Paper machine press area vacuum
Dip roller and paper guide roller
The suction and conveying roller uses a vacuum to transport the paper from the forming part to the pressing area and to guide the paper from one cloth to another in the pressing area.
A suction press mechanically extracts water from the paper. In the pressing section, large granite or hard rubber-covered rollers are in close contact to form a “rolling point”. As the paper passes through the rolling point, the water is pushed out of the paper and into the pressing blanket. As the paper passes through the pressing section, the pressing blanket is transported and buffered. The press may have suction or non-suction rollers to assist in the dewatering process.
When pressed, the pressed fabric (or “paper blanket”) contains a mixture of water and chemicals, pulp, and other contaminants. Since each paper blanket is a continuous ring, water and contaminants must be removed before the next extrusion. The suction chamber is fixed, across the width of the paper blanket, and extracts water and contaminants from the paper blanket during the extrusion process. Each paper blanket can have a maximum of two suction boxes. All suction tank applications require pre-separation to prevent process water residues from entering the vacuum pump.
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Vacuum pump in vacuum degree 10~3 below the vacuum operation
If the liquid ring vacuum pump is not suitable for a long time, the water inside should be cleaned after use and injected with anti-rust agent, otherwise the motor shaft and pump body and impeller will be rusted and lead to the next start. Liquid ring vacuum pump should be periodically replaced according to the extracted gas internal vacuum pump oil, otherwise it may lead to too many impurities in the vacuum pump can not start. In addition, the pump should not be placed in too humid environment, otherwise it may lead to the decrease of motor insulation and internal corrosion phenomenon. Correctly select the working point of vacuum pump. The working point of vacuum pump should be selected in this range is more suitable. All vacuum pumps have a certain range of working pressure, such as: 2BV series liquid ring vacuum pump working pressure range 760mmHg~25mmHg, in such a wide range of pressure, the pump pumping speed varies with the pressure, its stable working pressure range is 760~60mmHg. Therefore, pump working point should be selected in this range is more appropriate, and can not let it in 25~30mmHg under long-term work. The pump body is equipped with an appropriate amount of water as the working fluid. Liquid ring vacuum pump and liquid ring compressor are high energy consumption, low efficiency products, this is a recognized fact, small pump is generally 30-35%, large pump up to 40% or slightly higher, such low efficiency and national requirements on mechanical and electrical products and China’s current energy shortage is extremely incompatible with the status quo.
So as soon as possible using optimization design method, the influence of pump efficiency is the key of the geometric parameters of the impeller and the original position of the suction vent, area set up mathematical model of optimization design, choose the optimal combination parameter of each scheme, and using the theory of gas-liquid two phase flow and the calculation formula for design, to reduce the eddy current loss of liquid ring as far as possible, achieve the purpose of improving efficiency. Liquid ring vacuum pump can be used to directly obtain vacuum operation with vacuum degree below 10~3 brackets, and to cooperate with other vacuum operation. Vacuum pumps are generally used at room temperature not less than 5℃ and not more than 90% of the relative temperature environment. The gas enters the high vacuum chamber through the intake manifold. At first, the high and low vacuum chambers are filled with atmosphere, and both exhaust valves are opened for exhaust. As the air pressure decreases (i.e. the vacuum degree increases), the pressure of the high vacuum chamber is not enough to open the exhaust valve, and the gas enters the low vacuum chamber through the middle partition. At this time, the pressure is not enough to open the exhaust valve, but there is a certain amount of oil entering the low vacuum chamber to help open the exhaust valve, and the gas is also discharged.