MAIN FUNCTION OF BUTTERFLY VALVES 9881236139
BUTTERFLY VALVES
Rotating the actuator turns the disc either parallel or perpendicular to the flow. Unlike a ball valve, the disc is always present within the flow, so it induces a pressure drop, even when open. A butterfly valve is from a family of valves called quarter-turn valves.
Operation is similar to that of a ball valve, which allows for quick shut off. Butterfly valves are generally favored because they cost less than other valve designs, and are lighter weight so they need less support. The disc is positioned in the center of the pipe. A rod passes through the disc to an actuator on the outside of the valve. Rotating the actuator turns the disc either parallel or perpendicular to the flow. Unlike a ball valve, the disc is always present within the flow, so it induces a pressure drop, even when open.
A butterfly valve is from a family of valves called quarter-turn valves. In operation, the valve is fully open or closed when the disc is rotated a quarter turn. The "butterfly" is a metal disc mounted on a rod. When the valve is closed, the disc is turned so that it completely blocks off the passageway. When the valve is fully open, the disc is rotated a quarter turn so that it allows an almost unrestricted passage of the fluid. The valve may also be opened incrementally to throttle flow.
There are different kinds of butterfly valves, each adapted for different pressures and different usage. The zero-offset butterfly valve, which uses the flexibility of rubber, has the lowest pressure rating. The high-performance double offset butterfly valve, used in slightly higher-pressure systems, is offset from the centre line of the disc seat and body seal (offset one), and the centre line of the bore (offset two). This creates a cam action during operation to lift the seat out of the seal resulting in less friction than is created in the zero offset design and decreases its tendency to wear. The valve best suited for high-pressure systems is the triple offset butterfly valve. In this valve the disc seat contact axis is offset, which acts to virtually eliminate sliding contact between disc and seat. In the case of triple offset valves the seat is made of metal so that it can be machined such as to achieve a bubble tight shut-off when in contact with the disc.
TYPES-
- Concentric butterfly valves – this type of valve has a resilient rubber seat with a metal disc.
- Doubly-eccentric butterfly valves (high-performance butterfly valves or double-offset butterfly valves) – different type of materials is used for seat and disc.
- Triply-eccentric butterfly valves (triple-offset butterfly valves) – the seats are either laminated or solid metal seat design.
The wafer style butterfly valve is designed to maintain a seal against bi-directional pressure differential to prevent any backflow in systems designed for unidirectional flow. It accomplishes this with a tightly fitting seal; i.e., gasket, o-ring, precision machined, and a flat valve face on the upstream and downstream sides of the valve.
Lug-style butterfly valve
Lug-style valves have threaded inserts at both sides of the valve body. This allows them to be installed into a system using two sets of bolts and no nuts. The valve is installed between two flanges using a separate set of bolts for each flange. This setup permits either side of the piping system to be disconnected without disturbing the other side.
A lug-style butterfly valve used in dead end service generally has a reduced pressure rating. For example, a lug-style butterfly valve mounted between two flanges has a 1,000 kPa (150 psi) pressure rating. The same valve mounted with one flange, in dead end service, has a 520 kPa (75 psi) rating. Lugged valves are extremely resistant to chemicals and solvents and can handle temperatures up to 200 °C, which makes it a versatile solution.
Rotary valve
Rotary valves constitute a derivation of the general butterfly valves and are used mainly in powder processing industries. Instead of being flat, the butterfly is equipped with pockets. When closed, it acts exactly like a butterfly valve and is tight. But when it is in rotation, the pockets allow to drop a defined amount of solids[1], which makes the valve suitable for dosing bulk product by gravity. Such valves are usually of small size (less than 300 mm), pneumatically activated and rotate 180 degrees back and forth.
Use in industry
In the pharmaceutical, chemical, and food industries, a butterfly valve is used to interrupt product flow (solid, liquid, gas) within the process.[2] The valves used in these industries are usually manufactured according to cGMP guidelines (current good manufacturing practise). Butterfly valves generally replaced ball valves in many industries, particularly petroleum, due to lower cost and ease of installation, but pipelines containing butterfly valves cannot be 'pigged' for cleaning.
History
The butterfly valve has been in use since the late 18th century. James Watt used a butterfly valve in his steam engine prototypes. With advances in material manufacturing and technology, butterfly valves could be made smaller and withstand more-extreme temperatures. After World War II, synthetic rubbers were used in the sealer members, allowing the butterfly valve to be used in many more industries.[3] In 1969 James E. Hemphill patented an improvement to the butterfly valve, reducing the hydrodynamic torque needed to change the output of the valve. [4]
A butterfly valve is a type of quarter turn valve. A quarter turn valve
can open or close whenever the handle is turned 90 degrees (a quarter of
a turn). The main function of these valves is to control the flow of
liquids through a section of pipe. Butterfly valves are mainly used in
waste treatment systems. They are extremely durable and need minimal
maintenance.
Butterfly valves operate like other quarter turn
valves. Understanding the way a basic butterfly valve works is pretty
simple. It can help you to learn more about the components of valves.
Butterfly
valves are made of a number of components. The most important one is
the metal disc. This metal disc is the one commonly referred to as the
butterfly. The butterfly is mounted on a rod and when the valve is
closed it blocks passage of fluid. When the valve is fully open, the
metal disc or butterfly moves a quarter turn. The passageway is
unrestricted allowing fluids or air to pass.
In essence, the
movement of the disc will depend on whether the valve is open or closed
either partially or completely. If the valve is opened partially, it
means that the disc will not be rotated a full one quarter turn, thus it
cannot provide unrestricted passage. This means that, smaller amounts
of fluid or air will pass through. However, if the valve is opened
completely, the disc will be rotated 90 degrees then larger amounts of
air or fluid will pass through.
There are many other components
that form the butterfly valve. They include the resilient seat, body,
packing, a stem and an actuator. The resilient seat is mounted on the
body of the butterfly valve in order to provide the proper seal. The
packing provides an additional seal especially in case the resilient
seat is damaged.
Butterfly valves are configured differently.
There are some which operate manually whereas others operate
electronically depending on the system. They also come in different
styles. There are those which offer high performance in systems like
large pump lines and front suctions.
Butterfly vales can also be
used in automobile systems. For instance, you will find the butterfly
valve inside the carburetor of a car. In this case, the valve is used to
control the flow of air to the car’s engine. It can partially open and
close to regulate the amount of air passing through
What is the function of butterfly valve ?
Rotating the actuator turns the disc either parallel or perpendicular to the flow. Unlike a ball valve, the disc is always present within the flow, so it induces a pressure drop, even when open. A butterfly valve is from a family of valves called quarter-turn valves.
Where are butterfly valves used?
The Butterfly valve is used
to regulate and control, throttle the flow. They are featured by a fast
operation and low-pressure drop. To make an open position from the
closed, it requires only a quarter turn. Wafer, lug, Single-Flange,
Flange are the regular types of butterfly valves.
What is a lug style butterfly valve?
The difference between a Wafer and Lug type Butterfly valve is only the mounting scheme [1] and [2]. Lug type valve as the name suggests has lugs that are used to mount the valve to lugs
that are attached the flanges on then ends of sections of pipe so that
each length of pipe can be removed and replaced independently.
Below the video shows the Butterfly Valve in Working Condition .
https://www.youtube.com/watch?v=NBYKg7jGDV4
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