Restarting motor-driven centrifugal pumps after power failure

With storm season fast approaching it is always best to be prepared. Although we cannot control the weather, we can have these simple measures in place to help minimise down time and get your pump up and running again after the storm has passed.

Assuming that power failure will not cause the centrifugal pump to go into reverse rotation, that is, that a check valve will protect the pump against reverse flow, there is generally no reason why the pump would be permitted to restart once the current has been re-established. Whether the pump will start again automatically when the power is restored will depend on the type of motor control logic used.

Because pumps operating on a suction lift may lose their prime during the time that power is off, it is preferable to use starters with low load protection for such installations to prevent an automatic restart. This does not apply, of course, if the pumps are automatically primed, or if some protection device is incorporated so that the pump cannot run unless it is primed.

Starting the pump

Assuming that the centrifugal pump in question is motor-driven, that its shutoff power does not exceed the safe motor power, and that it is to be started against a closed or cracked open gate valve, the starting procedure is as follows:

  1. Prime the pump, opening the suction valve, closing the drains, etc. to prepare the pump for operation
  2. Open the valve in the cooling water supply to the bearings, where applicable
  3. Open the valve in the cooling water supply if the stuffing boxes are water cooled
  4. Open the valve in the sealing liquid supply if the pump is so fitted
  5. Open the warm-up valve of a pump handling hot liquids if the pump is not normally kept at operating temperature. When the pump is warmed up, close the valve
  6. Open the valve in the recirculating line if the pump should not be operated against dead shut off (if fitted) or slightly crack open the discharge valve
  7. Start the motor
  8. Open the discharge valve slowly
  9. Observe the leakage from the stuffing boxes and adjust the sealing liquid valve for proper flow to ensure the lubrication of the packing. If the packing is new, do not tighten up on the gland immediately, but let the packing run in before reducing the leakage through the stuffing boxes
  10. Check the general mechanical operation of pump and motor, for example, bearing temperature, noise vibration
  11. Close the valve in the recirculating line once there is sufficient flow through the pump to prevent overheating

If the pump is to be started against a closed check valve with the discharge gate valve open, the steps are the same, except the discharge gate valve is opened prior to the motor being started.

In certain cases, the cooling water to the bearings and the sealing water to the seal cages are provided by the pump. This, of course, eliminates the need for the steps listed for the cooling and sealing supply.

This article is brought to you by Kelair Pumps Australia, “When Pump Knowledge Matters”. Phone: 1300 789 466 or visit www.kelairpumps.com.au

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