The stationary sealing concept
The basic principle of a mechanical seal contains two main components - one of them to be adjusted in a rotary way on the shaft, the other one stationary, arranged in the casing or coverplate.

In customary mechanical seals the spring-loaded component rotates

within the stationary seal design the spring-loaded component is arranged in a stationary way in the casing/ cover.

This arrangement offers far-reaching advantages and benefits:
  • The stationary design renders a compensation of tolerances possible when angular error occurs with stable relations between the seal faces as a result of the compensation. Drawing no. 1 shows that the seal faces retain their plane-parallel configuration and the angular error is intercepted. See drawing no. 2 for the rotary arrangement of customary mechanical seals, with which angular error may cause tumbling motions.
  • Dynamic 0-ring in stationary arrangement = less radial and axial movements. Dynamic 0-ring runs on hard metal = no shrinking or scaring at the 0-ring fit as it may occur with rotary arrangement.
  • There is no need to finish the protective shaft sleeve in the 0-ring area with hard coating or to put up with shrinking or scaring at this position, as it may happen with ,,rotating" mechanical seals.
  • In addition, the wear of the dynamic secondary seal (0-ring) will be reduced to an essential degree.
  • Multiple springs outside the medium to be sealed prevent clogging of springs.
Owing to these advantages, CHETRA prefers to use the stationary design.
Amongst many other measures this is an important step towards extension of service life.