请确定所更换阀门的尺寸。
由于不用压井就能更换阀门，还不会对油井含油地层造成破坏，从而更好地保护了油气层。
As the valve can be replaced with pressure balance and the oil layer of the oil well can not be damaged, the oil and gas layer is better protected.
航天飞机发动机内的这三个阀门不断被更换，以确保它们是最有效的，能保障飞行的安全。
The three valves in the shuttle's engine compartment kept being replaced to ensure they were the best available and safe to fly.
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