Analysis of common causes of cylinder jam caused by heat pump compressor

Analysis of common causes of cylinder jam caused by heat pump compressor

What are the reasons for the jam of the heat pump compressor? Do you guys know? Let’s take a closer look with the editor of okmarts.com today!

　　 1. Cylinder jam phenomenon

　　1. Cylinder jam definition: refers to the phenomenon that the relative moving parts interlock and fail to operate due to poor lubrication, impurities, etc. during compressor operation. The compressor cylinder jam indicates that the compressor has been damaged. Compressor jams mostly occur on the friction surface of the bearing and crankshaft with relative sliding friction, the friction surface of the cylinder and the lower bearing, and the friction surface of the piston and cylinder with relative rolling friction.

Another phenomenon is sometimes misjudged as a cylinder jam, that is, poor compressor startup. Poor compressor startup means that the starting torque of the compressor cannot overcome the system resistance and the compressor cannot start normally. When the external conditions change, the compressor has It may start, the compressor is not damaged.

　　2. Conditions for normal compressor start: compressor starting torque> friction resistance + high and low pressure force + rotational inertia friction resistance: it is related to the friction between the compressor upper bearing, lower bearing, cylinder, crankshaft and the viscosity of compressor refrigerating oil. High and low pressure force: related to the high and low pressure balance of the system. Moment of inertia: related to rotor and cylinder design.

　　 2. Common causes of cylinder jam

　　 1. The compressor itself

　　1.1 The compressor is poorly processed, the matching surface is unevenly stressed, or the processing technology is unreasonable, and impurities enter the compressor during the production of the compressor. This is rarely the case for brand compressors.

　　1.2 Adaptation of compressor to system: Heat pump water heater is developed on the basis of air conditioner, so most heat pump manufacturers continue to use air conditioner compressor. The national standard for air conditioning operating conditions requires that the maximum temperature is 43°C, that is, the maximum temperature on the condensing side is 43°C. The maximum discharge pressure of the compressor at this temperature generally does not exceed 23kg/cm2. In the national standard of heat pump operating conditions, the water temperature is required to be 55°C, that is, the temperature on the condensing side is 55°C. The maximum exhaust pressure at this temperature is generally 25kg/cm2. If the ambient temperature on the evaporating side is 43°C, the exhaust pressure is generally at About 27kg/cm2, which makes the compressor often work under high load.

　　 Working under high load conditions will easily cause the carbonization of the refrigerating oil, resulting in insufficient lubrication of the compressor and cylinder jamming. In the past two years, a dedicated heat pump compressor has been developed. Through the optimization and adjustment of the internal structure such as the internal oil return hole and the exhaust hole, the compressor and the heat pump are more adapted to the working conditions.

　　2, transportation, handling and other collision causes

The compressor is a precision instrument. The pump body is precisely matched. Collision and severe vibration during handling and transportation will cause the size of the compressor pump body to change. When the compressor starts or runs, the crankshaft drives the piston to a certain position. The resistance increased significantly, and finally stuck. Therefore, the compressor should be handled with care from the factory to the assembly into the main engine, from the main engine storage to the transportation to the agent, and from the agent to the user's installation, so as to avoid the compressor from collision, rollover, lying down, etc. According to the relevant regulations of the compressor manufacturer, the handling tilt cannot exceed 30.

　　 3. Reasons for installation and use

　　 has a three-point quality for the air-conditioning and heat pump industries, and seven-point installation is an exaggeration, but it suffices to explain the great impact of installation on the use of the host. The installation level test, emptying, connecting pipe length, height difference, leak detection, etc. will affect the use of the host. Here are one by one.

　　3.1 Level test: The compressor manufacturer stipulates that the operating tilt of the compressor should be less than 5 during operation, and the main engine should be installed horizontally, and the tilt should be less than 5. Obviously tilted long-term work will cause local uneven force and high local friction. The user installs an application level meter for level detection.

　　3.2 Emptying: Excessive emptying time will cause insufficient refrigerant, the compressor does not have enough refrigerant to cool, the exhaust temperature will be high, the refrigerant oil is carbonized and deteriorated, and the lack of lubrication will cause the compressor to jam. Forgetting to empty or incomplete emptying, there will be air in the system. Air is a non-condensable gas, which will cause high pressure or abnormal fluctuations, and the life of the compressor will be affected. Therefore, when emptying, it must be accurately empty according to the standard requirements.

3.3 Length of the connecting pipe: The length of the connecting pipe and the length of the water tank coil are determined during the R&D experiment of the host. In the actual installation and use, the irregular lengthening of the connecting pipe and adjustment of the water tank will cause the internal volume of the system to deviate from the experimental standard. The matching between the amount of refrigerant and the host system will lose its balance. When the unit is running, the exhaust temperature, pressure, and heating time will be abnormal due to too much or too little refrigerant. The impact is related to the length of the connecting pipe and the water tank coil. When choosing the host and water tank, try to choose according to the technical requirements. When the connecting pipe must be lengthened, it should be added according to the standard of 15-20g/m.

