operation of centrifugal pumps

OPERATION OF CENTRIFUGAL PUMPS

Operation of centrifugal pumps

Some of the more important safety rules that apply to pump operation include the following:

Pump Safety

Know what sort of liquid is being pumped.

Specific gravity.

Vapor pressures.

Temperature.


Pump Safety

Observe proper purging precautions .

Venting vapor from casing, section line, discharge line and where necessary.

When pumps vent directly to the atmosphere, the operator should stand clear as the vapor is being purged.

The vent valve should be only cracked and not fully opened at the start of purging


Pump Safety

Maintain protective guards .

Guards are fitted to shield against accident and pumps must not be operated unless all guards are secured in place.

Maintain correct lubrication .

Checking for correct lubricant levels before starting.

Tidiness around pump area .

Free area around the pump ( no rubbish or debris).

Any spillage of lubricant should be immediately cleaned up.


Pump Place backA pump that has been out of service for a given period must be

properly placed back in service before it may be started.1. Check for safety hazards.

2. Checking lubricant level and cooling water flow .

3. Purging and priming the pump.

4. Purging and priming the pump:

If positive suction head is available, then the pump is purged as follows:


Pump Place backIf the pump is operating on suction lift (negative suction head)

then the pump must be purged and primed using one of the two following methods:

A. If there is liquid at the discharge side of the pump, then the pump can be purged and primed by opening the discharge

block valve and also the suction block valve.

B. When liquid is not available at either the suction or discharge sides of the pump, then liquid must be pumped into the pump

casing and suction line from another source, using an auxiliary pump.

5. Resetting the pump circuit breaker.

6. Lining up the pump.


Pump Start-upStarting up a centrifugal pump involves the following steps:

1. Close all drains and vent lines after priming the pump.

2. Check that force-feed lubricators, seal oil system and water cooling systems are fully operational.

3. Open the suction block valve to its fullest extent.

4. f the pump is being started to relieve another pump, then open the discharge block valve fully. If, however, the flow

will be through a line that has been out of service, then the discharge block valve should only be opened.

5. Press the pump start button or switch and check for an increase in lube oil pressure.


Pump Start-up

6. Gradually open the discharge block valve (if not already opened in step 4).

7. Check the discharge flow controller for the desired flow rate and make any adjustments to the set point that may

be necessary.


Monitoring Pump OperationAfter the pump has been started and running for several minutes, the

following checks should be made to make sure that the pump is operating normally without any problems:

1. Monitor discharge pressure for abnormal values.

2. Re-check lubricant levels.

3. Check operation of force feed lube systems.

4. Check for excessive motor temperatures.

5. Check pump bearings and packing for excessive temperature.

6. Listen for abnormal noises.

7. Check for excessive vibration.

8. Check packing or mechanical seals for excessive leakage.


Switching Pumps

Switching pumps involves shutting down one of two pumps arranged in parallel whilst at the same time starting up a relief pump.

Since it is important that the load be switched from one pump to the other with the least possible disturbance to the process, switching

should be carried out by two persons.

One person shuts down the pump to be taken out of service whilst the other person starts up the relief pump.


Switching Pumps

HP LFR

RP


Switching Pumps

HP LFR


Securing a pump for maintenance

When a pump is to be taken out of service for maintenance, the following steps should be carried out:

1. Shut down the pump using the stop button or switch. If necessary, the process should be switched to a standby

pump.

2. Isolate the electrical supply to the pump by tripping the circuit breaker in the switchgear building, then securing it

in the "open" position with a padlock and attaching a warning tag. As an additional precaution, check that the

pump does not start when its start button is pressed.

3. Close completely both the suction and the discharge block valves.


Securing a pump for maintenance

4. Open the vent valve to allow the liquid pressure inside the pump to be reduced to atmospheric.

5. Open drain valves (usually located at the bottom of the pump casing) and allow the liquid to drain off. Close the

drain valves after all the liquid has been drained from the pump.

6. Tag the pump for repairs.

SAFETY NOTE:

A pump which is locked out in the switchgear building or tagged for repairs should never be re-started without first

checking that all work on it has been completed and a permit to re-start has been issued.

operation of centrifugal pumps

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