Compressors inevitably experience malfunctions and even accidents during operation. A malfunction refers to an abnormal situation that occurs during compressor operation; once resolved, the compressor can return to normal operation. An accident, on the other hand, refers to a destructive situation. The two are often related; if a malfunction is not addressed promptly, it can lead to a major accident. A compressor is a machine used to increase gas pressure and transport gas. From an energy perspective, a compressor is a machine that converts the kinetic energy of a prime mover into the pressure energy of gas. With the development of science and technology, the application of pressure energy has become increasingly widespread, making compressors an indispensable key piece of equipment in many sectors of national economic construction. Compressors inevitably experience malfunctions and even accidents during operation. A malfunction refers to an abnormal situation that occurs during compressor operation; once resolved, the compressor can return to normal operation. An accident, on the other hand, refers to a destructive situation. The two are often related; if a malfunction is not addressed promptly, it can lead to a major accident. Common Malfunctions, Their Causes, and Solutions Insufficient Discharge Volume: Insufficient discharge volume refers to the amount of gas discharged compared to the compressor's design capacity. The main considerations are as follows: 1. Intake filter malfunction: Accumulated dirt and blockage reduce exhaust volume; an excessively long or small-diameter intake pipe increases intake resistance, affecting air volume. Regular cleaning of the filter is necessary. 2. Reduced compressor speed reduces exhaust volume: Improper use of the air compressor. Air compressors are designed for specific altitudes, intake temperatures, and humidity levels. Using them at altitudes exceeding these standards results in reduced intake pressure and consequently, lower exhaust volume. 3. Severe wear or exceeding tolerances in the cylinder, piston, and piston rings increases clearances and leakage, affecting exhaust volume. For normal wear, replace worn parts such as piston rings promptly. If the installation is incorrect or the clearance is inappropriate, it should be corrected according to the drawings. If no drawings are available, empirical data can be used. For the circumferential clearance between the piston and cylinder, for cast iron pistons, the clearance value is 0.06/100 to 0.09/100 of the cylinder diameter; for aluminum alloy pistons, the clearance is 0.12/100 to 0.18/100 of the cylinder diameter; for steel pistons, the smaller value of the aluminum alloy piston can be used. 4. Leakage caused by a faulty stuffing box reduces the air volume. The reasons are firstly, the stuffing box itself is not manufactured to the required standard; secondly, it may be due to poor alignment between the piston rod and the stuffing box center during installation, resulting in wear, scoring, etc., causing leakage. Generally, lubricating oil is added to the stuffing box, which has lubrication, sealing, and cooling functions. 5. The impact of compressor suction and discharge valve malfunctions on discharge volume. Metal fragments or other debris falling between the valve seat and valve plate can cause incomplete closure and leakage. This not only affects the exhaust volume but also the changes in interstage pressure and temperature. Poor contact between the valve seat and valve plate leads to leakage, affecting the exhaust volume. This can be due to manufacturing quality issues, such as valve plate warping, or severe wear of the valve seat and valve plate. 6. Poor matching between the valve spring force and the gas force. Excessive spring force results in slow valve opening, while insufficient spring force leads to delayed valve closing. This affects not only the gas volume but also the power output and the lifespan of the valve plate and spring. It also affects changes in gas pressure and temperature. 7. Improper clamping force on the valve. Insufficient clamping force leads to leakage, while excessive clamping force will deform and damage the valve cover. The clamping force can generally be calculated using the following formula: p = kπ/4 D²P², where D is the valve cavity diameter, P² is the maximum gas pressure, and K is a value greater than 1, typically 1.5–2.5. For low pressure, K = 1.5–2.0, and for high pressure, K = 1.5–2.5. Choosing K in this way has proven to be effective in practice. A malfunctioning valve will inevitably cause the valve cover to overheat, and the pressure will also be abnormal. Abnormal Exhaust Temperature Abnormal exhaust temperature means it exceeds the design value. Theoretically, factors affecting increased exhaust temperature include: intake temperature, pressure ratio, and compression index (for air, K=1.4). In practice, factors affecting high intake temperature include: low intercooling efficiency, or excessive scale buildup in the intercooler affecting heat exchange; in such cases, the intake temperature of subsequent stages will inevitably be high, leading to a higher exhaust temperature. Leaking valves and piston rings not only affect the increase in exhaust temperature but also cause changes in interstage pressure; any pressure ratio higher than normal will increase the exhaust temperature. Furthermore, in water-cooled machines, insufficient water or a lack of water will also increase the exhaust temperature. Abnormal Pressure and Reduced Exhaust Pressure If the compressor's output cannot meet the user's flow requirements at the rated pressure, the exhaust pressure will inevitably decrease. The apparent decrease in exhaust pressure is a symptom; the essence is that the exhaust volume cannot meet the user's needs. At this point, it's necessary to replace it with a machine that has the same exhaust pressure but a larger exhaust volume. The main reasons for abnormal interstage pressure are leaking valves or leaking due to worn piston rings. Therefore, the cause and measures should be taken from these aspects. Abnormal Noises When certain components of the compressor malfunction, they will emit abnormal noises. Generally speaking, operators can identify abnormal noises. Insufficient clearance between the piston and cylinder head, direct impact; loose or disengaged piston rod and piston connecting nut; piston end face plug failure; piston upward movement colliding with the cylinder head; metal fragments falling into the cylinder; and water accumulation in the cylinder can all produce knocking sounds within the cylinder. Loose, disengaged, or broken crankshaft bearing bolts, nuts, connecting rod bolts, and crosshead bolts in the crankcase; severely worn shaft diameter increasing clearance; excessive clearance or severe wear between the crosshead pin and bushing, etc., can all produce knocking sounds within the crankcase. A broken exhaust valve plate, a loose or damaged valve spring, or improper adjustment of the load regulator can all produce knocking sounds