4 Types of Manifolds for Pressure Transmitters

Pressure transmitters are often installed in conjunction with manifolds, primarily for isolation, calibration, and venting. Manifolds control the input of the medium, ensuring measurement accuracy and safety. Manifolds are typically configured with a specified number of valves based on the required operating conditions. Common configurations include single-valve (2-valve), two-valve, three-valve, and five-valve manifolds.

When purchasing pressure transmitters or differential pressure transmitters, you can inform us of the type of manifolds you require.

RFQ

Manifolds for Pressure Transmitters Are Important

Installing isolation manifolds and drain manifolds during transmitter installation is a key design element for ensuring the safe and reliable operation of the measurement system.

Online Maintenance Requirements: When the pressure transmitter requires calibration, replacement, or repair, closing the isolation valve cuts off the connection between the process medium and the instrument. This prevents media leakage (such as high-pressure, corrosive, or toxic media) and ensures operator safety.

Emergency Handling: If the pressure transmitter experiences diaphragm leakage, connector damage, or other malfunctions, the isolation valve can quickly cut off the media flow, preventing the accident from escalating (e.g., an explosion caused by a leak of flammable or explosive media).

Zero-Point Calibration: When measuring gases or liquids, closing the upstream and downstream isolation valves and opening the balancing valve (in a three-valve manifold scenario) allows for online zero-point calibration of the transmitter, avoiding measurement errors caused by zero-point drift (e.g., static pressure error correction for differential pressure transmitters).

Backup Instrument Switching: For critical process points, the isolation valve, in conjunction with the bypass pipeline, enables seamless switching between primary and backup transmitters (switching error ≤ ±0.1% FS), ensuring production continuity.

Sediment, rust, and other particles deposited in the liquid medium can be periodically discharged through the drain valve (recommended once a week, draining until clear each time) to prevent clogging of the pressure tap or pressure guide pipe (clogging can cause measurement lag ≥10s).

Condensate in gaseous media can be drained through a drain valve (e.g., in the air compressor outlet pipe) to prevent liquid accumulation that could cause measurement distortion in the differential pressure transmitter (error exceeding ±1% when liquid level > 50mm).

For viscous media (such as heavy oil), an angle ball valve (diameter ≥ 15mm) should be used for the drain valve, along with steam tracing (maintaining 50~80℃) to prevent solidification and blockage.

Negative pressure system scenario: In vacuum pipelines, the drain valve can be used for system venting (exhaust rate must be ≥ 5L/min when vacuum < -0.08MPa) to prevent backflow of external air during instrument disassembly, which could affect measurement.

Differential pressure transmitter exhaust: The positive pressure side drain valve removes air bubbles from the pressure guide pipe (measurement error exceeding ±0.5% when bubble volume > 5%), while the negative pressure side drain valve removes condensate to ensure accurate differential pressure measurement.

Manifolds for differential Pressure Transmitters

4 Types of Manifolds for Pressure Transmitters

We categorize Manifolds based on the number of valves configured.

1. Single-Shut-Off Manifolds

Also commonly known as instrument root valves, these are installed on process lines or equipment to isolate the instrument from the process medium.

2. Two-Valve Manifolds

Two-valve manifolds, also called dual-valve manifolds, consist of two on/off valves. In addition to the single-shut-off function, they also have a relief valve. Two-valve manifolds are used upstream of pressure transmitters (or pressure gauges).

Since pressure transmitters and pressure gauges require periodic disassembly and calibration, two-valve manifolds are typically used to release residual pressure in the pressure tapping branch line, and can also be used for sampling.

3. Three-Valve Manifolds

Three-valve manifolds are used in differential pressure transmitters or differential pressure gauges. High and low pressure are connected to two separate shut-off valves, with the middle valve being a balancing valve. When the differential pressure instrument is put into operation or under maintenance, to prevent excessive pressure on one side from exceeding the instrument’s range, the balancing valve must be opened first to achieve pressure balance between the high and low pressure sides, and then the shut-off valves on the high and low pressure sides should be opened or closed.

4. Five-valve Manifolds

A five-valve manifold is a three-valve manifold with two additional drain ports, serving a similar purpose. Essentially, a five-valve manifold adds drain valves to both the high and low pressure sides (for the same purpose as a two-valve manifold).

Purchase Pressure Transmitters/DP Transmitters with Manifolds

Our Sino-Inst pressure transmitters can all be configured with Manifolds, either as a complete product or as an accessory.

**SI-2088 Industrial Pressure Transmitter | Diffusion Silicon**

SI-3051T Direct Mount Pressure Transmitter | Smart Capacitive — **SI-3151T Direct Mount Pressure Transmitter | Smart Capacitive**

**Monocrystalline Silicon-High Accuracy Pressure Transducer**

**SI-3151 Capacitive-Absolute Pressure Transmitter**

Customizable ceramic capacitive pressure sensor (Cerabar) — **PMC133 Ceramic Capacitive Pressure Sensor – High Performance**

**SI-8051DG Monocrystalline Silicon High Accuracy Differential Pressure Transducer**

**SI-2088 High Temperature Pressure Sensor**

Why are three-valve Manifolds needed for differential pressure transmitters?

In most cases, differential pressure transmitters are configured with three-valve manifolds, primarily because:

Improved measurement accuracy: The three-valve manifold effectively balances the pressure on the positive and negative sides, significantly reducing measurement errors caused by pressure fluctuations and temperature changes.
Easier maintenance and repair: The three-valve manifold contains two shut-off valves that can control the positive and negative pressure sides separately. This greatly simplifies maintenance and repair.
Extended transmitter lifespan: Adjusting the pressure through the balancing valve effectively prevents damage to the diaphragm due to unidirectional pressure, thus extending the transmitter’s lifespan.
More accurate zero-point calibration: The three-valve manifold also keeps the positive and negative pressure sides of the differential pressure transmitter in a balanced state, resulting in more accurate zero-point calibration.

Manifolds Selection Guide

When selecting Manifolds for pressure transmitters, several factors need to be considered, such as media type, pressure range, temperature conditions, and interface size.

For corrosive media, stainless steel or other corrosion-resistant materials should be selected; high-pressure environments require valves with higher rated pressure.
During installation, ensure the valve is oriented correctly and connections are secure to prevent leakage.
Regularly inspect the valve’s condition and replace worn parts promptly to extend its service life.
Installation and maintenance by qualified professionals are recommended to ensure safety.

4 Types of Manifolds for Pressure Transmitters

Manifolds for Pressure Transmitters Are Important