The assembly shall consist of two positive seating check valves located between two resilient seated shutoffs with a hydraulically balanced bypass line and four test cocks 这种总成应该由两个正向密封止回阀，两边夹着两个弹性阀座关闭阀，并配置一个液压平衡旁路管线和四个测试旋塞构成。
2.
Series 774xdcda contains two independently operating check valves located between two resilient seated shutoffs with four ball valve type test cocks and a hydraulically balanced metered bypass line to detect low flows 系列774xdcda包含两个独立运行的止回阀，位于两个弹性阀座关闭阀之间，并配置四个球阀型测试旋塞，以及一个液压平衡仪表旁路管线用于检测低流量。
