Some Products are not compatible with a single Mechanical Seal. Example as above application. A more economical solution may lie in the application of double mechanical seals back-to-back.

A Clean barrier fluid, such as water, is circulated between the two seals at a higher pressure than the product. The inner seal prevents the barrier fluid from entering the product, while the outer seal prevents the barrier fluid from leaking to the atmosphere. In addition to acting as an effective barrier between the product and the atmosphere, the barrier fluid serves as a lubricant for both seal faces. Circulation of the barrier fluid through the seal chamber carries away both the frictional heat generated at the seal faces and the heat generated by turbulence around the seal.