Principles of Compressor Energy Regulation | Practical Points for Piston Cylinder Load Unloading Mechanism and Load Matching
The semi closed piston compressor relies on a cylinder load unloading mechanism to achieve energy regulation. The top rod is controlled by an electromagnetic valve to lift the suction valve plate, and the corresponding cylinder stops working, achieving a stepped cooling capacity regulation.
The conventional four cylinder model supports three levels of energy regulation: 0%, 50%, and 100%. The six cylinder model can achieve 33%, 66%, and 100% gears, which are suitable for stable control of storage temperature.
The Xitelidou small four cylinder and medium four cylinder piston compressors are equipped with unloading devices as standard, which reduce temperature fluctuations caused by frequent start stop during low load periods in pharmaceutical cold storage and dairy preservation warehouses.
The top rod spring of the unloading mechanism experiences long-term alternating fatigue, and after 8000 hours of operation, the elastic force decays, resulting in unloading failure. The unit continues to operate at full load, and the amplitude of temperature oscillations in the storage increases.
The power supply voltage of the energy regulating solenoid valve should be consistent with the main circuit of the compressor. If the voltage deviation exceeds ± 10%, the solenoid valve will be unstable and intermittent loading and unloading disorder will occur.
Many engineering companies neglect the lubrication of the unloading mechanism, and impurities in the refrigeration oil get stuck in the clearance between the top rods, causing jamming. The fault manifests as the inability to reduce the cooling capacity and the continuous high-pressure operation of the unit.
Compared to screw compressors with stepless adjustment, piston step adjustment has lower cost and simpler maintenance, making it suitable for small and medium-sized cold storage; Under high load continuous working conditions, the energy consumption advantage of screw stepless adjustment is obvious.
For the small fresh-keeping cold storage project in Southeast Asia, the purchaser prefers piston units with unloading, which have simpler electrical control and are easier to maintain and repair by local electricians compared to frequency conversion solutions.
The start stop frequency of the compressor is critical to the lifespan of the unit. Units with energy regulation can control the start stop frequency within 4 times per hour, while units without unloading can have a start stop frequency of up to 12 times.
The energy regulation logic should be coordinated with the temperature controller settings. When the storage temperature approaches the set value, it should be unloaded step by step. Do not wait until the temperature exceeds the limit before loading it all at once to avoid excessive load impact.
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FAQ
How many levels of adjustment are there for a four cylinder piston compressor? Common three tiered adjustment: 0%, 50%, and 100%.
How long does it take for the unloading mechanism spring to fatigue and fail? After approximately 8000 hours of operation, the elasticity is prone to decay.
3. What is the allowable deviation range for the voltage of the solenoid valve? Voltage fluctuations should be controlled within ± 10% as much as possible.
What is the difference between piston step adjustment and screw stepless adjustment? The cost of piston gear adjustment is low, and the screw adjustment is smoother.
5. How many times is it recommended to control the start and stop of the unloading unit per hour? Try to control within 4 times.
What are the typical fault phenomena of uninstallation card lag? The cooling capacity cannot be reduced and continues to operate at full load and high pressure.
7. Which scenarios prioritize the use of piston units with unloading? Small and medium-sized fresh-keeping and pharmaceutical constant temperature cold storage.
