wT 2860/02
Page 15
Operating stem
In the closed state of the valve, the ball valve cavity can be discharged and/or vented or
depressurized by means of a special sealing system via a test/drain cock. This allows for
testing the function of both sealing rings following depressurization (Block & Bleed).
Furthermore, repair work can also be carried out on a depressurized section between the
two ball valves belonging to the pressurized pipe without hazard: The medium cannot
enter the repair section.
An operating stem is utilized to operate the ball. The connection stem-hub is achieved via
fitting keys. The tightness to atmosphere is ensured by means of consecutively arranged
O-rings. In order to simplify their replacement, they are located in the bush inserts. The
occurring bearing forces are absorbed by the bearing bushes.
Fig. 4
Pressure of the
medium
Pressure of the
medium
Test and drain cock
Fig. 5
Bush insert, upper part
O-Rings
Bush insert, lower part
Bearing bush
Fitting key
Ball
