One-stage or two-stage pumps feature up and down movement of flexible diaphragm during the mechanical stage which induces a flow of gas through the pump head, generating a vacuum.
单级或双级泵是通过橡胶膜片上下往复运动，引导气流通过泵头，形成真空状态。
2
The pump has a two-stage, end suction, horizontally mounted back pull-out design for hot, abrasive and corrosive liquids.
该泵为两级、轴向吸入，卧式安装的后拉式泵，适用于热的、磨蚀的和腐蚀的介质。
3
Presents the two-stage heat pump test-bed designed by the authors, analyses the problem existed in experiment and offers the improving method.