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34 TRG-TRC010-EN
notes
period four
Maintenance Considerations
Scale deposits are best removed by chemical means. During this process, the
water-cooled condenser is commonly isolated from the rest of the cooling-
tower-water circuit by valves, while a pump circulates cleaning solution
through the condenser tubes.
Sludge is removed mechanically. This typically involves removing the water
boxes from the condenser and loosening the deposits with a stiff-bristled
brush. The loosened material is then flushed from the tubes with clear water. As
part of this procedure, the strainers in both the chilled-water and cooling-tower-
water circuits should be cleaned every year.
Every 3 years (more frequently in process or critical applications), a qualified
service organization should perform nondestructive inspections of the
evaporator and condenser tubes. The eddy-current tube test is a common
method.
Rarely, problems may arise that cause refrigerant or water leaks. These must be
repaired immediately.
Oil analysis is an important annual maintenance task required for centrifugal
water chillers. It may be conducted more frequently for chillers that run
continuously or more often than normal. This test, performed by a qualified
laboratory, verifies the integrity of the refrigeration system by testing the
concentrations of moisture, acidity, and metal. This analysis can determine
where problems exist or could potentially develop. By taking oil samples on a
regular basis, normal operating trends for the compressor and bearing metals
can be analyzed. Instead of adopting a “change the oil once a year whether it
needs it or not” approach, regular oil analyses can be used to determine proper
oil change intervals and predict major problems before they occur.
Refrigerant analysis measures contamination levels and determines suitability
for continued use. It can also determine if recycled refrigerant is suitable for
reuse. Refrigerant analysis helps extend the life of the existing charge and
ensures that the chiller is operating at peak efficiency.
Fluid Analysis
▲ Oil analysis
◆ Conduct annual analysis to verify
system integrity
◆ Measure oil pressure drop to
determine if filter needs changing
◆ Measure charge
▲ Refrigerant charge
◆ Conduct analysis of refrigerant
◆ Inspect purge system
Figure 49
trgtrc010_book.book Page 34 Wednesday, September 1, 1999 10:42 AM