wT 2860/02
Page 14
10
Mode of Operation
During assembly of the body and the end piece, the sealing system is elastically
deformed. The two pre-stressed, elastic sealing elements made of stainless steel,
together with the sealing rings and a seal at the periphery, create a sealing system with
the ball both upstream and downstream of the ball valve. A back-up ring protects the
elastic sealing element against overstressing, a wire ring serves to lock the sealing unit.
(Fig. 2)
Due to the elasticity and up to a certain pressure, two primary sealing points are
continuously maintained in the bore. The differential areas at the sealing element cause
the pressure of the medium on the upstream side of the ball valve to press the sealing
ring onto the surface of the ball. If pressurization, exceeding the nominal pressure,
originates from the cavity between the sealing rings, then the sealing element on the non-
pressurized side or the downstream side is lifted from the ball surface. (Fig. 3)
The ball valve can be pressurized in both flow directions.
Thermal expansions are compensated by the elasticity of the sealing elements.
Ball
Wire ring
Back-up ring
U-sleeve, O-ring
Sealing ring
Fig. 2
Fig. 3
Pressure removal from cavity
when nominal pressure is
exceeded
Pressure of the
medium
Zero pressure
