Fault Manifestations and Troubleshooting of Six Consumable Parts of Screw Air Compressors
Screw air compressors feature a series of unique advantages including simple structure, reliable operation and convenient operation, hence they have been widely adopted by the industrial sector since their launch. Nevertheless, regular replacement of consumable parts is required during daily production. Improper handling will directly impair the normal operation and safety of air compressors. This article summarizes the consumable parts of screw air compressors, as well as typical fault manifestations and corresponding solutions.
1. Air Filter
The air filter of an air compressor consists of an air filter assembly and filter element. It is connected to the air inlet valve of the air compressor via connectors and threaded pipes to filter dust, particles and other impurities in intake air. The air filter can be selected according to the air intake volume for different air compressor models.
Fault Manifestation: Filter Blockage
A clogged air filter increases energy consumption and power waste of the air compressor, and dust can easily penetrate the filter. Excessive dust entering the compressor will shorten the service life of compressor lubricating oil and cause blockage of the oil separator element.
Troubleshooting Measures
As the core component of the filter, the filter element is made of special materials and belongs to consumable parts requiring special maintenance.
After long-term operation, the filter element traps a large amount of impurities, resulting in increased pressure and reduced flow rate, so timely cleaning is necessary.
Avoid deformation or damage to the filter element during cleaning.
Filter paper is also a critical component. High-quality filter paper adopted in premium filters is ultra-fine fiber paper impregnated with synthetic resin, which effectively intercepts impurities and boasts high dust holding capacity. Sufficient mechanical strength is required for filter paper to withstand strong airflow, guarantee filtration efficiency and extend equipment service life.
The pore size of filter paper is approximately 10 μm. The filter element shall be removed every 1,000 hours to clear surface dust by blowing compressed air from inside out. A differential pressure detector is installed on the air filter. If the display panel indicates air filter blockage, the filter must be cleaned or replaced immediately.
2. Oil Filter
Generally a paper-type filter, the oil filter removes impurities such as metal particles and oil degradation products from lubricating oil. With a filtration precision ranging from 5 μm to 10 μm, it protects bearings and rotors.
Fault Manifestation: Oil Filter Failure
Troubleshooting Measures
Whether to replace the oil filter can be judged by the differential pressure indicator. If the differential pressure indicator lights up, the oil filter is clogged and must be replaced. Lubricating oil and oil filter shall be replaced after the first 500 hours of operation of a new unit. Subsequent replacement shall be carried out once the differential pressure alarm is triggered. If a clogged oil filter is not replaced in a timely manner, insufficient oil supply will lead to high exhaust temperature shutdown and shorten bearing service life.
The effective service life of the oil filter depends on two factors:
Quantity of impurities. The service life expires when the impurity adsorption capacity reaches saturation.
Unit operating temperature and carbonization resistance of filter paper. The service life varies greatly under high temperature and normal temperature; high operating temperature accelerates carbonization of filter paper significantly and shortens its service cycle. Inferior filter paper also has a short usable life. Under normal conditions, high-quality oil filters deliver an effective filtration period of roughly 2,000–2,500 hours.
Variable frequency screw compressors operating continuously at low frequency usually run at low temperature with abundant moisture inside the oil separator tank, which imposes high requirements on the waterproof performance of filter paper. Low-frequency operation also results in low pressure inside the oil circuit system, so the oil filter must feature low resistance and good air permeability.
Many users misunderstand the oil filter mechanism, believing that higher filtration precision always brings better filtration effect while worrying about frequent blockage. Research shows this view is incorrect. Although filtration precision is relevant to filtering performance, the decisive factor is the adsorption capacity of filter paper rather than precision. Greater dust holding capacity brings stronger adsorption and better filtration effect. Fiber filter paper achieves excellent performance due to large dust holding capacity, strong adsorption and good carbonization resistance. However, fiber filter paper is costly and only available for bulk customized orders. Customization is uneconomical for oil filters with low sales volume, which explains why fiber filter paper is rarely adopted.
3. Oil Separator Element
The oil separator element is constructed with multiple layers of fine glass fiber, which can almost completely remove misty oil aerosol from compressed air. Under normal operation, its service life is about 3,000 hours.
