The working principle, characteristics and advantages and disadvantages of the three-screw pump

The three-screw pump uses the rotation of the screw to suck and drain the liquid. The intermediate screw is an active screw, which is driven by the prime mover, and the screw on both sides is a driven screw, which rotates in reverse with the active screw. The threads of the main and driven screws are double-ended threads.

First, the working principle

1. The basic working principle of the three-screw pump: due to the mutual meshing of the screws and the close cooperation between the screw and the inner wall of the liner, it is divided into one or more sealed spaces between the suction port and the discharge port of the pump. With the rotation and engagement of the screw, these sealed spaces are continuously formed at the suction end of the pump, and the liquid in the suction chamber is sealed therein, and continuously pushed from the suction chamber in the axial direction of the screw to the discharge end, which is closed in each space. The continuous discharge of liquid is like the case where a nut is continuously pushed forward during the rotation of the thread. This is the basic working principle of the three-screw pump.

2. Working principle: The three-screw pump is a propulsion type positive displacement pump. The main components are the rotor and the stator. The rotor is a large lead large tooth height and a small spiral inner screw (rotor). The stator is matched with a double-headed spiral. And the nut sleeve, such that a space for storing the medium is formed between the rotor and the stator, and when the rotor is operated in the stator, the medium is axially discharged from the suction end.

3. The sealing surface between the rod and the housing is a spatial curved surface. There is a non-sealed area such as ab or de on this curved surface, and a plurality of triangular notches abc, def are formed with the groove portion of the screw. These triangular indentations form a passage for the liquid, allowing the active screw groove A to communicate with the grooves B, C on the driven screw. The grooves B and C are wound along the spiral to the back and communicate with the grooves D and E on the back. Since the grooves D, E and the groove F (which belongs to the other head spiral) are connected to the sealing surface, there is also a triangular notch a''''b''''c'''' D, F, E will also be connected. Thus, the groove ABCDEA also constitutes a ∞-shaped sealed space (if a single-head thread is used, the groove will be screwed in the axial direction, and the suction and discharge ports will pass through, failing to form a seal). It is not difficult to imagine that on such a screw, a plurality of independent dome-shaped sealing spaces will be formed, each of which occupies an axial length exactly equal to the lead t of the rod. Therefore, in order to separate the screw suction and discharge ports, the length of the threaded section of the screw is at least greater than one lead.

As can be seen from the above working principle, the three-screw pump has the following advantages:

1) Wide range of pressure and flow. The pressure is about 3.4-340 kgf/cm 2 and the flow rate can reach 18600 cm3/min. 2) The type and viscosity range of the liquid to be transported are wide; 3) Because the inertial force of the rotating parts in the pump is low, the high speed can be used. 4) Good suction performance and self-priming ability; 5) Uniform continuous flow, low vibration and low noise; 6) Less sensitive to incoming gas and dirt than other rotary pumps; 7) Solid structure, installation Easy to maintain.

Second, the characteristics:

1. The spiral sealing line that contacts the stator and the rotor completely separates the income chamber from the discharge chamber, so that the pump has the function of blocking the valve.

2, can achieve multiphase mixing of liquid, gas and solid

3. The volume does not change when the fluid in the pump flows, there is no turbulent agitation and pulse

4. The volume chamber formed by the elastic stator can effectively reduce the wear when conveying solid particle-containing medium.

5, the input medium viscosity can reach 50,000Mpa·s solid content up to 50%

6. The flow rate is proportional to the speed. The automatic adjustment pump can realize the positive and negative conveyance by means of the governor.

Three or three screw pumps have the following advantages and disadvantages:

(1): Advantages:
1. Compared with the centrifugal pump, the three-screw pump does not need to install the valve. The flow rate is stable and the linear flow is 2. Compared with the plunger pump, the three-screw pump has the self-priming ability, the suction height is strong, and the diaphragm pump is compared with the three-screw pump. It can transport various mixed impurities containing gas and solid particles or fibers. It can also transport various corrosive substances. 4. Compared with gears, the three-screw pump can transport high-viscosity substances, 5, and plunger pumps, diaphragm pumps and Unlike gear pumps, three-screw pumps can be used for filling and metering

(2): Disadvantages:
1. The disadvantages of the three-screw pump require high processing and assembly of the screw;
2. The performance of the pump is sensitive to changes in the viscosity of the liquid.