Insufficient exhaust volume
What are the common faults of air compressors
- Insufficient exhaust volume
Insufficient displacement is one of the most likely faults of compressors. Its appearance is mainly caused by the following reasons:
- Failure of the intake air filter: fouling is blocked, which reduces the exhaust volume; the intake pipe is too long and the pipe diameter is too small, which increases the suction resistance and affects the air volume. The filter should be cleaned regularly.
- The reduction of compressor speed reduces the exhaust volume: the air compressor is not used properly, because the exhaust volume of the air compressor is designed according to a certain altitude, suction temperature and humidity. When the plateau is on, the suction pressure decreases, etc., and the exhaust volume will inevitably decrease.
- The cylinder, piston and piston ring are seriously worn and out of tolerance, which increases the relevant clearance and increases the leakage, which affects the displacement. When it is normal wear and tear, it is necessary to replace the wearing parts in time, such as piston rings. If the installation is incorrect and the gap is not appropriate, it should be corrected according to the drawing. If there is no drawing, experience data can be obtained. For the gap between the piston and the cylinder along the circumference, such as a cast iron piston, the value of the gap is the diameter of the cylinder. 0.06/100～0.09/100; for aluminum alloy piston, the clearance is 0.12/100～0.18/100 of the diameter of the gas diameter; the steel piston can take the smaller value of the aluminum alloy piston.
- The stuffing box is not strict, resulting in air leakage and reducing the air volume. The reason is that the stuffing box itself does not meet the requirements during manufacture; secondly, it may be due to the poor alignment of the piston rod and the center of the stuffing box during installation, resulting in air leakage due to wear, strain, etc.; generally, lubricating oil is added to the stuffing box. , it can play the role of lubrication, sealing and cooling.
- The impact of compressor suction and exhaust valve failures on the displacement. Metal fragments or other sundries fall between the valve seat and the valve plate of the air valve, resulting in poor closing and air leakage. This not only affects the displacement, but also affects the changes in the pressure and temperature of the interstage?; This problem may be due to the first is the manufacturing quality problem, such as the warping of the valve plate, and the second is due to the wear of the valve seat and the valve plate Severe air leaks are formed.
- The valve spring force does not match the gas force well. If the elastic force is too strong, the valve will open slowly, and if the elastic force is too weak, the valve will not close in time. These will not only affect the air volume, but also affect the increase of power, as well as the life of the valve plate and spring. At the same time, it will also affect the changes in gas pressure and temperature.
- The compression force of the compression valve is improper. If the pressing force is small, it will leak air. Of course, it will not work if it is too tight, which will deform and damage the valve cover. Generally, the pressing force can be calculated by the following formula: p=kπ/4 D2P2, D is the diameter of the valve cavity, and P2 is the maximum gas Pressure, K is a value greater than 1, generally 1.5 to 2.5, K=1.5 to 2.0 at low pressure, and K=1.5 to 2.5 at high pressure. Taking K in this way has proved to be good. If the air valve is faulty, the valve cover must be hot, and the pressure is not normal.
- The pressure is abnormal
If the air volume discharged from the compressor cannot meet the user’s flow requirements under the rated pressure, the exhaust pressure must be reduced. At this time, it is necessary to replace another machine with the same exhaust pressure and large displacement. The main reason for the abnormal interstage pressure is the leakage of the air valve or the leakage of the piston ring after wear, so the reasons should be found and measures should be taken from these aspects.
- The temperature is abnormal
The abnormal exhaust temperature means that it is higher than the design value. Theoretically, the factors that affect the increase of exhaust temperature are: intake temperature, pressure ratio, and compression index (for air compression index K=1.4). The actual situation affects the factors of high suction temperature, such as: low intercooling efficiency, or more scale formation in the intercooler, which affects heat exchange, then the suction temperature of the subsequent stage must be high, and the exhaust temperature will also be high. In addition, the leakage of the valve and the leakage of the piston ring will not only affect the increase of the exhaust temperature, but also change the inter-stage pressure. As long as the pressure ratio is higher than the normal value, the exhaust temperature will increase. In addition, water-cooled machines, lack of water or insufficient water will increase the exhaust temperature.
- Abnormal noise
If some parts of the compressor fail, it will make an abnormal sound. Generally speaking, the operator can distinguish the abnormal sound. The gap between the piston and the cylinder head is too small, and it directly hits; the connecting nut between the piston rod and the piston is loose or tripped; the end face of the piston is blocked by the cypress, and the piston moves upward to collide with the cylinder head; metal fragments fall into the cylinder and water accumulates in the cylinder, etc. Can make a percussion sound in the cylinder. The crankcase bolts, nuts, connecting rod bolts and crosshead bolts in the crankcase are loose, tripped, broken, etc., the shaft diameter is severely worn, and the clearance increases, and the clearance between the crosshead pin and the bushing is too large or the wear is serious, etc. There is a banging sound in the crankcase. The exhaust valve piece is broken, the valve spring is soft or damaged, the load regulator is not adjusted properly, etc., all of which can make a knocking sound in the valve cavity. Find faults and take measures from this.
- Overheating failure
When the friction between the crankshaft and the bearing, the crosshead and the sliding plate, the packing and the piston rod, etc., the temperature exceeds the specified value, which is called overheating. Consequences of overheating: one is to speed up the wear between the friction pairs, and the other is that the heat energy of the overheating continues to accumulate until the friction surface is burned, causing a major accident of the machine. The main reasons for bearing overheating are: uneven fit between the bearing and the journal or too small contact area; the bearing is skewed, the crankshaft is bent, the viscosity of the lubricating oil is too small, the oil circuit is blocked, the oil pump is faulty and the oil is cut off, etc.; there is no leveling during installation , the gap is not found, the main shaft and the motor shaft are not aligned, the two axes are inclined, etc.