Difference between air coolers for shipboard reciprocating main air compressor and Large slow speed two stroke Marine diesel propulsion engines
- In both cases the air coolers are for increasing the efficiency of the compressors by inter cooling.
- Both T/C and Reciprocating compressors are meant to increase pressure , however to a different degree ( T/C : 4 for single stage , and 10 bar for 2stage turbo chargers)
- During the compression the air temp raises when the pressure is increased, and need to be cooled.
- Cooling is by fresh water / sea water / air in the Main Air Compressors and Either Sea water or Fresh Water(LT)
- Cooling is controlled in Engine Coolers to maintain the Air Temperature to the required value, to reduce water impingement on to the liners. Cooling is not controlled in air coolers of Main Air Compressors ( the lower the temp is better for the efficiency), hence there will be control valves for Engine Air Coolers and no control valves for Air Compressor coolers.
- Engine Coolers are very large in comparison to Main Air Compressors as the air flow is very large ( depend on the Engine power rating)
- Engine coolers are difficult to remove and maintain and hence there will be a system installed to clean the coolers by using the chemical, where as air compressor coolers are not fitted with cleaning arrangement.
- Engine Coolers are not required to be fitted with any pressure safety devices, as the pressure is lesser and safety can be achieved by the construction itself. However for Main Air Compressor coolers each and every cooler must be fitted with safety valve to relieve excessive pressure which can be due to leakage of interstage valves.
- Both Engine Coolers and Main Air Coolers are fitted with water ( condensate from air ) separators.