| 单词 | back-pressure valve | 
| 释义 | back-pressure valve [`bak ´presh·ǝr ´valv]  PETROLEUM ENGINEERING A check valve installed in a natural- gas well bore to shut off gas flow while replacing the blowout preventer (used during drilling) with a christmas tree piping arrangement, which controls gas flow out of the completed well.  | 
	
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