Single screw pump working principle, characteristics and selection method

● pump working principle

Single-screw pump is a kind of positive displacement internal volume eccentric pump, the pump's main components: a single-helix rotor and a usually made of flexible material with double-helical stator, when the rotor is fixed in the cavity around the stator Axis of rotation of the planet, the closed wrist formed between the stator is displaced along the helical spiral; therefore, the medium is continuously, uniformly and volumetrically delivered from the suction port to the extrusion end. Based on this Features, single-screw pump is particularly suitable for the following conditions of work.

Conveying High Viscosity Media: Depending on the pump size, media with viscosities from 37,000 to 200,000 centipoise can be delivered.

Medium containing particles or fibers: The particle diameter can be 30mm (not exceeding rotor eccentricity). The fiber length can be 350mm (equivalent to the pitch of 0.4 rotor). Its content is generally up to 40% of the media pit, the medium if the solid matter is a fine powder, the maximum content of up to 60% or more can also be transported. Requires delivery pressure is stable, the media do not like to destroy the inherent structure, the selection of single screw pump ideal delivery.

Pump characteristics

Single-screw pump due to structural and operational characteristics, compared with piston pump centrifugal pump, vane pump, gear pump has many advantages compared to the following:

Can transport high solids media;

Uniform pressure flow stability, more obvious when low speed;

The flow rate is proportional to the pump speed and thus has good variable regulation;

A pump can be used to transport different viscosity media;

Pump installation position can be any tilt;

Suitable for transporting sensitive items and susceptible to damage by centrifugal force and other items;

Small size, light weight, low noise, simple structure, easy maintenance.

● Use of the pump

Single screw pump can be widely used in the following industrial sectors, conveying a variety of media.

Chemical industry: acid, alkali, salt, all kinds of viscous, pasty milky chemical slurry.

Exploration Mining: Various drilling muds, mining water, floating pulp and floats.

Shipbuilding: bottom sewage, sewage oil, all kinds of fresh oil.

Ceramics industry: clay, clay, glaze.

Energy industry: all kinds of fuel, coal-oil slurry, coal-water slurry, slime and nuclear waste.

Sewage treatment: sewage, sewage sludge, sludge.

Paper industry: a variety of cellulose pulp, paint, black liquor.

Medicine, food, make-up industry: all kinds of grain pulp, starch paste, paste, mother liquor, mashed potatoes, wine and lees and so on.

Other agriculture, forestry, animal husbandry and fishery: There are also a wide range of uses.

● pump selection

Pump specifications are based on the nature of the fluid being transported and the pressure and pressure to determine the pump speed by the viscosity and corrosive liquid transport, as the main parameters to choose, to ensure the reliable operation of the pump. In this recommendation (Figure II) for reference.

Pump design speed for the transport of water or clear water similar non-corrosive liquids allow the maximum speed, in actual use due to the nature of the media and life requirements are different, the choice should generally be lower than the design speed, the high viscosity and medium containing particles , Generally used design speed of 1 / 2-1 / 3 or lower, low speed on the pump wear is beneficial, but after use due to the stator wear and tear flow rate decreased, then the appropriate increase in speed to compensate for the traffic drop is Regular policy. Transmission medium temperature should be -10 ℃ ~ 80 ℃ in special cases up to 120 ℃.

The normal pressure of each stage of the pump (one lead of the stator) is 0.6 Mpa, allowing up to 0.8 Mpa in a short period of time (less than 30 minutes), and gradually decreasing the volumetric efficiency at the same output pressure when worn.

Pumping water maximum suction is 8 meters, the actual use of recommendations not exceeding 6.5 meters, when pumping high-viscosity media, should be positive pressure inhalation.

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