BURGMANN ABC - Double mechanical seal

Double mechanical seal

(Double acting mechanical seal). The term covers mechanical seals with back-to-back arrangement, arrangements with a common drive collar and the face-to-face arrangement. They are employed:

when no leakage of the pumped medium is allowed to emerge from the machine (risk of explosion, environmental protection),
for gaseous media and media with a high vapour head or poor lubricating properties,
for very aggressive media under high pressure and at high temperatures,
for many polymerizing and bonding media, and media tending to form deposits. An external buffer fluid serves to separate the product and the atmosphere. Buffer

fluid pressure lies at around 2 to 3 bar or 10% above the pressure of the product. The buffer fluid is sealed against both the product chamber and the atmosphere by means of one stationary and one rotating sliding face, including the necessary secondary seals. The complete seal element is called a "double-acting mechanical seal". A chief criterion is that the buffer medium in the sealing gap on the product and atmosphere side be clean. In normal operation it is impossible for a product to leak into the atmosphere. Care must be taken to ensure the buffer fluid is compatible with the product.