Butterfly Valve Selection Guide
The appearance of a butterfly valve lives true to its name, it looks like a butterfly. Technically, it has a rotating disk mounted on a rod, and this rod runs through the center of the disk, making it look like the body of a butterfly with the half of the disk on each side as the wings. It may have gotten its name from a pretty and wimpy insect, but this butterfly has the power to act as a medium in controlling the flow of certain substances. Due to it being very much resistant in nature, it can with stand a great deal of pressure which makes it perfect as a device in isolating or regulating a flow, making it a high performance valve.
This butterfly comes in different assortments, depending on the usage and need. In the structure of these valves, there are two main styles or designs: the wafer and the lug.
- The wafer design is installed in between two pipe flanges. The valve is held in place since the flanges are surrounded by bolts attached to the flanges, which makes dead end service or disassembly of one end of the piping system impossible. The wafer is also the more common one being bought at hardware stores since most salesmen take it for granted that whenever a person is asking for a butterfly valve, he would automatically assume that the customer is looking for wafer type. This valve is designed to maintain an air tight seal against high amounts of pressure to prevent backflow in the system. The best advantage of this is that it is cheaper compared to the next style.
- The lug design takes pride in doing what the wafer style cannot do, by providing dead end service. Lug style valves have threads inserted at sides of the body. The valve is installed between two pipe flanges and each flange has a different set of bolts, which means that they have to be installed using two sets of bolts and no nuts. This kind of set-up allows it to be disconnected at one side while the other side is not bothered. The down side is that when this ball type valve is used in dead end service, the pressure that it can handle is drastically decreased.
When a valve is either classified as wafer or lug, there are still three types that would further separate each other. Aside from these two, there are also different types of valve according to its structure. The three types are, namely: the concentric, double eccentric, and triple eccentric type.
- The concentric type usually has a highly resilient rubber seat with a metal rotating disk.
- The double eccentric or also referred to as double offset valves, have varying materials used on the disc and seat to suit the need for use.
- The triple eccentric valve or also called as triple offset valves. The seat of these valves are either laminated or made out of solid metal.
Whichever type of butterfly valve a person buys, it would still serve its primary purpose of being a flow control valve. Even if a person buys the most expensive one on the market, proper installation is always a must and an incorrect valve set up would render the valve itself unfit for the use it was intended for (you can know more this at how to maintain a butterfly valve article).