ÖZKAN - Needle Valve
From Needle Valve
Needle valves are designed for flow control and regulation applications. Some shut-off valves like butterfly valves and gate valves are used for regulation but these valves are not suitable for continuous operation in regulating duty. Improper continuous use of butterfly and gate valves leads to material damage and decreases operation life. Another feature is the control characteristics. Asymmetrical cross section change in closure makes butterfly and gate valves nonlinear control devices.
The water flow is guided in ring shaped cross section which is steadily reduced from inlet to discharge port in needle valves. Ring shaped cross section of needle valves is kept in entire closing movement of piston and this feature makes needle valves ideal control valves. An axial moving piston controls the closing port in a linear characteristic.
Cavitation risk is another factor in regulation / control applications. Under extreme operation conditions control valves are subjected to high pressure differentials. The flow velocity increases in valve chamber through the flow path and the pressure energy simultaneously falls. If the medium pressure falls below the vapor pressure, vapor bubbles develop. Downstream of the outlet, the medium pressure increases again and vapor bubbles implode and produce microjets and pressure waves. These microjets and pressure waves hit the valve surfaces and damage the material where they hit.
The needle valves are so designed and equipped with special attachments that the outlet flow which is carrying vapor bubbles is guided to the center of valve. This design feature ensures that the vapor bubbles which creates cavitation damage do not come anywhere near the wall and other components of the valve. The cavitation bubbles at the center are dissipated by the increase in pressure during collision of water jets.
- Optimized body design for better flow guiding, minimum head losses in full open position
- Single piece compact body
- Maximum service life due to the cavitation-free location of seal ring
- Drive shaft supported on both sides in self-lubricating, maintenance free bushings
- Stainless steel internal parts and fittings
- Wear and corrosion resistant, bronze weld overlay-finished piston guides
- Double O-ring sealed shaft
- Optional control devices for optimum cavitation-free control requirements
- Without special tool requirement field replaceable seat and seal ring
- Fusion Bonded Epoxy coating
The piston and crank mechanism are located in teardrop shaped internal body.
The piston is axially guided inside the internal body and linear movement of piston changes cross-section. The piston is driven by crank mechanism which transforms rotational movement of gearbox or other actuation devices to linear movement.
- Bottom outlets
- Reservoir inlets
- Flow control
- Pipe burst safety valve
- Treatment plant flow control
- Pressure regulating
- Turbine by-pass