wT 2858/02
Page 19
The U-sleeve on the outer circumference of the holding disc is fully chambered (only refers
to holding disc design) and provides tightness to atmosphere towards the body
connector section.
The seal of the operating unit (operating stem) is formed by a STUFFING BOX supported
by a Belleville spring washer.
This type of seal is virtually maintenance-free, has a low setting behavior and only minor
contact forces are necessary to achieve tightness.
The Belleville spring washer is positioned in a manner that a contact force is always
exerted on the stuffing box. This ensures that temperature and pressure differences are
compensated for.
F1 + F2 + FV
FV
FV
F2
F1
F2
Exerted forces:
F1….Force of the medium exerted
on the ball
F2…Force of the medium exerted
on the sealing element
Fv….Pre-stress force of the
sealing element
F1+F2+Fv….Total force exerted
on the seat ring
