Principle and selection of air source processing unit

The air source processing unit generally consists of three parts, namely filter, pressure regulating valve, lubricator, and sometimes the filter and pressure regulating valve can be assembled together to form a pressure regulating filter. 1 Filter First, let's talk about the working principle of the filter: when the compressed air enters the filter from the air inlet, the compressed air is strongly rotated due to the guidance of the deflector. Under the action of centrifugal force, the compressed air is compressed. Large particles of solid impurities and liquid water droplets mixed in the air are thrown onto the inner surface of the filter cup, and settle to the bottom along the wall under the action of gravity. The compressed air thus pre-purified then flows out through the filter element. The filter element has different filtration pore size (that is, the filtration precision), which can block non-gaseous impurities larger than the pore size.

Selection Notes:

(1) Flow rate: Select the appropriate flow rate according to the gas consumption of the downstream equipment. In general, we choose a filter with a slightly larger gas consumption than the actual gas consumption, so as to avoid insufficient gas consumption and affect the operation of the equipment. There is no need to choose a filter with excessive flow, as it will be wasted. Our Rexroth filter flow ranges from 1000L/min to 50000L/min, we have many choices. Corresponding nozzle diameters are from G1/4 to G2. To meet the different gas demands of customers.

(2) Filtration accuracy: The pore diameter of the filter element determines the filtration accuracy of the filter. Because the downstream equipment has different requirements on the quality of the gas source. For example, industries such as metallurgy, iron and steel, coal and other industries do not require very high gas quality, so a filter with a larger pore size can be selected. Food, medicine, electronics and other industries have high requirements for gas quality, so we can choose a precision filter with a small pore size. The filter precision of our Rexroth filter ranges from 0.01um to 40um. The maximum pore size is 60um. Generally, the main filter will use a filter with a larger pore size, and the filter on the specific equipment should be selected according to the needs of the equipment. The more precise the filter, the greater the resistance to the compressed air, which will reduce the air pressure.

(3) Drainage: The water and oil in the filter cup must be kept below the highest water line, otherwise the rotating compressed air will suck the water, oil and solid impurities into the downstream pipeline, causing the filter element to be polluted and blocked, and the flow rate will drop. It will also cause secondary pollution of the gas. Automatic drainage and semi-automatic drainage are divided into automatic drainage, semi-automatic drainage, manual drainage, etc. Automatic drainage can be divided into two types: no-pressure opening and no-pressure closing. Pipelines that are inconvenient to control, such as high places, narrow places, places where people do not often reach, and pipelines that cannot stop downstream gas use. Semi-automatic is generally suitable for pipelines that are convenient for personnel to control, such as the outside of the machine, the accessories of the console, and the pipelines where the downstream gas consumption can be suspended.

(4) Use environment: Due to the different use environments of various occasions, the material requirements for the filter will also be different. For example, in high temperature occasions and corrosive occasions, it is necessary to choose high temperature and corrosion resistance filters. Our Rexroth has a variety of filters suitable for different use environments, and different materials are available for your convenience.

Pressure regulating valve

The working principle of the pressure regulating valve is: by rotating the knob to change the opening range of the diaphragm, the airflow through the aperture changes, and the airflow through the volume changes. The gas volume also increases. When the downstream gas consumption decreases, the diaphragm is forced to make the through hole smaller, reducing the gas volume, and excess gas will overflow from the overflow air. This adjustment keeps the air pressure stable. Generally, the pressure regulating valve of the triplet is a pilot diaphragm type, which can automatically adjust the air pressure, while the pressure reducing valve on the execution pipeline is generally a braking type (the upstream air source pressure is relatively stable and does not need self-adjustment).

Selection Notes:

(1) Flow rate: Under normal circumstances, the pressure regulating valve in the triplet should be selected with the same flow rate as the corresponding filter. For example, the pressure regulating filter does not need to be selected separately. If it is used alone, it is necessary to calculate the downstream gas consumption before selecting it. The flow of our Rexroth pressure regulator corresponds to the flow of the same filter, and there are also some small flow pressure regulators. Flow from 300L/min to 50000L/min.

(2) Adjustment accuracy: Generally, different equipments have different requirements for air pressure stability. For example, when performing simple actions does not require high output force stability, a common pressure regulating valve can be used. However, it is required that each movement should be precise and precise, and the output force should not be too large each time.