Centrifugal CompressorsCentrifugal Compressors

OperationOperation

By Eng. Alaa E. Omar

Starting Preparations1. The whole unit should be clean and free of

all loose material.

2. All control, alarm and trip circuits should be energized .

3. Open stop valves on all pressure and level instruments.

4. Make sure that the settings of all temperature, pressure and other alarm and trip devices are correct.

5. Make sure all valves of the lube oil and seal gas system are in their correct status.

Starting Preparations

Starting ProceduresStarting Procedures

1. Check the oil level in the oil reservoir at full mark, fill up if necessary and check the condition of the oil.

2. Start the instrument air supply to the oil guard between the dry gas seals and radial bearings.

! CAUTION To prevent lube oil carry over to the gas seal

area, always start the air supply to the labyrinths between the radial bearings and the dry gas seals before the oil pump is started.

Starting Procedures

3. Verify that the lube oil filter and the seal gas filter are ready to operate.

4. Make sure that the lube oil cooler and the cooling fans are ready to operate and that the cooling system of the electric motor – driver - is ready to operate .Make sure that all process equipment is ready to operate.

Starting Procedures

5. Make sure that the temperature of the oil is not below 10 C. Operate the oil reservoir heater if necessary.

6. Start the main oil pump .! WARNING

To prevent overloading of the oil pump driver, the oil pump should not be started at low oil temperature.

Starting Procedures

7. Vent the oil system thoroughly.

! NOTE To avoid interruption of the oil supply, the

standby oil filter should be filled with oil and vented before putting it on line.

Starting Procedures

8. Check the functioning of the standby oil pump.

• By closing valve in the sensing line to pressure transmitter and opening the bleed off valve before pressure transmitter.

• From pressure indicator see at what pressure the standby oil pump starts.

(After testing, put the valves in their original positions and stop the stand by oil pump)

• By start button on motor control station.

Starting Procedures

9. Check all components of the oil systems to see that they are operating properly.

10. Check the oil supply gauge pressure .

11. Make sure there is a normal flow of oil to all components requiring lubrication by checking the flow through the flow glasses.

Starting Procedures

12. Make sure that the compressor driver is prepared for operation .

13. Make sure that the gas vent systems are ready to accept gas.

14. Make sure that the compressor suction and discharge valves are closed.

Starting Procedures

15. Vent and pressurize the compressor casing, to suction pressure .

! WARNING During venting, the anti surge valve should

be forced to close in order to vent the compressor casing . After venting the anti surge valve should be opened.

Starting Procedures

16. Open the drain valves of the compressor to remove any condensate or moisture.

17. Close the drain valves of the compressor after condensate stops flowing.

18. Open the drain valves from the inboard seal chambers to remove any condensate from it.

Starting Procedures

19. Close the drain valves after condensate stops flowing.

Starting Procedures

20. Make sure there are no trips.The compressor permissive to start signal will be healthy if :

• There is no trips from either the compressor or the process.

• The buffer gas supply pressure to the labyrinths between the radial bearings and the dry gas seals is sufficient.

• The temperature of the oil at the cooler outlet is higher than 30 C.

• The level in the oil reservoir is high enough.• The level in the lube oil rundown tank is high

enough.

Starting Procedures

21. A D

B

C

Valve B is set at the minimum stop

Valve C is closed, A,D are fully open

Starting Procedures

22. Check dry gas seal leakage flow is normal.

23. Start the driver .

24. After reaching the final speed put valve B on automatic.

Valve B is controlled by the suction pressure

25. Put the anti surge valve on automatic mode.

Starting Procedures

26. The start up procedure is completed.

27. Check and record : oil pressure and temperature, oil flow, vibrations, axial position, and air supply.

Starting Procedures

Stopping

• EMERGENCY STOP = »a stop caused by one of the

compressor or process trip signals.

• AN OPERATOR’S STOP = »This stop is initiated by pushing

the stop button on the compressor control panel.

Operator’s Stop:

• An operator planned stop should done as follows:

• Reduce the load of the compressors to minimum.• Press the stop button at the compressor

control panel.

To Depressurize the compressor:

• The Suction valve should be closed.

• The discharge valve should be closed.

• The blow down valve should be opened.

= After the compressor is at stand still, the oil pump can be stopped.