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

intermediate-steam pressure supplied by the pilot valve. The pilot valve shall be controlled by the reduced-steam pressure supplied by means of an external feeler pipe connected at some point in the reduced-pressure line on the downstream side of the main valve.

3.1.5 Type V. Type V valves shall consist essentially of a main valve with a spring-loaded diaphragm operator, a pilot valve operated by hydraulic, pneumatic, or electrical means, and all accessory fittings required for a complete unit. The main valve shall be activated by a diaphragm and spring arrangement that will allow the valve to deliver the desired reduced pressure. The pilot valve shall cause activation of the diaphragm and spring.

3.2 Standard commercial product. The valves shall, as a minimum, be in accordance with the requirements of this commercial item description and shall be the manufacturer's standard commercial product. Additional or better features which are not specifically prohibited by this commercial item description but which are a part of the manufacturer's standard commercial product, shall be included in the valves being furnished. A standard commercial product is a product which has been sold or is being currently offered for sale on the commercial market through advertisements or manufacturer's catalogs, or brochures, and represents the latest production model.

3.3 Design. The unit shall be designed to permit easy accessibility for maintenance and service in the field. The design shall be such as to prevent conditions hazardous to personnel or deleterious to equipment.

3.4 End connections. Valve end connections shall be screwed, screwed unions or flanged, welding ends, tube ends, or tri clamp, as specified (see 7.2). Screwed ends shall conform to National Pipe Threads. All ends shall conform to the applicable requirements of ANSI B16.1 and ANSI B16.5.

3.5 Construction. Valves shall be designed and manufactured to meet the requirements as specified in the acquisition documents. The design and manufacture shall be the same as standard commercial practice.

3.5.1 Inner valves. Valves shall have single or double seats as specified (see 7.2), except that

type II valves shall have single seats only. When specified (see 7.2), double-seated valves shall be so designed that the action of the inner valve can be easily reversed without the use of additional parts.

3.5.2 Valve trim. Valve trim shall be in accordance with the manufacturer's standard practice, except as otherwise specified herein (see 7.2). Design shall be such that in the event of pressure failure of the operating medium, the valve shall go to the open or to the closed position as specified (see 7.2).

3.5.3 Type V control pilots. Type V control pilot shall be hydraulically, pneumatically, or electrically controlled, as specified (see 7.2). The instrument and control piping shall be in accordance with ANSI B31.1.