2bv series liquid ring vacuum pumps are suitable for pumping the gases and steam. its suction pressure canreach 33mbar (abs) (i.e. 97 % vacuum degree). lf the transformer oil is used as the operating liquid, these pumpsare called oil ring vacuum pump and the suction pressure can reach 6.7mbar (abs) (i.e. 99 % vacuum degree). sothe oil ring vacuum pumps can replace the reciprocated vacuum pumps completely. when the liquid ringvacuum pumps work under the condition near the limited vacuum for a long time, it is necessary to couple withthe cavitation protection pipe in order to get rid of the sereaming and protect the pump.when the compressor is working, the maximum pressure is 0.26mpa (abs). and the higher of discharge pressurethe larger of the power of the compressors. so it is necessary that the data of the discharge pressure is provided to choose the proper motor.