Working principle of dry screw vacuum pump
Dry vacuum pump technology, especially variable pitch chemical dry pumps, has significant and measurable advantages in various key applications. A properly designed dry screw vacuum pump can ensure that processing needs are met through a safe, reliable, and cost-effective solution.
Dry screw vacuum pumps can be sealed or lubricated in the vacuum stage without the need for water or oil. Therefore, these dry vacuum systems avoid the generation, pollution, and high treatment costs of wastewater.
Operation of Dry Screw Vacuum Pump
The dry screw vacuum pump consists of two parallel, non-contact spiral rotors (1) and (2) (Figure 1), which rotate synchronously at high speed through precision gears (3). They rotate in opposite directions, capturing a certain amount of gas at the intake port (5) and delivering it to the exhaust port (6) and entering the exhaust channel (7). The special shape of the cylinder body (9) wall and the interlocking screws forms a compression chamber or cavity (4) for transporting gas.
•The small gap between the screw and the cylinder body, as well as the small gap between the interlocking screws, ensures that the reverse leakage to the intake port is smaller compared to the forward flow of gas generated by the screw cavity.
•The length of the sealed boundary (i.e. number of spirals and tight gap) can prevent backflow of pumped gas. On pumps equipped with pressure plates, when the outlet valve or portfirst timeWhen exposed, the gas will slightly expand in reverse and enter the screw. Under the action of the screw, the amount of captured gas gradually decreases to zero, so it can be quickly discharged.
•The reverse flow of gas is mainly controlled by the width of the "sealing zone" at the end of the screw profile. These wide areas are closely adjacent to the stator, thereby reducing the reverse leakage of gasminimumThe maximum pressure of a screw pump can be less than 0.01 torr (0.01 mBar).
•In the variable pitch model, as the pitch changes, the gas is compressed, providing additional compression before the pump exhausts. This distributes the heat load more evenly throughout the entire length of the rotor. In the single pitch model, greater compression is achieved by pressing against the compression plate or valve in the last half of the turn, thereby directing the heat generation towards the exhaust port. In dry pumps, the temperature must be high enough to avoid overall condensation, while also being low enough to avoid self ignition and polymerization. The gradually increasing gas temperature towards the exhaust port in a variable pitch pump greatly helps prevent condensation of the pumped steam. Variable pitch screw pumps also utilize power more effectively than single pitch screw pumps.
•Cooling is achieved through the surrounding protective sheath (8). The pump can be configured for direct or indirect closed-loop cooling. The latter has many advantages, as it means that the cooling water of the device will never come into direct contact with the material of the pump, and the sheath will not accumulate or corrode due to poor cooling water quality.
•Gas Town Port (10). If necessary, gas towns can help quickly heat cold pumps or dry wet pumps, exclude flammable vapors from their flammable range, and help remove solids from the pump, especially during solvent flushing.