The oil-water separation element is designed for oil-water separation, comprising coalescing elements and separation elements.
Consequences of failure: Poor separation efficiency leads to excessive oil consumption and high oil content in compressed air, disrupting the operation of downstream purification equipment and end-user pneumatic devices. Blockage increases pressure drop, raising the actual exhaust pressure and energy consumption of the unit. After failure, detached glass fiber materials enter lubricating oil, shortening the service life of oil filters and causing abnormal wear of the main unit. Once the oil separator element ruptures, massive oil loss occurs, triggering high unit temperature due to insufficient lubrication, and in severe cases, the main rotor may seize.
Fault Manifestations: Blockage / Rupture / Burning / Poor Separation Efficiency
Troubleshooting Measures
The service life is greatly affected by lubricant quality and ambient pollution level. A pre-filter can be installed if the operating environment is heavily contaminated.
Blockage: A clogged oil separator element causes excessive motor current of the air compressor. Excessive pressure may deform the element, resulting in motor overload or even main rotor seizure. Excessive current also shortens contactor service life or burns contacts, which may trigger serious accidents. Most screw air compressors are equipped with pressure gauges before the filter element. The oil separator element needs replacement when the differential pressure between the pre-filter pressure gauge and air supply pressure gauge reaches 0.08 MPa.
Rupture: Obvious excessive oil consumption can be observed, accompanied by massive oil accumulation inside the air receiver and pipelines. In severe cases, compressor oil is discharged directly from the drain valve of the air receiver.
Main causes:
(1) Failure to replace the element on schedule;
(2) Adoption of inferior oil separator elements;
(3) Non-standard installation, such as piercing the element during return oil pipe installation.
Burning: Although infrequent, burning of oil separator elements occasionally occurs. Typical phenomena include partial or full carbonization of the filter screen, or even melting of the metal housing.
Main causes:
(1) Poor quality of compressor lubricating oil;
(2) Inferior quality of the oil separator element itself;
(3) Poor electrical connection and grounding between the element housing and oil separator tank during installation. Static electricity ignites oil mist and burns the element.
Poor separation efficiency: Characterized by excessive oil content in compressed air, damaging downstream treatment equipment and user machinery.
Main causes:
(1) Inferior quality of the oil separator element;
(2) Non-compliant installation operations.
4. Lubricating Oil
Compressor lubricating oil forms a protective film between the contact points of two meshing screw rotors to avoid direct contact, buffer friction and reduce wear. It also functions in cooling, noise reduction, sealing and rust prevention.
Fault Manifestation: Lubricating Oil Degradation
Troubleshooting Measures
The replacement cycle of 500 hours for new units and subsequent 4,000-hour intervals is defined under standard operating environments. In practical operation of screw air compressors, multiple factors affect lubricant performance. Therefore, the replacement cycle shall be determined according to actual working conditions.
Key influencing factors for lubricant replacement cycle:
Lubricant quality: Qualified lubricants from formal manufacturers can operate for 4,000 hours under standard environments, while inferior oil requires far shorter replacement intervals. Mixing different types of lubricants causes oil deterioration and shortens service life.
Air humidity: Higher ambient humidity means more moisture enters the compressor. Moisture mixed with lubricating oil leads to oil emulsification and failure.
Impurities: Impurities entering with intake air and wear debris generated inside the unit contaminate lubricating oil.
Acidic and alkaline gas: In certain working environments, acidic or alkaline gas deteriorates lubricating oil and reduces its service life.
5. Drive Belt
Drive belts feature good elasticity to absorb shock and vibration during operation, delivering stable and low-noise transmission. When overloaded, belt slippage protects other components from damage and serves as a safety protection mechanism.
Fault Manifestation: Loss of Belt Elasticity
Troubleshooting Measures
Shut down the air compressor, wait for the unit to cool down and release internal pressure before inspecting the drive belt. Due to the special structure of screw air compressors, replacement and adjustment shall be conducted according to belt tension status. If severe deformation is absent, adjust bolts to achieve proper tension. The belt must be replaced if damaged beyond repair.
Precautions: Ensure uniform tension across the entire belt and prevent slippage. Conduct trial operation for about 30 hours after installation and monitor changes. Proper tension control avoids unexpected breakage.
