该阀采用环空外压操作测试阀的开关，不需要保压，而且采用简单的机械压力平衡机构代替了专用计量套。
Without keeping annulus pressure to static and instead of special metering by simple mechanical pressure ba lance structure, this valve is conducted by annulus pressure.
该阀采用环空外压操作测试阀的开关，不需要保压，而且采用简单的机械压力平衡机构代替了专用计量套。
Without keeping annulus pressure to static and instead of special metering by simple mechanical pressure ba lance structure, this valve is conducted by annulus pressure.
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