For on-line calibration system of flowmeter, the working fluid flow is from the petroleum pipe line itself.
体积管工作时的液流，对于流量计在线检定系统，是来自输油管线本身。
It introduces characteristic and kinds of line pipe for petroleum and natural gas transmission.
简要介绍了石油天然气输送用管线钢管的种类及其特点。
Such valve can be used in medium, high pressure hydraulic and pneumatic pipe line of petroleum, chemical industry and power station.
本发明特别适用于石油、化工、电站等的中、高压液、气管道。
Such valve can be used in medium, high pressure hydraulic and pneumatic pipe line of petroleum, chemical industry and power station.
本发明特别适用于石油、化工、电站等的中、高压液、气管道。
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