The valve for abrasive and slurry on/off and control applications.
The key element of these on/off and control valves is a ball sector that can rotate by 90° and is used as a flow control element. Even under the toughest operating conditions, the ball sector seals the media using a simple, replaceable seat ring in the body. One part of the ball sector serves to shut off the valve, and the other has a hole with a diameter that normally corresponds to about 80% of the nominal size of the valve. To avoid effects of thermal or mechanical stresses, the bearings and the shaft seal are mounted in swiveling bearing bushings in the body. The shaft is sealed using a self-adjusting PTFE packing with an integrated spring element that protects the bearing against media particles. Ball sector valves have centric bearings and stable trunnions. This allows the ball sector to maintain constant contact with the valve seat seal while it is rotating. Changes in the differential pressure do only have a minor influence on the constant actuation torque.
Ball sector valves are frequently compared to rotary globe valves due to their design. The key difference between ball sector valves and rotary globe valves is the type of bearing. In general, rotary globe valves are equipped with an eccentric bearing. This causes the shut-off element to lift off the valve seat when the valve is opened. The result is that the sealing surfaces are continuously exposed to abrasive media when the valve is partially or fully open. For suspensions containing solid particles, the medium can get between the ball or plug and the seal ring, damage the surfaces, and cause leaks. Ball sector valves have centric bearings, which means the ball sector does not loose contact with the valve seat when rotating. Deposits on the surface of the ball sector are wiped off by the seat ring, and solids cannot get stuck between the valve seat ring and ball sector when the valve is closed.
The intelligent design of the seals in our ball sector valves, in combination with various materials and surface treatments for the ball sector and valve seat, form the basis for long life spans and reliable operation, especially in applications with abrasive, highly viscous, or fibrous media.