Lug Type Butterfly Valve – Wafer vs Lug Type – Lug vs Wafer

What is a Lug Type Butterfly Valve?

Lug-style butterfly valves are usually composed of metal such as ductile iron or steel. They feature threaded tapped lugs positioned on the valve flanges for bolt connections.

Lug Butterfly Valve

What is a Wafer Type Butterfly Valve?

A wafer butterfly valve’s function is to retain a seal to protect against dual-directional pressure differential in the flow of fluid. In other words, the wafer version of butterfly valves was designed to hold a tight seal, safeguarding against bi-directional pressure differential in order to avoid any backflow in systems that have been manufactured for uni-directional flow. This is accomplished by using a tightly fitted seal, such as an O-ring, gasket, precision machined, along with a flat valve face on the downstream and upstream sections of the valve.

Wafer Butterfly Valve

Wafer vs Lug

Wafer Type Butterfly Valve

  • Lighter
  • Cheaper
  • Easy installation
  • Pipe flanges required
  • More difficult to center
  • Not suitable as an end valve
    In the case of a Wafer-style butterfly valve, the body is annular with a few non-tapped centering holes. Some Wafer types have two while others have four.

Lug type Butterfly Valve

  • Suitable as an end valve
  • Easier to center
  • Less sensitive in case of large temperature differences
  • Heavier with larger sizes
  • More expensive

Lug vs Wafer

In the case of a Wafer-style butterfly valve, the body is annular with a few non-tapped centering holes. Some Wafer types have two while others have four.

The flange bolts are inserted through the bolt holes of the two pipe flanges and the centering holes of the butterfly valve. By tightening the flange bolts, the pipe flanges are pulled towards each other and the butterfly valve is clamped between the flanges and held in place.

In the case of a Lug-style butterfly valve, there are so-called “ears” over the entire circumference of the body into which threads were tapped. In this way, the butterfly valve can be tightened against each of the two pipe flanges by means of 2 separate bolts( one on each side).

Because the butterfly valve is attached to each flange on both sides with separate, shorter bolts, the chance of relaxation through thermal expansion is smaller than with a Wafer-style valve. As a result, the Lug version is more suitable for applications with large temperature differences.

Butterfly Valve Lug vs Wafer

The wafer-style valve usually has just two or four unthreaded holes to secure and align the valve within two mating flanges. The lug style has threaded holes which allow the user to take off one end of the line without affecting the opposite side as it is held securely against one flange with bolts that match the threaded lugs on the valve. This makes it easier to clean, inspect, repair, or replace other sections of pipework as there is no need to shut down the whole system.

About Me

ZECO Valve is established in 1991, as a professional industrial valve manufacturer and water valve manufacturer in Shanghai, China.

Email: commercial@zecovalve.com