Created on：2021-06-01 09:59

# Performance parameters of screw pump

Performance parameters of screw pump

① The commonly used working pressure range of three screw pump used in pressure hydraulic engineering is 2.5-20mpa, and individual can be as high as 35-40mpa.

② Displacement calculation and range in the process of screw meshing transmission, because the cross-sectional area of the formed gear remains unchanged, as shown in Figure J, the sum of the area of each cavity containing the working medium ∑ A is equal to a constant. When the active screw of the screw pump rotates for one revolution, the liquid filled in the spiral groove will move upward for one lead length, so the displacement V of the screw pump can be calculated by multiplying the sum of the cavity areas containing the working medium ∑ a by the lead length f, i.e

V=t∑A×10-3 (mL/r) (6-1)

Where T -- lead length of active screw, mm;

Σ a -- the sum of the area of each cavity containing the working medium, mm2.

Σ A is related to the pitch diameter of the screw.

The displacement range of screw pump is large, up to 25 ~ 1500ml / R.

③ The flow range of the flow screw pump is 3 ~ iooool / min, and the flow of the screw pump for conveying materials can reach 200m3 / min.

④ Due to the small rotational inertia of the slender screw, no unbalanced eccentric mass in the rotating parts and smooth oil suction channel, the allowable rotational speed of the screw pump is relatively high. The rotational speed of the small displacement pump can be as high as 6000r / min, and that of the large specification pump can be more than 1000-1500r / min.

⑤ The power of the largest screw pump is more than 600kW.

⑥ The volumetric efficiency of medium and high pressure screw pump is lower because it is difficult to compensate the clearance between the screw top circle and the meshing clearance on the spiral surface, which is roughly equivalent to that of gear pump with fixed clearance structure, and is generally η v = 0.75 ~ 0.95. From the efficiency curve of screw pump shown in Figure K, it can be seen that, different from other types of hydraulic pumps, the volumetric efficiency curve of screw pump is slightly concave with the increase of pressure, and has a closer relationship with the speed.

⑦ Flow pulsation and noise theoretically, the particles of the working medium in the screw pump only move in a straight line parallel to the screw axis. Of course, due to the internal and external friction, they will be dragged by the screw pair to make a slight tangential movement, but in any case, it is a much calmer continuous conveying process than other types of hydraulic pumps. This not only makes the screw pump have the lowest flow pulsation and noise, but also makes it suitable for conveying some special materials, such as milk crystal, gelatin, slurry, etc., which need to avoid disturbance as much as possible to keep the original mixing structure from being damaged. In hydraulic engineering, the use of screw pump can delay the aging of hydraulic oil molecules and prevent the composition segregation of water-based emulsion.

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