Butterfly Valve

what is a butterfly valve?A butterfly valve is a type of valve which belongs to a family of quarter-turn valves. Butterfly valves have a disc, which is rotated a quarter turn either clockwise or counter clockwise, to allow flow media. Butterfly valves are used to regulate and isolate the flow of media and butterfly valves are excellent to ensure complete shut off, and are widely used in all sectors of industry. 

How does a butterfly valve work? 

The butterfly is a metal disc mounted on a rod, or split rod, depending on the manufacture. Butterfly valves works, by an operator, or actuator which rotates the stem of the valve, and this in turn is connected directly to the disc. When the valve is closed, the disc is turned so that it completely stops the flow of media, when the valve is fully open, the disc is rotated to a quarter turn into the open position, so that it allows an almost unrestricted flow of media. The butterfly valve may also be opened incrementally to throttle the flow. 

Butterfly valves can be bi-directional but do have a preferred flow direction, indicated on the body of the valve, It’s however strongly recommended to install the valves in the preferred flow direction, as it will extend the valve’s life span and will also lower the torque required to operator the valve. 

What are the types of butterfly valves? 

 There are 2 types of butterfly valves; a wafer butterfly valve and a lug butterfly valve.

A wafer butterfly valve is used to provide sealing against bi-directional pressure difference in the fluid flow. In order to avoid any backflow in systems produced for one-way flow, the wafer version is designed to protect against a tight seal and two-way pressure difference.  

A lug butterfly valve has a lug body which has protruding lugs – this provides a passage to bolt the holes that match with those in the flanges, to hold the valve inline so that one end of the line can be removed without affecting the opposite side & this is due to using lugged butterfly valves. 

What is a concentric butterfly valve? 

 concentric butterfly valve is one where the stem and the disc are centred in the middle of the valve, this is the most basic types of butterfly design. 

Can you throttle a butterfly valve? 

 Butterfly valves can be used to throttle, but in most cases the butterfly valve’s purpose is for full, or zero flow of the gas or liquid. 

What is the difference between gate valve and butterfly valve? 

 A gate valve has a paddle which is used to allow flow in the open position, or raised position, and stop the flow in the closed or lowered position, gate valves raise and lower in the vertical plane. 

Butterfly valves have a disc, which is rotated a quarter turn either clockwise or counter clockwise, to allow flow media. 

Can butterfly valve be used for flow control? 

 Butterfly Valves are generally used for handling large flows of gases or liquids, including slurries, but should not be used for throttling for extended periods of time, as this can cause damage to the seat and disc. 

What is a high-performance butterfly valve? 

In a high performance butterfly valve, the disc is eccentric, or offset, from the valve seat. As the disc starts to rotate, it moves away from the seat instead of across it. This type of valve uses the line pressure to help it seal. This feature allows the use of offset butterfly valves in highpressure applications such as ethanol or HVAC. It generally uses PTFE or plastic as its seat material, but metal seats are also available to meet firetesting specifications 

What is triple offset butterfly valve? 

Triple offset butterfly valves ensure the safe function and tightness even in case of changing temperatures or in case of pressure peak. It also eliminates friction in the seat area when opening and closing the valve, minimising wear of the sealing elements, and significantly prolonging the service life of the valve.  

The first offset shifts the axis of the shaft rotation off the plane that lies on the pipeline axis.  The second offset moves the centre plane of the closing element parallel to its flat surface outside of the axis of its rotation.  

The third offset deflects the axis of rotational symmetry off the seat surface outside of the axis perpendicular to the flat surface of the disc, running through its centre. A set of all these offsets results in specific valve properties such as friction elimination during opening/closing cycle, ideal contact of disc and seat in closed position and its sophisticated geometry naturally prevents the disc from moving beyond the safe limit and directly defines the correct alignment of sealing elements. 

What is a double eccentric butterfly valve? 

 double eccentric butterfly valve is designed with tilted and fixated disc for extended service life and easy operation. 

What is a resilient seated butterfly valve? 

Resilient seated butterfly valves are a valve that has successfully passed the certification process of the German Institute DVGW CERT GmbH for potable water applications. Valves with this certification are available in sizes DN32-DN800 and are suited for conditions with working temperatures from 0 ° to 40 ° C and pressure ratings up to 16 bar. 

How Flexachem can help you?

Flexachem have over 37 years plus experience in actuating butterfly valves Metal, Lined and Hygienic. Butterfly valve sizes vary up to 48 inches in the TX range. We supply and have in stock Flowserve Norbro and Automax actuators.

We offer the following brands and types of butterfly valves;

Flowserve, Inoxpa, ABO, CORA and Garlock

We offer Metal high-performance butterfly valves with soft seats such as the Durco Big Max 2001 and the Valtek Torex or if it is nasty powders which you are handling than our lined butterfly valve range might be more of interest to you!

Do check out our rubber seated RX Butterfly valve which is ideally suited for all your utility requirements or our Inoxpa range for your sanitary butterfly valve applications.


Contact our Valve Specialist Team:

Brendan Merrigan (External) – mob: 087 2598124                            

Internal Team

Vicki McGrath – tel: 021 461 7207

Brian Barry – tel: 021 461 7211

Tim Quigley – tel:  021 461 7209

Shauna O’Connor- tel: 021 461 7237

Ross O’Donovan – tel: 021 461 7230

Tel: 021 461 7200