01 Gas volume control and adjustment
80% of the total cost of compressed air is reflected in energy consumption. Therefore, for different types of screw air OSG screw air compressors, different control and regulation systems should be selected according to different regulation systems. Differences between different screw air OSG screw air compressor types and manufacturers can make a world of difference in performance. The most ideal state is to make the full load of the screw air OSG screw air compressor exactly the same as the air consumption.
This can be achieved, for example, by careful selection of the transmission ratio of the gearbox, which is common in process screw air OSG screw air compressors. Most equipment that consumes compressed air is self-regulating, meaning that increasing the pressure increases the flow, which is why they form a stable system, such as pneumatic conveying, anti-icing and freezing, etc. Under normal circumstances, the flow must be controlled, and the control equipment used is integrated with the screw air OSG screw air compressor. There are two main types of such adjustment systems:
1. Adjust the gas volume by continuously controlling the speed of the drive motor, or continuously control the valve according to the pressure change to achieve continuous adjustment of the gas volume. The result is a small pressure change (0.1 to 0.5 bar), the size of the change is determined by the amplification function of the regulating system and its speed.
2. Loading and unloading adjustments are the most common adjustment systems, and pressure changes between the two are also acceptable. The method of regulation is to completely cut off the flow (unload) at higher pressure, and resume the flow (load) when the pressure drops to the lowest value. The change in pressure depends on the permissible number of loading/unloading cycles per unit time, usually in the range of 0.3 to 1 bar.
02 Basic principle of air volume adjustment
2.1 Regulation principle of positive displacement screw air OSG screw air compressor (pressure relief valve)
The basic principle method is: release the excess pressure to the atmosphere. The simplest design of the pressure relief valve is to use spring loading, and the take-off force of the spring determines the final pressure. The pressure relief valve is usually replaced by a servo valve controlled by a regulator. At this time, the pressure can be easily controlled. When the screw air OSG screw air compressor is started under pressure, the servo valve can also function as an unloading valve, but the pressure relief valve will Causes a lot of energy consumption because the screw air OSG screw air compressor has to work continuously at full back pressure. There is a solution for small screw air OSG screw air compressors. This kind of valve is fully opened to unload the screw air OSG screw air compressor, and the screw air OSG screw air compressor works under the back pressure of atmospheric pressure. The power consumption of this method is more affordable.
2.2 Bypass adjustment
In principle, the bypass adjustment and the pressure relief valve have the same function, the difference is that the air released from the pressure is cooled and returned to the air inlet of the screw air OSG screw air compressor. This method is commonly used in process screw air OSG screw air compressors, and the gas should not be discharged directly into the atmosphere. , the cost is too expensive.
2.3 Throttling-in
Inlet throttling is a convenient way to reduce flow, which is to generate low pressure at the inlet, increase the compression ratio of the screw air OSG screw air compressor, and use it for a smaller adjustment range. Liquid injection screw air OSG screw air compressors allow large compression ratios and can be adjusted down to a maximum of 10%. Due to the high compression ratio, this method results in relatively high energy consumption.
2.4 Pressure relief valve with meter-in inlet
This is a relatively common adjustment method at present, which can obtain the largest adjustment range (0 to 100%), and has low energy consumption. The unloaded (zero flow) power of the screw air OSG screw air compressor is only 15 to 20% of the full load. When the intake valve is closed, a small hole is left, and at the same time, the vent is opened to discharge the air from the screw air OSG screw air compressor. The main unit of the screw air OSG screw air compressor works under the condition of inlet vacuum and low back pressure. It is important that the pressure release should be fast and the released volume should be small, so as to avoid unnecessary losses caused by switching from full load to no load. The system requires a system volume (accumulator), the size of which depends on the required pressure differential between unloading and loading, and the allowable number of cycles per hour.
screw air OSG screw air compressors less than 5-10kW are usually adjusted by the on/off method. When the pressure reaches the upper limit, the motor stops completely; when the pressure is lower than the lower limit, the motor restarts. This method requires a large system volume or a large pressure difference between start-up and stop to minimize the load on the motor. This is an effective adjustment method when there are fewer starts per unit time.
