A-A-50558 Valves, Pressure Regulating, Steam No S/S DocumentThis commercial item description covers steam pressure regulating valves that transform steam from a specified initial pressure to a specified final reduced discharge pressure or range of pressures. The specified inlet steam pressures range from 15 pounds per square inch gage psig to 1,500 psig 103 kiloPascals gage kPagage to 10,343 kPagage. The steam pressure regulating valves covered by this commercial item description are intended for transforming steam from a specified initial pressure to a specified final reduced discharge pressure or range of pressures in steam systems.

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A-A-50558

3.5.4 Operators. Unless a particular type is specified (see 7.2), operators shall be any one of the following: diaphragms, bellows, or pistons.

3.5.5 Loading means. Unless a particular means is specified (see 7.2), loading shall be by any one of the following: springs, weights and levers, air domes, and tanks.

3.6 Operational requirements. The initial or inlet pressure (maximum/minimum), the total temperature or degrees superheat, the delivery or outlet pressure (maximum/minimum), the maximum flow required through regulator, and the character of the load (constant or intermittent) shall be as specified (see 7.2).

3.6.1 Accuracy of regulation. The controlled pressure shall not vary by more than the values indicated in table I. These values shall be based on the steam flow varying not more than

10 percent of the rated capacity, and the initial pressure varying not more than 20 percent of the specified initial pressure, except that for single-seated direct-operated valves, the initial pressure shall vary not more than 10 percent. Unless otherwise specified (see 7.2), accuracy of regulation for small flow valves shall conform to table I. Valves listed are for slow load or pressure changes. When abrupt changes occur, momentary deviations may be greater but shall result in immediate return to the limits indicated in table I.

TABLE I. Accuracy of regulation.

Types I and III

Range of controlled

(pressure psig)

Maximum deviation

(plus or minus)

2-20 13.9-137.9 kPa(gage)

21-50 144.8-344.8 kPa(gage)

51-1500 351.6-10,342.5 kPa(gage)

20 percent

10 percent

5 percent

Types II, IV, and V

2-20 13.9-137.9 kPa(gage)

21-50 144.8-344.8 kPa(gage)

51-1500 351.6-10,342.5 kPa(gage)

1/2 psig 3.5 kPa(gage)

1 psig 6.9 kPa(gage)

2 percent

3.6.2 Leakage. Leakage through single-seated valves shall be not greater than 0.01 percent of the maximum valve capacity. Leakage through double-seated valves shall be not greater than 0.5 percent of the specified maximum valve capacity.

3.6.3 Operating range. Unless otherwise specified (see 7.2), valves shall be adjustable over an operating range of not less than 10 percent of the specified reduced pressure.