Chemical pumps are frequently used to transport corrosive or toxic volatile media, making sealing performance a critical factor in determining the quality and reliability of the pump. When selecting a chemical pump, several key criteria should be considered. First, the type of seal is essential. Seals can be classified into static and dynamic seals. For static seals, common types include gaskets and O-rings, with O-rings being the most widely used due to their simplicity and effectiveness.
For dynamic seals, packing seals are rarely used today, as mechanical seals have become the standard. Mechanical seals come in different types, such as single-ended and double-ended, as well as balanced and unbalanced. Balanced mechanical seals are particularly suitable for high-pressure applications, typically when the pressure exceeds 1.0 MPa. Double-ended mechanical seals are preferred for handling high-temperature, crystallizing, viscous, particle-laden, or toxic and volatile media. In such cases, an isolation fluid is usually injected into the sealing chamber, maintaining a pressure that is generally 0.07 to 0.1 MPa higher than the process medium.
In addition to the type of seal, the choice of sealing materials is equally important. Static seals in chemical pumps are commonly made from fluorocarbon elastomers, while PTFE is used in special cases. For mechanical seals, the materials for both the stationary and rotating rings must be carefully selected. Not all seals use carbide; while carbide offers excellent wear resistance, it can significantly increase costs. Typically, the stationary ring is harder (such as silicon carbide), while the rotating ring is softer (like graphite) to reduce friction and wear. However, in extreme conditions—such as high temperatures or when the medium contains particles—both rings may need to be made from harder materials. The selection should always be based on the specific application requirements to ensure optimal performance and longevity.
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