How do I measure and monitor pressure in my process system?

Measuring process pressure starts with choosing between local indication and remote monitoring. A pressure gauge gives you a visual reading right at the point of measurement — ideal for operator rounds, maintenance checks, and quick local verification. If the pressure data needs to go to a PLC, DCS, or SCADA system for trending, alarming, or closed-loop control, you need a pressure transmitter that converts the measurement into a standard 4–20 mA or digital signal. Many installations use both — a gauge for local visibility and a transmitter for the control system. Pressure switches provide a discrete on/off output when pressure crosses a set threshold, used for high-pressure alarms and safety shutdowns. For corrosive, viscous, or high-temperature media that would damage a standard sensor, a diaphragm seal isolates the instrument with a flexible membrane and fill fluid. Accessories like snubbers (to dampen pulsation from pumps and compressors) and siphons (to protect gauges from live steam) extend instrument life and improve accuracy in challenging conditions.

What is the difference between a pressure gauge and a pressure transmitter?

A pressure gauge is a local, visual indicator — it displays the current pressure on a dial or digital screen at the point where it is installed. Gauges are used for operator rounds, maintenance checks, and local process verification. They do not send a signal to the control system. A pressure transmitter converts the measured pressure into a standard electrical signal (typically 4–20 mA) that is sent to a PLC, DCS, or SCADA system for monitoring, trending, alarming, and control. Transmitters enable remote pressure monitoring and closed-loop pressure control without requiring an operator to be physically present at the gauge. Many installations include both — a gauge for local visual indication and a transmitter for remote monitoring and control. When selecting between them, consider whether the pressure data needs to be available only locally (gauge) or integrated into the plant control system (transmitter, or both).

What is a diaphragm seal and when is it needed?

A diaphragm seal (also called a chemical seal or remote seal) is a flexible membrane that isolates the pressure-sensing element of a gauge or transmitter from direct contact with the process media. The space between the diaphragm and the instrument is filled with a compatible fill fluid (typically silicone oil or fluorinated fluid) that transmits the process pressure to the instrument's sensing element hydraulically. Diaphragm seals are needed when the process media would damage, clog, or contaminate a standard instrument — corrosive chemicals, viscous fluids, slurries, hot media that would damage the sensor, sanitary/food-grade applications requiring cleanable surfaces, or media that solidify or crystallize in instrument cavities. They are also used when the process temperature exceeds the instrument's rating — the diaphragm seal acts as a thermal barrier. Seals are available in a wide range of materials (316SS, Hastelloy, tantalum, PTFE-lined) and mounting configurations (direct mount, remote mount with capillary tubing).

How do I select the correct pressure gauge range for my application?

The gauge range should be selected so that the normal operating pressure falls in the middle third of the dial — between 25% and 75% of the full-scale range. This ensures accurate reading under normal conditions while providing headroom for pressure spikes without pegging the pointer. For example, if the normal operating pressure is 60 psi, a gauge with a range of 0–100 psi or 0–150 psi is appropriate — not 0–60 psi (too close to full scale, no headroom) or 0–300 psi (operating point is in the bottom 20% of the scale, reducing readability). ASME B40.100 recommends that the maximum operating pressure not exceed 75% of the gauge's full-scale range for steady pressure service, and 65% for fluctuating pressure service. Also consider the gauge's accuracy class, dial size (larger dials for better readability), connection size and type (NPT, socket weld), case material, wetted material compatibility, and whether a liquid-filled case is needed for vibration damping.

What are pressure gauge snubbers and siphons, and when are they needed?

Snubbers and siphons are protective accessories installed between the process and the pressure gauge to extend gauge life and accuracy. A snubber (also called a pulsation dampener or restrictor) contains a small orifice or porous element that restricts the flow of media into the gauge, damping out rapid pressure pulsations from pumps, compressors, or reciprocating equipment. Without a snubber, the gauge pointer oscillates rapidly, making reading impossible and wearing out the gauge mechanism prematurely. A siphon (pigtail siphon) is a U-shaped or coiled tube installed between a steam line and the gauge — it traps a column of condensed water that prevents live steam from reaching the gauge's Bourdon tube. Steam temperature would damage the gauge's internal mechanism; the water column transmits the pressure while keeping the gauge at a safe temperature. Use a snubber whenever the process pressure pulsates or fluctuates rapidly, and use a siphon whenever measuring steam or high-temperature vapors.

Pressure Control - Weksler

Pressure control products measure, monitor and regulate pressure in liquids, gases and steam. Accurate pressure control protects equipment and keeps processes stable.

Pressure Control Products

Categories from Weksler (3)

Industrial Gauges

Industrial pressure gauges are built for the vibration, pulsation and rough handling found in plants, pump rooms and machinery. They give operators a dependable local reading of pressure in water, air, oil, steam and process lines.

Industrial Gauge Options

Stainless steel cases – corrosion resistance and durability
Liquid-filled gauges – dampen vibration and pulsation for steady readings
Brass and stainless internals – match media compatibility
Bottom and back connections – for line and panel mounting
Dial sizes from 2" to 6" – readable at a distance

Selecting a Gauge

Choose a range so normal operating pressure sits in the middle of the dial, generally about twice the operating pressure. Use a liquid-filled gauge on pumps and compressors, and add a snubber for pressure spikes. Confirm the connection size and accuracy grade.

Centro carries industrial pressure gauges for plant, process and equipment applications.

Commercial Gauges

Commercial pressure gauges cover HVAC, plumbing, fire protection and general building services. They're economical, easy to read and available in many standard ranges.

Commercial Gauge Options

Dry and liquid-filled gauges – general service
Brass internals – water, air and oil
Common dial sizes – 2" to 4"
Bottom and back connections – line or panel mounting
Fire protection gauges – sprinkler system ratings

Choosing a Gauge

Select a range about twice normal operating pressure, and match connection size and dial type. Liquid-filled gauges handle vibration from pumps.

Centro supplies commercial gauges for HVAC, plumbing and building systems.

Process Gauges

Process pressure gauges are built for chemical, petrochemical, refining and power plant service. Heavy-duty cases, stainless wetted parts and high accuracy give dependable readings in demanding environments.

Process Gauge Features

Solid-front safety cases – operator protection
316 stainless steel internals – corrosive media
Liquid filling – vibration and pulsation damping
Accuracy to 0.5% – precise readings
4.5" and 6" dials – easy reading

Choosing a Process Gauge

Choose range, accuracy, connection and materials suited to the process. Add diaphragm seals for corrosive, viscous or high-temperature media.

Centro supplies process gauges and accessories for plant instrumentation.

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Pressure Control - Weksler

Pressure Control Products

Industrial Gauge Options

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