How to Install a Wafer Butterfly Valve Between Flanges

Wafer butterfly valves install between two pipe flanges with through-bolts. The job is straightforward, but a few details — disc clearance and bolt sequence in particular — prevent the most common failures. Always follow the manufacturer's instructions and your site's safety procedures; depressurize and drain the line first.

What you'll need

The valve, the mating flanges, the correct flange bolts/nuts and a torque wrench. Most resilient-seated butterfly valves do not require separate flange gaskets — the rubber seat faces seal against the flanges. Check your datasheet.

Step by step

  1. Confirm the line is depressurized and drained. Lock out as required.
  2. Open the disc slightly — about 10–15°. Never insert the valve fully closed; the disc edge can extend past the body and be damaged, and a closed disc makes alignment harder.
  3. Spread the flanges just enough to slip the valve in. Do not force it or pry against the seat.
  4. Center the valve in the flange bore so the disc clears the flange IDs when it swings open. Misalignment here is the #1 cause of disc/seat damage on startup.
  5. Insert the bolts hand-tight, then bring the flanges together evenly.
  6. Cycle the disc fully open to confirm it swings free and clears the pipe bore before final tightening.
  7. Torque the bolts in a star (criss-cross) pattern in stages to the flange manufacturer's spec, so the seat compresses evenly.
  8. Pressurize slowly and check for leaks.

Common mistakes

Installing the valve fully closed (disc damage), pipe bore smaller than the disc swing (disc hits the pipe ID), uneven bolt torque (seat leaks), and adding unnecessary gaskets that interfere with the seat faces.

Shop and learn more

Find the right valve first: Butterfly Valves and the selection guide. For seat compatibility with your media, see the valve seat material guide.