SELECTION When selecting a regulator, specify its complete designation including: pipe size code, outlet pressure range, orifice size, body position, vent position and indicate if a slam-shut device is required. Note, the 1½" and 2" sizes have the same capacities. Size selection should be based on piping preference and velocity through the piping. Example: Select a regulator for 20,000 scfh of 0.6 specific gravity natural gas from 25 psig supply pressure to 2 psig outlet pressure. A slam-shut device is not required for this example. Solution: Entering Table D, the required spring range is 1 to 3.25 psig. Further, the regulator with the appropriate capacity is determined to be the ¾" orifice size 7399-_. To determine the complete product number, refer to “ORDERING INSTRUCTIONS”. 7339 Regulators reduce high gas supply pressures to practical use levels. Since capacities will vary with the pressure drop across the regulator (see Table D), due care must be exercised in properly sizing both the regulator and downstream piping. These regulators are pilot operated. Therefore they are an excellent choice when the application requires precise pressure control. Since pilot operated regulators have slower response times, do not use these regulators on TwinBed, DMC, Stepfire or other high cycling applications. Products ending in “0.5, 1, 2 or 3” contain an integrated overpressure slam-shut device. SPECIFICATIONS Body Sizes and End Connections: 1 ½ " NPT, 2" NPT and 2" Class 125 FF Flanged Capacities: See Table D Maximum Emergency and Operating Inlet Pressure: See Table C Maximum Emergency and Operating Outlet (Casing) Pressure: 66 psig Temperature Capabilities: -20° to 150°F (-29° to 66°C) Pressure Registration: Dual-registration ( ¾ " NPT connection, external sensing line required) Slam-shut Sensing: External ( ¼ " NPT connection, external sensing line required)
Table A. Specific Gravity Correction Factor Sp Gr Factor 0.4 1.22 0.6 1.00 1.0 0.774 1.5 0.632 2.0 0.547
If the specific gravity of the gas is other than 0.6, divide desired flow by gravity factor to get equivalent flow of natural gas; then select regulator from Table D. Multiply a given size regulator's natural gas capacity by gravity factor to get regulator capacity with different gas. RELIEF VALVES All North American 7339 Regulators, except the 14 to 35 psig spring range model, come with a non-adjustable internal limited capacity relief valve feature. This internal relief valve is intended to minimize overpressure that could occur due to thermal expansion. If the downstream pressure exceeds the relief valve’s start to discharge pressure as indicated in Table B, the relief valve opens and excess gas is vented through the vent in the upper spring case. INSTALLATION The North American 7339 regulator may be installed in any orientation as long as the flow through it matches the direction arrow cast on the body. The 7339 regulator requires an external sensing line. If gas escaping through the internal relief could constitute a hazard the spring case vent must be piped to a location where escaping gas will not be hazardous. If the vented gas will be piped to another location use obstruction-free tubing or piping at least equal in size to the vent. The end of the vent pipe must be protected from anything that might clog it. OVERPRESSURE PROTECTION Like most pressure-reducing regulators, the 7339 Regulators have outlet pressure ratings that are lower than the inlet pressure ratings. Therefore, a pressure relieving or pressure limiting device is needed if the inlet pressure can exceed the outlet pressure rating, see "Table C" and “SPECIFICATIONS”. The internal relief in this regulator (all models except the 14 to 35 psig models) provides relief from minor overpressure caused by thermal expansion. It should not be considered complete overpressure protection. Refer to the capacity information section to determine the required relief valve capacity. The regulators ending in “0.5, 1, 2 or 3” provide overpressure protection by shutting off the flow of gas to the downstream system. This slam-shut device requires an external sensing line.
Bulletin 7339 Page 2
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