Duwan Environmental G85-2 Screw Pump with Variable Frequency Motor

Duwan Environmental G-Type Screw Pump Introduction:

A screw pump is a positive displacement pump consisting of a rotating screw and a rotor fixed within a stator, with a certain clearance between them. As the motor's rotational motion passes through the rotor, it drives the screw to rotate. The interlocking teeth on the screw and the rotor form a sealed cavity, creating a pressure difference within the stator. At this point, the liquid enters the screw cavity from the stator bore and is then pushed out of the screw cavity by the screw. Hence, the screw pump is also known as a displacement pump or a screw discharge pump.

Advantages and Applications of Screw Pumps:

Bolt pumps offer advantages such as low flow rate, low noise, minimal vibration, long lifespan, and high mechanical efficiency, and are widely used in systems like ships, passenger elevators, precision machine tools, and hydro turbine speed regulation.

Screw pump categories:

Single screw, double screw, and triple screw pumps by the number of screws; hydraulic pumps and conveying pumps by application.

Screw pump structure composition

Screw and rotor. As the motor drives the rotor to rotate via a coupling, the screw follows suit. When the screw rotates, its teeth mesh with the rotor to form a sealed cavity. After the meshing process is complete, the rotor comes to a stop, while the screw continues to rotate, expelling the liquid from the stator's inner hole.

Bearings and sealing devices. To ensure the screw pump operates normally over a long period, it is crucial that the motor's rotational motion can smoothly occur between the rotor and stator bore. Bearings primarily support the rotor and prevent vibration during rotation; sealing devices are measures taken to prevent oil leakage or spillage between the bearings and the rotor. Currently, the sealing devices for screw pumps include mechanical seals and packing seals.

Electric motors and control devices. The electric motor powers the screw pump and drives the motor operation, while the control device is used to monitor the operating status, working parameters, and operation of the motor.

Principle and Structure of Screw Pumps:

Once the motor starts, the gears on the motor shaft drive the impeller to rotate, causing the liquid inside the pump to be drawn in by centrifugal force. Subsequently, the liquid is propelled forward by the rotating screw pump.

During the meshing process, fluid is drawn into the pump and flows out through the sealed cavity formed between the stator and rotor; during the intake and exhaust processes, the fluid exchanges positions, thereby filling the entire volume with liquid.

1. Single Screw Pump Set: The single screw pump consists of a stator and a rotor. The stator is a cavity device formed by casting nitrile rubber and bonding it to the cylinder housing. The inner surface of the stator is a double helical surface. The rotor is made from alloy steel bar stock, precision turned, chrome plated, and polished, and comes in hollow and solid versions. The stator and rotor are eccentrically mounted with an eccentricity, mating with the outer surface of the rotor to form multiple sealed chambers. These chambers are used to fill working fluid, and as the rotor rotates, it continuously moves the sealed chamber along the axis, converting mechanical energy into hydraulic energy.

2. Twin-screw Pump Structure and Principle: Twin-screw pumps are divided into external bearing structure and internal bearing structure. They are very similar to gear pumps, with the driving screw rotating to drive the driven screw. The liquid is intercepted in the meshing chamber, propelled along the screw shaft, and forced out through the central oil outlet.

Installation Instructions for Screw Pumps:

1. When assembling screw pumps, relevant parts requiring lubrication with grease must be present, such as bearings and universal joints. Grease should be added, typically filling two-thirds of the cavity volume.

2. Inspect that all connections of the unit are securely fastened.

3. Screw pump units (including pumps, reducers, and prime movers installed independently) should have a solid, firm foundation. The units must be securely mounted on the foundation to prevent violent vibration during operation.

4. Check for a certain gap between universal joints and strictly control the neutral alignment of the two shafts. The跳动 of the outer circle of the universal joint must not exceed 0.1mm.

5. When designing the pipeline for the pump, it's essential to leave a space at the pump outlet larger than the stator length and ensure the pipeline is a removable structure for easy maintenance and replacement of the stator.

6. Identify the pump's inlet and outlet correctly before connecting the inlet and outlet piping.

Screw pump start-up:

Check if the connection between the intake pipe section and the instrument junction is sealed before starting up.

2. Prior to the first start-up or after disassembly and reassembly, or if the pump has not been started or used for an extended period, and the medium inside the pump has been removed, the intake chamber should be filled with the medium. Then, rotate the pump shaft a few times by hand or with a tool before starting the pump. This prevents starting the pump with no medium or only a small amount of medium, which can create a lubricating film of medium between the stator and rotor surfaces, avoiding dry friction between them and preventing damage to the stator or an excessively high starting torque that may prevent the pump from starting or reduce its suction performance.

3. For transporting highly viscous media, the pump's jacket layers should be heated before startup to reduce the viscosity of the residual media inside the pump, facilitating easy operation.

4. Inspect the original motor's rotation to prevent reversal.

Before starting, all valves on the inlet and outlet pipelines must be fully opened, ensuring the piping system is unobstructed.

Screw pump operation:

Check if the bearing's high temperature exceeds the temperature specified in the product manual.

2. Check if the shaft seal leakage exceeds the requirements specified in the product manual.

3. Pay attention to the indication of the vacuum pressure gauge on the import pipeline; the pointer should not have violent fluctuations. Check if the flow tube of the vacuum pressure gauge is installed correctly.

4. Pay attention to any abnormal noise or vibration of the pump; if cavitation occurs, stop immediately.

5. Be aware of any sudden changes in the pump's flow and pressure, and check promptly.

One-year warranty

Matching site variable frequency start cabinet installation and operation