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

I                           I           I                      Class

I                           I                                  Type

I                                                              Commercial item description number

7.3.1  Type and class.  The following is a sample that would define the marking for a type I class

125 valve:      AA50558-I-125

7.4  National Stock Numbers (NSNs):  The following is a list of NSNs assigned which correspond to this commercial item description.  The list may not be indicative of all possible NSNs

associated with the commercial item description.

NSN                                            TYPE                                          CLASS

4820-00-289-2150

4820-LLLC21441

7.5  Working steam pressures.  The valves should be designed and constructed for operation at the maximum WSP and temperatures indicated by the following pressure classes:

Type I                         - Classes 125 and 250.

Type II, III, and IV     - Classes 125, 150, 250, 300, 400, and 600. Type V                        - All classes.

7.6  Sizes.  The valves should have the following nominal pipe sizes: Type I     -  1/4-inch (8 mm) to 12 inches (300 mm).

Type II   -  1/2-inch (15 mm) to 6 inches (150 mm).

Type III  - 1/4-inch (8 mm) to 12 inches (300 mm). Type IV  - 1/4-inch (8 mm) to 12 inches (300 mm).

Type V   - 1/2-inch (15 mm) to 12 inches (300 mm) and 14 (355.5 mm) and 16 inches

(406.4 mm) outside diameter.

7.7  Key word listing.

Discharge pressure High pressure Reduced pressure Steel valve

7.8  Classification cross reference.  Classifications used in this commercial item description (see

2.) are identical to those found in the superseded military specification, MIL-V-16733D.

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