I looked away down stream, and saw a black speck on the water.
我向下游远远的望了一下，看见水面上漂着一个黑点。
Requirement: Air inlet must start to open when down stream pressure is 1.0 PSI or above.
要求：当下游流体压力在1.0PSI及以上时，空气进口必须开始打开。
Requirement: Air inlet must start to open when down stream pressure is 1.0 PSI or above.
要求：当下游流体压力在1.0PSI及以上时，空气进口必须开始打开。
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