Common faults and maintenance methods of PSA oxygen generators: 5 tips to extend the life of the equipment

In many fields such as medical treatment, plateau diffuse oxygen supply, fish and shrimp farming, ozone preparation, sewage treatment, oxygen-enriched combustion, etc., PSA (Pressure Swing Adsorption) oxygen generators, as core equipment, play a vital role. It separates oxygen from the air by physical methods, and has the advantages of simple operation, low operating cost, safety and environmental protection. However, any precision equipment will inevitably have problems of one kind or another during long-term operation. Understanding the common faults of PSA oxygen generators, mastering their maintenance methods and skills to extend the life of the equipment can not only ensure the continuity and stability of oxygen supply, but also significantly reduce operating costs and improve production efficiency. This article will deeply explore the six common faults of PSA oxygen generators, and provide detailed maintenance strategies and five practical tips to extend the life of the equipment, aiming to help users better maintain and manage their oxygen equipment.

Overview of common faults of PSA oxygen generators

Although the technology of PSA oxygen generators is mature, they may still encounter various faults in actual applications. These faults may be caused by a variety of factors such as electrical systems, pneumatic systems, adsorption systems, control systems or aging of accessories. Common faults include decreased oxygen purity, inability to start the system or difficulty in starting, excessive equipment noise, unstable pressure fluctuations, failure or poor effect of air dryers, and molecular sieve pulverization. These faults not only affect the oxygen production efficiency and oxygen quality, but in severe cases may even cause equipment shutdown, affecting normal production or medical needs. Therefore, the ability to identify and handle these faults is the key to ensuring the efficient and stable operation of PSA oxygen generators.

Decreased oxygen purity

Decreased oxygen purity is one of the most common and most troublesome faults of PSA oxygen generators. It directly affects the application effect of oxygen, especially in medical or industrial fields with high requirements for oxygen purity.

Cause analysis:

Degradation or poisoning of molecular sieve performance: Molecular sieve is the core adsorption material of PSA oxygen generators, and its adsorption performance directly determines the purity of oxygen. Long-term use or inhalation of air containing impurities such as oil, water, and hydrocarbons will cause the molecular sieve to have a decreased adsorption capacity or even poisoning failure. In addition, molecular sieve pulverization is also a common problem. The adsorption area of the pulverized molecular sieve is reduced, resulting in a decrease in purity.

Abnormal pressure or cycle of the adsorption tower: The pressure swing adsorption process depends on pressure changes. If the adsorption pressure of the adsorption tower is insufficient, the desorption is not thorough, or the adsorption/desorption cycle is improperly set, the oxygen purity will decrease. For example, too short an adsorption time will lead to unsaturated adsorption, and too short a desorption time will lead to insufficient discharge of nitrogen.

Gas line leakage: There are many pneumatic valves and pipeline connections inside the oxygen generator. Any leakage may cause air or adsorbed nitrogen to mix into the output oxygen, thereby reducing the purity of oxygen. In particular, the internal or external leakage of key valves such as the adsorption tower switching valve and the drain valve.

Insufficient air supply or poor air quality from the air compressor: The air compressor is the gas source of the oxygen generator. If the air compressor produces insufficient gas, the air flow or pressure entering the oxygen generator will not meet the design requirements, which will affect the normal adsorption of the molecular sieve. At the same time, if the air output by the air compressor contains a large amount of moisture, oil or particulate matter, these impurities will enter the molecular sieve tower with the air flow, contaminating the molecular sieve and reducing its adsorption efficiency.

Flow meter or oxygen analyzer failure: The flow meter is used to monitor the oxygen flow, and the oxygen analyzer is used to detect the oxygen purity in real time. If these instruments fail, they may give incorrect readings, causing users to misjudge or fail to detect the problem of purity reduction in time.

Repair method:

Replace the molecular sieve: If it is determined that the molecular sieve performance has deteriorated or pulverized, the only effective solution is to replace it with a new, high-quality molecular sieve. Before replacement, the old molecular sieve powder and impurities in the adsorption tower must be thoroughly removed.

Check and adjust the pressure and cycle: Refer to the equipment manual to check whether the adsorption pressure and desorption pressure of the adsorption tower are within the normal range. Use a pressure gauge for measurement. At the same time, check the program settings of the PLC (programmable logic controller) to ensure that the adsorption/desorption cycle meets the design requirements. Make fine adjustments if necessary to optimize the adsorption effect.

