Axial locking of the stationary seat (on product side). If there is a risk of the stationary seat being forced out of position (due to a drop in buffer fluid pressure in the case of double mechanical seals or to vacuum in the case of single mechanical seals), design measures must be taken to prevent this from happening. DIN 24 960 recommends installation of a locking ring (see figure). Alternatively it is possible to use double elastic bearings or to clamp the stationary seat in position. The same purpose can be achieved without any great design outlay by integrating a stop in the rotating part of the mechanical seal (figure).

Stationary seat locks in accordance with DIN 24 960

Stationary seat locking by clamping

An integrated stop (1) in the rotating part prevents axial ejection of the stationary seat and stops the mechanical seal from opening (for hard carbon stationary seats 0.5 mm maximum wear height) – a locking ring as specified in DIN 24 960 is unnecessary. p₁ = pressure to be sealed; p₃ = buffer fluid pressure