　　3.4 High drop: High drop refers to the height difference between the main engine and the water tank. The high drop will cause difficulty in oil return. Generally, the customer's water tank and main engine are required to be within the allowable length of the connecting pipe as much as possible, and the two are at the best level.

　　3.5 Leak detection: After connecting the refrigerant pipe and emptying it, perform a leak detection. Use soap, washing powder, detergent and other foam, evenly spread on the valve nut, and no bubbles can be blown out. If the refrigerant leaks, it will also cause insufficient refrigerant, and the compressor will not be able to cool down normally, causing the exhaust temperature to rise and the refrigerant oil to deteriorate.

　　4. Reasons for host production process control

　　4.1 Compressor transport: When transporting the compressor assembly, horizontal transport, side transport, and violent landing are all irregular actions, and should be handled gently and transported vertically.

　　4.2 The compressor sealing rubber plug should not be removed prematurely before welding, and other refrigerant system pipelines should also be effectively sealed. Some major manufacturers in the industry stipulate that the system should be welded and sealed within 30 minutes after removing the sealing rubber plug, especially in rainy weather. The reason is that the air contains a certain amount of water vapor, and the refrigerating oil has a certain degree of water absorption. If it is in contact with the air for a long time, it is inevitable that moisture will invade, the oil will be diluted, and the lubrication will decrease. The presence of water in the system will cause "ice blockage", that is, when the water is below 0℃, it will freeze at the throttle and cause system blockage; the water will chemically react with the refrigerating oil to produce acid, resulting in "copper plating", that is, the acid and the copper pipe of the system When a reaction occurs, the dissolved copper ions will adhere to the surface of the steel to form a film, which is the "copper plating phenomenon". Copper plating will cause the compressor to block; or cause the plastic seal to produce a "swelling effect", which will cause the system The refrigerant leaks. During production, the contact time between the inside of the compressor and the outside air should be minimized.

4.3 Water vapor enters the pipeline during welding: When welding four-way valves and other parts that need water cooling, avoid water rushing into the pipeline. If the structure is restricted, the nozzle should be plugged with a rubber plug before welding. After welding, use high pressure. Blow dry with nitrogen.

4.4 Nitrogen-filled welding requirements: Nitrogen is an inert shielding gas, which can prevent air from contacting the surface of high-temperature copper pipes to form oxide skin during welding. Although the oxide skin is powder, the hand can hardly feel the solid existence, but it will cause some stickiness. Changes affect lubrication. Nitrogen charging is an express ban on air conditioner and heat pump manufacturers and should be strictly enforced. Failures caused by not charging nitrogen are serious, but also difficult to find.

　　4.5 Unqualified vacuum: It is recommended that the vacuum of the system be below 20P to ensure that the water content of the system is below the allowable value. Unqualified vacuuming may cause residual air and water vapor. The consequences are also analyzed above. The reasons for the unqualified vacuum degree are generally short evacuation time, system leakage, or failure to pump both high and low pressure at the same time.

　　4.6 Pipeline cutting should avoid copper scraps remaining in the holes or nozzles, and the secondary processed holes and nozzles should be cleaned.

4.7 Workshop cleanliness requirements: the heat pump production is clean production. The floor and walls of the workshop, including instruments and equipment, should be cleaned in time to avoid messiness. The doors and windows of the workshop should be properly closed, and special vents should be set up to avoid idle personnel, dust, and humidity. Air enters the workshop. The workshop is not clean, and the consequences of dust entering the system are dirt, blockage, and decreased lubrication.

　　5. The heat pump system design is unreasonable

　　5.1 In the R&D experiment, the determined filling amount of refrigerant is unreasonable, and the experimental items are not complete. The pressure temperature and pressure are reasonable at room temperature, but the pressure and temperature are abnormal at high and low temperatures. Therefore, it is necessary to verify the experimental effects of high temperature (ambient temperature of 43℃), nominal (ambient temperature of 20℃), low temperature (ambient temperature of -7℃), and defrosting (ambient temperature of 0℃) during the development stage.

5.2 Insufficient oil return: The oil return must be considered when designing the system. The oil return generally increases the flow rate through changes in direction or pressure, and carries the oil back to the compressor. By designing an oil return bend on the system pipeline, the return bend can move in a certain direction The flow rate of the flowing refrigerant is increased while ensuring sufficient oil return.

5.3 The system volume is too large. Under normal circumstances, the size of a certain type of compressor and the heat exchanger is compatible, because the internal oil volume of the compressor is fixed, and the heat exchanger will cause insufficient oil volume, which is not an outsider's opinion. The larger the heat exchanger, the better.