What Are Manifold Valves?

A manifold valve is an integrated assembly of two or more valves, often combined with ports and channels, designed to provide a centralized control point for fluid or gas systems. They are primarily used to isolate, block, or bypass pressure measurement instruments like gauges, transmitters, and sensors. This allows for safe calibration, maintenance, and replacement without needing to shut down the entire process line.

Primary Function

The core function of a manifold valve is to simplify and secure the connection between a process line and an instrument. It provides a compact and leak-proof solution for critical tasks such as:

• Isolation: Shutting off the pressure from the instrument to allow for safe removal.

Equalizing: Balancing pressure before opening valves to prevent damage to sensitive equipment.

• Venting/Purging: Releasing trapped pressure or fluids from the chamber for a safe zero-reference check or to clear the line.
• Calibration: Allowing technicians to connect calibration equipment without process interruption.

Key Industries and Applications

Manifold valves are indispensable in industries that require precise pressure monitoring and control within complex piping systems. Their main applications include:

• Oil & Gas: Widely used on upstream and downstream equipment, wellheads, and pipelines to isolate pressure transmitters and differential pressure (DP) cells.
• Chemical & Petrochemical: Protecting instruments from corrosive and hazardous fluids during maintenance procedures.
• Power Generation: Employed in boiler systems, steam lines, and other critical points for pressure measurement.
• Water Treatment & Pharmaceuticals: Ensuring hygienic and safe isolation of instruments in processes requiring high purity.
• HVAC & Refrigeration: Used on pressure and temperature gauges for system monitoring and servicing.

Common Types and Materials

Manifold valves come in various configurations and are constructed from materials compatible with the process media.

• Types:
  • 2-Valve Manifold: Typically used for gauge pressure applications to isolate and vent.
  • 3-Valve Manifold: Standard for differential pressure applications, allowing for isolation of the high/low sides and equalization.
  • 5-Valve Manifold: Provides more complex control for DP applications, including separate vent valves for the high and low chambers.
• Materials:
  • Body: Commonly made from stainless steel (SS304, SS316) for corrosion resistance. Carbon steel and brass are also used for specific applications.
  • Seals: Utilized materials like PTFE (Teflon), Viton, and Buna-N to ensure a tight seal against various chemicals and temperatures.

How It Works

A manifold valve operates by using its hand-operated valves to control the flow path to the instrument. In a typical 3-valve manifold for a DP transmitter:

1. During normal operation, the two block valves are open, and the equalizing valve is closed, allowing process pressure to reach the transmitter.
2. To isolate the transmitter for maintenance, the two block valves are closed, cutting off process pressure.
3. The equalizing valve is then carefully opened to balance any residual pressure between the high and low sides of the transmitter, making it safe to disconnect.
4. Vent plugs can be opened to drain any trapped fluid and bring the pressure to atmospheric levels.