gas ballast造句

• Gas ballast rotary pump
  气镇旋转泵
• The series h ? 2h ? h3 rotary piston vacuum pump is a sort of vacuum pro - duction equipment suitable for pumping ordinary gase and condensable gases ( when a gas ballast used )
  H3型系列滑阀式机械真空泵是抽除一般性气体或含有少量可凝性气体（此时应使用气镇）的真空获得设备之一。