How to Extend the Service Life of High-Viscosity Gear Pumps

High-viscosity pumps are ideal gear pumps for conveying highly viscous media, capable of handling viscosities of up to 200,000 cP. When pumping such media, the gear pump must deliver a high flow rate under significant pressure, with low power consumption and minimal internal leakage. Excessive viscosity increases flow resistance and reduces output power. Therefore, when selecting the medium to be conveyed, it is essential to strictly ensure that the operating temperature falls within the pump's adaptive range.

When used correctly, high-viscosity pumps can deliver excellent performance and value. By following proper operating principles, control methods, and maintenance practices, their service life can be significantly extended. However, if the rotational speed is too high, the internal rotors may essentially idle, slipping against the conveyed medium. This can lead to a failure to draw in the material or result in a very low flow rate. In such cases, the pump's speed must be reduced, the motor's power increased, and the inlet/outlet pipe diameters enlarged to decrease flow resistance and ensure proper conveying. While reducing the speed will lower noise and paradoxically increase the actual flow rate, it will not reach the theoretical flow rate. Therefore, if the required flow rate differs significantly from the actual operating conditions, a larger pump model must be selected.

(Note: The following paragraph in the source text regarding "applying adhesive to cleaned parts" appears to be a translation or copy-paste error from a different context, as it contradicts the mechanical nature of high-viscosity gear pumps. It has been omitted to maintain technical accuracy.)

Methods to Extend the Service Life of High-Viscosity Gear Pumps:

Do not use the high-viscosity gear pump to transfer cleaning fluids. Disassemble the internal components for cleaning, and reassemble them only after the transfer is complete to prevent foreign objects from entering the pump.

Perform hot alignment of the coupling after the pump body has warmed up to prevent additional torque during operation.

Install interlocking shutdown alarms on the inlet and outlet pressure measurement points. If the discharge pipeline becomes blocked, this will prevent severe damage to the pump body.

Regularly replace the melt filter located after the pump's inlet/outlet. Avoid prolonged operation at high pressures or near the upper pressure limit.

In the event of a power outage or heat medium circulation interruption lasting over 30 minutes, disassemble and clean the pump before reassembly. This prevents damage caused by solidified or degraded melt leading to poor bearing lubrication.

The temperature of the pump body's heat medium jacket should be slightly lower than that of the front and rear jackets. Because melt viscosity and shear rate have an inverse relationship, the shear from the gears and bearings can raise the melt temperature by 35°C after passing through the pump. Lowering the heat medium temperature helps prevent melt degradation.

Increase the speed gradually. Avoid sudden spikes in inlet and outlet pressures to prevent bearing damage or blockage of the melt lubrication channels.

During startup, do not blindly increase the speed if inlet and outlet pressures have not yet been established, as this can cause premature failure of the shaft or bearings.

Regularly replacing bearings can save maintenance costs. If the wear on the inner surface of the shaft or bearing approaches the thickness of the hardened layer, the shaft can be polished for reuse while only replacing the bearing. This can extend the pump shaft's lifespan by 8 to 10 years.

Because the pump body operates at high temperatures, hinged supports should be installed on the piping during cold-state installation to accommodate thermal expansion and prevent pipe displacement as temperatures rise.

Methods for Proper Piping Layout for High-Viscosity Pumps:

Piping should be as straight as possible, minimizing the number of fittings and reducing overall pipe length. When bends are necessary, the bending radius should be 3 to 5 times the pipe diameter, and the bend angle should ideally be greater than 90°.

Select the appropriate pipe diameter carefully. A larger diameter reduces fluid velocity and resistance losses at the same flow rate but increases material costs. Conversely, a smaller diameter drastically increases resistance losses, requiring a higher pump head and motor power, which raises both capital and operating costs. Therefore, a comprehensive technical and economic evaluation is necessary.

Install valves (such as ball or globe valves) and check valves on the discharge side. Valves are used to adjust the pump's operating point, while check valves prevent reverse rotation during backflow and protect the pump from water hammer (severe reverse pressure surges caused by backflow).

The discharge pipe and its joints must be rated to withstand the maximum system pressure.