Valve Sandwich Design: Compact Installation Between Flanges

Sandwich-designed valves (wafer or lug type) install between mating flanges without additional flange connections. This guide covers design, selection, and installation per API 609 and EN 593.

Sandwich design means the valve body is sandwiched between two mating flanges. The valve has no integral flanges. Installation uses the stud bolts of the mating flanges to secure the valve in place.

Wafer type: Centered by flange bolts but not rigidly connected. Suitable for bidirectional flow. Cannot be used as a line-end isolation valve (downstream flange cannot be removed without shutting off upstream).

Lug type: Has threaded inserts (lugs) that accept bolts from both sides. Can be used as a line-end isolation valve. More expensive than wafer type.

1. Compact: Shorter face-to-face dimension than flanged valves. Saves space in tight installations.

2. Lightweight: No heavy flange connections. Reduces pipe support load.

3. Cost-effective: Fewer flange connections, lower material cost.

4. Easy installation: No alignment issues. Simply insert between flanges.

1. Not suitable for high pressure: Typically limited to Class 150 or 300 for sandwich butterfly valves. Wafer check valves may be limited to Class 600.

2. Cannot be used as line-end isolation (wafer type): Downsteam side cannot be disconnected without shutting off the upstream side.

3. Limited to certain valve types: Butterfly, check, and some knife gate valves. Not suitable for gate or globe valves.

1. Ensure flange faces are clean and gasket is properly positioned. Use full-face gasket or O-ring seal depending on valve design.

2. Tighten bolts in a star pattern. Do not over-tighten which can distort the valve body.

3. Verify valve is centered between flanges. Misalignment can cause operating torque increase or seat damage.

Generally no. Sandwich butterfly valves are typically limited to Class 150 or 300. For high-pressure steam, use a flanged globe or gate valve with proper pressure rating.

Wafer type is held in place by flange bolts but not rigidly connected. Lug type has threaded inserts allowing independent bolting from both sides. Lug type can be used as line-end isolation; wafer type cannot.

Ted Wang

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