Selecting the Right Butterfly Valve for Your Application

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Fluid handling presents many of the challenges faced by industries that deal with the transference of media. It is not uncommon to find different fluid states (gas, liquid, slurry or fluidized solid) within a piping system that require a way to control the flow of the fluid.

Strategically placed valves are a powerful means to facilitate, impede or throttle this flow. Due to its versatility, the butterfly valve is one of the most commonly used industrial valves.  

A butterfly valve is a quarter-turn bidirectional valve that can be fully opened or closed with a quarter-turn of the disc. The disc control can be a lever, a handwheel, or a pneumatic or electric actuator. Valve designs include zero offset (also referred to as concentric), double offset and triple offset.

The zero offset butterfly valve is most commonly used in general service applications. More demanding applications that see higher pressures and temperatures (such as superheated steam) require double or triple offset designs that use a cam action to seal.

IMAGE 1 (left): Open/close control on a characteristic curve (Images courtesy of Garlock). IMAGE 2 (right): Continuous control on a characteristic curve

An advantage of the butterfly valve is the simple, compact design. This simplified design results in a more cost-effective valve that is easy to install and work with. It also typically has lower overall maintenance costs. This combination can be beneficial for large valve applications.

Throttling will be limited to low differential pressure services with this design. Additionally, there is a risk of cavitation and choke due to constant exposure of the disc to the media flow. To mitigate the effects of cavitation, many valve manufacturers will present a characteristic curve or optimal angle of aperture. It is important to operate within this linear boundary.

Butterfly valves are comprised of four main components: the body, stem, disc and seat. The body can be manufactured in either the lug or wafer style. The difference between the two is in the mounting design.

The lug can be considerably larger as it incorporates threaded alignment inserts, allowing it to be installed directly into a system with bolts. This also provides the option to use the valve in a dead-end service. The wafer is designed to sandwich tightly between two flanges and seals against bidirectional pressure.

IMAGE 3: Sand slurry test" data-entity-type=

IMAGE 3: Sand slurry test" data-entity-type=

The stem in a butterfly valve holds the disc in its proper position and provides its rotational direction when actuated. Successful control of flow is attributed to the disc and seat combination. When in a closed position, the disc seals against the (typically) soft seat that lines the internal periphery of the valve body. Depending on the manufacturer, some valve designs will incorporate a backing or energizing ring to help establish a sufficient seal.

Proper seat and disc material choices are essential when choosing a valve for an application. Selecting the wrong valve can damage the entire operation. It is important to know the STAMPS (size, temperature, application, media, pressure and speed) details to make a proper selection. With this, valve manufacturers can help identify the optimal valve type for the application.

Typical butterfly valve soft seats and, when applicable, lined disc materials include ethylene propylene diene monomer (EPDM), polytetrafluoroethylene (PTFE), and ultra-high-molecular-weight polyethylene (UHMWPE). EPDM is commonly used in the HVAC industry. It is resistant to polar compounds such as water, alcohols and glycols, as well as alkaline solutions like concentrated sulfuric acid and chlorinated water. It does not, however, perform well in petroleum-based oils. PTFE, often branded as Teflon, is one of the most suitable materials for use in highly corrosive and aggressive chemical applications. 

Lastly, UHMWPE offers abrasion resistance combined with strong chemical resistance. UHMWPE shines in weight loss tests and provides an alternative to expensive exotic alloys such as Inconel, Stellite, titanium and duplex stainless.

Water purification processes are a perfect example of a seemingly innocuous application with hidden challenges. A closer look at the purification process shows multistage treatments to ensure the highest purity possible is provided for consumption. With multiple filtration layers involving different chemicals, the water ultimately comes to a final stage where it is mixed with ozone (O3) to eradicate undesirable microorganisms. Because it dissipates so quickly, ozone is an effective and efficient method of sterilization. 

It is, however, a highly toxic gas (a mere 100 micrograms per cubic meter of air can have significant health effects) and the need for a leak-free seal is crucial in this application. In addition to being chemically compatible with the chemicals purifying the water, the valve must meet the food and drug compliance regulations of the governing countries since they will be in contact with the media.

Application Example

An operation needs a butterfly valve for a 10-inch Class 150 flange. The media is sand at ambient temperatures. A butterfly valve with an abrasion-resistant disc and liner are recommended to help improve the valve longevity and reduce downtime. The two best material options for this would be UHMWPE or a ceramic disc and liner.

Both materials are more resistant to abrasives than stainless steel, but their prices are different. While zirconia ceramic valves are abrasion-resistant, UHMWPE may have a better economical price and general longevity.  

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Wafer VS Flanged Butterfly Valve: How To Choose The Right Valve For Your Use

Now, we have learned in detail about wafer vs. flanged butterfly valves. But the main point is not wafer and flanged butterfly valves. It is finding the most effective valve for our use. So, how do you choose the right valve? What factors do you need to consider? We will discuss them in detail here.

• Operating Pressure and Temperature

The primary factor to consider is the operating pressure and temperature at which the valve works.

Wafer valve bolts are generally relatively long. Under high-temperature conditions, the expansion of the bolts may cause leakage. So, they are not suitable for large-diameter pipes under high-temperature conditions. Hence, choose a flanged butterfly valve if there is high temperature and pressure. You will choose the other one if the pressure and temperature are low.

• Budget

When choosing the correct valve, consider the budget demands. Make sure you know the money involved.

Integral flanges require additional materials and processing, so flange butterfly valves are more expensive. In comparison, wafer butterfly valves are more cost-effective. They require less material to install and are easier to manufacture. With wafer butterfly valves, we get an initial cost-cutting. However, in the long term, the flanged butterfly valves will provide durability.

• Consideration of Space

Everyone&#;s use of valves will be different. Thus, consider the amount of space you have before choosing the valve.

Flanged butterfly valves are larger and heavier because of the integral flanges on both ends. In comparison, wafer butterfly valves are more compact and lighter. You can go with the wafer butterfly valve if you have a compact space. If you have enough space, you can go for the other type of valve for your construction.

• Installation and Maintenance

Some people are not aware of the installation process, which later creates problems for them. Thus, you should know the installation need when choosing a valve.

The wafer butterfly valve does not have integral flanges at both ends. Instead, the valve is connected to the flanges at both ends with bolts or nuts. This means it requires less space for installation and is easier to disassemble and repair.
Flanged butterfly valves have integral flanges on both ends. This require additional space and more effort to disassemble and repair. The reason is that they require the removal of bolts or studs from the integral flange.

• Industry Regulation And Company

One of the things that you should always consider is the brand. Maintaining industry standards in manufacturing and production is prime. Hence, choosing a reputed brand that delivers top-notch industry-standard valves is important.

As an industrial valve manufacturer in China, ZFA Valve specializes in producing soft and hard seal wafer and flange butterfly valves. We have 10+ years of experience and a professional sales and technical team. So, we are here to provide service if you have any questions.