How To Install a Butterfly Valve
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Figure 1: Butterfly valves are installed in various systems to control flow.
Correct butterfly valve installation is essential for ensuring efficient fluid control and prolonging the lifespan of the system. Incorrectly installed butterfly valves can leak or not open/close properly, causing issues for the system. These valves are vital components in various industries, from water distribution to chemical processing, due to their simple design and ability to manage flow with minimal pressure drops. This article offers guidance on the different types of butterfly valves. Step-by-step instructions for installation are also included.
Butterfly valve body design
Whether a butterfly valve is actuated manually, electrically, or pneumatically, it will likely have one of two body designs: lug type or wafer type.
- Lug type: Lug type butterfly valves have threaded inserts around the entire flange, meaning the system can be disassembled without downstream leaking.
- Wafer type: Wafer type butterfly valves fit between two pipe flanges. These valves do not provide end-to-end isolation, meaning the system cannot be disassembled without downstream leaks.
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Figure 2: Butterfly valve body types: lug (left) and wafer (right).
How to install lug and wafer butterfly valve types
The installation processes for lug and wafer type butterfly valves are similar. The primary difference is how bolts connect the valves to the pipe flanges.
- Lug: There are threaded bolt holes on both sides of the valve. Bolts screw into the valve on both sides and do not need nuts.
- Wafer: Bolts go through unthread bolt holes and are tightened using a nut.
Besides the mentioned differences, the following steps outline how to install a lug type or wafer type butterfly valve to a pipe.
Pre-installation considerations
- Make sure the pipe is well aligned.
- Make sure the gap between the pipe flanges is wide enough for the butterfly valve to fit without needing to force the valve into the gap. If the valve is forced through the gap, the liner may be dislodged from the valve.
- If the gap is not wide enough, use a spreader (e.g., hydraulic spreader) to increase the gap.
- Make sure the disc, the closing element, is slightly open. However, ensure the edge of the disc is not sticking out from the valve body.
- Do not use additional gaskets or grease on the face of the valve body.
- The bolts may need grease to install
- Refer to the manufacturer's installation instructions to determine the correct length of the bolts.
- For lug type butterfly valves, if the bolt is too long, the bolt ends may touch in the middle and break the "ear" of the valve. If the bolts are too short, they may be ripped out of the threads.
Installation
As stated above, the butterfly valve installation process is essentially the same for both lug- and wafer-type butterfly valves.
- Center the valve by inserting bolts into the top of the flange first (Figure 3 labeled 1)
- Insert bolts on the bottom of the flange (Figure 3 labeled 2)
- Insert the remaining bolts
- Tighten the bolts crosswise
- When both faces of the butterfly valve touch the pipe flange faces, installation is complete.

Figure 3: A lug type butterfly valve. First (1) insert the top bolts to center the valve and second (2) insert the bottom bolts. Then insert and tighten the remaining bolts crosswise.
FAQs
How do you install a butterfly valve?
To install a butterfly valve, align the valve with flanges, insert bolts, tighten evenly, and check for leaks.
What tools are needed to install a butterfly valve?
Tools needed to install a butterfly valve include wrenches, screwdrivers, a torque wrench, and possibly a gasket sealant.
Can a butterfly valve be installed vertically?
Yes, a butterfly valve can be installed vertically, but ensure the disc is aligned properly to avoid flow obstruction.
What are common mistakes when installing a butterfly valve?
Common mistakes include misalignment, over-tightening bolts, and not checking for leaks after installation.