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Screw air compressor series
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1. Main propulsion
Main propulsion is the heart of screw air compressor. Main propulsion’s capability affects directly the whole machine’s working life and its economic operation. Also it costs 30% of the whole machine. OLG screw air compressor series have the original Germany main propulsions which are produced by world-famous compressor manufacture.
Rotor of main propulsion is made of hammered steel and its unsymmetrical lines are gained through two individual processing steps. The first step is using special digital control rotor milling machine to get perform. The second step is accurate processing, using five-axis CNC rotor grinding machine to get firm and accurate surface and the tolerance of grinding machine is 0.05% of one inch. During the second step, negative rotor will get a seal line. Just as its name implies, the seal line is to reduce clearance between rotor and cylinder as well as lessen leak. The seal line is just like piston ring of reciprocal compressor. After being processed by machines, every rotor will be checked by three-coordinate machine to insure the size accuracy. Rotors are put into body after paring up and being marked. The body is made of high mass cast iron with compact grain. After processing, bodies also need to be done size test to insure accuracy. The noise of OLG screw air compressor series is 64-65 db, which shows the operation parts of compressor are made of high quality material and processed accurately, thus cause little crash and vibration and rotors get long work life. These actually reflect the high level of machine’s design and processing. The work life of main propulsion is over 30 years under normal operation. Meanwhile, main propulsion is with high efficiency. The best screw speed makes it able to save over 5% energy sources, compared with similar products in market.
Mean Time between Failure and work life of main propulsion’s rotor in a large degree are decided by the work life of axletree. Main propulsion’s axletree is over loading axletree which is specially designed by German company SKF. Its work life is more than 20% longer than other ordinary axletrees and that can be over 100 thousand hours under normal operation.
2. Unique machine design
Dual duct structure is unique for Dong Fang screw air compressor. The compressor is divided to two individual ducts by sound insulation board set in the center of the case. One duct is from fan directly to condenser and then to the exit. The other duct begins from the back of main electric motor and goes to the exit after cooling the electric motor. Therefore, there are two air intakes at the back and two air exits at the top. Such structure is able to make noise be sealed in case but not come out. Extreme low noise of the whole machine makes Dong Fang screw air compressor stand at the leading level for noise control in the industry.
The condenser of Dong Fang screw air compressor is at the top of case and above draught fan. The sound insulation board at the center makes cooling air blow to condenser directly without going into the case to avoid the cold air to be heated up by electric motor, main propulsion and oil cask and ensure low temperature of inlet air to condenser. At the same time, dual duct air compressor can work without air baffle which gets less resistance on intake air and better efficiency for cooling. Condenser is designed to work under 50℃ for a long time and can work stably under every conditions.
Connection pipes of Dong Fang screw air compressor are all made of hard stainless steel, unlike hosepipes and other soft pipes which will cause leak of oil after being heated with age, these hard pipes can make sure machine works for a long time without leak.
3. Electric motor
With protect level IP54, insulation level F, SKF heavy axletree for electric motor is able to get more than 95% efficiency rate, good insulation, 10% overload power and bear high temperature.
4. Drive way
 90KW～450KW Dong Fang compressor series are applied with flexible coupling directly. Electric motor is connected with gear case’s flange to make sure drive system is ever at the center and get less vibration. In such drive way, gears and rotors can avoid sudden wallop to each other because of the rigidity rubber between them, in despite of starting or stopping compressor suddenly. Flexible coupling decreases the start-up moment and increases driving efficiency. The drive way of electric motor/ flexible coupling + gear case/main propulsion gives drive gears high accuracy.
5. High-quality shock absorption equipment
Main propulsion and electric motor is placed onto shockproof frames which are welded by clamps and with good plane horizontal degree. That makes sure each extension shafts of main propulsion and electric motor are parallel at every direction, straps get few jumpiness and finally machine drives stably. Meanwhile, the machine is applied with high flexible shock absorber which is selected through accurate dynamic calculation and vibration values of main propulsion at every direction are all less than 5mm/s.
6. Air amount control, adjustment system
 Machines’ inlet valves are designed by AIR-CON from U.S.A. with ON-OFF self-regulation for air amount adjustment. Compressor lets air in or out according to air amount set by users and when inlet valve closes, compressor reduces load. Once air amount of system is reduced, pressure of system becomes higher, the open degree of inlet valve is decreasing after controller gets message of pressure increase and certainly electric current of electric motor decreases. When air amount goes up, system pressure decreases, the open degree of inlet valve is increasing after controller gets message of pressure reduction and at the time air delivery of screw machine is increasing to complete output. If air amount of system keeps decreasing, controller closes inlet valve totally when the system pressure is as high as the design pressure for empty machine. At that moment, air compressor operates with no air until buffer time set beforehand finishes and electric motor stops. When pressure or air output changes, electric controlling part will start electric motor without load and air compressor starts automatically. The realization of 24H nobody on duty at the same time save a great deal of sources and production costs for enterprises.
