Butterfly Valve Basics

Butterfly Valves Basics

Butterfly valves are commonly used in a wide range of applications. Chances are if you’re researching valves, you’ve come across the various offerings of butterfly valves. Flomatic is here to help answer all of your questions related to valve basics:

What is a Butterfly Valve?

Butterfly valves are a family of valves called quarter-turn valves that feature a rotating disc (the “butterfly”) fixed to a valve stem. The entire valve is made up of a valve body, disc, stem, seat, and use handles, gears, or automatic actuators for operation. The internal disc pivots on a center axis when the valve stem is turned, allowing 90° of movement – fully open or closed. Butterfly valves, unlike gate valves, are also a popular choice for throttling & regulating flow with actuation.

When are Butterfly Valves used and what are their applications?

The various sizes and versatile designs of butterfly valves make them applicable for a wide variety of uses for municipal water supply, industrial and sanitary applications, HVAC systems, slurries, and beyond. Butterfly valves are commonly used for flow regulation in large-diameter pipes. The design and small footprint of the wafer and lug style valve make them a great option for space-restrictive applications – compared to many other types of shutoff valves which are bulkier and require a significant amount of space within the pipeline.

Butterfly Valves – Glossary of Terms

Due to their wide flow range capabilities, the following terms are often associated with butterfly valves:

Near linear – This expression is used to describe flow regulation when flow rates are proportional to the angular motion of the internal disc. It simply means if the disc is turned and set at 60% open, the flow rate through the valve is 60% of the max flow. Near linear flow is common with high-performance valves like Flomatic’s azure series or of flanged butterfly valves series.

Quick opening – This feature is displayed when the valve is seated. When the disc begins opening from the fully closed position flow rates are lowest, then increase slowly as the valve gets closer to fully open.

Flow isolation – This is a common reference for butterfly valves. Because butterfly valves offer reliable on/off control, they are great for isolating and directing flow elsewhere during times of maintenance for example.

How Are Butterfly Valves Installed?

Once you verify a butterfly valve is the correct model for your application, installation is very simple as long as you follow a few good recommendations.

  1. Clean the surface of the flange the valve will be attached to. Make sure there is no rust, corrosion, welding residue or debris that would prevent creating a good seal. This is a great time to inspect the flange further to make sure it is not warped or misaligned, a common cause of butterfly valve problem in various systems.
  2. Install carefully and be sure to not damage the valve seat and adjust the faces of the two pipe flanges to ensure there is enough space between them to remove the valve in the future for maintenance or replacement.
  3. Insert the valve’s bolts once the valves are centered in place but do not fully tighten. First operate the valve to confirm it can operate freely. Once confirmed, tighten the bolts one at a time in stages, like changing a vehicle tire, so even pressure is applied across the flange. While butterfly valves can be placed in any position for larger sizes it’s good to note an upright orientation is preferred to reduce load on the shaft caused by an actuator or gearbox. It’s important to keep in mind when attaching directly to a pump or another valve to make sure there is enough space for the motion of the rotating disc. If the disc is not fully within the valve body at 100%, open use of a spacer or spool may be required to provide clearance.

What are the advantages of Butterfly Valves?

There are many advantages to butterfly valves when they are used in the proper circumstances. Key advantages include:

  • Low maintenance and cost efficient
  • High flow capacity
  • Corrosion resistant for chemical applications
  • Low pressure drop and high pressure recovery
  • Simple operation

How should you maintain Butterfly Valves?

PLEASE NOTE: Please refer to Flomatic’s operational manual for different configurations. Valves may require different maintenance based on the model.

Anything mechanical needs proper and consistent maintenance to prolong its function and optimal performance. Butterfly valves are no different. A very simple and effective form of maintenance is ensuring the valves are being used. Develop a routine to cycle them regularly especially if they are not often used. This could be monthly or more often if necessary.

The valve seat is another area that should be on your radar for maintenance. This part can wear out over time making it so the valve does not fully seal. Depending on valve model, seat replacements or complete valve assembly, replacement may be required.

If the butterfly valve in your system is operating in a dry environment, lubrication may be required to keep the internal parts functioning properly. Making sure the disc and seat are lubricated will prolong lifespan significantly.

What makes a high quality Butterfly Valve?

Many factors go into manufacturing a high quality valve no matter the application. Therefore, it’s important to pay attention to the fine details when purchasing a butterfly valve.

A great example is Flomatic’s azure line of butterfly valves. Flomatic’s azure butterfly valves series are manufactured in accordance to AWWA C504 – a standard which establishes industry requirements for rubber-seated butterfly valves. In addition to that, Flomatic’s Azure valves are NSF/ANSI 61 approved which means they meet stringent requirements for safe drinking water. Certifications like these that are approved by a third party are tell-tale signs that a manufacturer produces high quality products suitable for drinking water.

When every component of the valve is made from quality materials, you know the product is built for reliability. When breaking down Flomatic’s Azure® line, you’ll find a ductile iron body with fusion bonded epoxy coating, a ductile iron epoxy coated disc with 316 stainless steel welded edge, a vulcanized seat, and a 316 stainless steel shaft. All state of the art materials that ensure longevity.

Lastly, when in doubt the best way to know if a particular butterfly valve is worth your investment is to call and ask the manufacturer. True valve experts will make themselves known in a conversation about their products by confidently delivering knowledgeable advice in a helpful manner.