The commonly used Dongguan water chillers mainly include air-cooled water chillers, water-cooled water chillers, screw water chillers, anti-corrosion water chillers, electroplating water chillers, etcCause analysis of high pressure alarm of Dongguan water chiller
1. The cooling water is not turned on. This problem is very easy to solve, but it is a common mistake. Solution: Please open the water valve.
2. The cooling water flow is too low or the temperature is too high. Solution: increase the cooling water flow or reduce the water temperature (the cooling water allows 21 ℃ - 38 ℃).
3. The condenser copper pipe has many scales, small diameter and poor heat dissipation. Solution: Clean the condenser copper pipe.
4. Too much refrigerant. Solution: discharge excess refrigerant (R22).
5. The expansion valve opens too large. Solution: properly reduce the opening of the expansion valve, press the compressor thermal relay protection switch (RESTET), and find out the cause
Cause analysis of low pressure alarm of Dongguan water chiller
1. Insufficient refrigerant. Solution: leak detection, is there any leakage point at the pipe joint? Replenish refrigerant after repair.
2. The filter is blocked. Solution: disassemble and wash or replace the filter.
3. The condenser copper pipe has many scales, smaller diameter and poor heat dissipation. Solution: Clean the condenser copper pipe.
4. The opening of expansion valve is too small. Solution: properly reduce the opening of the expansion valve, and automatically reset the high and low pressure protection after removal.
Water-cooled screw chiller, chiller maintenance: screw compressor is a very important part of the unit, and the quality of the compressor is directly related to the stability of the unit. In case of compressor failure, screw compressor requires high installation accuracy, so it is generally required to ask the manufacturer for maintenance.
Condenser maintenance
As the cooling water of the water-cooled condenser is an open circulating circuit, the tap water generally used is recycled through the cooling tower. When the content of calcium salt and magnesium salt in the water is large, it is easy to decompose and deposit on the cooling water pipe to form scale, affecting heat transfer. Too thick scaling will also reduce the flow section of cooling water, reduce the water volume and increase the condensation pressure. Therefore, when the quality of the cooling water used is poor, clean the cooling water pipes at least once a year to remove scale and other dirt in the pipes.
The exhaust pressure of screw chiller is too low
1. The water flow through the condenser is too large: at this time, the valve should be reduced
2. The inlet water temperature of the condenser is too low: adjust the fan speed of the cooling water tower or the number of fans.
3. A large amount of liquid refrigerant enters the compressor: check the expansion valve and its temperature sensor
4. Insufficient refrigerant filling: fill the refrigerant to the specified amount
5. Suction pressure is lower than the standard: refer to "suction pressure is too low" fault handling
The suction pressure of screw chiller is too low
1. The condenser refrigerant liquid outlet valve is not fully opened: the valve should be fully opened
2. The refrigerant filter is blocked: clean or replace the filter regularly
3. Improper adjustment or failure of expansion valve: correct adjustment or troubleshooting is required, and replace it if necessary
4. Insufficient refrigerant filling: it should be replenished to the specified amount
5. Excessive lubricating oil circulates in the cooling system of the water chiller: find out the cause and reduce it to the appropriate value
6. The inlet water temperature of evaporator is too low: increase the inlet water temperature setting value
7. Insufficient water flow through evaporator: check water pump and water valve
Precautions for maintenance of screw chiller
1. Refrigeration compressor: screw compressor is the heart of the unit, and its quality is directly related to the stability of the chiller. Due to the high installation accuracy requirements of screw compressor, if the compressor fails, it is generally necessary to ask the chiller plant to arrange personnel for maintenance.
2. Clean the evaporator/condenser: the company has considered the later maintenance when designing the evaporator and condenser, so it uses the side cover design. We should clean the whole cooling water system at least once a year, including the cooling water tower and all pipes. When cleaning, we should buy special cleaning agent for circulating flushing, or fill it in cooling water, and then change the solution after 24h until it is cleaned.
3. Replace the drying filter: the drying filter is an important part to ensure the normal circulation of refrigerant. Since water and refrigerant are not miscible with each other, if the system contains water, it will greatly affect the operation efficiency of the unit. Therefore, it is very important to keep the system dry inside. The filter element inside the drying filter must be replaced regularly.
The chiller is responsible for providing cooling capacity during the operation of the central air conditioning system. As an operation manager, in addition to correct operation and careful maintenance, it can timely find and remove some common problems and faults, which plays an important role in ensuring the normal operation of the central air conditioning system and reducing the losses and costs caused by the problems and faults.
1. Early detection and analysis of faults in the operation of water chillers
Careful maintenance of the chiller can minimize the occurrence of faults, but it is impossible to eliminate the occurrence of faults. Because of the chiller itself and the objective external conditions, the structural manufacturing, installation quality, use method and operation level of the chiller are different, and it is impossible to completely eliminate the potential adverse factors, so the unsafe factors that constitute the failure of the chiller always exist.
