Maintenance of General-purpose Screw-type Water-cooled Chillers

2024-09-09

I. Purpose
Standardize the maintenance work of air-conditioning equipment and devices to ensure that the air-conditioning equipment and devices operate in a good condition.

II. Tasks and Key Points

It is required to be in line with the actual work arrangements of the department. Focus on preventive maintenance to ensure the normal operation of the equipment and the daily supply operation. Carry out three-level maintenance (including daily/Level 1: monthly/quarterly, Level 2: semi-annual/annual).
The maintenance and water quality treatment of the chiller unit shall be in the charge of a professional company.
The air-conditioning system is responsible for the maintenance of the equipment and devices belonging to the air-conditioning system, and complete the equipment maintenance according to the air-conditioning system maintenance plan.
When the on-duty personnel find a system equipment failure during inspection, they should carry out maintenance immediately and report to the system supervisor.
Detailed records must be made for the parts to be replaced during the equipment maintenance process.
According to the characteristics of the system equipment, focus on dust removal, lubrication, replacement of aging parts, tightening screws, etc.
Pay attention to electrical safety and fire prevention. If welding is required, a hot work permit must be obtained and the hot work operation regulations must be strictly observed.
The principle of system maintenance is not to affect the normal production of the workshop. Sudden failures should be eliminated within 4 hours. If it exceeds the time limit, it should be reported to the superiors so as to notify the affected users in a timely manner.

III. Equipment Maintenance Outline

Maintenance of fan coil units: generally including the cleaning of the water receiving tray, air filter screen, air inlet louver, air supply outlet, coil fin, and the daily maintenance of the temperature control switch motor;
Maintenance of cooling towers: daily maintenance of the water replenishment system, water quality treatment, motor and fan, and cleaning of the cooling tower;
Maintenance of air supply, exhaust and smoke exhaust equipment: cleaning of air filter screen, air inlet louver, air supply outlet, fan room, air duct, and fan equipment, and daily maintenance of motors and bearings;
Maintenance of water pipe systems: anti-rust painting of pipes, maintenance of various valves, pressure gauges, etc.;
Maintenance of motor pumps: coupling, packing, and bearing lubrication of cooling, freezing, and heat medium pumps with motors. Also pay attention to the motor safety inspection every quarter;
Maintenance of the electric control part: mainly the maintenance of the electrical and automatic control parts related to the main air-conditioning equipment;
Maintenance of the chiller unit
(1) Daily maintenance
① Clean the surface of the unit.
③ Check whether the three-phase voltage of the power supply is normal at 380V.
④ Check whether the oil heater works normally under power supply (ensure the oil temperature is between 25 - 30℃ during standby).
⑤ Check whether there is water leakage or oil seepage in all parts of the unit.
⑥ Check whether the temperature control probe is normal.
⑦ Check whether the parameters during the unit operation are within the standard values (see the host manual for specific parameters).
⑧ Check whether the action of the energy regulating mechanism during the unit operation is flexible (that is, the loading and unloading solenoid valves and the sliding valve mechanism).
⑨ Check whether the sound during the normal operation of the unit is normal.
⑩ Check whether the temperature during the normal operation of the unit is normal (including the main motor, compressor, exhaust temperature, oil temperature, etc.).
(2) First-level maintenance
① Execute the maintenance content of the electric control part.
② Measure the insulation resistance of the main motor and check whether it meets the value specified by the unit.
③ Check whether the seal between the main motor and the compressor is normal.
④ Check whether the setting and positioning of each safety protection device meet the specified requirements.
⑤ Check whether the water flow protection switch operates normally. If it fails to operate, repair or replace it in time.
⑥ Check the condition of the insulation layer of the evaporator part. If it is damaged, repair or replace it in time.
(3) Second-level maintenance
① Execute the content of daily maintenance and first-level maintenance.
② Clean the pipe scale and cover plate scale of the evaporator and condenser (water quality treatment part).
③ Replace the oil filter element according to the usage situation.
④ Replace the dry filter according to the usage situation.
⑤ Replace new refrigeration oil according to the oil quality situation.
⑥ Lubricate the main motor bearings with grease.
⑦ Remove rust and paint the surface of the unit.
⑧ Calibrate the pressure sensor.
⑨ Add or replace the electric control coolant.

I. Daily Maintenance Work
(A) Chiller Unit

Check and record the water temperature, water pressure, refrigerant temperature, temperature and pressure of the evaporator and condenser, and the voltage and current of the host during the operation of the host.
Determine whether the above data is normal and how to adjust it.
Check whether there is abnormal vibration and noise in the rotating part.
Check whether there is oil leakage or water leakage in the pipelines and joints.
Keep all parts of the host clean.
(B) Circulating Water Pump
Check whether the temperature of the motor bearing and the running sound are normal.
Check and record the voltage and current of the motor.
Check the inlet and outlet water temperature and water pressure.
Check whether the gasket is in good condition and whether there is water leakage.
(C) Cooling Tower
Check whether the make-up water and pipeline valves are normal.
Check whether there are pollutants such as floating oil and impurities in the stored water.
Check the water level and the floating ball control switch.
Check the operation of the fan motor and the voltage and current situation.
Pay attention to the cleanliness of the water outlet and the filter screen.
(D) Pipelines
Check whether the valves and water pipes are in good condition.
Check whether the make-up water tank and the float valve are normal.
Record the daily inspection points in the daily inspection record form once every 4 hours.

