由于罗茨泵是一种无内压缩的真空泵，通常压缩比很低，故高、中真空泵需要前级泵。
As the Roots pump is a non-vacuum inside the compression, the compression ratio is usually very low, so high, medium and vacuum pumps need to pump before.
着重论述了在制药企业中真空泵运转过程中排气管发生爆鸣现象的安全技术控制措施。
The safety technical measures against explosion whistle happened on exhaust pipes during the running of vacuum pumps in pharmaceutical enterprises are discussest.
水环式真空泵中废弃的水和空气一起被排到水箱里。
Water ring vacuum pump in the waste water and air into the tank together.
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