[Mechanical Equipment Technology Edition] Daily Question 201801026: Common Faults in Refrigeration Systems (8.3)
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This post was last edited by YORK Industrial Refrigeration on 2018-1-29 at 08:20. Starting from now, in order to enhance communication among users, a 【Daily Question】 campaign has been launched on the Mechanical Equipment Technology forum; we hope everyone will participate actively to progress and improve together! ! ! Rewards: 3 wealth points for active participation, 10-15 wealth points for correct answers. This question is valid for two days; no score will be assigned if more than two days pass. Reasons for low suction pressure in the compressor. Answer: First, the suction pressure is low; we need to start by examining the suction side. The main refrigeration equipment and components on the suction side (the low-pressure side) include the suction valve, evaporator, and throttle valve. Let’s analyze each of these one by one: 1. The suction valve is not opened enough. 2. The evaporator does not perform evaporation properly (poor heat exchange). 3. There is insufficient liquid supply from the throttle valve, or there are issues with the throttle valve itself—such as blockages due to dirt or other problems. Other issues include insufficient liquid supply caused by a lack of refrigerant, as well as abnormally low pressures. ============================== Premium promotions: Mechanical equipment—maintenance procedures for York screw compressors https://bbs.hcbbs.com/thread-1806833-1-1.html Mechanical equipment—upgrading York Quinton control systems https://bbs.hcbbs.com/thread-1804837-1-1.html Mechanical equipment—major repairs for GEA Grasso screw compressors https://bbs.hcbbs.com/thread-1800467-1-1.html Mechanical equipment—disassembly and maintenance of British HOWDEN screw compressors https://bbs.hcbbs.com/thread-1832529-1-1.html Mechanical equipment—disassembly and maintenance of Japanese MYCOM screw compressors https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=
1. The expansion valve is clogged or has a low opening degree. 2. Insufficient refrigerant. 3. The heat load on the evaporator is too low, resulting in a lower evaporation temperature
The opening degree of the expansion valve or control valve is too low; the filter or throttle orifice is clogged with ice, there are leaks in the temperature sensor; the low-pressure pipeline is blocked by ice; the liquid line is obstructed, the outlet valve or other valves on the liquid line are not fully open, and the filter is blocked; there is insufficient refrigerant in the system; too much lubricating oil is circulating in the system; the evaporator has excessive frost buildup; dirt on the surface of the evaporator reduces its heat transfer efficiency.
1. Contaminants in the liquid supply pipe, expansion valve, or filter of the refrigeration system, excessive restriction in the flow, malfunctioning float valves, a low volume of ammonia circulation within the system, insufficient height difference for liquid supply in the intercooler, or too small pipe diameters – all of these can result in too low suction pressure in the compressor. 2. Insufficient refrigerant charge or supply in the cooling system, as well as improper adjustment of the throttle valve, can all cause low suction pressure in the plastic molding machine. 3. If the evaporator piping is too long, or if too many compressors are used in parallel with an improperly designed suction manifold, this can also result in low suction pressure in the compressors. 4. An excessive oil content in the fluorocarbon system with easily soluble oil reduces the suction pressure. 5. Thick frosting on the warehouse evaporator or oil accumulation on its inner walls increases the thermal resistance, resulting in a lower suction pressure.
1. Contaminants in the liquid supply pipe, expansion valve, or filter of the refrigeration system, excessive restriction in the flow, malfunctioning float valves, a low volume of ammonia circulation within the system, insufficient height difference for liquid supply in the intercooler, or too small pipe diameters – all of these can result in too low suction pressure in the compressor. 2. Insufficient refrigerant charge or supply in the cooling system, as well as improper adjustment of the throttle valve, can all cause low suction pressure in the plastic molding machine. 3. If the evaporator piping is too long, or if too many compressors are used in parallel with an improperly designed suction manifold, this can also result in low suction pressure in the compressors. 4. An excessive oil content in the fluorocarbon system with easily soluble oil reduces the suction pressure. 5. Thick frosting on the evaporator or oil accumulation on its inner walls increases the thermal resistance, resulting in a lower suction pressure.
1. Contaminants in the refrigeration system’s supply lines, expansion valve, or filter can cause blockages; an excessively small opening size, a malfunctioning float valve, a low volume of refrigerant circulation in the system, insufficient head pressure in the intermediate cooler, or too small pipe diameters can all lead to too low suction pressure in the compressor. 2. Insufficient refrigerant charge or supply in the cooling system, as well as improper adjustment of the throttle valve, can all cause low suction pressure in the plastic molding machine. 3. If the evaporator piping is too long, or if too many compressors are used in parallel with an improperly designed suction manifold, this can also result in low suction pressure in the compressors. 4. An excessive oil content in the fluorocarbon system with easily soluble oil reduces the suction pressure. 5. Thick frosting on the evaporator or oil accumulation on its inner walls increases the thermal resistance, resulting in a lower suction pressure.
The inlet pipeline is blocked, and the valve disc of the inlet valve is stuck
1. Insufficient refrigerant. 2. Inadequate setting of the expansion valve. 3. Too low temperature on the condensing side.
Reasons for low pressure: 1. Contaminants blocking the liquid supply pipes, expansion valves, or filters in the refrigeration system, or an excessively small opening size, a malfunctioning float valve, a low volume of ammonia circulation within the system, insufficient height difference in the liquid supply to the intercooler, or too small pipe diameters – all of these can lead to low suction pressure in the compressor. 2. Insufficient refrigerant charge or supply in the cooling system, as well as improper adjustment of the throttle valve, can all cause low suction pressure in the plastic molding machine. 3. If the evaporator piping is too long, or if too many compressors are used in parallel with an improperly designed suction manifold, this can also result in low suction pressure in the compressors. 4. An excessive oil content in the fluorocarbon system with easily soluble oil reduces the suction pressure. 5. Thick frosting on the warehouse evaporator or oil accumulation on its inner walls increases the thermal resistance, resulting in a lower suction pressure.
1. Contaminants in the liquid supply pipe, expansion valve, or filter of the refrigeration system, excessive restriction in the flow, malfunctioning float valves, a low volume of ammonia circulation within the system, insufficient height difference for liquid supply in the intercooler, or too small pipe diameters – all of these can result in too low suction pressure in the compressor. 2. Insufficient refrigerant charge or supply in the cooling system, as well as improper adjustment of the throttle valve, can all cause low suction pressure in the plastic molding machine. 3. If the evaporator piping is too long, or if too many compressors are used in parallel with an improperly designed suction manifold, this can also result in low suction pressure in the compressors. 4. An excessive oil content in the fluorocarbon system with easily soluble oil reduces the suction pressure. 5. Thick frosting on the warehouse evaporator or oil accumulation on its inner walls increases the thermal resistance, resulting in a lower suction pressure.
1. Insufficient refrigerant. 2. Inadequate setting of the expansion valve. 3. Too low temperature on the condensing side.