在这些活塞中，活塞环的数量减少到三个，即两个气环，一个油环。

On these pistons the number piston rings was reduced to three, two compression and one oil-control.

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进口油用减压阀属于先导活塞式减压阀。

Oil reducing valve belongs to the pilot valve piston valve.

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实际压力控制涉及很多因素，如油移动进入或离开的油的体积的压缩下，活塞是否正在改变的油在压缩下的体积。

Real pressure control involves many more factors like the oil moving into or out of the volume of oil under compression and whether the piston is changing the volume of oil under compression.

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