Factors affecting compressor production capacity

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I. Mechanical aspects: 1. Clearance volume: The greater the clearance in the cylinder, the more the high-pressure gas within this clearance expands during inhalation as the piston moves back to its starting position. This expansion reduces the effective volume of the cylinder, resulting in less fresh air being drawn in. As a consequence, the compressor’s capacity to produce air decreases, and its volumetric efficiency drops. As can be seen from the above, reducing the clearance volume of the cylinder can increase the production capacity of the compressor. However, too small a clearance can also allow carbon deposits or other small debris to enter the cylinder, increasing the risk of cylinder damage; therefore, some compressors are equipped with valves for adjusting the clearance size. 2. Leakage losses: The production capacity of a compressor is highly dependent on the airtightness of the piston rings, intake valves, exhaust valves, and cylinder gaskets. Piston rings are fitted over the piston; their function is to seal the gap between the piston and the cylinder using lubricating oil or their own lubrication, thereby preventing gas from leaking between the two sides of the piston. Therefore, when installing piston rings, they should be able to expand and contract freely to achieve a good seal, but at the same time, friction between them and the cylinder should not be too high. If the friction between the piston rings and the cylinder is too great, or if the rings are not installed properly and do not form a complete seal, then the high-pressure gas during the compression process will partially leak past the exhaust valve into the outlet pipe, seeping through any gaps in the piston rings to the other side of the piston. As a result, with less gas being expelled, the compressor’s production capacity also decreases; in actual operation, the piston rings or thrust plates need to be replaced every six months. Inadequate sealing and damage to the intake and exhaust valves have a significant impact on the compressor’s production capacity. If the exhaust valve is not tight enough, during the piston’s intake process, some of the high-pressure gas in the outlet pipe will leak back into the cylinder through the weak point ； If the intake valve is not airtight, during compression, the highly pressurized gas will flow back from the intake valve into the inlet pipe. Both of these situations lead to a decrease in the compressor’s production capacity. In the actual production process, we often need to replace some intake and exhaust valves every three months or so. During the operation of the compressor, air leakage can also occur due to friction between the cylinder packing box and the piston rod, or because the installation is not tight enough. The leaked gas not only affects the compressor’s production capacity but also impacts the cleanliness and safety of the surrounding air. This is even more important for the gas compressors in our company, as leaks of gas can easily lead to excessive levels of carbon monoxide in the surrounding environment. Our company has specialized collection pipes to capture leaks from the packing. During mechanical maintenance, the intake and exhaust valves in each section are also prone to leakage due to factors such as the quality of the maintenance work; this kind of leakage can be eliminated promptly every time a leak test is conducted. The oil and water release valves as well as the vent valves in each section are operated frequently on a regular basis. Especially with the oil and water release valves, debris that passes through these valves can remain on their sealing surfaces, resulting in poor sealing and air leakage. Additionally, if the valves are closed too forcefully, it can also damage the sealing surfaces and lead to air leakage. II. Process aspects: 1. Water content in the gas: Since our company uses wet desulfurization before sending the gas directly to the gas compressor, and although a vapor-liquid separator is installed at the inlet of the gas compressor, some water still manages to get into the cylinder. The gas contains small amounts of hydrogen sulfide and sulfur monoxide, which produce acids when in contact with water; this accelerates the corrosion of the intake and exhaust valves, making leaks more likely to occur. Water gas contains saturated water, and mechanical water is generated upon compression; therefore, improving the drainage at the first and second stages is very important for the compressor’s production capacity. If a large amount of water enters the cylinder, it can also cause water hammer, and in severe cases it may damage the equipment; therefore, the water content in the gas is very important for the operation of gas compressors. 2. Dust content in the gas: A large amount of gas containing dust and tar enters the gas compressor. These dusts and tar will block the passages of the intake valves; in severe cases, they can block up to half of those valve passages. Another section of the cylinders is lubricated with oil, and this oil can carbonize at high temperatures, resulting in carbon deposits on the gas valves; this also affects the compressor’s capacity to produce air. We have now replaced those valves with anti-fouling ones, and there has been a significant improvement in this situation. 3. Temperature of the gas: The volume of the compressor cylinder is fixed. If the temperature of the gas being drawn in is too high, the gas expands due to heating, resulting in an increase in the distance between gas molecules. This reduces the density of the gas inside the cylinder and its weight, thereby decreasing the compressor’s capacity to produce compressed air. Furthermore, the higher the temperature of the inhaled gas, the greater the amount of saturated water vapor it contains. By reducing the amount of effective gas drawn in per unit volume by the compressor, controlling the intake temperature can increase the compressor’s production capacity. According to available data, for every 10-degree increase in the compressor’s inlet temperature, its air handling capacity decreases by about 10%. If, like other manufacturers, a scrubber tower is used after rough desulfurization, this temperature can be reduced completely. 4. Cylinder cooling condition: Poor cylinder cooling leads to an increase in the temperature of the intake valve. As gas passes through this valve, heat exchange causes its temperature to rise, which in turn reduces the compressor’s capacity to produce air. At the same time, poor cylinder cooling leads to an increase in the temperature inside the cylinder, which causes the lubricating oil to lose its lubricating properties, resulting in a poor seal between the piston rings and the cylinder walls and gas leakage. 5. Pressure of the inlet gas: The level of pressure of the gas entering the compressor in its first stage has a significant impact on the compressor’s production capacity. A higher intake pressure results in a higher production capacity. Nevertheless, it is also affected by factors such as the compression ratio, the final exhaust pressure, and the load on the gas conveyor, so it should be kept within an appropriate range. However, other aspects cannot be ignored when it comes to the impact on the compressor’s production capacity. For example, internal leakage in the control loop valves of the instruments, as well as other leaks, drips, and seeps at the site, also affect the compressor’s production capacity. Therefore, strengthening equipment maintenance to promptly eliminate leaks and other issues, as well as addressing minor defects in the equipment, is also a very important aspect for increasing the production capacity of compressors.