Tubular oil cooler

Introduction to Tubular Oil Cooler:

The column tube oil cooler is a turbine oil cooling equipment used in conjunction with the power system and steam turbine. The column tube oil cooler is a smooth tube surface type, using circulating water as the medium for on-site heat exchange to ensure that the inlet oil temperature of the bearing reaches the specified value and ensure the normal operation of the unit.

Tubular oil cooler structure -

The main components of a column tube oil cooler include an upper and lower water chamber, a shell piping system, and an oil filling pipeline assembly. The shell is connected to an inlet and outlet water pipe, an inlet and outlet oil pipe, a drainage pipe, an exhaust pipe, and a temperature gauge seat. The cooling water process is generally a dual process, and the column tube oil cooler is usually installed vertically or horizontally (horizontal column tube oil cooler is optional).

The main components of the tubular oil cooler are:

1. Copper or stainless steel pipes and titanium pipes are used as heat exchange components, with high heat transfer coefficient, large heat area per unit length, and high heat transfer.

2. Reasonable structure, able to maintain stable oil temperature within a large range of temperature changes, and has good resistance to temperature changes and vibration.

3. Assembly structure - reliable, ensuring that cooling water does not enter the turbine unit.

4. The fins are smooth, prickly, and wrinkled, not prone to dust and scaling, and have low fluid resistance.

Purchase instructions for column tube oil coolers:

1. When purchasing a column tube oil cooler, should the cooling area be informed?

2. Is the cooling method divided into LY type light tube type (- use) and LYC type fin type?

3. Is the material used for heat exchange and cooling tubes stainless steel tubes, copper tubes, titanium tubes, and other heat exchange components?

Using a tubular oil cooler -:

In order to ensure sufficient safety and recovery of turbine oil cooling during turbine operation, the dual tube oil cooler consists of two tube oil coolers with the same area and a three-way valve, which can only work and be used as a backup. If the cooling effect is poor due to high oil temperature or high inlet water temperature of the unit, or when cleaning and repairing the tube oil cooler is required during operation, the backup tube oil cooler can be opened without stopping the machine.

The function of a tubular oil cooler:

During the normal operation of the steam turbine generator set, some power is consumed due to bearing friction. The tube cooler will convert it into heat, causing the lubricating oil temperature of the bearings to increase. If the oil temperature is too high, the bearings may experience softening, deformation, or burning accidents. In order to ensure the normal operation of the bearing, the lubricating oil temperature must be maintained within a certain range. Generally, the oil temperature entering the bearing should be between 35-45 ℃, and the discharge oil temperature of the bearing should rise to 10-15 ℃. Therefore, the oil discharged from the bearing must be cooled before it can be recycled into the bearing lubrication. The auxiliary column 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 tube cooler, and control the lubricating oil temperature by adjusting the cooling water flow rate (at the same time, due to the higher rotor temperature, especially on the inlet side of the high-pressure cylinder, the journal of the tube cooler also transfers heat outward, so the lubricating oil also has the function of cooling the journal).

Series and parallel - deficiency-

1. The series operation of the tubular oil cooler includes cooling and uniform oil temperature.

2. Shortcomings in the series operation of tube coolers: high oil pressure drop and inability to isolate oil during operation.

3. Parallel operation of column tube oil coolers: with small oil pressure drop, convenient isolation, and can be repaired during operation.

4. The shortcomings of parallel operation of column tube oil coolers include poor cooling performance and uneven oil temperature.

Process requirements for replacing stainless steel pipes

1. Preparation of stainless steel pipes: After passing the inspection, cut the stainless steel pipes according to the size of the column oil cooler. The stainless steel pipes should be 4-5 millimeters longer than the pipe plate. Remove burrs from both ends of the stainless steel pipes, polish the expanded parts smooth, and perform tempering treatment at about 50 millimeters on both ends.

2. Remove old stainless steel pipes: Use a semi-circular triangular chisel to remove them. When removing, be careful not to damage the pipe plate. Polish the stainless steel pipes, remove the old stainless steel pipes, clean the pipe holes on the pipe plate, polish them with a fine sandcloth, and wipe off the dust with a cloth.

3. Pipe threading and expansion: After both the pipe plate and stainless steel pipe are prepared, they can be threaded through the stainless steel pipe. Be careful not to use too much force or force, align them with your own hole position, and install them. The exposed parts at both ends of the pipe should be equal. The diameter of the pipe plate hole is slightly larger than the pipe diameter, about 0.5 millimeters, and should not be too large or too small. After the stainless steel pipe is threaded, a pipe expander can be used to expand the mouth. When expanding the pipe, the force and speed should not be too large or too small. The length of the expanded pipe should be 2/3 of the thickness of the pipe plate, and should not be greater than the thickness of the pipe plate. After the expansion is completed, both ends should be flanged with a punch.

4. When replacing stainless steel pipes, it is necessary to replace them half by half, and then disassemble the other half.

