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display cases Refrigeration failures and maintenance methods (2)

author: supermarket refrigerated showcase category: walk-in display coolers Views: 981Time: 2016-08-22

display cases

Refrigeration failures and maintenance methods (2)

poor cooling and cooling The pipeline (old) has oil stains. Troubles: poor cooling, oil stains on the exposed refrigeration pipes or welds. Failure analysis: 95% of the oil stains are leaking points, causing refrigerant leakage, causing poor cooling, and even non-stop. Very rarely, leakage in other parts or poor compressor discharge performance. Troubleshooting: Open the system to discharge the refrigerant, install a pressure gauge at the compressor process nozzle, and perform

according to the following four steps. ① Check for leaks. Hit the total pressure of the refrigeration system to 0.8MPa. Apply soapy water to the oily area of the

display cases

. If there are bubbles in the oily area, it indicates that there is a leak. Use zero-size sandpaper to polish 0.5 cm near the oily area, release the nitrogen in the system, and repair the leaking point. . If there are no air bubbles in the oil stain, continue to check other welds and suspected leaks with soapy water.

② check the high and low pressure in sections. Clamp the capillary tube at a distance of 2 cm from the filter port, and weld the two disconnected nozzles together. Separately press 1.2 MPa for the high-pressure pipeline and check for leakage by 1.2 MPa for the low-pressure pipeline. Continue to use soapy water to continue to check for leaks in the oil stains and exposed refrigeration pipelines, and keep the pressure for 24 hours when the leaks are still not found. If the pressure of the high-pressure pipeline drops, remove the anti-dew pipe: If the pressure gauge of the low-pressure pipeline drops, repair welding or inlay the evaporator depending on whether the evaporator can be removed.

③The exhaust performance of the test compressor is poor, open the compressor exhaust (relay) pipe, plug in the power supply to run the compressor, press the exhaust port with your thumb , The normal size should not be blocked, otherwise it means that the compressor has poor exhaust performance, and the compressor of the same model should be replaced.

④ Replace the filter drier, apply a total pressure of 0.8 MPa to the system again, use soapy water to check the tightness of the repaired welds or the newly welded joints, and then vacuum the system After that, add refrigerant, and by observing the display cases of the evaporator, touching the temperature of the condenser, and observing the frosting of the return pipe, it is confirmed that the filling amount is appropriate, and then the sealing process is performed. [Note] Regardless of whether there are leaks in the oil stains, the oil stains must be polished before the refrigeration system is evacuated before repair welding.

poor cooling and oil stains on the welded joint of the condenser pipe. Failure phenomenon: poor cooling, There is an oil burst somewhere in the weld of the condenser pipeline. Failure analysis: 90% of the weld leakage is caused by oil stains. Individually, other parts leak or the compressor has poor exhaust. Troubleshooting: unplug the

display cases, listen to the vibration of the metal sheet when the compressor is running, open the display cases

and vent the compressor process nozzle and observe carefully, pressure the condenser separately by 1.2MPa, and apply soapy water to the oil stains Place. There may be the following four situations.

① The refrigerant displacement is small, and the soapy water bubbles at the oil stain of the condenser. This shows that there is indeed a leak in the oil stain. Let off the nitrogen in the condenser, cut the oil stain and the surrounding 2 cm pipeline, and replace the welding with a short copper tube (usually 6 mm in diameter). Press 1.2MPa on the condenser again to check the tightness of the short copper pipe weld.

② The refrigerant displacement is small, and the soapy water at the condenser oil stain does not foam, but the pressure of the condenser drops below 1.1MPa after the pressure is maintained for 24 hours. This shows that there are leaks in the condensation stagnation, and other parts should be checked for leaks. After the leak is detected, in addition to the treatment of the leak, the oil stain must be repaired or replaced with a short copper tube.

③ The refrigerant displacement is small, the soapy water at the condenser oil stain does not foam, and the pressure gauge value does not drop for 24 hours. Continue to suppress leaks in other parts of the refrigeration system, such as suppressing the anti-exposure pipe (1.2MPa) to check for leaks, and suppressing the low-pressure pipeline (0.8MPa) for leaks.

④ The refrigerant is discharged, or there is a metal sheet vibration when the compressor is running. The compressor exhaust may be dangerous. When confirming that there is no refrigerant in the system, open the compressor exhaust pipe port by welding, start the compressor, and block the pipe port with your thumb. If it is easy to block, the compressor exhaust performance is insufficient. It should be repaired and replaced by opening the shell. Compressors of the same model. display cases After repairing the leaking parts of the refrigeration system, blow through the system with nitrogen, replace the filter drier, evacuate the system, fill with refrigerant, and seal. [Note] Regardless of whether the oil stain of the condenser is checked for leaks, it must be repaired.

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display cases Refrigeration failures and maintenance methods (2)

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