The cut-off valve type, the internal leakage is not allowed.

对于截断阀类来说，内漏是不允许的。

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Note: for mechanical seal, in most cases, due to evaporation from seal leakage of fluid leaking hole in observation, but sometimes a small amount and stable leakage is allowed.

注意：对于机械密封，在大多数情况下，由于汽化导致从密封泄液孔处观察不到泄漏，但有时少量而又稳定的泄漏是允许的。

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