5. The welded joint after pipe replacement needs to undergo leakage or damage testing.

The main function of a tubular oil cooler is to cool lubricating oil and maintain the temperature of its bearings within a positive range during the operation of the steam turbine and generator# 1. # 2, # 5, and # 6 units are all manufactured by Shanghai Steam Turbine Factory. During the operation of the oil coolers, there are frequent bottom end cover oil or water failures. In the process of maintenance, the causes of frequent failures were identified, and corresponding technical improvement measures were proposed, which has certain reference significance for the design and operation maintenance of column tube oil coolers.

Working principle of column tube oil cooler

Closed cooling water enters the column tube oil cooler through the end cap of the column tube oil cooler, and then flows through the small pipes inside the column tube oil cooler. The small cooling water pipes are fixed by partitions distributed inside the column tube oil cooler. Through the partitions, the column tube oil cooler is divided into several small spaces, and lubricating oil flows in an S-shape outside the cooling water pipes. This arrangement can increase the heat exchange area and improve the cooling effect. At the bottom of the column oil cooler, a cooling water chamber is formed. Lubricating oil and cooling water are separated and sealed by two O-rings (rollers) and a copper bed.

Analysis of the causes of the malfunction of the column tube oil cooler

During the operation of the unit, # 1, # 2, # 5, and # 6 units experienced a water or oil failure at the bottom cover of the tube cooler, especially during the start-up or shutdown of the unit. The failure occurred frequently. The isolation between oil and water in the oil cooler and the leakage of oil and water all rely on two O-ring seals. If the two O-rings are damaged or displaced, causing a change in clearance, it can cause leakage. Because the cover of the O-ring is on the left and right sides, rather than the upper and lower sides of the transmission, once leakage occurs, increasing the tightening force of the flange bolt cannot reduce the leakage amount.

After analysis, the following reasons that can easily cause changes and damage to the O-ring seal gap have been summarized.

1) During the start-up or shutdown process of the unit, pressure fluctuations occur on the oil and water sides of the tube cooler, causing the O-ring to move and causing leakage.

2) During the installation of the unit, if there is eccentric installation inside the column tube oil cooler, it will cause abnormal clearance of the O-ring seal. During operation, slight pressure fluctuations (oil side, water side) can cause leakage.

3) During each repair process, when replacing the O-ring seal, due to the narrow position of the bottom cover, the installation is inconvenient, and often the O-ring is crushed by the copper bed, resulting in leakage. After each repair, the probability of leakage on the water side is higher than that on the oil side, and it should be noted that the current design is not convenient for repair and maintenance.

Feasibility Analysis of Technical Transformation for Tubular Oil Chillers

Add a polytetrafluoroethylene pad between the bottom cover of the column oil cooler and the flange joint surface between the column oil cooler and the barrel body. On the basis of maintaining the original cover inconvenient, add two more cover surfaces. Due to the stretchability of polytetrafluoroethylene material compared to copper bed, it meets the requirement of increasing sealing energy by relying on flange bolt tightening force. The difficulty of implementing this measure is much lower than other measures.

Economic Analysis of Technical Renovation of Tubular Oil Coolers

1) Every time there is a leak in the oil cooler, it usually needs to wait until the unit undergoes major and minor repairs to carry out the repair work. In the stage of operation with damage, the cleaning work of the oil and water leaks is increased, which increases the workload of the team.

2) The volume of the end cover of the column oil cooler is large and the repair space is narrow, so every time when installing the O-ring, 5 people need to work simultaneously, which results in a considerable labor cost for each repair.

3) Repairing - replacing O-ring seals often results in high consumables and increases repair costs.

Based on the above analysis, it can be concluded that the technical transformation of the tube oil cooler is necessary and feasible, as well as the economic benefits that can be brought by the transformation. In the renovation, a gradual approach can be adopted, utilizing unit maintenance and overhaul to gradually renovate the column tube oil coolers of Units # 1, # 2, # 5, and # 6. After the renovation, it is likely to bring corresponding economic benefits and save equipment maintenance and repair costs.

When purchasing a column tube oil cooler, the cooling area and other parameters should be informed:

1. According to the form of cooling pipes, there are LY type light tube type (- use) and LYC type fin type.

2. According to the material of cooling pipes, they are divided into three types: carbon steel, stainless steel pipes (TP304, TP304L, TP316, TP316L), and copper pipes (T2, HSN70-1, H63).

3. What is the model of the steam turbine unit?

4. Cooling oil quantity?

5. Cooling area?

6. It is divided into two types according to installation form: vertical and horizontal.

7. Inform the on-site operation of the chloride ion content in the medium water for convenient pipe selection (please refer to the table below for comparison of the chloride ion content in the medium).

Note: The correct selection should be based on different occasions, usage requirements, etc. (or we recommend you to use the specifications)

Model parameters of steam turbine tube oil cooler: