Detailed description of the lubrication and cooling system of the melt pump

The lubrication and cooling systems of a melt gear pump are crucial components ensuring its stable operation and prolonging its service life. Below is a detailed description of the lubrication and cooling systems of a melt pump:

I. Lubrication System

The lubrication system of a melt pump typically adopts a self-lubricating method, which is determined by the characteristics of the medium it conveys—polymer melt.

Self-lubricating Principle:

The melt pump utilizes the melt it conveys as the lubricant. In the pump's structural design, a stable pressure difference exists between the suction chamber and the discharge chamber of the melt pump. Leveraging this pressure difference, the melt from the high-pressure chamber is pressed into the bearings by the meshing gears. As the gear shaft rotates, a lubricating film forms on the surface of the gear shaft. This lubricating film not only serves the lubrication purpose but also prevents the melt from staying too long in the bearings, thereby avoiding melt decomposition caused by shear thinning.

Features of the Lubrication System:

Non-pollution: Using the melt itself as the lubricant avoids pollution issues that may arise from traditional grease lubrication.

Self-renewal: The lubricating film constantly renews within the bearings, ensuring continuous and stable lubrication.

High adaptability: Suitable for conveying various polymer melts without the need to change lubricants.

II. Cooling System

The cooling system of a melt pump is primarily used to reduce the pump body's temperature, preventing melt decomposition at high temperatures and ensuring the quality of extruded products. Common cooling methods include air cooling, water cooling, and hot oil circulation cooling.

Air Cooling:

Utilizes fans to dissipate the heat generated by the pump body into the air.

Suitable for small melt pumps with limited heat dissipation capacity but lower maintenance costs.

Water Cooling:

Circulates coolant inside and outside the pump body to carry away and dissipate the heat generated by the pump body.

High heat dissipation efficiency, suitable for melt pumps in high-temperature environments.

It can be divided into internal and external water cooling. Internal water cooling involves setting cooling water channels inside the pump body, while external water cooling introduces coolant through pipes into the pump body casing for heat exchange.

Hot Oil Circulation Cooling:

Uses hot oil for heat exchange to cool the pump body.

Suitable for melt pumps requiring high-precision temperature control.

The system typically includes components such as an oil tank, oil pump, and heat exchanger. The oil pump draws hot oil from the tank and transports it to the heat exchanger for heat exchange, then returns the cooled oil to the tank for recycling.

III. Maintenance of Lubrication and Cooling Systems

To ensure the stable operation of the melt pump, regular maintenance of the lubrication and cooling systems is required:

Check the formation of the lubricating film: Ensure that a stable lubricating film always exists on the surface of the gear shaft.

Clean the cooling system: Regularly clean the coolant pipes and radiators in the cooling system to prevent clogging and fouling.

Check the quality and quantity of the coolant: Ensure that the coolant is in good condition and sufficient in quantity.

Monitor temperature and pressure: Use temperature sensors and pressure sensors to monitor the pump body's temperature and pressure in real-time, ensuring it operates within a safe range.

In summary, the lubrication and cooling systems of a melt pump are vital safeguards for its stable operation and extended service life. By selecting and maintaining these systems appropriately, the melt pump can perform optimally in plastic broom production lines.

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