Oil Cooler use and maintenance
Oil cooler is corroded
The main causes of corrosion are materials, environment (water quality, gas) and electrochemical reactions.
The use of corrosion-resistant materials is an important measure to prevent corrosion. At present, the tubular oil coolers are often made of copper tubes with good heat dissipation, and their ionization tendency is strong, which may cause contact corrosion due to contact with different kinds of metals ( The potential difference is different. For example, in the fixed orifice plate, the moving orifice plate and the cooling copper pipe nozzle, severe corrosion often occurs. The solution is to improve the cooling water quality, and the second is to use a cooling tube made of aluminum alloy drill alloy.
Further, the environment of the cooler includes dissolved oxygen, water quality (pH) of the cooling water, temperature, flow rate, foreign matter, and the like. The more oxygen dissolved in water, the more intense the corrosion reaction; in the acidic range, the pH value decreases, the corrosion reaction is more active, and the corrosion is more serious. In the alkaline range, the amphoteric metal such as aluminum may corrode with the increase of pH value. Increase in the flow rate; on the one hand, the oxygen supply on the metal surface is increased, on the other hand, the flow rate is too large, and turbulent eddy currents are generated, causing cavitation corrosion; in addition, sandstone and microshellfish in the water are attached to the water. Localized erosion is also often generated on the cooling tubes.
Also, the presence of chloride ions increases the conductivity of the liquid used, resulting in increased corrosion caused by electrochemical reactions. In particular, the adsorption of chloride ions on stainless steel and aluminum alloy will also partially damage the protective film, causing pitting corrosion and stress corrosion. Generally, the temperature increases and the corrosion increases.
In order to prevent corrosion, attention should be paid to the selection of materials and water treatment of the cooler. The former is often difficult to change, and the latter can find a solution. Zinc rods installed in water-cooled oil coolers to prevent electrical corrosion should be inspected and replaced in a timely manner.
2. Cooling performance degradation
The main reason is that the blockage and sediment are retained on the wall of the cooling pipe, and the hard block and the pipe scale are formed, so that the heat dissipation heat transfer function is lowered. In addition, insufficient cooling water and gas accumulation in the water and oil chamber of the cooler also cause a decrease in heat dissipation and cooling performance. The solution is to first adopt a structure that is difficult to block and easy to clean; when selecting the cooling capacity of the cooler, it should be based on practice as much as possible, and leave a large room (increased by 10% to 25% capacity). When necessary, use mechanical methods (such as brush, pressure, water, steam, etc.) or chemical methods (such as Na3003 solution and cleaning agent) to clean; increase the water intake or use lower temperature water Cool down; unscrew the screw plug; clean the internal and external surface area.ld be inspected and replaced in a timely manner.
Due to the temperature difference between the two fluids, the oil cooler material is affected by thermal expansion, generates thermal stress, or the oil pressure is too high; it may cause damage to the relevant components. In addition, in cold areas or winter, when the machine is shut down at night, the expansion of the tube inside the ice will burst the cooling water pipe. Therefore, it is necessary to use materials that are not affected by thermal expansion as much as possible, and use a deformation compensation structure such as a floating head; the water in the cooler should be drained every night during the cold season.
4. Oil leakage, water leakage
The oil that flows out is white, and the discharged water has oily flowers. Leakage and oil leakage often occur in the end cover of the oil cooler and the simplified joint surface, or due to poor welding, cracking of the cooling water pipe, and the like. At this time, according to the situation, replace the seal, repair welding and other measures to solve. When replacing the seal, wash the joint surface and apply a layer of adhesive.
The overflow of some cooling circuit relief valves varies with the load flow of the system, so the heat generation will also change, sometimes resulting in overcooling and waste. In order to ensure that the system has a suitable oil temperature, a temperature control system that automatically adjusts the amount of cooling water can be used. If it is lower than the normal oil temperature, stop the operation of the cooler, or even turn on the heater.
The cooling water quality is not good (hard water), and the scale inside the copper tube is cooled, resulting in a decrease in cooling efficiency.
The oil cooler can be cleaned at this time as follows:
1,Use a hose to guide the clean water to flush the back cover, the inner wall of the back cover and the inner surface of the cooling tube at the same time, and wash it with the cleaning strip, and finally blow it with compressed air; 2,rinse with trichloroethylene solution to cool the cleaning solution. The circulating flow in the device is about 0.5 MPa, and the cleaning time depends on the solution. Finally, the fresh water is introduced into the tube until the water flows out. 3,is poured into the cooler with a solution of carbon tetrachloride. After 15 to 20 minutes, the color of the solution is determined. If the turbidity is unclear, replace the new solution and re-soak until the solution flows out. It is almost the same as clean liquid, then rinsed with clean water. This operation should be carried out in a ventilated environment to avoid poisoning. After the cleaning, the hydrostatic test is carried out and it can be used only after passing the test.