To describe a standard operating procedure for the breakdown rectification of refrigeration unit.
1.0 PURPOSE:
To describe a standard operating procedure for the breakdown rectification of refrigeration unit.
2.0 SCOPE:
The standard operating procedure describes in detail the method of breakdown rectification of refrigeration unit.
3.0 RESPONSIBILITY:
The responsibility of breakdown rectification of refrigeration unit lies with the staff of rank not lower than the junior utility operator.
The responsibility of preparing, reviewing and approving the standard operating procedure lies with the Manager - Maintenance, Head of Production and Head of QAD respectively.
4.0 METHOD:
4.1 If the compressor does not start the possible causes and their respective remedies are:
4.1.1 The auxiliary contacts of the cooling tower fan may not be in position. Set the auxiliary contacts of cooling tower fan in position either by replacing the auxiliary contact or by setting right the auxiliary contacts.
4.1.2 The auxiliary contacts of the condenser water pump may not be in position. Set the auxiliary contacts of cooling tower fan in position either by replacing the auxiliary contacts or by setting right the auxiliary contact.
4.1.3 The auxiliary contacts of the brine/chilled primary pump may not be in position. Set the auxiliary contacts of cooling tower fan in position either by replacing the auxiliary contacts or by setting right the auxiliary contact.
4.1.4 Check the three phase power supply of the compressor in the main feeder. Replace burnt fuses if any.
4.1.5 Compressor contactor thermal relay may be tripped. Reset the relay by pressing the reset button on relay.
4.1.6 Reset the thermostat, if tripped.
4.1.7 Reset low water pressure, low brine/chilled pressure, HP/LP cut out, low oil pressure cut out switches if tripped, by pressing the reset button.
4.1.8 Wiring may be defective. Check the wiring with wiring diagram.
4.1.9 Loose electrical connection or any defect in wires. check the continuity of wires with continuity meter, replace the defective wires.
4.2 Low suction pressure.
4.2.1 If the temperature of the brine water/chilled water is less than the set temperature of the thermostat. Stop the compressor and replace the thermostat if found defective.
4.2.2 Close the angular valve on the suction line. Open the flarenut of suction angular valve and ensure that gauge is under working condition. If found defective, replace the gauge.
4.2.3 Charge the gas not exceeding the discharge pressure 250 PSI.
4.2.4 Pump down the compressor as mentioned in SOP CHANGING/ADDITION OF OIL OF REFRIGERATION UNIT.from step 4.1 to 4.7.
4.2.5 Open the gas strainer and clean the strainer with carbon tetrachloride.
4.2.6 Open the expansion valve and clean the expansion valve with carbon tetrachloride as per SOP SERVICING OF EXPANSION VALVE OF REFRIGERATION UNIT. .
4.2.7 Refix the strainer and expansion valve.
4.2.8 Start the compressor and observe the suction pressure gauge. If the suction pressure is still low, call for external service engineer from an authorised refrigeration service center.
4.3 High discharge pressure.
4.3.1 If condenser inlet water temperature exceeds 32 degree C, add ice in the cooling tower.
4.3.2 If condenser inlet water pressure is less than 1.5 kg/cm2, outlet flow is less than 250 L./min rectify as given below.
4.3.2.1 Open and clean the pump strainer.
4.3.2.2 Ensure the foot valve is under working condition.
4.3.2.3 Remove the obstruction in water lines if any.
4.3.2.4 Ensure that the pump is creating required head and discharge.
4.3.3 If the tubes in condenser are plugged or scaled, open the condenser and clean the tubes as per SOP CLEANING OF CONDENSER TUBES OF REFRIGERATION COMPRESSORS
4.3.4 The pressure on suction pressure gauge should not be more than 30 PSI and 55 PSI for brine and chilled compressor respectively.
4.3.5 If the suction pressure is more, throttle the liquid line valve to the required pressure.
4.3.6 If air is in system purge air by slightly opening the angular valve on top of the compressor.
4.3.7 If the discharge pressure is still high call for external service engineer from any authorised refrigeration center.
4.4 Low discharge pressure.
4.4.1 If the flow and pressure of condenser water exceed 600 L./min and 2.5 kg/cm2 respectively, adjust the condenser inlet valve to the required pressure and flow.
4.4.2 Suction "SHUT-OFF" gun valve may be partially closed. Check and open the valve.
4.4.3 If pressure gauge is defective, replace the gauge.
4.4.4 If gas in the system is less charge gas as per SOP CHARGING OF GAS TO REFRIGERATION UNIT. to the required pressure.
4.5 Low oil pressure/control oil pressure.
4.5.1 If oil level is low add oil as per SOP CHANGING/ADDITION OF OIL OF REFRIGERATION UNIT.steps 4.1 to 4.10 and 4.18 to 4.24.
4.5.2 If oil gauge is faulty, replace with the new gauge.
4.5.3 If oil suction strainer is clogged, open the oil tank as per SOP CHANGING/ADDITION OF OIL OF REFRIGERATION UNIT. Remove the strainer of the oil pump clean the strainer with carbon tetrachloride and refix it.
4.5.4 Check the solenoid coil with meggar. If continuity of the coil is not found replace the coil element.
4.5.5 If fault is not rectified by the above remedies, call an external service representative from an authorised servicing organization.
4.6 Compressor flooding.
4.6.1 If the brine flow and specific gravity are less than 250 L./min and 1.14 respectively rectify as described in 4.6.1.1 to 4.6.1.2.
4.6.1.1 Check the brine pump as per 4.3.2.1 to 4.3.2.4.
4.6.1.2 If brine specific gravity is less than 1.14 add brine solution with 1.25 specific gravity.
4.6.2 Discharge excessive refrigerant from the system if any.
4.6.3 If setting of thermostat cut out is defective, set the thermostat to the actuals.
4.6.4 If the expansion valve is defective or improperly set rectify as per SOP SERVICING OF EXPANSION VALVE OF REFRIGERATION UNIT.
4.6.5 If the power element assembly is defective, replace the power element assembly as per SOP SERVICING OF EXPANSION VALVE OF REFRIGERATION UNIT..
4.7 Compressor Noisy.
4.7.1 If couplings are lose or misaligned, loosen all the coupling bolts, align properly and tighten the bolts.
4.7.2 If coupling tyre is broken or defective replace the tyre as per SOP REPLACEMENT OF SHAFT OIL SEAL/ COUPLING TYRE OF REFRIGERATION UNIT.follow step No.4.17.
4.7.3 If foundation bolts are loose, tighten the bolts. If the supports are broken weld them.
4.7.4 Replace the worn out bearings of compressor and motor.
4.8 If oil leaks from oil seal, replace the seal as per SOP REPLACEMENT OF SHAFT OIL SEAL/ COUPLING TYRE OF REFRIGERATION UNIT.
4.9 If the breakdown is major, call for an external service engineer from an authorised service organization.
5.0 RECORDING:
The responsibility of recording the breakdown in the history card lies with the staff of rank not lower than the maintenance supervisor.
Refrigeration unit, engineering, breakdown rectification
