Butterfly Valves

Butterfly Valve China 

Youyi is an industrial butterfly valve manufacturer offering four types of butterfly valves. Our valve factory in China supplies metal sealed and high performance butterfly valves for high pressure industrial applications.
Youyi is also a supplier of two types of eccentric butterfly valves, double and triple eccentric. The double eccentric type is commonly used in power generation and petrochemical applications, while the triple eccentric type is used in more demanding industrial applications.
The butterfly valve belongs to the angular travel valve family. It is named after its butterfly-shaped disc which acts as a gate to open or close the valve. The butterfly valve looks similar to a ball valve.The advantages of the Youyi butterfly valve include reliability, ease of operation and the need for less maintenance.

The butterfly valve has a disc that acts as a gate to open or close the flow path. The design allows the valve to be bi-directional. For many industrial applications, the hydraulic system is responsible for opening and closing the valve.

Because of their light weight and low cost, these valves are often used by industries that require fluid control. In addition, many industries prefer these valves because of their small size and ease of operation and maintenance. Butterfly valves can be operated manually, pneumatically or electrically.

What are butterfly valves used for?

Irrigation
Oil industry
Compressed air services
Agricultural industry
Cooling and recycled water
Wastewater industry
Corrosive applications
Fire protection
Slurries

Butterfly valve fittings

Industrial valves have very similar components and functions. Despite the slight differences, the main components and their uses are practically identical. Butterfly valves have four main components. The design of each component depends on the material used, the flow medium, the application, etc.
The body
The body contains the internal parts of the butterfly valve. Depending on the application and the medium flowing through it, the body can be made of different materials, such as brass, stainless steel or PVC. for example, when the pressure and temperature are high, metal is usually used. On the other hand, for aggressive media, alloy 20 is usually used as it is resistant to strong acids, such as sulphuric acid.
Discs
Discs allow or prohibit the passage of media through the valve. Many variations of the disc provide different degrees of flow control or sealing force.
Seats
The seat and disc together form the leak-proof seal of a butterfly valve. Media flow is stopped when the seat seals the disc around the inner diameter of the valve body. While resilient seals such as Teflon are more common, sealing materials also include clamping rings, O-rings or rubber rings.
Dry
The stem connects the disc to the actuator, sometimes called the wheel or handle, depending on the design and orientation. The stem transmits the movement of the handle to the disc. Without it, the actuator cannot open or close the disc manually.
Actuator
Also known as a handle, the actuator controls the opening and closing of the valve from outside the valve body. In the event of a failure, three actuator styles are designed for safety.
Failure to open
This means that the valve remains open in the event of an actuator failure.
Fail closed
This means that the actuator stays closed when an actuator failure occurs.
Manual
This means that the actuator can be operated manually in the event of a fault.

How do butterfly valves work?

Butterfly valves are mainly used as control valves. When the valve needs to be opened, a thin disc in the middle moves sideways; it is perpendicular to the bore and the stem moves in the same way as the disc.
The size of this disc is almost the same as the inner diameter of the piper. When the valve is closed, the piper and stem move sideways again.  Throttling occurs when the flow control section of the valve is partially open.

Considerations when buying a butterfly valve

Sometimes valves do not operate at optimum speed even when they are relatively new. Why is this the case? The answer lies in the knowledge and application of these valves. Understanding these considerations is part of extending the life of such valves.
Flowing media
Perhaps this is the most important consideration. Knowing the type of medium can narrow down the range of suitable valves to be used. In addition, knowing the corrosiveness or the amount of slurry to be trapped in the valve cavity is part of the consideration. Having said that, high viscosity media are not suitable for butterfly valves.
Piping considerations
The valve should be able to withstand the weight of the piping system; otherwise, the valve may be subjected to large bending loads, which can lead to leaks and internal damage to the valve.
Materials used
The material of the valve body, valve flap and seat should be able to withstand the corrosion of the passing medium. Another fact to consider is the concentration of the acid, if indeed the acid is a flowing medium.