Correct replacement and adjustment of drive belts reduce the load on the motor and other accessories. Secure the main unit after all operations. All procedures must be carried out strictly in sequence to avoid operational errors, which are the primary cause of component damage. Maintain vigilance, make adequate preparations and adjust parameters in a timely manner.
6. Solenoid Valve
Fault Manifestation: Failure to Actuate
Solenoid valve faults on screw air compressors directly affect the operation of switching valves and regulating valves. Troubleshooting steps for non-actuating solenoid valves are listed below:
Troubleshooting Measures
Loose or detached wiring terminals result in power loss. Tighten the wiring terminals to solve the problem.
Burned solenoid coil. Disconnect wiring and test with a multimeter; an open circuit indicates coil burnout. Common causes include coil dampness leading to poor insulation, magnetic leakage and excessive internal current. Prevent rainwater ingress into the solenoid valve. Besides, excessively stiff springs with large reaction force or insufficient coil turns resulting in inadequate suction may also burn the coil. For emergency treatment, toggle the manual button on the coil from position "0" to "1" to open the valve.
Solenoid valve jamming. The clearance between the spool sleeve and spool is very small (less than 0.008 mm). Mechanical impurities or insufficient lubrication easily cause jamming. A steel wire can be inserted into the small hole on the top to reset the spool temporarily. The fundamental solution is to dismantle the solenoid valve, take out the spool and sleeve, and clean them with carbon tetrachloride (CCl₄) to ensure flexible movement. Record component assembly sequence and wiring positions during disassembly for correct reassembly. Inspect the oil mist injector hole for blockage and confirm sufficient lubricating oil supply.
Solenoid valve air leakage. Air leakage causes insufficient air pressure and difficult valve switching, which is usually induced by damaged sealing gaskets or spool wear leading to inter-chamber air cross-flow.
Fault inspection and maintenance of solenoid valves shall be performed when the valve is de-energized. Solutions include direct replacement of the solenoid valve, replacement of burned coils or repairing valve body leakage.
Summary
The above troubleshooting methods for six core consumable parts of screw air compressors are provided for reference. Carefully observe fault phenomena to accurately identify root causes and shorten maintenance downtime. For equipment safety, maintenance personnel need to accumulate more operation and maintenance experience instead of only relying on these typical fault cases.
1. Air Filter
The air filter of an air compressor consists of an air filter assembly and filter element. It is connected to the air inlet valve of the air compressor via connectors and threaded pipes to filter dust, particles and other impurities in intake air. The air filter can be selected according to the air intake volume for different air compressor models.
Fault Manifestation: Filter Blockage
A clogged air filter increases energy consumption and power waste of the air compressor, and dust can easily penetrate the filter. Excessive dust entering the compressor will shorten the service life of compressor lubricating oil and cause blockage of the oil separator element.
Troubleshooting Measures
As the core component of the filter, the filter element is made of special materials and belongs to consumable parts requiring special maintenance.
After long-term operation, the filter element traps a large amount of impurities, resulting in increased pressure and reduced flow rate, so timely cleaning is necessary.
Avoid deformation or damage to the filter element during cleaning.
Filter paper is also a critical component. High-quality filter paper adopted in premium filters is ultra-fine fiber paper impregnated with synthetic resin, which effectively intercepts impurities and boasts high dust holding capacity. Sufficient mechanical strength is required for filter paper to withstand strong airflow, guarantee filtration efficiency and extend equipment service life.
The pore size of filter paper is approximately 10 μm. The filter element shall be removed every 1,000 hours to clear surface dust by blowing compressed air from inside out. A differential pressure detector is installed on the air filter. If the display panel indicates air filter blockage, the filter must be cleaned or replaced immediately.
2. Oil Filter
Generally a paper-type filter, the oil filter removes impurities such as metal particles and oil degradation products from lubricating oil. With a filtration precision ranging from 5 μm to 10 μm, it protects bearings and rotors.