In order to ensure the safe, efficient and economical long-term normal operation of the chiller, it is very important to find the hidden trouble of the failure as early as possible in its use. As an operator, you can achieve this goal by "seeing, touching, listening and thinking".
First look: see the high and low pressure values of water chiller operation. The size of oil pressure, the water pressure at the inlet and outlet of cooling water and chilled water, and other parameters. The parameter values that meet the set operating condition requirements are normal, and the parameter values that deviate from the operating condition requirements are abnormal. Each abnormal operating condition parameter may contain certain fault factors. In addition, pay attention to the appearance of the water chiller. For example, if the suction pipe of the compressor frosts, it means that the cooling capacity of the water chiller is too large, the evaporation temperature is too low, the suction superheat of the compressor is small, and the suction pressure is low. This is true for piston escapes. The unit will cause "liquid shock"; For centrifugal water chiller, it will cause kick vibration.
Second touch: on the basis of comprehensive observation of the operating parameters of each part, t further experience the temperature of each part, touch each part of the water chiller and pipes (including air pipe, liquid pipe, water pipe, oil pipe, etc.) by hand, and feel the working temperature and vibration of the compressor; Inlet and outlet temperature of the two devices; Oil stains and distribution at pipe joints. Under normal conditions, the compressor operates smoothly, the temperature difference between suction and exhaust is large, and the temperature rise of the body is not high; Low evaporation temperature and large temperature difference between inlet and outlet of chilled water; High condensation temperature, large temperature difference between inlet and outlet of cooling water; If there is no refrigerant leakage at each pipe joint, there is no oil stain, etc; Any performance contrary to the above situation means that there are fault factors in corresponding parts.
See Table 1 for the sensory characteristics of temperature by touching objects with hands.
Table 1 Sensory characteristics of temperature measurement by touching objects
Temperature/℃
Handfeel characteristics
Temperature/℃
Handfeel characteristics
thirty-five
Below body temperature, slightly cool
sixty-five
Strong scalding feeling, retracted after touching for 3s
forty
Slightly higher than - body temperature, lukewarm tank clothing
seventy
Excessive scalding feeling, fingers retract after touching for 3s
forty-five
Mild and slightly warm
seventy-five
Fingers feel acupuncture, ls~2s retract
fifty
Slightly hot but endurable for a long time
eighty
There is a feeling of drying, and the hand will return at the touch of it. If it stays a little, it will cause slight drinking injury
fifty-five
Have a strong sense of heat. Generate avoidance awareness
eighty-five
There is radiant heat, burning feeling, and scalding
sixty
It feels hot and retracts quickly after touching for 4s
ninety
Extremely hot, cringing, untouchable
Although it is only an experiential and approximate method to measure temperature by touching objects with hands, it has important practical value for mastering the temperature situation and change trend of components and pipes without temperature measuring points, and for quickly and accurately judging faults.
Third listen: analyze and judge the character and location of the fault by analyzing the abnormal sound of the water chiller in operation. In addition to listening to whether the total sound of the water chiller during operation conforms to the sound rule of normal operation, it is important to listen to whether the electromagnetic valve, throttle valve and other equipment of the small compressor i system of the compressor, lubricating oil pump and the extraction recovery device of the centrifugal water chiller have abnormal sound. For example, when a piston or centrifugal compressor is in operation, it makes a slight "chum, chum, chum" sound or a continuous and even slight "hum, hum" sound, which indicates that the compressor operates normally; If you hear "Dong, Dong, Dong" or leaves_ The rotating sound of the wheel is fast and slow, or there is abnormal vibration sound, which indicates that the compressor has liquid hammer or end vibration.
Four thoughts: comprehensive analysis should be carried out on the data and materials of the chiller operation obtained from the relevant indicating instruments and the ways of seeing, listening and touching, to find out the basic causes of the failure, consider what emergency measures should be taken, and how to save time, materials and money to eliminate the failure.
2. Basic procedures for fault handling
The treatment of water chiller faults must strictly follow scientific procedures. It is forbidden to act blindly and dismantle at will when the situation is unclear, the fault is unclear, and the mind is numberless. The consequence of doing so will often enlarge the existing faults or cause new faults; Even cause serious damage to the chiller. The basic procedure of fault handling is shown in Figure 1.
Figure 1 Basic procedure of fault handling
2.1 Investigate and understand the process of failure
① Carefully carry out site inspection to understand the working condition of each part of the water chiller when the fault occurs, the location of the fault and the severity of the hazard.
② Carefully listen to the site operators to introduce the reason why the fault occurred and the emergency measures taken. If necessary, the water chiller or auxiliary device that can operate in a short time without further deterioration of the fault shall be started and operated in person, so as to grasp accurate perceptual knowledge basis for correct analysis of the fault cause.
