Turbocharged air cooling technology is the key to the economic and reliable running of diesel engine. The proper maintenance method of air cooler directly affects combined working of engine and turbocharge,and also affects the service life of air cooler and subsequent maintenance cost. As users, we must strengthen awareness and pay attention to daily maintenance for cooler. Followings are the statement for cooler of the initial use、usual operation and shutdown period: 1.Initial use:
The corrosion resistance of copper and copper alloys is that they can form a natural protective film which is difficult to dissolve. Never use sewage cooling that does not form a proper film in the tubes, as the sediment in tube surface is not conducive to form a protective film more effectively. we should follow up 3 aspects as below: 1.1 Control the cooling water flow.
When the diesel engine accelerates to the normal load, it is very necessary to adjust the flow of cooling water. Frequently changing
the flow rate of water is not conducive to form a protective film on the inner surface of the cooling tube, and the protective film
is crucial for corrosion prevention. In particular, it should not keep water flow at the low rate for a long time. 1.2 Install a device to control cooling water flow
The improper position of the pipeline’s throttle or inlet is easy to produce oxygen-rich ions in the water and cause corrosion. So a control device should be installed so that the cooling water flow 、rate and air outlet temperature of the air cooler can be kept within recommended range in case of any various loads, meanwhile effectively promoting the formation of a protective film. 1.3 Feed chemicals into cooling water during initial use
In order to form a good protective film,feeding FeSO4·7H2O(5mg/L) into the water during initial use and keeping it running for one hour per day
2.The maintenance of usual operation 2.1 The condensed water should be discharged in time
If there is a large amount of condensate on the outlet side of the air cooler, it can be avoided by using by-pass control device.It is necessary to ensure that the condensate should be discharged in time.
2.2 To keep maximum differences temperature between water and air in proper range.
If the temperature go beyond the scope during the normal operation of the air cooler, this problem can be solved by air exhaust through water injection.However, if the performance is not improved after processing according to above method, also no other faults are found, then the air cooler needs to be cleaned with methods: routine cleaning, mechanical cleaning, hydraulic cleaning and chemical cleaning. Choose different cleaning methods depend on materials and equipment parts. 2.3 Water side cleaning
The cleaning of the water side should be carried out regularly, and its period is determined by the cooling water quality. The water side cleaning is not only to maintain the heat exchange performance of the air cooler; but also remove the risk of corrosion caused by scaling or other substance in the cooling tubes.
Mechanical cleaning is carried out by using a nylon brush mounted on a rod. cleaning the tubes should be one by one.washing away the dirt until no residue. After cleaning, replace the new gasket and reinstall end cover, and then fully feed cooling water.
(2) Hydraulic cleaning.
the air cooler should be dismantled while hydraulic cleaning, A Hydraulic spray gun (water pressure 60～80bar) equipped with a special nozzle (diameter 3mm) can be used to remove the sediment in the cooling tubes.
(3) Chemical cleaning.
Clean in place for the cooler , a cyclic system of chemical cleaning would be installed to connect with the cooler. Chemicals must be used in accordance with the instructions and usage guidelines provided by the manufacturer; If there are scale deposits in the cooling water pipeline,10% HCL and 0.5% antioxidant can be configured to clean.so that cleaning is particularly benefit to tubes. Completely drain out the water in the cooler after cleaning. Very important:the chemicals could not be retained in the cooler, and the cooler needs to air exhaust through water injection. 2.4 Gas Side Cleaning
Cleaning on the gas side should be carried out asap to avoid the accumulation of oil fumes on the tube fins and the formation of sulfides which cause corrosion.
(1)Hydraulic cleaning. The cooler will be dismantled during hydraulic cleaning. Sediments on the tube fines can be removed by using a hydraulic gun with nozzle (diameter 3mm) (water pressure 60～80bar), spraying water running parallel to the tube fines at a distance of 2m.
(2)Chemical cleaning.Remove end cover of cooler, then immerse the tube bundle into the chemicals container (soaking time depends on the oil fumes or sediments). Washing the cooler with hydraulic gun after cleaning.
3.Maintenance during shutdown
When the air cooler is shut down, the water in the whole cooling system should be drained clean, otherwise, it will endanger the components of the air cooler which are made of copper, copper alloy and cast iron etc. Make sure that no deposits in the tubes. If the air cooler is shut down after two-month commissioning period, cleaning procedures should be followed for each shutdown if the period exceeds two weeks in order to avoid corrosion.
If need to temporary stop the cooler during normal working, the times of shutdown which do not drain water for more than three days during the shutdown period must be limited and operated as required during the commissioning period. If it is short time stop, the air cooler can run at low water flow, which can wash away corrosive components such as ammonium compounds and hydrogen sulfide.
The water in the cooler must be drained off if it is stopped even for very shortest time during the winter, otherwise the frost will damage the air cooler.