Fault Manifestation: Oil Filter Failure
Troubleshooting Measures
Whether to replace the oil filter can be judged by the differential pressure indicator. If the differential pressure indicator lights up, the oil filter is clogged and must be replaced. Lubricating oil and oil filter shall be replaced after the first 500 hours of operation of a new unit. Subsequent replacement shall be carried out once the differential pressure alarm is triggered. If a clogged oil filter is not replaced in a timely manner, insufficient oil supply will lead to high exhaust temperature shutdown and shorten bearing service life.
The effective service life of the oil filter depends on two factors:
Quantity of impurities. The service life expires when the impurity adsorption capacity reaches saturation.
Unit operating temperature and carbonization resistance of filter paper. The service life varies greatly under high temperature and normal temperature; high operating temperature accelerates carbonization of filter paper significantly and shortens its service cycle. Inferior filter paper also has a short usable life. Under normal conditions, high-quality oil filters deliver an effective filtration period of roughly 2,000–2,500 hours.
Variable frequency screw compressors operating continuously at low frequency usually run at low temperature with abundant moisture inside the oil separator tank, which imposes high requirements on the waterproof performance of filter paper. Low-frequency operation also results in low pressure inside the oil circuit system, so the oil filter must feature low resistance and good air permeability.
Many users misunderstand the oil filter mechanism, believing that higher filtration precision always brings better filtration effect while worrying about frequent blockage. Research shows this view is incorrect. Although filtration precision is relevant to filtering performance, the decisive factor is the adsorption capacity of filter paper rather than precision. Greater dust holding capacity brings stronger adsorption and better filtration effect. Fiber filter paper achieves excellent performance due to large dust holding capacity, strong adsorption and good carbonization resistance. However, fiber filter paper is costly and only available for bulk customized orders. Customization is uneconomical for oil filters with low sales volume, which explains why fiber filter paper is rarely adopted.
3. Oil Separator Element
The oil separator element is constructed with multiple layers of fine glass fiber, which can almost completely remove misty oil aerosol from compressed air. Under normal operation, its service life is about 3,000 hours.
The oil-water separation element is designed for oil-water separation, comprising coalescing elements and separation elements.
Consequences of failure: Poor separation efficiency leads to excessive oil consumption and high oil content in compressed air, disrupting the operation of downstream purification equipment and end-user pneumatic devices. Blockage increases pressure drop, raising the actual exhaust pressure and energy consumption of the unit. After failure, detached glass fiber materials enter lubricating oil, shortening the service life of oil filters and causing abnormal wear of the main unit. Once the oil separator element ruptures, massive oil loss occurs, triggering high unit temperature due to insufficient lubrication, and in severe cases, the main rotor may seize.
Fault Manifestations: Blockage / Rupture / Burning / Poor Separation Efficiency
Troubleshooting Measures
The service life is greatly affected by lubricant quality and ambient pollution level. A pre-filter can be installed if the operating environment is heavily contaminated.
Blockage: A clogged oil separator element causes excessive motor current of the air compressor. Excessive pressure may deform the element, resulting in motor overload or even main rotor seizure. Excessive current also shortens contactor service life or burns contacts, which may trigger serious accidents. Most screw air compressors are equipped with pressure gauges before the filter element. The oil separator element needs replacement when the differential pressure between the pre-filter pressure gauge and air supply pressure gauge reaches 0.08 MPa.
Rupture: Obvious excessive oil consumption can be observed, accompanied by massive oil accumulation inside the air receiver and pipelines. In severe cases, compressor oil is discharged directly from the drain valve of the air receiver.
Main causes:
(1) Failure to replace the element on schedule;
(2) Adoption of inferior oil separator elements;
(3) Non-standard installation, such as piercing the element during return oil pipe installation.
Burning: Although infrequent, burning of oil separator elements occasionally occurs. Typical phenomena include partial or full carbonization of the filter screen, or even melting of the metal housing.
Main causes:
(1) Poor quality of compressor lubricating oil;
(2) Inferior quality of the oil separator element itself;
(3) Poor electrical connection and grounding between the element housing and oil separator tank during installation. Static electricity ignites oil mist and burns the element.
Poor separation efficiency: Characterized by excessive oil content in compressed air, damaging downstream treatment equipment and user machinery.
Main causes:
(1) Inferior quality of the oil separator element;
(2) Non-compliant installation operations.
