Methods For Judging Damage To Condensers And Evaporators

 

Condensers and evaporators are two core heat exchange components of refrigeration systems.

 

Once suffering leakage, blockage, deformation or corrosion, they will directly trigger faults such as poor cooling capacity, abnormal pressure and unit alarms.

 

Comprehensive judgment can be carried out through four approaches: visual inspection, operating parameter detection, sectional pressure test and system working condition comparison, to distinguish minor faults from complete damage.

 

 

I. Preliminary Visual Inspection to Rapidly Identify Visible Damage

 

Cut off power and shut down the unit before inspecting the exterior, where most irreversible damages can be found with naked eyes. First, check corrosion on pipelines and shells.

 

The shell side of water-cooled condensers and coils of closed evaporators are exposed to water media for long-term operation. Scaling on inner walls and acid-base corrosion on outer walls will form rust spots, perforations and water seepage marks.

 

Damaged coils in Freon systems will leave oil stains, as refrigerant leaks together with refrigeration oil, and oil accumulation marks pinpoint leakage points. If fins of air-cooled condensers and evaporators are largely collapsed or extruded to block heat exchange channels, the heat exchange function fails, which counts as functional damage.

 

 

Second, inspect welding joints and tube expansion positions. Alternating cold and heat easily causes cracks at expanded joints, leading to water dripping and refrigerant leakage.

 

Bulged or deformed plates of plate heat exchangers indicate plate rupture caused by excessive internal pressure.

 

If oil and water accumulate at the unit bottom for a long time after eliminating faults of valves and pipe joints, the heat exchanger body is basically damaged. Besides, check the thermal insulation layer: cracked, swollen insulation on evaporators with persistent frost and ice that recurs shortly after cleaning mostly implies internal pipeline blockage or partial leakage.

 

 

II. Operating Parameter Detection to Judge Heat Transfer Performance Degradation

 

 

 

 

Run the unit at full load, record high/low pressure, inlet and outlet water temperature, temperature difference and current of fans/water pumps, and compare with rated parameters to evaluate damage severity.

 

Fault Characteristics of Condensers

 

For water-cooled condensers, the temperature difference between inlet and outlet water is far below the standard 5℃~8℃, with continuously high pressure that cannot be relieved even when fans run at full speed.

 

For air-cooled condensers with clean fins yet persistent high pressure and abnormally slow pressure drop after shutdown, internal coil blockage or partial pipe rupture leads to ineffective heat exchange area.

 

A sharp drop in high pressure accompanied by synchronous low low pressure and drastically reduced cooling capacity signals condenser perforation leakage and massive refrigerant loss.

 

 

Fault Characteristics of Evaporators

A normal evaporator coil shall be covered with even thin frost. Local thick ice with frost-free areas elsewhere indicates internal pipeline blockage. Severe frosting over the whole unit, normal fan air volume yet cool-less outlet air and excessively low low pressure result in sharply weakened heat exchange efficiency.

 

If the air temperature difference between evaporator inlet and outlet is less than 3℃ under full load after excluding insufficient air volume and refrigerant charge, the evaporator heat exchange function fails. Continuous compressor overload and frequent startup/shutdown also stem from abnormal loads caused by damaged heat exchange components.

 

 

III. Sectional Pressure Test for Precise Leakage Damage Verification

 

 

Visual inspection and parameter monitoring only provide preliminary judgment. Hydraulic and pneumatic sectional pressure tests serve as core methods to confirm perforation leakage, which thoroughly distinguish joint leakage from heat exchanger body damage.

 

Disconnect condensers and evaporators from compressors and expansion valves, then seal both ends of the heat exchangers independently. Apply hydraulic pressure to the shell side of shell-and-tube water-cooled condensers and conduct pressure test on the tube side to inspect refrigerant pipelines.

 

 

Charge dry nitrogen into air-cooled coils and plate evaporators for pressure holding with a standard pressure of 1.6~2.5MPa for 24 hours static standing. Obvious pressure drop without external oil stains or weld seepage proves tiny internal coil perforations, which are irreversible component damages.

 

Distinguish minor leakage from complete damage: slight pressure drop with slow refrigerant consumption refers to micro leakage; rapid pressure drop to zero accompanied by massive refrigeration oil outflow means large-area rupture and immediate component scrappage.

 

Cooperate with soapy water and electronic leak detectors: continuous bubbles at coil gaps and persistent detector alarms confirm rupture of the heat exchanger body.

 

 

IV. System Working Condition Comparison to Differentiate Two Damage Types: Blockage and Rupture

 

 

Damages of heat exchange components fall into two categories with completely different fault manifestations, which can be quickly distinguished via working conditions.

Blockage Damage

 

 

Pipeline scaling, oil sludge and impurities block internal channels. No pressure drop occurs during pressure holding with no refrigerant leakage, yet heat transfer performance is extremely poor.

 

Condenser blockage triggers soaring high pressure while evaporator blockage causes low low pressure. If working conditions recover after cleaning and dredging, it is minor blockage.

 

If temperature difference and pressure remain abnormal after repeated chemical cleaning and high-pressure water flushing, large-area pipeline clogging or local welding blockage leads to permanent heat exchange failure and component replacement is mandatory.

Leakage Damage

 

 

Continuous pressure drop during pressure testing, insufficient cooling capacity despite frequent refrigerant refills and refrigeration oil loss are typical signs. Tiny leakage points can be repaired by welding; multi-point corrosion perforations and large-area damaged fin coils incur repair costs close to new equipment price, which are judged as complete damage with no repair value.

 

 

Conclusion

 

Comprehensive judgment procedure: First visually inspect for corrosion, oil stains and deformed fins;

 

then start the unit to read operating pressure and temperature difference to assess heat transfer efficiency;

 

finally perform sectional nitrogen/hydraulic pressure test to confirm leakage. Slight scaling and minor fin bending are minor faults recoverable via cleaning and straightening.

 

If perforation leakage, large-area pipeline blockage, bulged and corroded shells, or heat transfer temperature difference far deviated from rated values with no repair solutions occur, the condenser or evaporator is fully damaged and needs overall replacement.