Consider this information when deciding if butterfly valves are the best fit for a job
Butterfly valves are one of the most common types of valves for industrial and commercial process applications. Here’s a look at what makes them unique and some of the more unusual, niche applications they can prove beneficial in.
All About Butterfly Valves
From a design perspective, most butterfly valves are very simple. They consist of a round body that contains a round disc. This disc rotates around a central stem that connects to the handle on top. Butterfly valves are quarter-turn valves, meaning they go from “opened” to “closed” with only a 90-degree turn of the handle. When the disc of a butterfly valve is in line with the flow of fluid through the pipeline, fluid is allowed through, with some pressure drop from the central disc. When the disc is perpendicular to flow, no fluid is able to get through and flow is stopped.
Butterfly valves are primarily used to isolate or regulate flow. They are ideal for isolating certain parts of a system for maintenance and inspection. They can also be partially opened to throttle flow, allowing for precise control of flow rates. These valves, due to their versatility and low cost, are used in just about every industry in which liquid or gas is piped.
Types of Butterfly Valves
Butterfly valves come in two styles: lug and wafer. The basic difference is that wafer style must be installed on flanges and lug style acts as its own flange. Lug-style butterfly valves are more expensive, but are designed to keep a tight seal regardless of what direction fluid is flowing.
For application, most experts split butterfly valves into the categories of “general service” and “high performance.” General-service butterfly valves typically have a 10-position handle, a one-piece shaft, can hold pressures up to 285 psi, and are found in sizes up to 30 inches. High-performance butterfly valves are the specialists, with the ability to handle viscous and corrosive liquids, harsh gases, and steam. High-performance butterfly valves also provide more options in terms of seats, sizes, and materials. They are the ones that are typically used for the more unusual applications.
Here are a few niche jobs for butterfly valves, as well as the exact type of butterfly valve that is best to use.
Applications involving HVAC, steam, and dead-end service generate a massive amount of pressure. Butterfly valves for high-pressure jobs must be specially made to handle extreme pressures. HVAC is a high-pressure application due to the fact that it deals with moving air, a gas. Gases leak easily, so the seals in valves must be completely airtight. The same is true in jobs related to steam transport, as it is not only a gas but also a very high temperature.
Dead-end service applications could involve gas or liquids, but they still require resilient butterfly valves. Because the contents are flowing against a complete stop, the pressure builds higher than it typically would. For these high-pressure uses, resilient-seat butterfly valves are an ideal option. They have seats and seals that are made of strong materials like EPDM, Viton, or Buna-N, allowing them to withstand pressures of well over 250 psi.
A problem that sometimes appears in high-demand piping applications is that the temperatures are too high for a butterfly valve’s seat and disc materials. These components are often made of rubber or plastic, which can be helpful for keeping operation simple and costs low. But when things get hot, those parts are the first to fail. When dealing with steam or exhaust gases, this is especially true. The solution to this problem is simple. Instead of using plastic and rubber for disc and seat materials, many manufacturers also make butterfly valves with all-metal construction. Metals like stainless and carbon steel have high temperature tolerances, so they are ideal for disc and seat materials in high-temperature butterfly valves.
Some jobs take place in harsh and even corrosive environments. These include jobs around seawater, harmful chemicals, and more. Seawater can be extremely corrosive and even when a valve is not under the water, being near that environment for extended periods can be very harmful to standard butterfly valves. This is also true of environments with high chemical content. Chemicals in the air can break down and corrode butterfly valves and their seat materials over time.
Many of the top butterfly valve manufacturers recognize this problem and make specialized valves for corrosive environments. These valves are made of corrosion-resistant metals, such as stainless steel, which has high chemical, temperature, and pressure resistances. They also have tough seat materials, such as Buna, EPDM, Viton, and PTFE for maximum chemical resistance.
Standard butterfly valves are extremely useful but will not always stand up to the toughest jobs. Sometimes you need a specialized valve to do a specialized job. Consider these factors:
- Butterfly valves are great for creating a seal and isolating flow when you are piping on a budget or when the extra performance of ball valves is not necessary.
- If perfection and purity is a priority, purchasing a ball valve is usually the best option. The cost will be higher, but you will get slightly better performance.
- When buying a butterfly valve, you need to consider the cost, materials, pressure and temperature tolerance, and body type of the valve before purchase.
About the Author
A division of Commercial Industrial Supply, PVC Fittings Online carries a wide range of PVC and CPVC butterfly valves and can provide professional assistance and customized piping solutions. For more information, call 866/777-7990 or visit PVCFittingsOnline.com.