Product Overview

It is used to convey media with a temperature ≤150°C, a viscosity of 3–760 cSt, no solid particles, non-corrosive properties, and lubricating performance.

Applicable pressure range: 0.6–2.5 MPa;

Applicable flow range: 0.6–123 m³/h.

Primarily used in fuel delivery, hydraulic engineering, marine engineering, petrochemicals, and other industries.

1. The medium is conveyed in a straight, continuous line, with no stirring and no pulsation.

2. Low vibration and low noise.

3. High pressure.

4. Simple structure and easy to disassemble and assemble.

5. Small size and light weight.

6. Minimal wear and long service life.

Structural Configuration of the 3G Series Screw Pumps

Mechanical seals are generally used. The pump is driven by an electric motor via a claw-type coupling. When viewed from the extended end of the main shaft, the rotation is clockwise.

Material of the 3G Series Screw Pump

Main and auxiliary screws: 16MnCrS5, 40Cr, 45, 38CrMoALA

Pump body: HT200, QT450-10, ZCuSn10Pb, ZG270-500

Troubleshooting Methods for Common Faults in 3G-Series Screw Pumps

1. Severe vibration or noise from the pump body

Causes: The pump is not securely installed or is mounted too high; the motor’s ball bearings are damaged; the pump shaft is bent, or the pump shaft is misaligned or not parallel with the motor shaft, among other issues.

Troubleshooting methods: securely mount the pump or lower its installation height; replace the motor’s ball bearings; straighten a bent pump shaft or properly adjust the relative alignment between the pump and the motor.

2. Overheating of the drive shaft or motor bearings

Causes: lack of lubricant or bearing failure, among others.

Remedy: Add lubricant or replace the bearing.

3. The water pump does not deliver water.

Causes: the pump casing and suction pipe are not completely filled with water; the dynamic water level is lower than the pump’s filter pipe; the suction pipe is ruptured, etc.

Treatment method: The sealing surface between the screw and the housing is a spatial curved surface. On this curved surface, non-sealing zones such as ab or de exist, and together with the grooves of the screw they form numerous triangular gaps—abc, def, and so on. These triangular gaps serve as fluid passages, connecting groove A on the driving screw with grooves B and C on the driven screw. Grooves B and C, in turn, follow their respective helical paths toward the back side and connect respectively with grooves D and E on the back side. Since the sealing surfaces where grooves D and E join groove F (which belongs to the opposite helix) also feature triangular gaps similar to those on the front side—namely a’b’c’—grooves D, F, and E are likewise interconnected. In this way, the sequence of grooves ABCDEA forms an “∞”-shaped sealed space (if a single-start thread were used, the grooves would wind axially around the screw, thereby connecting the suction and discharge ports and preventing the formation of a seal). It is easy to imagine that on such a screw many independent “∞”-shaped sealed spaces would be formed, each occupying an axial length exactly equal to the lead t of the screw. Therefore, in order to ensure that the suction and discharge ports are properly separated, the length of the threaded portion of the screw must be at least greater than one lead.

Five Causes of Screw Wear in the 3G Series Screw Pumps

1. Each type of plastic has an optimal processing temperature range for plasticization, and the barrel temperature should be carefully controlled to remain close to this range. Granular plastic enters the barrel from the hopper and first reaches the feeding section, where dry friction is inevitable. If the plastic is insufficiently heated and melts unevenly, wear on the inner wall of the barrel and the screw surface will increase significantly. Similarly, in the compression and metering sections, if the molten plastic exhibits chaotic and non-uniform flow, wear will also accelerate.

2. The screw speed should be properly adjusted. Some plastics are compounded with additives such as glass fibers, minerals, or other fillers. These additives often exhibit significantly higher abrasive wear on metal components than molten plastic itself. When injection-molding such materials at high screw speeds, the increased shear force not only enhances the plastic’s flow but also leads to greater fiber breakage. The resulting short, shredded fibers have sharp ends, which markedly increase wear. Moreover, inorganic mineral fillers can exert considerable scraping action as they slide rapidly across metal surfaces. Therefore, the screw speed should not be set too high.

3. As the screw rotates inside the barrel, the friction between the material and both components causes gradual wear on the working surfaces of the screw and the barrel: the screw diameter gradually decreases, while the inner bore diameter of the barrel gradually increases. Consequently, the fit diameter clearance between the screw and the barrel progressively increases as both components wear down. However, since the resistance from the head and the breaker plate at the front of the barrel remains unchanged, this increases the leakage flow of the extruded material during forward movement—that is, the amount of material flowing backward through the diameter clearance toward the feed direction increases. As a result, the output of the plastic processing machinery decreases. This phenomenon also increases the residence time of the material inside the barrel, causing material degradation. In the case of polyethylene, the hydrogen chloride gas generated from decomposition exacerbates corrosion on the screw and barrel.

4. The presence of fillers such as calcium carbonate and glass fibers in the material can accelerate wear on the screw and barrel.

5. If the material is not uniformly plasticized or if metallic foreign objects are mixed into the feed, the torque required for screw rotation may increase suddenly. When this torque exceeds the screw’s strength, the screw can twist and break. This constitutes an abnormal failure mode.