Because the host head is the core component of the screw air compressor, the quality of the host directly determines the quality and competitive advantage of the brand's products. So it is necessary for us to explain it in detail. At present, most domestic users are relatively lagging behind in understanding this information, and their understanding of the screw compressor host is still ten years ago, and they are superstitious about imported hosts. In fact, in the past ten years, China has gradually become the manufacturing center of the global screw host. Through the following points, we will analyze the basic situation of the current domestic market air compressor host fashion in detail, so that everyone can understand it.
1. The basic situation of the screw compressor host in the current market
The host of Liuzhou Fidelity Air Compressor is manufactured in Liuzhou, the host of Atlas Air Compressor is manufactured in Wuxi, the host of Ingersoll Rand is manufactured in Shanghai, the host of GHH is manufactured in Wujiang, Suzhou, and the host of GD is OEM in China, etc. At present, the truly original imported hosts are all third- and fourth-tier brands, such as RC host, EU host, TMC host, aerzen host, Yuzhen host, etc. There are also some brands of main engines, such as CompAir, Ailiwei, and Sullair, which import rotors, bearings, and shaft seals, and other parts are processed and assembled in China. In today's domestic screw machine market, the main engines that use original imported main engines are basically low-end brands.
2. Basic situation of German main engines
German screw main engines entered China relatively early and are well-known. Its representative is the GHH main engine. Technically, the GHH main engine is very suitable for the climate and geographical environment of Europe. It is aimed at environments with low humidity, small annual temperature difference, and low extreme temperature. The production scale of screw machines in Germany is relatively small, so the German main engine is mainly used as a public version main engine to provide main engine matching for small and medium-sized assembly plants in Western Europe, so the commercialization degree of German main engines is relatively high. It is characterized by high speed, small size, light weight, and few specifications. Even under 60Hz power system, gear or belt drive must be used to cover the full spectrum through speed increase. German main engines focus on the economic interests of the main engine manufacturer itself. It is impossible to manufacture highly energy-saving screw compressors using high-speed German heads.
3. Basic information of British main engine
British main engines entered China relatively late, but they are popularized very quickly, represented by SKK main engines. Britain is the center of research on rotor tooth profile of screw main engines in the world. It is also the research and development and manufacturing center of screw auxiliary processing equipment in the world. SKK tooth profile is a new generation of rotor tooth profile produced under the environment of world energy crisis, so energy saving is its outstanding feature. Clearance is the most important factor affecting the performance and efficiency of screw compressors. SKK tooth profile adopts the sealing method of curved surface to curved surface. Under the same clearance value, the sealing effect is far greater than the line sealing of the early tooth profile. The higher the machining accuracy of the rotor, the smaller the transfer clearance of the main engine can be, so the SKK tooth profile is a tooth profile based on grinding processing. After 2000, all major screw auxiliary processing equipment manufacturers shifted their research and development focus to rotor grinders. Low speed is the only effective means to improve the compression process. The SKK main engine is designed with a low speed, which provides enough time for heat exchange between oil and gas, making the compression process close to isothermal and reducing the compression work to the theoretical minimum value.
4. The difference between German and British engines
Unlike German engines, British engines emphasize efficiency, and cost is not the main business goal. Therefore, British engines have low speed, large size, heavy weight, and many specifications. British engine manufacturers generally have a close cooperative relationship with complete machine manufacturers and provide targeted supply. Commercial British engines are not available on the market. Kaishan Company is the only manufacturer in China that uses SKK engines. This SKK engine is completely oriented to 50Hz electricity and is designed and manufactured for China's high humidity, high dust, large annual temperature difference and extreme temperature geographical climate environment.
Because gear transmission and belt transmission require 3%~5% more motor power consumption, British engines strongly advocate direct drive mode in which the male rotor speed is equal to the motor speed. Therefore, most screw compressors assembled using British engines have direct drive specifications. Kaishan Company has direct-connected models for 7.5KW, 18.5KW, 22KW, 30KW, 37KW, 45KW, 55KW, 75KW, 90KW, 110KW, 132KW, 160KW, 185KW, 200KW, 220KW, 250KW, and 280KW. Among them, 132KW, 160KW, 185KW, 200KW, 220KW, 250KW, and 280KW also have models with direct connection of four-pole motors, that is, the positive rotor speed is lower than 1500rpm.
For large screw compressors that must use gear speed change, the British main engine adheres to the speed limit of 2200 rpm, because beyond this speed limit, under the action of centrifugal force, the lubricating oil is difficult to adhere to the metal surface, and the gear lubrication is affected. Below the exhaust pressure of 1.3MPa, the British main engine does not advocate multi-stage compression. Because screw compressors mainly rely on oil injection internal cooling to improve compression efficiency. The temperature rise of screw compressors is small during operation, and the air temperature is very close to the dew point temperature under the corresponding pressure. If multi-stage compression is adopted, the consequence of inter-stage cooling will inevitably lead to a large amount of water precipitation between stages, and the precipitated water will mix with the lubricating oil and enter the next stage, which will inevitably deteriorate the lubrication of the next stage parts and cause excessive wear. If there is no inter-stage cooling, the effect of multi-stage compression is the same as that of single-stage compression. The publicity of energy saving of two-stage compression of screw compressors under normal pressure is a pseudoscience based on commercial hype. Due to the large increase in parts, the reliability of screw compressors with two-stage compression under normal pressure is greatly reduced, and the life of the machine is significantly shortened.