Check for gas line leaks: Use soapy water or a professional leak detector to check all pneumatic pipelines and valve connections one by one. If a leak is found, tighten the joints, replace the sealing rings, or repair/replace the faulty valves in time. Pay special attention to the sealing of the switching valve and the drain valve.

Maintain the air compressor and air handling system: Check the operation of the air compressor regularly to ensure that its air supply and pressure meet the requirements. At the same time, strengthen the maintenance and replacement of air dryers and filters (such as precision filters, oil removal filters, and dust removal filters) to ensure that the air entering the oxygen generator is clean, dry, and oil-free.

Calibrate or replace instruments: Calibrate the flow meter and oxygen analyzer regularly. If it still does not work properly after calibration, you need to consider replacing a new instrument.

The system cannot start or is difficult to start

The oxygen generator cannot start or is difficult to start, which means that the equipment cannot operate normally, which may cause oxygen supply interruption and cause serious impact on production or medical treatment.

Cause analysis:

Power failure: including loose power cord connection, blown fuse, damaged power switch, overload protection trip, or unstable power supply voltage.

Control system failure: PLC controller failure, touch screen (HMI) failure, control line break or short circuit, sensor (such as pressure sensor, temperature sensor) failure, resulting in signal failure to transmit normally.

Gas source problem: air compressor failed to start, air compressor outlet pressure was insufficient, or air intake valve was not opened, etc. Oxygen generators usually have low pressure protection function, which will prevent the system from starting when the gas source pressure is insufficient.

Emergency stop button pressed: The emergency stop button is accidentally pressed or stuck, causing the system to stop.

Valve failure: Some key pneumatic valves (such as intake valves, exhaust valves, etc.) cannot be opened or closed normally, resulting in air circuit blockage or the system cannot establish normal working pressure.

Equipment protection function triggering: such as overpressure protection, overheating protection, motor overload protection, etc. These protection functions will force the equipment to shut down when abnormalities are detected to prevent damage.

Repair method:

Check the power supply: First check whether the power supply connection of the oxygen generator is firm and whether the power indicator light is on. Check whether the fuse and circuit breaker in the distribution box are tripped or blown. Use a multimeter to measure whether the power supply voltage is within the normal range.

Check the control system: Check whether the PLC and touch screen are powered on normally and whether there is any error information displayed. Check whether the control line connection is loose or broken. If the PLC or touch screen is damaged, it may require professional diagnosis and replacement. Check whether all sensors are working properly and whether the signal output is correct.

Check the gas source: Confirm whether the air compressor starts normally and provides sufficient air pressure. Check whether the main air intake valve is fully open. If there is a problem with the air compressor itself, the air compressor failure needs to be solved first.

Reset the emergency stop button: Check whether the emergency stop button is pressed, and if so, reset it.

Check the valve: Check whether all pneumatic valves on the oxygen concentrator are flexible. You can use the manual operation button or PLC to force the valve action to observe whether it can open and close normally. If the valve is stuck or damaged, it needs to be cleaned, lubricated or replaced.

Troubleshoot the cause of the protection function triggering: Check the historical alarm records of the equipment control panel or PLC to see if there are alarm messages such as overpressure, overheating or motor overload. According to the alarm information, check the specific causes one by one and solve them. For example, if it is overpressure protection, check whether the drain valve is blocked or the pressure regulating valve is malfunctioning.

Excessive equipment noise

It is normal for the oxygen generator to produce a certain amount of noise during operation, but if the noise suddenly increases or exceeds the normal range, it needs to be taken seriously. Excessive noise not only affects the operating environment, but may also be a signal of equipment failure.

Cause analysis:

Air compressor failure: The air compressor is one of the main sources of noise. If the internal bearings of the air compressor are worn, the parts are loose, the piston rings are worn or the lubrication is insufficient, the noise will increase. The screw gap may be too large for the screw compressor, and the connecting rod bearing or crankshaft bearing may be worn for the piston compressor.

The pressure relief sound of the adsorption tower is too loud: During the desorption process of the PSA oxygen generator, the gas in the adsorption tower is quickly discharged through the drain valve, which will produce a certain amount of exhaust noise. If the drain valve fails, the muffler is blocked or damaged, or the exhaust pipeline design is unreasonable, it may cause abnormal increase in noise.

