Double Check Valve Assemblies shall consist of two positive seating check valves located between two resilient seated shutoffs with four ball valve type test cocks.是什么意思_Double Check Valve Assemblies shall consist of two positive seating check valves located between two resilient seated shutoffs with four ball valve type test cocks.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句