Butterfly Valve Working Principle
Butterfly Valve Specification
Relatively clean, neutral or aggressive liquid and gaseous fluids
Flow in both directions is possible in center seat valves. Flow direction should be specified in eccentrically actuated valves.
Very dirty fluid, very frequent opening and closing and high temperature is not an issue, wherever in all applications
Manual, motorized, hydraulic, pneumatic actuators.
It can be reached from DN 40 to DN 3000 and even above that. (The nominal pressure decreases as the diameter increases)
PN 10-16 in center-mounted valves, up to PN 40 in eccentric-operated valves.
Working Temperature Range
It can expand from -2000C to + 4000C. However, they are generally manufactured for the range of –100C and + 1200C.
Copper alloys (Brass, Bronze), Cast iron, ductile iron, steel and stainless steel Casting, Titanium, Aluminum, PVC, PP
Sealing gasket material
Various Elastomers (EPDM, PTFE- Teflon, NBR, Natural rubber, etc.), metal material for high pressure and temperature
Connection to Installation
Flanged, compression type (Wafer), with ears
Some related product standards
DIN 3354, API 609, ANSI / AWWA C504-80, BS 5155
Butterfly valve Advantage and Disadvantage
They are lightweight. Installation lengths are short.
They reduce the cost after a certain size.
In their open positions, no fluid residue is formed or occurs very little.
They are easily mounted.
Maintenance needs are low.
The parts that come into contact with the fluid are few.
They provide a relatively free, comfortable passage of fluid.
It is easy to use.
They can be used with actuators.
It is not suitable for high pressures.
Sudden opening and closing can create ram blows.
Elastomer-coated valves have relatively low operating temperatures, depending on the temperature resistance of the elastomer.
Butterfly Valve Types
According to the flap (Disc) bearing
Center-mounted valves : These are the valves where the opening-closing shaft axis and the rotation center axis of the disc (disc) coincide and meet the same axis as the body center axis.
The rotational movement of the clapper does not create a sealing force component in the peripheral seal
The sealing is only provided by a peripheral surface pressure dependent on the elasticity of the seal.
Advantages: It provides suitable flow form. Valve length can be very short.
Disadvantages: Shaft bearing points create interruptions in sealing surfaces, which limits the operating pressure. (COOKING ≤ PN 16).
In addition, the flow torque always acts in the direction of closing the valve.
This raises the risk of ram blow. Precautions should be taken to prevent rapid movement of the clapper.
Eccentric bearing valves
The opening-closing shaft is on the central axis of the body. However, the flap is on a plane away from the spindle axis in the direction of the flow axis.
In the fully open valve, the valve remains offset from the central axis. During opening, closing
the flap forms a sphere that is off the central sealing surface but on the flow axis.
The flap; During its rotation, it does not form a sealing force component on the sealing surface, it is tangent to the surface.
Advantages: Shaft bearing points do not create interruptions in sealing surfaces. The sealing ring can be replaced without disassembling the plug.
Double eccentric bearing valves
The opening-closing spindle is positioned offset from the central axis of the body.
The flap is on a plane away from the spindle axis in the direction of the flow axis.
In the fully open valve, the valve remains offset from the central axis.
During opening and closing, the valve forms a sphere that is off the central sealing surface, but on the flow axis.
However, the center of rotation of the sphere is off the center of the sphere. So the flap; It forms a sealing force component on the sealing surface close to the closure.
Advantages: As a force component is applied on the sealing surface and the shaft bearings do not cause any interruption on the sealing surface, higher pressure levels can be achieved. In addition, even at small opening angles, the valve separates from the sealing surface and removes friction.
According to the type of sealing gasket:
Gasket inserted into the body as an inner sheath or inner surface (Gasket on the body)
Gasket or outer surface sealed around the disc (Seal on the disc)
With metal seal
Butterfly Valve Application Examples
Since butterfly valves can reach very high values, the valves are assembled and assembled with “Disassembly Parts”, which can lengthen and shorten in the pipe axis, so that the valves can be installed and removed without problems.
With the development of technology, “Fire Safe-Fire Safe” can be manufactured with butterfly valves that can operate at operating pressures up to 200 Bar, even in small diameters.
When it comes to keeping the valves closed for a long time, even for small temperature differences, the valve is embedded in the expanded gasket, creating difficulties during opening and closing and working by wearing the gasket. Therefore, when it comes to gasket replacement, gasket material suitable for working conditions should be determined and gasket should be used from this material.
Butterfly Valve Maintenance
Butterfly valves are the type of valves that cause less trouble than other valves, and their common failures are the wear of the sealing gaskets and the flap.
If the seal is on the plug, it is possible and easy to replace the seal.