What Is a Butterfly Valve?

Butterfly valves belong to the family of quarter-turn rotational motion valves that are found in pipelines to shut-off flow. In some cases, butterfly valves are utilized to regulate flow, though it is not recommended because it can damage the valve disk and have a negative effect on their sealing properties. Nonetheless, they are used for a variety of process media and industries, especially in water supply, collection, and distribution. Other uses include pumping stations and for flow isolation in the marine industry.

As they are implemented in many industries, it becomes clear that butterfly valves offer many advantages over their counterparts. Beyond their simple construction and compact design, butterfly valves produce end products with lightweight characteristics, lower price points, smaller installation footprints, and faster actuation speeds. Like other valve types, butterfly valves have many components, all of which will be outlined in the next section.

Valve Body

The valve body sits between the pipe flanges, with the most common end connection types being flanged, double lug, and wafer variations.


Attached to the valve body, the disk functions as a gate that stops or throttles fluid flow. It acts as an equivalent to the gate in a gate valve, or a ball in a ball valve. There are many variations in disk design, orientation, and material, each of which improve flow, sealing, and operating torque.


Within the internal valve body, a strong metal anti-leak seal secures the disk in a closed position in order to achieve complete shutoff. For example, the 9881k series’ stainless steel weld filled and microfinished integral body seat provides a corrosion and erosion resistant seat face. With this design, the valve can be manufactured according EN12266-A standards.


The stem, or valve shaft, is the component that links the disk to the actuation mechanism and transmits the torque through its body.


Seals are located at different sections within the valve, ensuring either a tight seal during operation or to isolate the process media from the valve’s internal components. When used to isolate, the design can be more flexible and cost-efficient.

Working Principle

Now that you are familiar with all the components that make up a butterfly valve, we will cover how a butterfly valve works. In a closed position, the disk blocks the valve bore. Meanwhile, in an open position, the disk is positioned perpendicular to the flow direction in order to allow flow. Generally, butterfly valves are designed to provide bi-directional flow and shut off capability. However, it is important to note that they are not full-bore which makes them unfit for pigging or swabbing.

The material that is used for the body of the butterfly valve is composed of ductile iron with an epoxy powder coat on both the internal and external surfaces. Moreover, the valves are usually operated by handwheels, gears, actuators, or a combination of those. For butterfly valve actuation, they can be operated manually, hydraulically, pneumatically, and electrically.


If you find yourself in need of butterfly valves, isolation valves, need valves, or other related components, rely on NSN Axis. NSN Axis is a trusted distributor for all kinds of aircraft parts, NSN components, and more all on an easy-to-use interface. Equipped with over 2 billion ready-to-purchase products in our inventory, fulfilling your operational requirements is quick and easy. Get started by completing an RFQ form which you can access via our Instant RFQ service. When filling out a form, we ask that you include as many details as you can so we can better tailor a solution that works for you. For additional questions, call or email us directly; we are available around-the-clock!


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