Check the valve parts before installation. Open and close the valve by hand for a period check the open-close position of the valve gate.

检查阀门各部位是否有松动现象，对阀门进行手动开启、关闭一个周期是否有异常现象，同时检查阀门的启闭位置是否准确。

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A pressure drop through the bit maintains the tool in the open position while the return springs close the pistons when flow decreases.

随后钻头处的压力降使扩眼工具处于打开状态，当流速下降时弹簧将活塞收回至原处。

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But after Giteau was harshly penalised for a forward pass, the Boks made the most of their superb field position to open the scoring with a close-range try from Van Heerden.

BBC: Australia 25-17 South Africa

The number of shares short is then compared to the average daily volume, in order to calculate the total number of trading days it would take to close out all of the open short positions if every share traded represented a short position being closed.

FORBES: Connect

The number of shares short is then compared to the average daily volume, in order to calculate the total number of trading days (at the average volume) it would take to close out all of the open short positions if every share traded represented a short position being closed.

FORBES: Connect