1. What is an oil cooler?
Oil cooler is turbine oil cooling equipment used in conjunction with steam turbine in power systems. It has a smooth tube surface design and uses circulating water as the medium for heat exchange. This helps to maintain the temperature of the oil at the bearing inlet within the specified range, thus ensuring normal operation of the unit.
2. What is the function of the oil cooler?
During normal operation of the steam turbine generating unit, some energy is consumed due to the friction of the bearings, which leads to an increase in the temperature of the lubricating oil. If the oil temperature becomes too high, the bearing may soften, deform or even burn.
To ensure proper bearing function, it is important to maintain the lubricating oil temperature within a specific range. Normally, the temperature of the oil entering the bearing should be between 35-45°C, and the temperature rise of the oil leaving the bearing should be around 10-15°C.
To achieve this, the oil leaving the bearing must be cooled before it can be reused for lubrication. This is where the main engine oil cooler comes into play.
The main engine oil cooler is used to cool the main engine lubricating oil. It operates by exchanging heat between hot lubricating oil and cold cooling water. By adjusting the cooling water flow, the lubricating oil temperature can be controlled effectively. In addition, due to the high temperature of the rotor, especially on the steam inlet side of the high-pressure cylinder, the oil cooler journal also transfers heat to the outside, and the lubricating oil also helps to cool the journal.
3. Where is the oil cooler mainly used?
Oil coolers are necessary when lubricating oil needs to circulate and cool. In thermal power plants, oil coolers typically include:
- Main engine lube oil cooler
- EH oil cooler
- Feed pump lube oil cooler
- Hydraulic Coupling Working Oil Cooler
- Small Turbine Lube Oil Cooler
- Seal Oil Cooler
- Coal Mill Lubricating Oil Station Cooler
- Control the oil station oil cooler
- Induced Draft Fan Oil Station
- Air Supply Oil Station Oil Cooler
- Primary Air Oil Station Oil Cooler
These oil coolers help regulate the temperature of the lubricating oil used in the different parts of the thermoelectric plant, ensuring the proper functioning of these components.
4. What is the cooling medium of the oil cooler?
Typically, the medium used in oil coolers is circulating water. There are two types of circulating water: initial circulating water and closed circulating water. To improve reliability and safety, the cooling medium of oil coolers mainly uses closed-circulation water with water quality equivalent to demineralized and condensed water.
5. What are the types and characteristics of oil coolers?
Oil coolers can be classified into two categories based on their structure: tubular oil coolers and plate oil coolers.
Tubular oil coolers have low heat exchange performance, but are low in cost and take up minimal space. These coolers are commonly used for small generator sets.
On the other hand, plate-type oil coolers have excellent heat exchange capabilities, but are more expensive and occupy a larger area. These coolers are mainly used for large generator sets.
6. What is the working process of steam turbine unit oil cooler?
The lubricating oil enters the oil cooler from the bottom of the casing and flows alternately through the large diaphragm with a hole in the center and the small diaphragm without a hole. It moves in a zigzag pattern outside the tube and finally exits through the hull's upper oil outlet. The water is then discharged into the four cooling chambers.
When filling the oil cooler, the inlet and outlet butterfly valves and vent valves must be opened, and the low-pressure oil pump outlet valve must be used to limit the oil pressure. It is important not to fill oil too quickly, drain and shut off any air on the oil side, and avoid overpressure on the oil side to prevent equipment damage. Cooling water can only be supplied after the oil cooler is filled with oil.
To adjust the oil temperature, the water outlet valve must be kept fully open and the inlet cooling water must be adjusted. Typically, two oil coolers are operated in parallel, one of them as a reserve.
7. Precautions for changing the oil cooler
When changing the oil cooler during unit operation, it is important to follow the principle of first turning it on and then turning it off. This task should only be carried out by experienced personnel, with supervision from specialized personnel.
It is necessary to monitor the lubricating oil temperature, oil pressure and bearing bushing temperature to prevent incorrect operation, unit tripping and equipment damage. The exchange process must be done slowly.
When putting the oil cooler into operation, the inlet throttle must be opened gradually to avoid fluctuations in oil pressure and at the same time release all air. When turning off the oil cooler, the outlet throttle and cooling water inlet valve must be closed.
It is important to have someone monitoring the switching process and in direct contact with DCS personnel to ensure that the air is exhausted and that the process is carried out slowly to avoid fluctuations and spikes in oil pressure.
8. Brief introduction of oil cooler operation sequence
- Check that the oil cooler drain valve is closed.
- Gently open the oil cooler inlet throttle, turn on the air valve and vent all air. Once the air is exhausted, close the air valve on the oil side.
- Carefully monitor normal oil pressure, oil temperature, oil odor and oil flow during operation.
- Gradually close and exit the oil cooler outlet throttle, taking care to adjust the oil temperature and ensuring that the lubricating oil pressure does not fall below the acceptable range until it is completely closed.
- When the lubricating oil pressure is stable, close the inlet throttle.
9. Briefly describe the output sequence of the single oil cooler
(1) Make sure all oil coolers except the one being turned on are operating normally.
(2) Gradually close the water outlet valve leaving the oil cooler and open the water inlet valves of the other oil coolers, making sure to maintain the oil outlet temperature of the oil cooler within the acceptable range .
(3) Once the oil outlet temperature of the oil cooler is stable, gradually close the water inlet valve until it is completely closed.
(4) Close and gradually exit the oil outlet of the oil cooler, taking care to adjust the oil temperature and ensuring that the lubricating oil pressure does not fall below the acceptable range until it is fully closed.
(5) After the lubricating oil pressure is stable, close the inlet throttle.
10. Precautions for oil cooler operation.
- During operation, be aware of changes in inlet and outlet oil temperature and water temperature and make adjustments as necessary to ensure that the lubricating oil temperature remains in the range of 35-45°C, typically around 38- 42°C.
- During operation, the cooling water pressure must be lower than the oil pressure to prevent water from leaking into the oil and affecting its lubricating properties.
- If oil is found in the water, immediately investigate the cause and closely monitor the quality and level of the oil in the oil tank.
- In the event of a leak, switch to the backup oil cooler for immediate operation.
