Butterfly valves are quarter-turn valves that commence the flow control of fluids. You can visualize it as a thin metal disc fluttering about definite access or stem assembly. The closing and opening mechanism restrict and enable the flow of a medium between the downstream pipe and upstream pipe. It comprises a rotating disc that channels the fluid’s flow in a system. It is called a quarter-turn valve as the rotating disc is operable to 90 degrees. You can find a butterfly valve in wafer, double-flanged, lugged, and stainless steel styles. They are present with electric and manual actuation. You can select a suitable one considering the material, style, and proper upkeep. These three factors will allow you to invest in a valve that can tolerate even the harshest conditions. 

Know about the Material

Polyvinyl chloride and chlorinated polyvinyl chloride are commonly used to make butterfly valves in various industries. Both these materials possess a high working pressure (150 psi). However, chlorinated polyvinyl chloride has a greater working temperature than polyvinyl chloride. 

These materials are suited for applications in places such as a swimming pool. But polyvinyl chloride will not remain an option for an application like hot water service, with a temperature greater than 140 F. Here, chlorinated polyvinyl chloride will be an ideal choice. It is because it has a greater limit of 195 degrees F. 

Another point to consider is the valve liner material. Your selection of this material will get influenced by temperature. Common liner materials include ethylene propylene diene terpolymer and fluorinated elastomer. Both these materials have upper-temperature limits more than or equal to Polyvinyl chloride and chlorinated polyvinyl chloride. However, valves with a fluorinated elastomer material may not be operable below 23 degrees F as it causes their rubber compound to harden. 

Pay Attention to the Body Styles

The body styles of butterfly valves primarily rely on the valve’s location inside a piping system. Wafer style valves are in the middle of a process line, between two mating flanges with bolts that go through the valve and aren’t threaded in the valve body.

Lug style butterfly valves are perfect for end-of-line applications. They enable one mating flange to get removed. Threaded metal lug inserts are over-moulded into its body. Sometimes, the valve body is machined to receive a lug having an internal thread for mating flange bolts. After removing the downstream piping, the end-of-line valve must get secured with a blind flange.

Know about the Pressure Drop

Knowing about pressure drops is important for making the right selection. Pressure drop refers to the pressure modifications between the inlet and outlet of the valve. In case of a smaller pressure drop throughout the opened valve, there won’t be much fluid flow until the valve closes. Therefore, a fast-acting valve proves to be appropriate. Note that if you choose butterfly valves for a control system, they should absorb 25-50 per cent of the total system pressure drop.

Know About the Maintenance of Butterfly Valves

It would be best to operate butterfly valves regularly to ensure reliability. If you keep it in a closed position for a long time, it will get stuck closed and turn inoperable. Sediment builds up against the disc, which isn’t easy to push away. In the case of a chemical attack, the liner swells around the disc, thus restricting its motion. You must know the varied maintenance requirements according to the kind of media in the system. You must also know how fluids passing through the valve can affect it.

Butterfly valves can get effectively used in varied applications. You must select a Butterfly Valve that comes with a year’s warranty and has undergone stringent quality controls. Such a valve is free of any issues and will prove highly reliable.

By Hemant Kumar

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