needle Plunger Valve for water flow regulaiton an pressure regulaiton
Brief Introduction of the Plunger needle valve
The plunger valve has an annular flow cross section in any open position. The valve has an optimal control behavior generating low turbulence upstream and low cavitation. The outlet
flow converges towards the center of the pipeline therefore if any vapor bubbles are generated, they go to the center imploding surrounded by water without damage. The plunger is driven by a rod-crank mechanism and can be provided with additional adjusting cylinders to customize the valve behavior curve to the needs of the installation. It is a versatile valve, with low torque, which can be used as a control valve (flow, pressure, level, pumping) and The bottom discharge valve or turbine bypass.
The construction as below:
The Outlets Design:
Features:
Design acc. To manufacture Std or EN 1074-5
Size range: DN150 – DN2200
Pressure Range: PN10, PN16, PN25, PN40 PN63 (CLASS 150 LBS & CLASS 300LBS)
Flanges to EN 1092-2 /ANSI B16.5, ANSI B16.47A
Material available
Body Material: Ductile iron body EN-JS 1030 (GGG-40) , GGG50, WCB
Surface: Inside and outside epoxy-coated minimum 250 μm
Plunger 1.4301 * Seals EPDM * Internal parts and rod-crank mechanism in stainless Steel Auto lubricating maintenance-free shaft bearings
Piston guide of bronze overlay
Bolts stainless steel A4 (EN ISO 3506)
Operation Option:
Actuator possibilities: handwheel and gearbox, electric actuator, pneumatic actuator, hydraulic brake-and-lift cylinder, own-medium pilot controlled
ow to make the Valve sizing:
We are sizing the correct valve according to the specific process data, please provide the following 1) Inlet pressure
2) Outlet Pressure
3) Alternatively, desired differential pressure
4) Flow Rate
we will provide Kvs values along with a flow graph of the valve control performance.
Where:
Kv = Valve flow coefficient (flow in m'/h at 1bar Diff. Press.)
CV = Valve flow coefficient (flow in gpm at Diff. Press. 1 psi)
Q=Flow rate (m3/h ; gpm)
AP = Differential pressure (bar; psi)
Gf = Liquid specific gravity (Water=1.0)
Where:
K=Flow resistance or Head loss coefficient (dimensionless)
AH = Head loss (m ; feet)
V= Nominal size flow velocity (m /sec ; feet /sec.)
g=Acceleration of gravity (9.81 m/sec^2, 32.18 feet/sec^2)
How to choose outlet Design:
- Cavitation occurs
There are three fundamental requirements for cavitation to occur. First, there must be gas bubbles (nuclei) or voids in the fluid that serves as a basis for vaporization to occur. Second, the internal pressure in the fluid must drop to or below vapor pressure. Third, the pressure surrounding the vapor bubble must be greater than the vapor pressure for it to collapse.
- Eliminated the cavitation: (Anti-cavitation design of the plunger valve )
Cavitation prevention and protection is an important consideration in the design and operation of valves used in water distribution systems. One should be able to determine if cavitation exists, and if so its intensity and effects on the system. Cavitation in valves is a destructive condition that seriously affects the operation and service of the valve and occurs when fluid passing through the valve lowers to the vapor pressure of the fluid causing vapor
cavities (bubbles) to form. When the fluid passes out of the low-pressure area into a higher-pressure area, the vapor cavity becomes unstable and collapses. This collapse is what can sometimes be heard or seen and is the reason we must be concerned about its presence in pipeline systems. The collapse can be violent and is accompanied by noise, vibrations, and possible erosion damage to the valve or surrounding pipeline.
Cavitation diagram 'sigma'
The cavitation risk in needle valves can be evaluated using the following equation: σ> σL
The valve won’t operate under cavitation until σ> σL.
Where is it:
- Cavitation value σ = Pout / (ΔP + v2/2g)
- Cavitation limit σL see diagram
- ΔP = head loss [mhw]
- Pout = valve outlet pressure
- v = fl uid velocity referred to DN [m/s]
- g = 9.81 m/s2
THE VALVE SHALL NOT CONTINUOUSLY OPERATE UNDER CAVITATION RISK CONDITIONS. IT CAN BE ACCEPTED THAT THE VALVE OPERATES UNDER SLIGHT CAVITATION CONDITIONS FOR SHORT PERIODS
