The screw compressor belongs to the class of rotational compressor devices and is intended for pressure reduction by means of rotational motions of rotors. The equipment was widely used still in the mid-thirties the last century, but keeps the relevance and now at the expense of malogabaritnost, profitability and automatic work.
The principle of operation of compressors of screw type is based on rotation of two rotors which call screws. The air screw compressor has forced out devices of other types. At its mounting the special base as the vibration level has low indicators in comparison with other models is not required.
The screw compressor is capable to compress air to 15 atmospheres, giving performance to 100 m³/мин. At the expense of small dimensions it can be used on different construction sites, without spending many forces when transporting.
Principle of operation of the screw compressor
During the operation of the screw compressor there is air intake from the atmosphere via the valve in the rotor mechanism, before it air undergoes cleaning in the filter. Further it mixes up with oil and then comes to special capacity for compression. At the same time air-oil mix performs the following operations:
- interferes with contact of rotors with each other;
- eliminates gaps between the body and screws thanks to what emergence of leakages is minimized;
- takes away heat which is developed in the course of compression.
Compressed mix comes to the oil separator where there is its division into components. The separated oil is purified in the filter and comes back to the block, in need of it in addition cool. Air also passes through the air cooler, and then is removed from the compressor.
Device of the screw compressor
The simplest equipment of the screw compressor has the following elements. First of all, the main part — the screw block. In it two connected rotors made of high-quality steel are located. The thermoprotective controller necessary for engine operation stop at achievement of temperature of 105 wasps by it is provided in design of such element.
The drive of the device consists of two pulleys installed in the rotor and the engine. It serves for reduction or increase in rotational speed. The speed is higher, the more air will compress. But working pressure at the same time decreases. Speed of turns of the rotor depends on pulleys.
Motor. Rotational motions are provided at the expense of the belt gear. The thermoprotective sensor which is switching-off the engine at achievement of high temperatures and also preventing emergence of emergencies is included in the package of the motor.
The filter serves for purification of air coming to work element. Usually the filter consists of two parts. The first is established on the body, the second is mounted in front of the valve.
Suction valve. At stop of the compressor it is necessary in order that oil and air were not removed from the device. The valve is operated with the help of pneumatics, but on exterior does not differ from the normal spring valve.
Oil filter. Purifies oil for screw compressors before its receipt in the engine. The oil separator is necessary for separation of air from oil at the expense of centrifugal force. Oil cooler. After separation from air cools oil in special capacity.
The Maslootdelitelny filter purifies lubricant after division it with air. The safety valve works when pressure in the oil separator exceeds admissible norms.
The thermostat regulates temperature of oil mix. The air cooler cools the air returned to the room up to the temperature of 20 wasps. For distillation of air the fan serves. For pressure monitoring in the unit the special manometer is installed.
The relay ensures automatic functioning of the unit, performs function of electronic guidance system. The valve of minimum pressure is in closed position until pressure exceeds mark in 4 Bara.
The screw compressor is built in the body and is manufactured of high-quality steel. Its surface is processed by special substance which is not affected by oil and other substances.
Advantages and shortcomings of the screw compressor
In comparison with other compression devices, the screw unit has number of advantages:
- Low noise level and vibrations. Thanks to the small sizes the installation of the device is carried out without the special noise-absorbing base. Such feature helps to equip with air various portable devices.
- The low consumption of oil which is directly affecting quality of the given air. In the cleaned look it is used for operation of the various pneumatic equipment. And installation of complementary filters is not required here.
- The screw compressor is equipped with air-cooling. Thanks to it it is possible not only to cool different elements, but also at the expense of again developed heat to heat rooms.
- Ability of the screw compressor to automatic functioning, simplicity of operation and installation. The equipment is operated with the help of special automatic systems.
Usually distinguish the high cost of the device and complexity of its design from negative sides of the screw compressor. In addition, the device demands additional equipment at removal of hot air which is necessary for heating of the room. It is separately noted that screw compressors are forbidden to be used in the environment with aggressive gases, it in some cases causes certain inconveniences.
Operating modes of the screw compressor
The screw compressor can function in the following operating modes:
- At the beginning of this mode the screw compressor is started and turns on in the power supply network according to the scheme "star". Several seconds later the device passes to the working scheme "triangle".
- Operating mode. In the compressor pressure begins to increase. At achievement of certain line the idling of the unit is started.
- In this mode there is rotation of the rotor at which movement of the gas environment, necessary for cooling of air, is carried out. Idling provides transfer of the compressor to waiting mode before switching off of the unit.
- Waiting mode. The screw compressor will be in this mode until the indicator of pressure does not fall to the minimum value.
- At start of this mode the compressor equipment at first adjusts to idling, and then is completely switched off.
- Alarm-stop. This mode is used as a last resort when it is necessary to complete the work of the air screw compressor urgently.
Repair of the screw compressor
At due service all elements of the screw compressor can regularly function and work more than 50 thousand hours. But over time there is need under repair even the best screw compressors. This equipment contains difficult mechanisms and can be implemented in various complete sets.
Most often in such device electronics fails. Compressor devices are equipped with complex electronic systems in which various parts can fuse. Replacement of all electronic fittings of the compressor is most often made, but in simple cases repair is sometimes possible.
The cost of the control unit of the compressor is rather big. Especially if at it there is dehumidifier. Therefore replacement of the whole system comes out expensively, in this case it is desirable to make repairs of screw compressors. As the equipment is the difficult mechanism, highly qualified specialists can execute it.