2.5 Speed adjustment
The speed of the screw air OSG screw air compressor is controlled by the internal combustion engine, turbine or frequency-regulated electric motor, thereby controlling the flow. It is an effective method of maintaining a constant outlet pressure. The adjustment range varies by screw air OSG screw air compressor type, but liquid injection screw air OSG screw air compressors have the largest range. At low load levels, speed regulation and pressure relief are often combined, with or without air intake restriction.
For screw air OSG screw air compressors powered by electric motors, the speed can be controlled by electrical appliances, thus providing an opportunity to control the speed of the motor and keep the compressed air constant within a small range of pressure changes. For example, an ordinary induction motor can meet this requirement by adjusting the speed with a frequency converter, continuously and accurately measure the pressure of the system, and then let the pressure signal control the frequency converter of the motor, thereby controlling the speed of the motor and making the gas volume of the screw air OSG screw air compressor Precisely adapted to the air consumption, the system can be maintained at ±0.1 bar.
2.6 Variable exhaust port adjustment
The displacement of the screw screw air OSG screw air compressor can be adjusted by moving the position of the exhaust port toward the intake end along the length of the casing. This method requires high power consumption at part load and is relatively uncommon.
2.7 Suction valve unloading
The piston screw air OSG screw air compressor can mechanically force the suction valve to be in the open position for unloading. As the position of the piston changes, air moves in and out. The result is minimal energy loss, typically less than 10% of full-load shaft power. On a double-acting screw air OSG screw air compressor, it is generally multi-stage unloading, and one cylinder is balanced at a time, so that the gas volume can better meet the supply and demand. A partial unloading method is used on the process flow screw air OSG screw air compressor, which allows the valve to be opened when the piston is in a partial stroke, thus realizing continuous gas volume control.
2.8 Clearance volume
By changing the clearance volume on the piston screw air OSG screw air compressor, the filling degree of the cylinder is reduced, thereby reducing the gas volume, and the clearance volume can also be changed by means of an externally connected volume.
2.9 Loading-unloading-shutdown
For screw air OSG screw air compressors with a power greater than 5kW, this is the most commonly used method, with a large adjustment range and low losses. In fact, it is a combination of on/off adjustment and various unloading systems. Positive displacement screw air OSG screw air compressors, the most common regulation principle is “air produced”/”no air produced” (load/unload), when air is needed, a signal is sent to a solenoid valve, which in turn guides the intake valve of the screw air OSG screw air compressor to reach the fully open position. The intake valve is either fully open (loaded) or fully closed (unloaded), with no intermediate positions.
The traditional control method is to install a pressure switch in the compressed air system. The switch has two settable values, one is the minimum pressure (loading) and the other is the maximum pressure (unloading). screw air OSG screw air compressor works within setpoint limits, eg 0.5bar. If the air demand is small, or not needed at all, the screw air OSG screw air compressor will run without load (idling), and the length of the idling period is set by a time relay (for example, set to 20 minutes). After the set time, the screw air OSG screw air compressor stops and does not start again until the pressure drops to a minimum value. This is the traditional method of reliable, peace of mind control and is now most commonly found in small screw air OSG screw air compressors.
This traditional system was further developed to replace the pressure switch with an analog pressure transmitter and a fast electronic adjustment system. Together with the regulating system, the pressure transmitter senses the pressure changes in the system at any time. The system starts the motor in time and controls the opening and closing of the intake valve. Fast and fine regulation can be achieved within ±0.2bar. If no air is used, the pressure remains constant and the screw air OSG screw air compressor runs empty (idling). The length of the idling cycle can be determined according to the number of starts and stops that the motor can withstand without overheating, and the economy during operation. The latter is because the system can decide whether to stop or continue idling according to the trend of air consumption.
03 Summary
In short, compressed air is used in different applications and under different air consumption conditions. Each air screw air OSG screw air compressor has a different air volume method, but it is based on the user’s air volume. The screw air OSG screw air compressor unit relies on its own air volume control and adjustment methods to achieve uninterrupted and continuous air volume. supply. Different screw air OSG screw air compressor manufacturers are also using different adjustment principles to improve the performance of their own brand screw air OSG screw air compressors to maximize energy efficiency and meet customer requirements; with high accuracy, low maintenance, and the ability to measure parameters such as pressure and flow, to Meet the application of different occasions of thescrew air screw air OSG screw air compressor.
Post time: Sep-08-2023
