单项选择题
A.橡胶密封面老化B.密封面间夹有杂质C.预紧弹簧失效D.摇杆变形
A.阀前阀后压力接近平衡或波动大B.密封面间夹有杂质C.预紧弹簧失效D.摇杆变形
A.30%~65%B.80%~105%C.70%~105%D.60%~105%
A.0.5倍B.1.5倍C.0.8倍D.1倍
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