Vacuum level drops
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Vacuum pump unit: screw pump (100 L/s) + Roots pump (150 L/s). After the screw pump was started, the vacuum level was -0.09 MPa; after the Roots pump was started as well, the vacuum level dropped to -0.07 MPa. What went wrong?
Check whether the outlet and inlet of the Roots pump are properly connected, and also verify that the pump is not running in reverse – it’s important that the power connection is correct.
1. Is the cooling water in the condenser flowing smoothly? 2. Is the pressure-boosting steam flow set too high? 3. Is the discharge of condensate from the condenser unobstructed?
If it is a dry rotary vane pump, it is required that the incoming medium contain as little liquid as possible. Therefore, the outlet of the screw pump should be condensed as much as possible to separate the liquids. If this condition is met, experience suggests that the outlet backpressure is likely high, and it is necessary to investigate the reasons for the high backpressure.
You can check the location of the vacuum gauge. During our factory’s last renovation, a screw pump was added at the back to compress the gas in advance before it reaches the vacuum pump; using the old vacuum pump would result in an even lower level of vacuum. You can check the vacuum level of the equipment at the earlier stage
First of all, there’s an issue with your ratio – the Roots vacuum pump chosen is a bit too small. Secondly, the rotation direction of the motor in the Roots vacuum pump should be reversed; adjust the direction accordingly
The Roots vacuum pump should be installed later; check whether the wiring of the Roots pump’s motor is reversed – just swap any two of the live wires.
The Roots pump is too large, but the vacuum level won’t decrease anyway