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    Troubleshooting Rotary Vane Vacuum Pump

    The installed rotor of a rotary vane vacuum pump is tangent to the stator fixed surface inside the pump eccentric, two or more rotary vanes slide in the rotor slot and contact with the inner wall of the stator, which makes the pump chamber divided into several variable volumes.

    Generally, the clearance between the rotary vane and pump chamber is sealed by oil, so the rotary vane vacuum pump is usually an oil seal mechanical vacuum pump.

    A rotary vane vacuum pump can remove the dry gas from the sealed container. It can remove a certain amount of condensable gas if it has gas ballast device. However, it is not appropriate to remove some gases that are highly oxygenated, corrosive to metals, react chemically to pump oil, and contain particulate dust.

    The rotary vane vacuum pump failure is divided into operation failure and performance failure.

    Operation failure

    1. The pump doesn’t run

    The vacuum pump can’t be started until the situation is clear, avoiding aggravating the fault. This kind of circumstance divides into the pump can move or can’t move by hand.

    • The pump can move but without turning. The reasons are coupling failure, belt slipping, wrong connection with motor, motor damaged, power out and so on.
    • The pump can’t move or move heavily. There are several reasons.
      • Starting pump temperature is too low, pump oil viscosity is too high, and stopping pump return too much oil.
      • Oil level is too high that makes stopping pump return too much oil (add too much oil, there is water condensing in the pump or the condensed water in the exhaust pipe returns to the pump).
      • There are foreign matters in the pump, such as welding slag and oxide in the inlet pipe, scraps of pump parts and so on. The rotary vane is deformation stuck.

    2. Extremely high temperature of the pump

    Rotary Vane Vacuum Pump

    It means the highest oil temperature measured near a low level exhaust valve exceed the specified value of the operating instruction. The pump oil viscosity sharply drops because temperature of the pump elevated, which makes the saturated vapor pressure on the pump oil and the limit pressure in the pump increase and the pumping efficiency decrease.

    There are some reasons for temperature of the pump is too high:

    • Ambient temperature of the pump is too high.
    • Intake air temperature is too high.
    • Failure of inlet cooling device and pump long-term continuous operation in high pressure.
    • Water cooling pump cooling water shortage and circulating water designed effect is not good.
    • Failure of temperature-controlled water regulating valve.

    3. Oil leakage

    Oil leakage occurs to the sealing surface of shaft seal, oil box and pump parts, oil drain plug, oil label, oil hole plug, through hole connection between the stator components and bearing and gas ballast valve, which is caused by aging of sealing parts, improper installation, damage and failure, uneven surface, impurities, rough and loose casting. If stopping pump return oil, the oil will enter the gas ballast valve. Close the gas ballast valve, otherwise oil leaks. When making the rubber mat, it should be sure to use oil resistant rubber, and be shaped according to the original design. If the sealing surface is too big, it will cause oil leakage.

    4. Water leakage

    Water leakage occurs to some places, including pipe head, water jacket sealing surface, the drain hole screw plug and drain valve, etc. Water jacket drilling, casting defects, freezing crack, may lead to water leakage as well.

    5. Maximum power exceeded

    Continuous working for a long period of time will lead to excessive maximum power, mainly reflected in the inlet and exhaust pressure are too high, temperature of the pump is too high, and the clearance of rotary vanes is too small, high voltage and pump liquid back into the pump. Excessive maximum power will lead to the motor damage. Continuous operation near the maximum power should be avoided as far as possible. If there are some sediments, it should be regularly cleaned.

    Performance failure

    1. The ultimate pressure is not up to standard

    It can be caused by external leakage, internal leakage, oil hole blockage, poor pump oil quality or pollution deterioration, water vapor and other condensable substances, instrument distortion and pump operation is not normal.

    If external leakage is too much, white steam can be seen at the exhaust vent. There are a lot of bubbles in the oil mark and low level exhaust valve. The exhaust pressure is felt when a hand is put on the exhaust vent, the power will increase as well. At this moment, first check whether the gas ballast valve has been closed. In case of external leakage, check the pump port, pipe, valve and container one by one. In addition, seal failure of the outer shaft no oil in the oil cup, oil hole leakage can cause external leakage as well. Internal leakage can cause by the movement gap between the pump, exhaust valve plane, exhaust valve sealing surface, internal shaft seals, pump cover plates, air intake pipe, sealing parts of the valve will cause to wear, corrosion, and bite, which makes the operation gap increase. When the fuel tank is well sealed, if the hand feels sucked on the vent, the exhaust valve may fail.

    If pump oil is clean and long storage unused, the gas ballast valve can be open to purify the water vapor in the pump. If pump oil is yellow, white or have been emulsified, fully open the air ballast, adjust air quantity and purify operation. When necessary can put the right amount of gas into the pump mouth operation, which can speed up the purification process. If the pump oil is mixed with other volatile gas or liquid, it is necessary to change oil timely and clean the oil tank. Some vacuum pumps, the pump fluid will be deposited in the interstage airway. In order to achieve a good oil exchanges effect, try to discharge the sedimentary pump fluid.

    Ultimate pressure is measured by compression mercury vacuum gauge, when it is measured with a calibrated thermocouple gauge, the measured value increases. It is recommended to reserve a parallel calibration regulator for comparison in case of suspected regulatory pollution distortion. Ultimate pressure increasing will make the extraction efficiency decrease in high vacuum period as well as ultimate fully pressure increase. The above can be used to judge, check and deal with failures of reduced pumping efficiency and increased ultimate fully pressure.

    2. Noises

    There are many reasons for vacuum pumps making noise, such as the structure design of vacuum pump, the motor and pump bearing making noise, rotary vanes not smooth, large intake volume, loose parts in the vacuum pump and unequal installation making vibration.

    3. Oil spouts

    There are many factors that influence the oil spouts of vacuum pump, which are the size, position and sealing condition of the oil box return hole as well as the design and installation of the oil baffle plate. The Mist eliminator, oil baffle cap and oil and gas separator of exhaust port and the height of the oil level and the size of the oil intake influences the oil spouts of vacuum pump as well.

    6/15/2021 3:07 AM
    Thanks for sharing such an informative post.
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