within the valve cavity. These factors help identify the fault and take corrective action. Overheating Faults Overheating occurs when the temperature exceeds specified values ​​at friction points such as the crankshaft and bearings, crosshead and slide plate, and packing and piston rod. The consequences of overheating are twofold: firstly, it accelerates wear between friction pairs; secondly, the continuous accumulation of excess heat can burn out the friction surfaces and cause serious machine accidents. The main causes of bearing overheating include: uneven contact between the bearing and journal or insufficient contact area; bearing misalignment, crankshaft bending or twisting; lubricating oil viscosity too low, oil passage blockage, oil pump malfunction causing oil shortage, etc.; improper leveling during installation, inadequate clearance, misalignment of the main shaft and motor shaft, and tilting of the two shafts. Compressor Accidents Fracture Accidents Crankshaft Fracture: Most fractures occur at the fillet transition between the journal and the crank arm. The causes are generally as follows: the fillet radius is too small (r represents the crankshaft journal); the fillet was not properly treated during heat treatment, causing stress concentration at the junction; irregular fillet machining, resulting in abrupt changes in the cross-section; long-term overload operation, and some users arbitrarily increasing the speed to improve output, worsening the stress conditions; defects in the material itself, such as sand holes or shrinkage cavities in castings. Additionally, fractures caused by cracks in the oil holes on the crankshaft are also observed. Connecting Rod Fracture: Several situations can occur: connecting rod screw fracture, caused by: plastic deformation of the connecting rod screw after long-term use; poor contact between the screw head or nut and the large end face, resulting in eccentric loads. This load can be as large as seven times the simple axial tensile force on the bolt. Therefore, even slight misalignment is not allowed; contact should be evenly distributed, and the maximum distance between contact points should not exceed 1/8 of the circumference, i.e., 45°; problems with the bolt material and machining quality. Piston rod fracture: The main fracture sites are the threads connecting to the crosshead and the threads securing the piston. These two areas are the weakest points of the piston rod, and fractures are more common due to design negligence, manufacturing sloppiness, or operational issues. If there are no problems with the design, machining, and materials, the preload during installation should not be too high; otherwise, the piston rod will fracture when the maximum force reaches the yield limit. After long-term operation, excessive cylinder wear can cause the piston in a horizontal cylinder to sink, creating additional loads at the connecting threads. Continued operation may then lead to piston rod fracture; this should be carefully considered during maintenance. Furthermore, damage to other parts or strong impacts to the piston rod can also cause it to fracture. Cylinder and cylinder head rupture: Main causes: For water-cooled machines, if the cooling water in the cylinder and cylinder head is not drained after shutdown in winter, the cooling water will freeze and rupture the cylinder and cylinder head, especially in northern China where it is essential to drain the cooling water after shutdown. Failure to promptly detect a water supply interruption during operation can cause the cylinder temperature to rise, and sudden addition of cooling water can lead to cylinder rupture. Insufficient dead center clearance, loose piston nuts, metal objects falling into the cylinder, and dislodged piston plugs can all cause the piston to impact the cylinder head, resulting in rupture. Combustion and explosion accidents : Oil-lubricated compressors often produce carbon deposits, which is undesirable. Carbon deposits can cause piston rings to become stuck in their grooves, valves to malfunction, and the airflow channel area to increase resistance. Under certain conditions, carbon deposits can also burn, leading to compressor explosions. Therefore, the lubricating oil supply to the cylinder should not be excessive, and poorly filtered gas containing a large amount of dust should not be drawn into the cylinder; otherwise, the carbon deposits coming into contact with gas containing a large amount of volatiles can lead to an explosion. To prevent combustion and explosion, scheduled maintenance and regular cleaning of the gas tank and pipelines are essential. Besides these, operational factors can also cause compressor combustion and explosion accidents: 1. Failure to purge air with low-pressure nitrogen before the compressor is tested with hydrogen, oxygen, or nitrogen can cause an explosion. 2. Lack of operational knowledge leading to failure to open the valve between the compressor and the gas tank after startup, causing a rapid increase in exhaust pressure and resulting in an explosion. Therefore, to prevent such accidents, operators must be familiar with the operating procedures before starting the compressor and closely monitor pressure gauge readings after startup. In general small and medium-sized compressors, it is best to remove the gate valve on the pipeline between the compressor and the gas tank, leaving only the check valve. Furthermore, compressor operators should receive pre-job training. 3. A faulty high-pressure stage valve can cause high-pressure, high-temperature gas to return to the cylinder, generating high temperatures near the exhaust valve. If carbon deposits are present, this can lead to an explosion. To avoid this, the exhaust valve must be inspected, leaks checked, and the fault rectified. During compressor operation, some malfunctions and even accidents are inevitable. A malfunction refers to an abnormal situation that occurs during the operation of a compressor. Once resolved, the compressor can return to normal operation. An accident, on the other hand, refers to a situation of destruction. The two are often related; if a malfunction is not addressed promptly, it can lead to a major accident. A compressor is a machine used to increase gas pressure and transport gas. From an energy perspective, a compressor is a machine that converts the kinetic energy of a prime mover into the pressure energy of gas. With the development of science and technology, the application of pressure energy has become increasingly widespread, making compressors one of the essential key pieces of equipment in many sectors of national economic construction. During the operation of a compressor, some malfunctions and even accidents are inevitable. A malfunction refers to an abnormal situation that occurs during the operation of a compressor. Once resolved, the compressor can return to normal operation. An accident, on the other hand, refers to a situation of destruction. The two are often related; if a malfunction is not addressed promptly, it can lead to a major accident.