Types of butterfly valves by valve body design

The two common body designs for butterfly valves are lug and counterclip. These refer to the mounting solutions commonly used by butterfly valve manufacturers.
Clamp-on butterfly valves
The butt-clamp type is the economical choice for butterfly valves. In detail, an O-ring and gasket seal the pipe valve to the pipe flange. Bolts attach the valve to the pipe flange. There may be flange holes in the body; however, this is not standard as other designs do not have these. This connection is better suited to systems that resist differential pressure in both directions and are more susceptible to backflow.
Lug butterfly valve
This type of design has lugs that connect to the valve body. Dead end connections are a common use for this type of butterfly valve.

Butterfly valve types by flap closure design

Concentric (zero bias) butterfly valves
In a concentric valve design, the stem passes through the centre of the gate into a pipe bore also located in the centre of the valve. To seal the flow, a concentric valve should have a very flexible seat rubber, as the disc first contacts the seat during a quarter turn.

As the disc and seat are always in contact, the valve body is less prone to corrosion when the medium is flowing. It only touches the seat which acts as a sleeve.

Low pressure applications are a common use for this valve. They are also known by these names: centre butterfly valve, centreline butterfly valve or resilient seat valve.
Eccentric (double or triple eccentric) butterfly valves
The stem passes through the centre back of the disc and attaches to the centre bore. Also known as a single offset butterfly valve, this design extends the life of the valve. For this reason, the valve flap and seat are in less contact before the valve is closed.
Double offset butterfly valve
The double offset is a high performance valve with two offsets radiating from the centre. This means that the stem is placed behind the disc and the other offset is placed on one side of the disc.
The design creates a cam action that transforms the rotary motion into a more linear movement. In addition, it creates less friction on the seat. An in-depth explanation of what a double offset butterfly valve is can be viewed in the video above.
Industry standards specify that this valve conforms to ANSI Class 600 for stainless steel and carbon steel. Most seats in this design are made from Teflon, but as high pressure use is also common, metal seats can also be used. Most applications include chemical, gas, oil, HVAC, water treatment and power generation.
Triple Eccentric Butterfly Valves
In contrast to the double eccentric, the triple eccentric butterfly valve has three. There is an additional offset in the disc seat. Compared to the other two offset designs, this is the most efficient and less wear-resistant design.
In addition to this, the seal is stronger due to the offsets on both sides. The triple offset design requires a metal seat as most applications must handle high temperatures and pressures in excess of 150 psi.

Butterfly Valve Types by Material

PVC Butterfly Valves
Plastic butterfly valves have been on the rise because they are cost effective. They may be light, but this type of material still has strong structural capabilities, making it ideal for low to medium pressure applications. Compared to metallic materials, PVC will not react with most fluids and gases.
Cast iron butterfly valves
If metal is the material of choice, cast iron is the typical choice for industrial applications. Cast iron can withstand higher temperatures and pressure levels than PVC, making it a better choice for industrial applications.

Butterfly valve types by material

There are two methods of operating butterfly valves. The manual method uses gears or levers. Automation is the other mode of operation.
The gear is actually a combination of a gear and a wheel-like device which rotates only a quarter of the way to open or close the valve. It is then attached to the stem so that it can move the valve flap located inside the valve.
Another method of opening and closing the gear manually is the lever method. The lever type, usually with a locking mechanism, is the most practical but is not usually suitable for larger operations as it requires more force. It has a wrench-like extension that can be moved to the left or right to open or close the disc.
Automation of actuators is most commonly used in industrial applications and is best suited to larger sized valves. Actuator automation can be one of the following three types.
Electric butterfly valves
Electric motors help to open and close the valve.
Hydraulic butterfly valves
The valve opens or closes with the help of hydraulic pressure acting on a piston.
Pneumatic butterfly valves
Compressed air helps the gear to open or close the valve.

Butterfly valve with ball valve

Butterfly valves and ball valves are the two most commonly used angle-stroke valves. Both are popular in industrial applications; however, there is little difference.
Butterfly valves are cheaper and easier to install than ball valves. However, butterfly discs are complimentary. Cleaning requires some effort due to the design. Ball valves have an advantage over butterfly valves in terms of their ability to withstand high pressures and temperatures.
In addition, ball valves have a low pressure drop which cannot be replicated by butterfly valves. On the other hand, butterfly valves have fewer body parts and less space to trap debris. It is also important to emphasise that ball valves are unable to do the one ability that butterfly valves excel at - throttling.