③ Check the water chiller operation record sheet, pay special attention to the operation data of different normal conditions and the problems occurred in the record sheet, as well as the operation time and reliability of the replaced and repaired parts; Understand the safety protection shutdown and other conditions caused by any reason. The situation directly related to the failure cannot be ignored.
④ Ask relevant personnel for their understanding and opinions on the fault. If necessary, the operator is required to explain and demonstrate his own operation method.
2.2 Collect data and find out the cause of failure
① Detailed reading of the Operation Manual of the chiller is an important source for understanding various data of the chiller. The Operation Manual can provide various parameters of the water chiller (such as the refrigerating capacity of the unit, the type of compressor, the power, speed, voltage and current of the motor, the type and filling amount of refrigerant, the quantity and oil level of lubricating oil, the date of manufacture and the number of the machine, etc.), and list the possible causes of various failures. The comprehensive comparison between the parameters provided in the Operation Manual and the data in the chiller operation record sheet can provide important basis for correct fault diagnosis:
② The unit shall be checked according to the electrical system (including power and control system), water system (including cooling water and chilled water system), oil system, refrigeration system (including compressor, condenser, throttle valve, evaporator and pipeline). The four major parts shall be carried out in sequence, and attention shall be paid to finding the complex factors that cause the fault to ensure stable, accurate and fast troubleshooting.
2.3 Analyze data and diagnose fault causes
① Combined with the basic theory of refrigeration cycle, the collected data and information are analyzed, and various parameters of normal conditions of refrigeration cycle are taken as an important basis for comparative analysis of the collected data. For example, according to the refrigeration principle, the suction pressure of the compressor of the chiller is too high, resulting in the increase of refrigerant circulation and the overload of the main motor. The reasons for the high suction pressure of the compressor are related to such factors as too much refrigerant charge, too large opening of the thermal expansion valve and float valve, too high condensation pressure, and too large evaporator load. If the collected data shows that the suction pressure in the refrigeration system is higher than the suction pressure value specified in the theoretical cycle or the motor is overloaded, the causes of the above failures can be checked from the aspects of refrigerant charge, evaporator load, condenser heat transfer effect, cooling water temperature, etc.
② Use actual work experience to analyze data and information. After mastering all aspects of the normal operation of the chiller, once there is a difference between the actual situation and the accumulated experience, the cause of the fault can be found immediately from this difference. For example, when the piston chiller is started normally, there will be no "liquid hammer" phenomenon. When the "liquid hammer" occurs during the actual startup process, and the oil level of the sight glass does not show the phenomenon of lubricating oil bubble, it can be determined that the liquid refrigerant sucked by the piston compressor is not from the lubricating oil in the crankcase, but from the evaporator. In the piston chiller, the liquid refrigerant in the evaporator during shutdown can only come from the high-pressure part, that is, the high-pressure liquid refrigerant enters the evaporator through the solenoid valve and the thermal expansion valve. " The expansion valve is controlled by a temperature sensor. After the chiller is shut down, the temperature at the outlet of the evaporator at the IZL end rises, and the expansion valve core automatically opens. This is normal. Therefore, when the chiller is shut down, the only factor that causes the high-pressure liquid refrigerant to enter the evaporator is the untight closing of the solenoid valve. From this analysis, it can be seen that the solenoid valve has a fault, and the above "liquid hammer" phenomenon will be eliminated automatically after the fault is eliminated. It can be seen that combining practical experience with theoretical analysis and analyzing the collected data and information is conducive to grasping the essential cause of the fault through all phenomena and eliminating it accurately and quickly.
③ Analyze the data and data according to the logical relationship of the technical faults of the chiller. The logical relationship and inspection method of technical failures of water chillers are effective measures for analyzing and inspecting the causes of various failures. Connecting various actual collected data with this logical relationship can greatly improve the accuracy of judging the cause of failure and the speed of maintenance progress. Generally, the faults occurred in the operation of the water chiller are divided into three categories: ① the unit does not start; ② The unit operates but the cooling effect is poor. ③ The unit starts and stops frequently. The logical relationship of various faults is shown in Figure 2.
2.4 Determine the maintenance plan
① Consider the maintenance plan from the perspective of feasibility
The first thing is how to complete the maintenance task with the most economical funds (including materials, spare parts, labor, downtime, etc.). The funds should be controlled within the planned amount of maintenance funds. When the total repair cost is close to or exceeds the cost of the newly purchased complete machine
If possible, the old machine should be scrapped.
② Consider the maintenance plan from the perspective of reliability
Generally, the treatment and maintenance scheme of the chiller failure is not single. From the perspective of the function of the water chiller after maintenance, it can be divided into three situations: temporary, transitional and long-term. Various maintenance schemes have obvious differences in the investment of funds, personnel input, maintenance process requirements, the length of maintenance time, the number of spare parts used and the quality of the quality, and should be determined according to the specific situation