II. Weekly Maintenance Work
(A) Chiller Unit

Check whether each safety and operation controller is normal.
Check whether the refrigerant pipeline system is normal (especially the dryer, expansion valve, solenoid valve, sight window, and joints everywhere).
Check the refrigeration oil and replenish or replace it if necessary.
Check the safety relief valve.
Check the oil filter screen and clean or replace it if necessary.
(B) Circulating Water Pump
Check the bearings and add lubricating oil if necessary.
Check whether the sealing gasket leaks water.
Check whether the motor and the valve body, and the valve body and the base are loose.
(C) Cooling Tower
Clean the water storage tray, the outlet water filter screen, and change the water.
Check the insulation of the motor and wiring.
(D) Combined Air Conditioning Unit
Clean the filter screen and replace it if necessary.
Check and adjust the tightness of the belt and replace it if necessary.
Check and clean the windmill and copper tube row.
Check whether the current of all motors is normal.
(E) Distribution Box
Check whether the wire ends and contacts at each part are in good condition.
Remove the dust in the electrical components and the box.
(F) Pipelines and Others
Check whether the accessories such as valves, flexible joints, temperature and pressure gauges of the pipelines are in good condition.
Check the clogging situation of the filter and clean it.
Check whether each hanger and joint is in good condition and safe.

III. Monthly Maintenance Work
(A) Chiller Unit

Check and pay attention to whether the refrigerant amount is insufficient. If it is insufficient, it needs to be refilled.
Check each safety controller.
Check the pipelines and exhaust devices.
Check the pollution situation of the circulating water and replace it if necessary.
(B) Circulating Water Pump
Check and replace the oil seal, add or replace the lubricating oil.
Check whether the bearings and couplings are damaged.
(C) Cooling Tower
Check the water storage tray, shell, and mesh plate and clean or paint them if necessary.
Check the water quality of the stored water, clean and change the water.
Check whether the sprinkler head is normal. If it is still blocked, take it out and clean it.
(D) Combined Air Conditioning Unit
Check the pipelines and remove the air.
Clean the windmill and copper tube row.
Check the belt.
(E) Pipelines and Others
Open and close various valve switches once or twice to avoid clogging.
Check whether each electric valve operates normally.

IV. Major Maintenance Items and Cycles
(A) Chiller Unit

Check the control circuit and control equipment safety instruments.
Check the insulation of the motor and check and replace the bearings. (Replace the bearings once every 40,000 hours)
Inspect the insulation safety of the power distribution power system and equipment.
Clean and anti-rust treatment of the whole unit.
(B) Cooling Tower
Clean the water storage tray, heat sink, steel plate, etc.
Remove rust and paint the iron parts.
Fix the motor frame and base and check the transmission part.
Test the insulation of the motor, check the safety of the wiring and wire tube and fix them.
Check and replace the motor bearings.
Replace the heat dissipation PVC filler once every 4 years.
(C) Circulating Water Pump
Check the water pump, impeller, coupling, bearings, and shaft seal.
Test the insulation of the motor.
Clean and anti-rust treatment.
(D) Combined Air Conditioning Unit
Clean the filter screen and coil.
Clean the wind drum impeller and calibrate the axis to make the operation stable.
Check the safety of the motor wiring and control wiring for any broken skin and leakage.
Chemically remove the scale in the coil and clean the dirt on the surface of the fins with compressed air or water once a year.
(E) Distribution Box
Clean and check all main parts inside and outside, wiring, joints, etc.
Check and calibrate the relays and instruments.
Insulation and grounding safety test.
(F) Pipelines and Others
Check and clean the filter screen.
Check and calibrate the inlet and outlet water temperature gauges and pressure gauges.
Remove rust from all pipelines.

V. Annual Use and Discontinuation Methods
(A) Central air-conditioning start-up method in summer

Before starting the machine, carefully check all machine parts and refill the bearings with oil.
Clean and fill water in the cooling water and ice water systems.
Remove the air in the system.
Leak detection for the whole system (including the ice water host and water pipelines).
Check that the power supply voltage is within 90% of the rated voltage, and the phase voltage imbalance does not exceed 2%. Open the suction and discharge stop valves and the liquid supply stop valve of the compressor. Check the system valves and air-conditioning auxiliary equipment, pumps, cooling towers, etc.
Preheat the refrigeration oil in the compressor by power on. (24 hours)
Start the central air-conditioning system according to the operation procedure.
(B) Central air-conditioning shutdown method in winter
The condensing system shall not be unused for more than one month. If it exceeds, the refrigerant must be sealed in the condenser.
Leak detection for the condenser to avoid refrigerant loss.
Remove the water in the condenser and cooling system.
Close the valve of the expansion tank.
Turn off the power of the host and stick a seal.