Compared with method of throttling inlet air, such adjustment way is with higher efficiency and saves more energy. That’s because for the method of throttling inlet air, the compression rate of main propulsion rises up when it reduces load and load of axletree increases. Meanwhile, ON-OFF adjustment system has the advantage of highly reliable.
7. Condenser
The oil cooler and condenser for air compressed of Dong Fang air-cooled screw air compressor are welded together and both of them use plate-fin heat exchanger. Because of special fin structure, heat transfer area as well as spoil increases, and heat transfer coefficient increases also.
The heat transfer area of this condenser is 30% more than that of other similar kinds of condensers. With big residual amount, it operates normally even under warm and wet weather of southern regions. Meanwhile, cooling fans are moved to the back of main electric motor. There is no fan on the two sides of condenser and it’s convenient for cleaning.
8. MAM-KY Electronic Intelligent controller
 MAM-KY electronic intelligent controller is designed especially for screw air compressor. The controller ensures normal operation of the whole machine and through LBD screen to display every operation situations. Controller includes below main functions:
Load, unload, stop and restart compressor
Control and adjust machine
Display failure information
Give alarm when compressor stops
Display maintenance information of machine
Control several machines together
9. Energy saving
Operating under unloaded condition, machine with MAM-KY electronic intelligent controller, through “Intelligent stop” function of controller, calculates and controls automatically according to actual used air amount, and then chooses best machine stop moment based on startup times allowed during each hour, in order to save energy. When it goes to rated pressure, compressor operates under unloaded condition. To save energy through shortening time used for operating under unloaded condition and meanwhile to ensure bellows:
Not exceed most startup times for each hour
Machine starts immediately when air is needed
 10 Controlling way for temperature
Temperature of oil provided for compressor should not be lower than +50℃, the environment temperature. Otherwise, water vapor will be separated from oil and emulsification of lubricating oil causes. Therefore, temperature-controlling valve is needed to get temperature of oil provided not be lower than design temperature.
The compressor is applied with circuit temperature-controlling valve to make sure that on different temperature conditions, temperature of oil is at best range and lubricant has long use life through avoiding water vapor to be separated from compressed air. Temperature sensing element controls proportion of oil going to condenser and that to side-through according to outlet air temperature, with the aim to control temperature.
11. Equipment of big-area Inspiratory filter to decrease inspiratory noise
Surface speed refers to the air flow speed through fracture-surface of filter and it’s an important index for filter. If the filter has bigger area of fracture-surface, the surface speed is smaller. With smaller surface speed, it’s harder to get through filter and filter gets better filtration effect. Inspiratory filter we use has big area, good filtration effect and little noise.
12. High-efficiency oil isolation system
Inner-placed oil isolation cores of Dong Fang screw air compressor are all imported from Germany originally. Also compressor is equipped with stand-up oil-gas barrel and applied with vortex three times isolation, including filtration isolation, gravity isolation and centrifugation. To make sure oil percentage of outlet air is less than 3ppm, the inlet speed of oil-gas barrel, barrel liner size, speed of vortex and flow rate of isolation are all under particular calculation and strict test.
13. Long work life and high efficiency
From parameters of the machine, Dong Fang products have lowest noise and oil usage amount. Apparently, noise degree is environment index for people’s life and work and oil usage amount is one economic index for using compressor. Actually, these two parameters have close relation with efficiency and work life of compressor. Noise is caused by vibration and attrition. Low accuracy of accessories and assembly as well as rough surfaces will increase vibration and attrition of accessories, and thus lessen work life of the machine. Big oil usage amount means big quantity of heat will be brought away, so the machine needs more power and gets low efficiency.
14. Low cost for maintenance and operation
Because of innovation on the design of compressor, unnecessary maintenance cost is avoided for new design and selection and design of every accessory follow concept of pursuing longer work life. Big size inspiratory filter, oil isolation core and famous oil filter essentially ensure quality of compressed air. Human-based design makes it available for completing maintenance during a few minutes and thus save time spending on maintenance as well as save costs.
Because products are applied with advanced microcomputer control system and automatically load and unload adjustment, compressors are able to operate in a way of saving energy automatically according to the demand air amount. Compressor supplies air amount which is needed. It stops automatically when pressure keeps unchanged and no air is needed, in order to keep lowest cost of equipment’s operation. At the same time, temperature controlled fans for cooling also just start when the environment temperature goes to specific degree and stop automatically when the environment temperature goes to lower degree than designed, and thus a great deal of electric energy is saved.
15. Easy assembly and convenient maintenance
Machines are fully with lubricant when they leave factory and they are ready for electricity supply connection. Because machines have vibration reduction system, they can be connected to electricity power and operate directly after they are assembled. Display panel with pictures and Chinese characters shows actual operation situation of machine and users can stop machine immediately without waiting for unloading.
Dong Fang compressor has gemel doors and it’s convenient to open four sides of the machine. Air cleaner, oil filter, oil isolation core, oil inlet and oil outlet are placed on the easily touchable positions and it’s convenient to remove and assemble them. Cleaning of condenser is quite convenient, for two sides of it can be opened easily. Air outlet is placed on the top and people can open machine to check its operation situation without stopping the machine.
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