Rotary Valves by Dellstar Overseas

Principle of operation
The actuator opens the closure member of a rotary valve from 0 to 270°. This causes the medium flow through the valve to be either throttled or shut off.
Special features
Rotary valves have a more compact design than globe valves. Consequently, these valves are more cost-efficient in large nominal sizes. Additionally, they have a higher flow capacities. The advantages and disadvantages as well as the fields of application depend on the rotary valve design.
Designs
Butterfly valves The shaft turns the butterfly disk used to shut off or to control the medium flow by up to 90°. The various butterfly valve designs, in particular the bearing design of the disk, allows the valves to be used for throttling or on/off service. Butterfly valves in the wafer-type or lug-type design are cost-effective and use less material. They are primarily used for large nominal sizes. Butterfly valves are only suitable in applications where the pressure drop is relatively low. Higher differential pressures cause higher noise emissions and increase the load on the valve components. Possible countermeasures are restricted by the valve construction and space available in the valve.
Ball valves
Either a ball with a cylindrical passage or a segmented V-notch ball is used in ball valves to control the flow rate or shut off the process medium. The ball is located between two metal or PTFE seat rings. The ball can be rotated by 90° (quarter-turn ball valve). The seat rings press against the ball and the sharp edges of the hole through the ball help wipe off particles that stick to the ball and cut off any long fibers. When the valve is open, the full pipe cross-section is released, which causes a negligible loss in pressure and allows its use in pigging systems. Careful machining of valve inside surfaces ensures that a gastight shut-off can be achieved even at high pressure drops. Due to the high friction torques and gas-tight shut-off, ball valves are mainly used in on/off service. There are two types of ball valves: floating and trunnion-mounted ball valves. The ball of the trunnion-mounted ball valve is mounted on both sides, resulting in less friction torque which means smaller actuators can be used. Additionally, higher torques can be transferred which allows higher differential pressures to be controlled. However, mounting the ball on both sides makes the construction more complicated.