VI. Equipment Maintenance and Precautions
(A) Maintenance and Maintenance System of Water Pumps

Check the lubricating oil level of the bearings every day. Add oil in time when there is a lack of oil.
Check every day whether the nuts of the anchor bolts and connecting bolts are loose. Tighten them in time if they are loose.
Check whether the shaft seal leaks water every day and adjust or replace the damaged one at any time.
Dismantle and clean the body once a year. Replace the damaged parts in time if any are found.
Brush anti-rust paint on the water pump body once every one to two years according to the situation.
(B) Maintenance and Maintenance System of Valves
Keep the valves clean and the paint in good condition.
Apply butter to the threaded part of the valve stem: once every six months indoors and once every three months outdoors to increase the lubrication effect when the screw and the nut are rubbed and reduce wear.
Valves that are not frequently adjusted or opened and closed must be rotated regularly by handwheel or handle to prevent rust and seizure.
For valves used on frozen water pipelines and hot water pipelines, ensure the integrity of their insulation layers to avoid heat and cold loss and the occurrence of condensation and dripping phenomena.
For automatic valves such as check valves, automatic air valves, and various solenoid valves, check frequently whether they work normally and whether their actions are flexible. Repair or replace the faulty ones in time.
In addition, note that valves cannot be used to bear heavy objects, and it is strictly prohibited to stand on the valves for work or maintenance during operation or maintenance to avoid damage to the valves or affecting the performance of the valves.
(C) Maintenance and Maintenance System of Water Pipelines
Frozen water pipes: Frozen water pipes need insulation. The main task of their daily maintenance is to ensure that the insulation layer and the surface moisture-proof layer are not damaged or peeled off. If found, repair them in time.
Cooling water pipes: If galvanized steel pipes are used, there is no need to brush anti-rust paint on the outside. Cooling water is generally treated with chemical agents. After a long time of use, it is inevitable to damage the pipe wall. Pay attention to the corrosion problem of the pipe after a long time.
(D) Maintenance and Maintenance System of Water Filters
Water filters installed at the inlet of water pumps, the inlet of chiller units, and the inlet of fan coil units should be cleaned regularly. Generally, take out the filter screen and clean it once every three months. For newly put into use cooling water systems and systems with a long service life, the cleaning cycle should be shorter.

(E) Maintenance and Maintenance System of Expansion Tanks
Check once a day to ensure that the water level in the tank is moderate, the float valve operates flexibly, and the water output is normal. Clean the tank once a year and remove rust and paint the tank body and base.

VII. Maintenance of Fan Coil Units
Main parts for maintenance:

Filter screen → The air filter screen is an important part of the fan coil unit for purifying the return air. It is installed at the return air outlet of the fan coil unit. Due to different environments and different working hours, the cleaning cycle and method are also different. Generally, it should be cleaned once a month during continuous use.
Water receiving tray → The water receiving tray is used to receive the condensate water generated by the fan coil unit. After a period of time, a lot of dust will fall into the water receiving tray of the fan coil unit, causing the drainage port of the water receiving tray to be blocked. When the condensate water is full, the condensate water overflows, resulting in accidents such as damp ceilings. So the water receiving tray is generally cleaned once a year.
Coil → It is responsible for transferring the cold and heat of cold and hot water to the air passing through the fan coil unit to raise or lower the indoor temperature. To ensure high-efficiency heat transfer, the surface of the coil must be kept as smooth as possible. If it is not cleaned in time, the heat exchange amount between the cold and hot water in the coil and the air flowing outside the coil will be reduced. The cleaning cycle of the coil can be longer, generally once a year. When cleaning, first brush the fins with a stiff brush, and then use a vacuum cleaner to clean.
Fan → That is, the motor part of the fan coil unit. Use a small powerful vacuum cleaner for cleaning. Generally, it is cleaned once a year or once an air-conditioning season.
Condensate water pipe → It is a unique non-pressure self-flowing discharge water pipe without return water in the fan coil unit system. To prevent the pipe wall from condensing and dripping everywhere, the main tasks of the daily maintenance of the condensate water pipe are two aspects:

Ensure the smooth flow of condensate water. Due to the non-pressure self-flowing type, its flow rate is often affected by the slope, resistance, pipe diameter, and turbidity of the water. When there are lumps or masses of dirt, it is more difficult to flow and the pipe is easy to be blocked.
Ensure that the insulation layer and the surface moisture-proof layer are not damaged or peeled off.