The sealing methods for masterbatch granulating melt gear pumps

The sealing methods for masterbatch granulating melt gear pumps are crucial, as they directly impact the pump's performance, reliability, and service life. Below are the common sealing methods for masterbatch granulating melt gear pumps:

I. Packing Seal

Overview: Packing seal is a traditional sealing method that prevents melt leakage through packing materials (such as PTFE, flexible graphite braided materials, etc.).

Characteristics: It features a simple structure, low cost, and easy installation and disassembly, making it a cost-effective sealing method. However, due to the high pressure inside the pump body of the melt gear pump, the sealing material exerts a significant compressive force on the axial direction, leading to significant wear on both the shaft and the sealing material over time, which can easily cause seal failure. Therefore, the packing needs to be replaced after a period of use.

II. Magnetic Seal

Overview: Magnetic seal utilizes the principle of magnetic coupling to achieve sealing through the interaction between internal and external magnets.

Characteristics: It is reliable in operation, with low wear and long service life. The magnetic seal does not need to directly contact the melt, thus reducing the wear and leakage risk of the sealing parts.

III. Combined Seal

Lip Seal + Packing Combined Seal: Combines the advantages of both lip seal and packing seal, improving the reliability and service life of the seal.

piral Seal + External Cooling (or + Packing): The spiral seal prevents melt leakage through the back pressure generated by the shaft rotation. External cooling can reduce the temperature of the sealing area and improve the sealing effect. When higher sealing performance is required, packing seal can be used in combination.

IV. Mechanical Seal

Overview: Mechanical seal is a sealing method achieved through mechanical devices, including single-ended and double-ended mechanical seals.

Characteristics: It has strong sealing performance, capable of achieving minimal or even no leakage of the medium. However, polymers are prone to overheating and decomposition at high shear rates on the sealing surface. Moreover, when the rotational speed of the melt gear pump is low, the high viscosity of the polymer melt makes it difficult to form a lubricating film between the sealing surfaces, easily causing leakage. Therefore, mechanical seals are usually not used alone on melt gear pumps but in combination with other sealing methods.

In summary, there are various sealing methods for masterbatch granulating melt gear pumps, each with its unique advantages and applicable scenarios. When selecting a sealing method, it is necessary to comprehensively consider factors such as the pump's operating conditions, medium characteristics, and usage requirements.

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