Check valve and butterfly valve combinations are very popular; normally a short spool piece is required between the valves.
止回阀与蝶阀的连接是经常发生的事，通常需要在这两种阀门之间加上一节短短的阀槽。
Besides the vegetables, they held a piece of bread, a pocketknife, sometimes the Alpine Club guidebook, and always a spool of wire for emergency repairs.
除了那些蔬菜，他们还拿一块面包，一把小折刀，有时还带上阿尔卑斯山俱乐部旅游指南，还有一轴紧急时用的维修线。
They employ a unique, one piece center spool design that accommodates a user-supplied padlock in the closed position.
他们采用的是独特，一件中心轴设计，可容纳用户提供在关闭位置锁。
They employ a unique, one piece center spool design that accommodates a user-supplied padlock in the closed position.
他们采用的是独特，一件中心轴设计，可容纳用户提供在关闭位置锁。
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