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The Difference Between a Lug and Wafer Butterfly Valve

Valves Study | Dec.23.2019

Butterfly Valve has existed for a long time and has a wide range of applications. They first appeared in the 1930s and have been used by many industries since then. Butterfly Valves are usually made of cast iron and the name comes from the functionality of the disc. There are several different types of butterfly valves, however, they are divided into two basic types-lug and wafer valves.

Butterfly Valves are classified as quarter-turn valves. When the metal disc (as part of the valve design) is rotated 1/4 turn, it opens or closes. This disk, known as the “butterfly”, is attached to a pole. When the butterfly valve is fully open, the disc is rotated 1 / 4 turn, allowing almost unlimited flow. You can also gradually open the valve to reduce flow. Turn the butterfly disc to close the valve and block the flow path. This is because the disc is always perpendicular to or parallel to the fluid, causing pressure to drop regardless of its position.

Connected to threaded inserts on both sides of the valve body, lug butterfly valves are suitable for installation in systems with two sets of bolts without nuts. The valve must be installed between two flanges, each with a separate set of bolts. With this setting, each side of the piping system can be disconnected without interfering with the other side.

The function of the wafer butterfly valve is to maintain the seal to prevent bidirectional pressure in fluid flow. In other words, the wafer butterfly valve is designed to be tightly sealed to prevent two-way differential pressure to avoid any backflow in a system manufactured for one-way flow. This is achieved by using tightly embedded seals such as o-rings, gaskets, precision machining and flat faces on downstream and upstream parts of the valve.

Both lug and wafer butterfly valves are wildly used in various industrial sector, including food processing, pharmaceutical, chemical, petroleum, water and wastewater management. In many industries, butterfly valves have mostly replaced ball valves. This is especially true for companies that handle oil because they are cheaper and easier to install.


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