When looking for the right equipment and parts for your project, you’ll need to make sure you have all the right information before purchasing anything. Not all butterfly valves are created equal. There are a variety of types of quarter-turn valves: Resilient Seated, Double Offset(High Performance) and Triple Offset Butterfly valves. Here’s a bit more about each type so you can be confident that you’re choosing the right valve for your needs.
- Resilient Seated: These are basically a general service valve with a stem seal formed by the interference fit between the shaft and the seat, top, and bottom. The flow shutoff is created by the interference fit between the disc edge and the seat. These should be used in non-critical, relatively low temperatures and when cost is the driving factor as eventually either the rubber seat or disc will fail or the fit between the shaft and the top and bottom seat will enlarge and leak to atmosphere. This valve is good for 230 psig at 250 F or 150 psig at 400F depending on the rubber selected. Cost reference $1
- Double Offset: The first improvement in the Butterfly valves design is the double offset High-Performance design. It addresses the wear of the disc against the seat by moving the stem off center and to the side. The result is the lifting of the disc off the seat within a few degrees of turn. The stem leakage is contained via a traditional packing gland up high on the stem with adjustment for occasional leakage. This means the stem and body are a wetted part and pressure is contained up high. This increases the cycle life by approximately 20 times. The seat was improved by using Teflon instead of rubber or metal which will withstand much more pressure and temperature. This valve is god for ANSI pressures i.e. 150# or 285 psig at 100F up to 1000F depending on the body material and seat selected. Cost reference $3
- Triple Offset: The latest improvement in the Butterfly valves series features the same double offset, back and to the side, but with a special seat the only engages the seat in the last few degrees reducing almost all wear between the disc and seat. Uses the same adjustable packing high on the stem. The seat now is a Stellite/Graphite laminate that engages the disc edge, also a stellite material. This makes the valve last much longer and makes it inherently “Fire Safe”. Temperatures and pressures are dictated only by the Body and Disc material selected. Cost reference $10 or 10X the price of a resilient seat valve!
- Lug butterfly valves: Lug-style features threaded ears to fit ANSI 125/150 # flanges and allows precise locating of valve between flanges and allows the downstream piping to be removed under pressure
- Wafer butterfly valves: Little more difficult to center between flanges but has locating ears that get the valve close. Does not allow removal under pressure
- Double Flanged: Normally used in very large sizes that need the extra Bulk to withstand the temperatures, pressure and piping torques seen in the large sizes. The HPBFV and Triple Offset valves can have the same Face to Face as Gate and Globe valves when an upgrade to a better valve is desired.
Choosing the right equipment for the job is essential in any project. This is why it’s so important to learn about the different types of butterfly valves in order to make the right selection for your specific project needs. Each type of butterfly valve is best in different situations, so make sure you purchase the right type for your project. When you’re ready to purchase parts for your next project, you’ll want to make sure the equipment you’re buying is able to handle the conditions you’ll be putting it through. Otherwise, you could end up with parts and components of your overall plumbing design wearing out sooner, which will mean more expensive repairs later on. Before you make any purchases, check to see whether your butterfly valve is able to handle the job it needs to do.
Pay Attention To Pressure
When picking out butterfly valves, one of the main elements you’ll need to consider is whether it’s able to withstand the pressure of the piping system and the media passing through it. Choosing the right valve when it comes to withstanding pressure is essential; using the wrong quarter-turn valve can cause your entire system to break down due to pressure-related problems. Pay attention to the specifications of each valve you’re looking to purchase to make sure it will withstand the pressure demands you need.
Another factor that’s relevant when picking out butterfly valves is the pressure they’ll have to withstand. If a system gets too hot, it can cause damage to these otherwise low maintenance components. For example, a centric, or rubber seated, butterfly valve is limited to 200 psig and up to 400 degrees Fahrenheit. Pushing this type of valve beyond this threshold can cause damage to your overall system, so be sure to keep this in mind when selecting your valves.
Finally, the largest factor in selecting the correct butterfly valve for your project is paying attention to the overall design of your system. Certain types of high-performance butterfly valves won’t work for certain projects simply due to the fit; when purchasing a valve, look at which butterfly valve will fit best in your design and work from there.
Choosing the right butterfly valves for your system can be a challenge, but by paying attention to the pressure needs, the temperature demands, and the overall design of your system, you’ll be able to make the right choice and even extend valve life. For more information on butterfly valves, contact Butterfly Valves and Controls today.