Vacuum Pumps

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Accumulation of water scale, lime, mud and rust in vacuum pumps not only drastically reduces volume and overall efficiency but also increases electrical load.

The following instructions should be followed removal of the water scale, lime, mud, and rust from the casing, rotor, hub, cones and associated piping of your equipment.

  1. Write down the current of “before” amperage readings, cfm at vacuum capacity and the vacuum in inches of mercury.
  2. Take unit out of service.
  3. Remove the bottom drain plug and allow all water to drain from pump casing. Replace bottom plug after the unit is drained.
  4. Break seal on water piping and attach a pumping discharge hose.
  5. Remove top plug and attach return hose between there and the re-circulating bucket.
  6. Insert “blanks” in flanges of discharge and suction piping.
  7. Add prescribed quantity of Alpha Descaler or Alpha Descaler FG into the circulation loop.
  8. In some instances, additional water may be required to maintain circulation.
  9. Tighten vacuum pump seal packing to minimize leakage.
  10. After 15 minutes of Alpha Descaler circulation, turn pump rotor 90 degrees by pulling on the drive belts or jacking the starter switch.
  11. Every 15 minutes thereafter, turn rotor 90 degrees to assure a thorough cleaning of interior parts of your pump, including hub and rotor.
  12. Continue the circulation of for at least two hours or until the foaming stops. Lack of foam indicates depleted or clean equipment.
  13. After several hours of circulation time, with intermittent turning of the rotor, the pump should be clean and the rotor should turn freely.
  14. Shut off the circulating pump and add flush water to the re-circulation bucket.
  15. Disconnect return hose and run to drain.
  16. Restart circulation pump and flush until water runs clear.
  17. Disconnect pump and all hoses. Remove all the “blanks” in the flanges and reconnect all piping.
  18. Open seal water valve, start the vacuum pump and operate for 10-20 minutes to thoroughly flush the pump. During this time adjust the seal water rate to the manufacturers’ recommendations. Also readjust the packing compression to the correct setting.
  19. Return pump to service.
  20. After unit has stabilized, write down the “after” amperage readings, cfm at vacuum capacity and vacuum in inches of mercury.
  21. Compare the “before” and the “after” readings to determine the effectiveness of Alpha Descaler and Alpha Descaler FG cleaning. Record all information for future reference to schedule Next preventive maintenance cleaning.


  • The quantities mentioned are averaged for size and model.
  • The time required for cleaning will vary with the thickness and hardness of the deposit.
  • The average Alpha Descaler cleaning time is about two (2) hours, for the Premier series we recommend four (4) hours. Additional Alpha Descaler or Alpha Descaler FG may be required to thoroughly remove all deposits in your vacuum pump.
  • For other manufacturers and models, please consult with you Alpha Descaler supplier.
  • Multiple vacuum pumps can be cleaned at the same time with Alpha Descaler.



It is a common problem when water scale, rust, lime and mud completely seizes the rotor causing immediate shutdown. Follow the instructions below for cleaning when this problem occurs:

a. Complete 1-7 in vacuum pump cleaning.
b. Remove both plugs from the top of the pump (if passage is blocked by scale, poke it through with a screwdriver).
c. Add pure Alpha Descaler or Alpha Descaler FG into the top ports as well as pumping some into the seal water passage. Allow Descaler to sit and soak for 30-45 minutes. Doing this will allow the chemical to free the pump. Do not put the plugs back until you start the circulation process.
d. After pumping Alpha Descaler for 10-15 minutes, turn rotor 180 degrees with wrench and pump another 15 minutes.
e. Should the rotor remain seized after circulating with Alpha Descaler for 10-15 minutes, disconnect the hose from the plug (discharge hose from pump) and attach this hose to the opening to the top of the casing. Circulate Alpha Descaler into this opening for 10 minutes while periodically testing to see if the rotor is freed. When the rotor is free proceed according to instructions.


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Vacuum pumps


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