Chemical pumps are frequently used to transport corrosive, toxic, or 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 sealing system consists of both static and dynamic seal points. For static seals, common sealing methods include gaskets and O-rings, with O-rings being the most widely used due to their flexibility and effectiveness. On the other hand, dynamic seals typically rely on mechanical seals rather than packing seals, which are less commonly used today. Mechanical seals come in two main types: single-acting and double-acting, as well as balanced and unbalanced designs. Balanced mechanical seals are more suitable for high-pressure applications, generally when the pressure exceeds 1.0 MPa. Double-acting mechanical seals are ideal for handling high-temperature, crystallizing, viscous, particulate-laden, or toxic and volatile media. In such cases, an isolation fluid is usually injected into the sealing chamber, with the pressure maintained slightly higher than the process medium by 0.07 to 0.1 MPa to ensure proper sealing.
Second, the choice of sealing materials is equally important. Static seals in chemical pumps often use fluorocarbon elastomers, while PTFE may be used in special conditions. For mechanical seals, the materials for the stationary and rotating rings must be carefully selected. Not all seals are made of carbide; using only cemented carbide would significantly increase costs. Typically, the stationary ring is harder, while the rotating ring is softer—such as silicon carbide paired with graphite. This combination offers a good balance between cost and performance. However, in extreme high-temperature environments or when handling media with abrasive particles, both the stationary and rotating rings may need to be made of hard materials. The selection should always depend on the specific application requirements.
By carefully evaluating these factors, you can ensure that the chemical pump chosen is not only efficient but also safe and durable under challenging operating conditions.
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