Standard Specification for Pressure-Reducing Valves for Steam Service

Abstract

This specification covers self-contained, internally operated, globe style, pressure-reducing valves for use in steam service. In these valves, the downstream pressure feedback is sensed by a spring-loaded diaphragm to position a pilot valve—the pilot valve uses the inlet steam pressure to position the main valve plug via an operating piston. The valves shall be of the following compositions: Composition B made with 1.25% chromium, 0.5% molybdenum and Composition B made with carbon steel. All materials shall be selected to prevent corrosion, galling, seizing, and excessive wear or erosion where applicable. Clearances shall prevent interference as a result of the thermal expansion. Cadmium plating is prohibited. Components of these valves shall include body, bonnet, bottom cover, internal trim, cylinder liner, piston, gaskets, diaphragm, springs, and bolts. Valves will be operated, maintained, and repaired on board ships and shall emphasize simplicity, maintainability, ruggedness, and reliability. Design shall permit access for adjustment and repair when working from either side of the valve and without requiring removal of the valve body from the line. Each production valve shall be subjected to the following tests: nondestructive test, hydrostatic test, seat tightness test, and external leakage test.