What Is an Oil Cooler?

1. What is an oil cooler?

The oil cooler is a turbine oil cooling equipment matched with the steam turbine in the power system.

The oil cooler is of smooth tube surface type and uses circulating water as the medium to realize heat exchange, so as to ensure that the oil temperature at the bearing inlet reaches the specified value and ensure the normal operation of the unit.

Oil Cooler

2. What is the function of oil cooler?

During the normal operation of steam turbine generator unit, some work is consumed due to bearing friction, and the oil cooler will convert into heat to increase the lubricating oil temperature of the bearing. If the oil temperature is too high, the bearing may soften, deform or burn.

In order to ensure the normal operation of the bearing, the lubricating oil temperature must be kept within a certain range.

Generally, the oil temperature entering the bearing is required to be 35-45 ℃, and the temperature rise of the oil discharged from the bearing is generally 10-15 ℃.

Therefore, the oil discharged from the bearing must be cooled before it can be recycled into the bearing lubrication.

The main engine oil cooler is used to cool the lubricating oil of the main engine.

The lubricating oil with higher temperature and the cooling water with lower temperature exchange heat in the oil cooler, and the purpose of controlling the lubricating oil temperature is achieved by adjusting the cooling water flow (at the same time, due to the high temperature of the rotor, especially at the steam inlet side of the high-pressure cylinder, the Journal of the oil cooler also transfers heat outward, and the lubricating oil also has the function of cooling the Journal).

3. Where is the oil cooler mainly used?

Oil coolers are required where the lubricating oil needs to be circulated and cooled.

Taking thermal power plant as an example, the oil coolers mainly include: main engine lubricating oil cooler, EH oil cooler, feed pump lubricating oil cooler, hydraulic coupling working oil cooler, small turbine lubricating oil cooler, seal oil cooler, coal mill lubricating oil station cooler, control oil station oil cooler, induced draft fan oil station, Oil cooler of air supply oil station and primary air oil station.

4. What is the cooling medium of oil cooler?

In general, the medium of oil cooler is circulating water.

Since the circulating water is startup circulating water and closed circulating water, with the improvement of operation reliability and safety, the cooling medium of oil cooler mostly uses closed circulating water, and its water quality is equal to that of demineralized water and condensate.

5. What are the types and characteristics of oil coolers?

Oil coolers can be divided into tubular oil coolers and plate oil coolers according to their structure.

The heat exchange effect of tubular oil cooler is poor, but the cost is low and the floor area is small. It is used for small generator sets.

Plate type oil cooler has good heat exchange effect, but it has high cost and covers a large area. It is mainly used for large generator sets.

6. What is the working process of oil cooler of steam turbine unit?

The lubricating oil enters from the lower part of the shell and flows alternately to the center or around through the large diaphragm with hole in the middle and the small diaphragm without hole.

The oil moves in a zigzag way outside the pipe and finally flows out from the upper oil outlet of the shell.

The water is discharged into the four cooling chambers through the process.

When the oil cooler is filled with oil, the inlet and outlet throttle and vent valve are opened, and the outlet valve of the low-pressure oil pump is used to limit the oil pressure for oil filling.

Note that the oil filling speed cannot be too fast, the air at the oil side is drained and closed, and the oil filling is completed.

During oil filling, pay attention to prevent overpressure at the oil side and equipment damage. Cooling water can be supplied only after the oil cooler is filled with oil.

Keep the outlet water valve fully open and adjust the oil temperature with the inlet cooling water.

Two oil coolers operate in parallel and one is standby.

7. Precautions for oil cooler switching

When switching the oil cooler during the operation of the unit, the principle of putting it into operation first and then cutting it off shall be observed.

The operation shall be carried out by experienced personnel and supervised by special personnel.

Monitor the lubricating oil temperature, oil pressure and bearing bush temperature to prevent misoperation, unit tripping and equipment damage.

The operation shall be carried out slowly.

When the oil cooler is put into operation, slowly open the inlet throttle to prevent oil pressure fluctuation and exhaust the air at the same time.

Close the outlet throttle and the cooling water inlet valve when stopping.

(there must be someone to monitor the switching and contact the DCS personnel in real time to ensure that the air is exhausted and operate slowly to prevent oil pressure fluctuation and tripping.)

8. Brief introduction of operation sequence of oil cooler

1. Check whether the oil cooler drain valve is closed

2. Slightly open the oil cooler inlet throttle, open the air valve, exhaust the air, and close the oil side air valve

3. Strictly monitor the normal oil pressure, oil temperature, oil smell and oil flow during operation

4. Slowly close and exit the outlet throttle of the oil cooler, pay attention to adjusting the oil temperature, and pay attention that the lubricating oil pressure should not be lower than the allowable range until it is fully closed.

5. When the lubricating oil pressure is stable, close the inlet throttle.

9. Briefly describe the exit sequence of single oil cooler

(1) Make sure that the oil cooler other than the oil cooler is operating normally

(2) Slowly close the water outlet valve exiting the oil cooler, open the water inlet valves of other oil coolers, and keep the oil outlet temperature of the oil cooler within the allowable range

(3) After the oil outlet temperature of the oil cooler is stable, slowly close the water inlet valve until it is fully closed

(4) Slowly close and exit the oil outlet of the oil cooler. Pay attention to adjust the oil temperature and ensure that the lubricating oil pressure is not lower than the allowable range until it is fully closed

(5) When the lubricating oil pressure is stable, close the inlet throttle.

10. Precautions for operation of oil cooler.

1. During operation, monitor the changes of inlet and outlet oil temperature and water temperature, and adjust them in time to ensure that the lubricating oil temperature is between 35-45 ℃, generally 38-42 ℃.

2. During operation, the pressure of cooling water shall be less than the oil pressure to prevent water from leaking into the oil and affecting the lubrication effect.

3. If oil is found in the water, find out the cause in time, and closely monitor the oil quality and oil level of the oil tank.

In case of leakage, immediately switch to the standby oil cooler for operation.

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