Loose pipes or parts: If the pipes, valves, electrical components or racks inside the equipment are not installed firmly or loosened due to long-term vibration, resonance or knocking sounds will occur during the operation of the equipment.

Fan failure: The bearing wear, blade deformation or foreign matter stuck in the cooling fan (such as the air compressor fan, the electric control box fan) will produce abnormal noise.

Solenoid valve or pneumatic valve failure: When the solenoid valve or pneumatic valve is switched, if the internal parts are worn or the control air pressure is unstable, an abnormal “click” sound or a harsh whistle may be emitted.

Maintenance method:

Check and maintain the air compressor: Listen carefully to see if the source of the noise is the air compressor. If it is suspected that there is an air compressor problem, contact a professional air compressor maintenance personnel for inspection. It may be necessary to replace worn parts (such as bearings, piston rings), add lubricating oil or adjust the gap between parts.

Check the muffler and exhaust pipe: Check whether the muffler at the exhaust end of the adsorption tower is blocked or damaged, and clean or replace it if necessary. Check whether the exhaust pipe is loose or has foreign matter. Ensure that the design of the exhaust pipe meets the specifications to avoid resonance.

Tighten loose parts: Carefully check all visible pipes, valves, connecting bolts and brackets inside the oxygen concentrator. Use a wrench to check and tighten all loose parts one by one.

Check the cooling fan: After turning off the power, turn the fan blades by hand to check for signs of foreign matter stuck or bearing wear. Clean the dust on the fan blades and replace the fan or bearing if the bearing is damaged.

Check the solenoid valve and pneumatic valve: Observe the sound when the valve switches. If the sound is abnormal, you can try to clean the inside of the valve or replace the damaged solenoid coil/pneumatic actuator. Check whether the control air source pressure is stable to ensure that the valve can switch quickly and smoothly.

Unstable pressure fluctuations

The working principle of the PSA oxygen generator determines that its internal pressure will change periodically, but this change should be within the set range. If the oxygen production pressure or adsorption tower pressure fluctuates violently and irregularly, it may indicate a fault.

Cause analysis:

Unstable intake pressure or flow: Fluctuations in the air pressure or gas volume output by the air compressor will directly affect the working pressure inside the oxygen generator. If the air compressor itself fails to adjust or the air supply is unstable, it will cause the oxygen generator pressure to fluctuate.

Adsorption tower switching valve failure: If the switching valves between the adsorption towers (such as the intake valve, equalizing valve, and exhaust valve) are not coordinated, opened or closed incompletely, the internal pressure of the adsorption tower will be abnormally established or released, causing pressure fluctuations. For example, failure of the equalizing valve to fully open will result in insufficient equalization.

Pressure regulating valve failure: Oxygen generators are usually equipped with pressure regulating valves (such as back pressure valves) to stabilize the oxygen production pressure. If the regulating valve diaphragm is aged, the spring is fatigued or blocked internally, the regulation will fail and the oxygen production pressure will be unstable.

Pipeline leakage or blockage: Leakage in the oxygen production pipeline or gas delivery pipeline will cause pressure drop. On the contrary, if there is a blockage inside the pipeline, it will cause local pressure to rise or fluctuate.

PLC control program error or sensor failure: The PLC program controls the opening and closing timing of the valve and the pressure equalization process. If the program logic is wrong or the pressure sensor provides an incorrect signal, it will cause the control system to misjudge, thereby causing pressure fluctuations.

Molecular sieve problem: The pulverization or severe reduction of the adsorption capacity of the molecular sieve may cause the adsorption tower to fail to build up pressure or the pressure to drop sharply during the adsorption process, thereby affecting the pressure stability of the entire system.

Repair method:

Check and stabilize the air supply of the air compressor: Ensure that the air pressure output by the air compressor is stable, and check whether the pressure of its gas storage tank is normal. If there is a problem with the air compressor itself, it should be solved first.

Check and calibrate the pressure regulating valve: Check whether the setting value of the back pressure valve or other pressure regulating valve is correct. Try manual adjustment to observe the changes in oxygen production pressure. If the adjustment is ineffective or the valve is stuck, it may need to be cleaned, repaired or replaced.

Check the action and sealing of the switching valve: Check whether the action of all switching valves is smooth and in place by observation or manual operation of the PLC. Check whether there is leakage inside the valve (use soapy water or stethoscope). If there is internal leakage, the valve seal or the entire valve may need to be replaced.

