Better Without: The Must–Know Facts About Sealless Pumps

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DÜPERTHAL Sicherheitstechnik GmbH & Co. KG

All of the traditional pump technologies have one thing in common: They rely on various types of seals to prevent shaft leakage. The two most common types of seals, packing and mechanical, though used in many applications, have their own potential shortcomings:

Packing Rings: This method utilizes braided packing material that includes a set of formed rings wrapped around the pump shaft and held in place by an adjustable gland. A small amount of leakage is needed for lubrication and cooling. Packing has been widely used in a variety of industries, but should not be generally considered a best practice for hazardous chemicals.

Mechanical Seals: These seals come in two general variations: single and double. Single mechanical seals can usually adequately address the problem of fluid leakage, but when used with liquids of higher viscosity, the product drag can distort the seal or cause it to break away from the shaft. Single mechanical seals also are incapable of containing hazardous vapors. Double mechanical seals can prevent the escape of vapors and are more reliable when handling viscous liquids, but they can be expensive to acquire, repair, clean and maintain.

Chemicals can not only be hazardous if mishandled, but hard-to-seal and expensive. That’s why chemical processors who require full product containment would be wise to consider the benefits of seal-less pumps when compared to traditional pumps.
(Picture: PSG)

While any of the various types of seals can perform admirably for long periods of time, they will eventually need maintenance or need replacement. Replacing the seals, not only after they fail but also as a form of preventative maintenance, is costly. The cost of a leak to a manufacturer includes the loss of valuable raw materials or finished products, downtime in production, and the costs and potential penalties associated with the chemical cleanup. Leaks of hazardous materials that reach the outside environment can be subject to fines and remediation costs from the US Environmental Protection Agency, as well as other regulatory agencies. Additionally, other countries have their own sets of regulations, which can often be more stringent than those in the US. Spilled hazardous materials also pose safety risks for site personnel and cleanup crews, which raises liability issues.

Can seal-less pump designs do better? Lets find out... on page 3!

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