ABSTRACT
Mechanical seals have rapidly evolved from machined shaft shoulders contacting a stationary casing face through replaceable faces at shaft shoulders and gasket-backed inserts to the many modern mechanical seals available in the marketplace today. To re-state an earlier point, all mechanical seals can be either of “conventional” or “stationary” construction. Similarly, single seals can be mounted either inside or outside the stuffing box, although a user would want to be well aware of the vulnerabilities of outside-mounted seals. The tandem seal arrangement is the safest of all dual seal combinations. In effect, it is made up of two inside seals, both with the advantage of inside seals and double seals. In this arrangement a separate clean barrier fluid is sealed by the outside seal and process liquid is sealed by the inner seal. Virtually all mechanical seals are available in either unbalanced or balanced versions.
