What Are Butterfly Valves?

7 October

What is a butterfly valve?

The name of a butterfly valve simply comes from its design of the body, which resembles a butterfly’s wings. In the centre of the valve is a large disc, normally stainless steel in FlowCon IVC valves, which rotates to control the flow.

How does a butterfly valve work?

There are three ways to operate the valve:

Lever – A squeezable lever which rotates the disc a quarter turn to the fully open position when pressed. Because this relies on human strength, this type of operation is only suitable up to butterfly valves of DN150, as anything bigger becomes difficult to impossible to open manually, due to the size of the disc and the corresponding pressure of the liquid in the pipe.

Gear – A gearbox is fitted to the top of the valve and is operated by a protruding wheel. Similar to a big steering wheel, this is rotated externally and opens the valve using the gearbox mechanism. This allows for operation of much bigger valves with relatively little effort from the operator.

Actuator – There is also an actuated butterfly valve, which unlike the other two types, is not manually operated. The valve’s control system monitors the conditions in the flow, and sends a signal to the actuator, and using its internal motors, the actuator adjusts the aperture of the valve to open or close the disc.

What is the difference between semi-lugged and fully lugged butterfly valves?

This refers to the shape of the body, where you’ll find “lugs”. These are looped tags on the edge of the body. A semi-lugged valve from FloControl will have four lugs, two each near the top and bottom of the disc. These are more suited to the middle of a pipeline, as it can only be bolted between two flanges. A fully lugged valve has eight lugs and is more suited to the end of a pipeline. If a semi-lugged valve is fitted to the end of a pipe without another flanged pipe being attached, it will fall off.

Where are butterfly valves commonly used?

Butterfly valves are found in a huge variety of projects, and are a big part in controlling the flow of liquid or gas. We at FloControl provide them largely for hydronic systems with HVAC (heating, ventilation and air conditioning) systems being big users of FlowCon IVC butterfly valves. You’ll also use them regularly if you work in construction of the oil and gas industry, fire protection industry, and marine industry. Anything that requires precise control of large scale liquids or gas will deal with butterfly valves.

How do I select the right size and material for my butterfly valve?

The size of the butterfly valve refers to the size of the disc. For example, a DN65 butterfly valve will fit onto the flanged end of a DN65 pipe, so while the disc itself measures 65mm across, the body of the valve is much larger. Always refer to the data sheets for exact measurements to ensure it will fit in your system.

The material of our butterfly valves is generally a ductile iron body with a stainless steel disc, but make sure to check the data sheets as it can very. In some instances we use cast iron as this is good for low-pressure HVAC systems but we have moved most of the products to a stronger ductile iron body.

Can butterfly valves be used for both on/off and throttling applications?

Yes. Actuated butterfly valves are able to do this automatically and make minute adjustments to the valve to allow for effective throttling. But manual valves also have this functionality. On the lever-controlled butterfly valve, for example, there is a metal notched disc under the handle, and you can stop at any point in your turn and slot the lever into an angle. This can then be locked in place with additional parts. Check the data sheets for flow rates to make sure you can get your desired output. You will find our actuated butterfly valves in our Control Valves range.

I’ve got so many more questions!

Get in touch with our technical team or our sales team on the Contact page and we’ll happily help you out with any additional questions you might have about the intricate workings of our butterfly valves and whether they are suitable for your project.