4. Lubricating Oil
Compressor lubricating oil forms a protective film between the contact points of two meshing screw rotors to avoid direct contact, buffer friction and reduce wear. It also functions in cooling, noise reduction, sealing and rust prevention.
Fault Manifestation: Lubricating Oil Degradation
Troubleshooting Measures
The replacement cycle of 500 hours for new units and subsequent 4,000-hour intervals is defined under standard operating environments. In practical operation of screw air compressors, multiple factors affect lubricant performance. Therefore, the replacement cycle shall be determined according to actual working conditions.
Key influencing factors for lubricant replacement cycle:
Lubricant quality: Qualified lubricants from formal manufacturers can operate for 4,000 hours under standard environments, while inferior oil requires far shorter replacement intervals. Mixing different types of lubricants causes oil deterioration and shortens service life.
Air humidity: Higher ambient humidity means more moisture enters the compressor. Moisture mixed with lubricating oil leads to oil emulsification and failure.
Impurities: Impurities entering with intake air and wear debris generated inside the unit contaminate lubricating oil.
Acidic and alkaline gas: In certain working environments, acidic or alkaline gas deteriorates lubricating oil and reduces its service life.
5. Drive Belt
Drive belts feature good elasticity to absorb shock and vibration during operation, delivering stable and low-noise transmission. When overloaded, belt slippage protects other components from damage and serves as a safety protection mechanism.
Fault Manifestation: Loss of Belt Elasticity
Troubleshooting Measures
Shut down the air compressor, wait for the unit to cool down and release internal pressure before inspecting the drive belt. Due to the special structure of screw air compressors, replacement and adjustment shall be conducted according to belt tension status. If severe deformation is absent, adjust bolts to achieve proper tension. The belt must be replaced if damaged beyond repair.
Precautions: Ensure uniform tension across the entire belt and prevent slippage. Conduct trial operation for about 30 hours after installation and monitor changes. Proper tension control avoids unexpected breakage.
Correct replacement and adjustment of drive belts reduce the load on the motor and other accessories. Secure the main unit after all operations. All procedures must be carried out strictly in sequence to avoid operational errors, which are the primary cause of component damage. Maintain vigilance, make adequate preparations and adjust parameters in a timely manner.
6. Solenoid Valve
Fault Manifestation: Failure to Actuate
Solenoid valve faults on screw air compressors directly affect the operation of switching valves and regulating valves. Troubleshooting steps for non-actuating solenoid valves are listed below:
Troubleshooting Measures
Loose or detached wiring terminals result in power loss. Tighten the wiring terminals to solve the problem.
Burned solenoid coil. Disconnect wiring and test with a multimeter; an open circuit indicates coil burnout. Common causes include coil dampness leading to poor insulation, magnetic leakage and excessive internal current. Prevent rainwater ingress into the solenoid valve. Besides, excessively stiff springs with large reaction force or insufficient coil turns resulting in inadequate suction may also burn the coil. For emergency treatment, toggle the manual button on the coil from position "0" to "1" to open the valve.
Solenoid valve jamming. The clearance between the spool sleeve and spool is very small (less than 0.008 mm). Mechanical impurities or insufficient lubrication easily cause jamming. A steel wire can be inserted into the small hole on the top to reset the spool temporarily. The fundamental solution is to dismantle the solenoid valve, take out the spool and sleeve, and clean them with carbon tetrachloride (CCl₄) to ensure flexible movement. Record component assembly sequence and wiring positions during disassembly for correct reassembly. Inspect the oil mist injector hole for blockage and confirm sufficient lubricating oil supply.
Solenoid valve air leakage. Air leakage causes insufficient air pressure and difficult valve switching, which is usually induced by damaged sealing gaskets or spool wear leading to inter-chamber air cross-flow.
Fault inspection and maintenance of solenoid valves shall be performed when the valve is de-energized. Solutions include direct replacement of the solenoid valve, replacement of burned coils or repairing valve body leakage.
Summary
The above troubleshooting methods for six core consumable parts of screw air compressors are provided for reference. Carefully observe fault phenomena to accurately identify root causes and shorten maintenance downtime. For equipment safety, maintenance personnel need to accumulate more operation and maintenance experience instead of only relying on these typical fault cases.