Check for pipeline leakage or blockage: Check all pipelines related to oxygen production for leaks. For blockages, it may be necessary to disassemble the pipeline for cleaning.

Check the PLC program and pressure sensor: Check whether the PLC program is running normally and whether there are any errors. Calibrate the pressure sensor or compare the measurement with a standard table with known pressure to confirm that the sensor reading is accurate. If the sensor fails, replace it in time.

Evaluate the condition of the molecular sieve: If the above methods are ineffective and there is a problem with the purity of the oxygen generator, consider whether the molecular sieve is severely powdered or the performance is degraded. You can remove a small amount of molecular sieve for visual inspection and simple performance testing. Replace the molecular sieve if necessary.

Failure of air dryer or poor effect

The air dryer (usually a cold dryer or adsorption dryer) is an important part of the oxygen generator pretreatment system. Its function is to remove moisture from compressed air and protect the subsequent molecular sieve. If the dryer fails or has poor effect, a large amount of water vapor will enter the molecular sieve, seriously affecting the life of the molecular sieve and the purity of oxygen.

Cause analysis:

Failure of cold dryer: Common failures of cold dryers include refrigerant leakage, compressor failure, condenser or evaporator blockage, expansion valve failure, drainer blockage or failure, etc., which will cause its dehumidification effect to decrease.

Adsorption dryer failure: Common failures of adsorption dryers (such as double-tower adsorption dryers) include adsorbent (such as activated alumina, molecular sieve) saturation failure, regeneration heater failure, switching valve internal leakage, program controller failure or insufficient regeneration gas volume.

Poor drainage: Whether it is a cold dryer or an adsorption dryer, if the automatic drainer is blocked or damaged, the condensed water cannot be discharged in time, which will cause moisture to re-enter the gas path.

Filter blockage or failure: Precision filters, oil removal filters, etc. are usually configured before and after the dryer. If these filters are blocked or failed, impurities such as oil, particulate matter, etc. in the air will enter the dryer, contaminating the desiccant or affecting its performance.

Ambient temperature or humidity is too high: If the ambient temperature or humidity of the oxygen generator is too high, it will increase the burden on the dryer, making its dehumidification effect worse, or even exceeding its design capacity.

Repair method:

Check the dryer:

Refrigeration system: Check whether the refrigerant pressure is normal and whether there is leakage. Check whether the compressor is operating normally and whether there is any abnormal sound. Clean the heat sink of the condenser and evaporator to ensure good heat dissipation.

Drainage system: Check whether the automatic drainer is working properly and whether there is any blockage. You can try to drain manually to see if a lot of water is discharged.

Dew point: If there is a dew point meter, measure the dew point of the air after drying to see if it meets the standard (usually between -20℃ and -40℃).

Check the adsorption dryer:

Adsorbent: Check whether the adsorbent is discolored, deliquesced or powdered. If the adsorbent is saturated or failed, it needs to be replaced.

Regeneration system: Check whether the regeneration heater is heating normally and whether the regeneration gas path is unobstructed. Check whether the switching valve is operating accurately and whether there is any internal leakage.

Program control: Check whether the PLC or controller program of the dryer is normal to ensure that the regeneration cycle and parameter settings are correct.

Maintain the drainage system and filter: Check and clean the automatic drainer regularly to ensure that it is unobstructed. Regularly replace the precision filter element before and after the cold dryer or adsorption dryer to ensure clean air.

Improve environmental conditions: If the ambient temperature or humidity is too high, consider adding air conditioning or dehumidification equipment to the oxygen generator room to reduce the environmental load.

Contact professional maintenance: For complex refrigeration system failures of cold dryers or internal program problems of adsorption dryers, it is recommended to contact professional refrigeration or air compressor equipment maintenance personnel for diagnosis and treatment.

Conclusion

As a key oxygen supply equipment, the stable operation of PSA oxygen concentrator is crucial to all industries. Mastering the troubleshooting and repair methods of its common faults is the basis for ensuring the efficient operation of the equipment. However, in addition to passively repairing faults, it is more important to extend the overall life of the equipment through active maintenance and care to prevent problems before they occur. The following will elaborate on five practical tips for extending the life of PSA oxygen concentrators, hoping to provide a useful reference for your equipment management.