Centrifugal Chillers

Centrif. maintenance and shaft seal replacement

A centrifugal compressor sucks in the refrigerant vapour in the middle of the impeller then discharges it off the tip. The discharge gas goes into a shell and tube condenser with the refrigerant vapour condensing on the cool tubes. It is a flooded condenser so the refrigerant level is, by gravity, the same as the evaporator. The liquid is subcooled several degrees. The refrigerant expansion is achieved through an orifice on the liquid line between the two vessels. The shell and tube evaporator receives the expanded, now low temperature and pressure liquid which is flooded around the tubes with warm water from the process flowing through. This causes the refrigerant to boil- cooling the process water. The vapour does not get superheated because it is sucked round a baffle back to the middle of the impeller

The compressor in the picture left is open drive: the rate of oil collecting in the oil bottle is monitored each maintenance visit. When the rate starts to go up, this indicates that the shaft seal needs to be replaced. Because the issue has been nipped in the bud- the repair can be arranged to take place during a factory shut down

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