2-Valve, 3-Valve and 5-Valve Manifolds Explained

1. 2-Valve Manifolds (Static & Gauge Pressure)

A 2-valve manifold is typically used with standard pressure transmitters, pressure gauges, or switches measuring line pressure relative to atmosphere:

• Block Valve (Isolating): Shuts off process pressure from the instrument sensor.
• Bleed / Vent Valve: Vents residual trapped pressure between the block valve and transmitter to atmosphere or test line, allowing zero calibration in the field.

2. 3-Valve Manifolds (Differential Pressure)

A 3-valve manifold is configured specifically for differential pressure (DP) transmitters measuring flow (across orifice plates) or liquid level:

• High-Pressure (HP) Block Valve: Isolates the upstream side of the DP cell.
• Low-Pressure (LP) Block Valve: Isolates the downstream side of the DP cell.
• Equalizer Valve: Connects the HP and LP chambers together. During zero calibration, the block valves are closed and the equalizer is opened so both sides of the sensor diaphragm experience equal static pressure.

3. 5-Valve Manifolds (Enhanced DP Protection & Venting)

A 5-valve manifold contains two block valves, two vent/bleed valves, and one equalizer valve (or dual equalizers):

• Allows complete venting of both HP and LP chambers to a safe recovery line or atmosphere.
• Prevents high-pressure cross-contamination between high and low ports during calibration.
• Essential for gas custody transfer, toxic fluids, and critical power generation instrumentation.

4. Summary Comparison Table

5. Conclusion

Selecting the correct manifold configuration ensures accurate sensor calibration, prevents diaphragm overpressure distortion, and streamlines plant instrument maintenance.