1.1 本规范涵盖蒸汽服务中使用的独立式、内部操作的截止式减压阀。在这些阀门中，下游压力反馈由弹簧加载的隔膜感测以定位先导阀——先导阀利用入口蒸汽压力通过操作活塞定位主阀塞。 1.2 以英寸-磅单位表示的值应被视为标准值。本标准不包括其他计量单位。 1.3 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。

1.1 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 by means of an operating piston. 1.2 The values stated in inch-pound units are to be regarded as standard. No other units of measurement are included in this standard. 1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.