annual maintenance短语¹³¹⁶²⁰⁺³ 基本例句 年度养护 请求酒店服务 This article presents isolation scheme which is the proper means for annual maintenance or testing of safety valves, and also summaries some ways used to isolate safety valves. 本文提出了隔离方案来解决现有装置安全阀的定期校验问题，并提出了几种具体的隔离方法供选用。 chemyq