorporates the excess-flow and a positive shutoff