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Pressure Gauges — Selection, Design, and Application in Industrial Plants

Pressure gauges are used for reliable visual and mechanical monitoring of fluid and gas pressures in pipelines, hydraulic and pneumatic systems, and process plants. On this category page, you will find instruments characterized by a wide variety of designs, connections, measuring ranges, and sealing materials. Crucial for correct use are measuring range, connection type, material compatibility, tightness, and mounting options. The following information focuses on technical criteria, practical application, and selection criteria for industrial environments.

Types and Designs

Capsule pressure gauges are suitable for low to medium pressures and offer good sensitivity to small pressure fluctuations. They are robust and frequently used in air and gas lines as well as in hydraulic components with low temperature loads. Bourdon tube pressure gauges are the classic design for a wide range of measuring applications and are characterized by a longer service life under fluctuating operating pressures. Differential pressure gauges show the difference between two pressure points and are used for filter monitoring or checking flow conditions. For high-pressure applications and corrosive media, diaphragm-based pressure gauges and bellows designs are available, offering better isolation against aggressive fluids.

Materials and Media Compatibility

Material selection influences service life, measurement accuracy, and tightness. Commonly used materials include brass, stainless steel (1.4301/1.4404), Hastelloy, and Monel. Brass is cost-effective and suitable for non-corrosive media. Stainless steel AISI 316L (1.4404) offers high corrosion resistance and is standard for food, pharmaceutical, and chemical applications. Hastelloy and Monel are used for highly corrosive or oxidizing media. The choice of material for the measuring cell and housing must consider chemical resistance, thermal cycling stress, and potential erosion. For gaseous media with pollutant content or in vacuum operation, stainless steel and hermetically sealed versions are preferred.

Connections, Sealing Systems, and Mounting Position

Connections are available as cylindrical threads (G, NPT), compression fittings, flange connections, or special connections. In contaminated systems and where frequent disassembly is required, a compression fitting or a flange connection is recommended for secure, repeatable tightness. Sealing systems vary between PTFE fiber packs, elastomeric O-rings (NBR, FKM/Viton, EPDM), and metallic seals. For high temperatures and aggressive media, PTFE and metal-graphite seals are more suitable. For gas applications with minimized leakage, spherical or ring seats with metal-to-metal seals are advisable. The mounting position influences measurement accuracy; Bourdon tube or capsule pressure gauges are preferably mounted vertically or in a defined position to avoid moisture and dirt accumulation in the measuring system.

Measuring Ranges, Accuracy, and Scaling

Pressure gauges are available in measuring ranges from a few mbar to several 1,000 bar. Select the measuring range so that the operating pressure is optimally within the scale; a rule of thumb is that the normal operating pressure should be between 25 and 75% of the scale to optimize precision and readability. Accuracy classes (e.g., 1.0, 1.6, 2.5) indicate the tolerance as a percentage of the full-scale value. For control and quality-critical applications, classes ≤1.0 are preferred. Bimetallic temperature compensation, special pointer couplings, and fine scale divisions improve readability under dynamic pressure conditions.

Protection Classes, Mounting, and Environmental Conditions

Select the housing and protection concept according to the environment: IP54 or IP65 for dust and splash-proof environments, certified Ex versions for hazardous areas. Silicone or glycerin fillings increase vibration and shock resistance, damping internal components and extending service life under pulsating pressure. Mounting is done via threads, flanges, or plug connections; for vibration stress, additional brackets and decoupling are required. Temperature ranges are primarily determined by the sealing material and filling medium; standard measuring devices typically cover -20 °C to +60 °C, special versions up to >200 °C are possible with metal bellows or special seals.

Electrical Variants and Signal Transmission

Mechanical displays offer direct visualization, while electrical variants (switching contact, 4–20 mA, HART) integrate process control systems. Switching contacts or reed switches enable simple alarm functions; for precise remote monitoring, transducers with 4–20 mA output or digital interfaces such as HART or IO-Link should be used. For electrical versions, EMC-compliant shielding and overvoltage protection must be considered, as well as the power supply and grounding concepts of the plant.

Practical Examples

Filter monitoring in a paint shop: A differential pressure gauge with a stainless steel housing and PTFE seals measures the pressure drop across the pre-filter. The pressure range is chosen so that the operating pressure is in the middle third of the scale. An integrated reed contact provides a switching signal to the PLC when the differential pressure exceeds a predefined threshold. The connection is made via a compression fitting to allow for quick replacement. Housing protection IP65 and glycerin filling dampen pump vibrations. Hydraulic test benches in production: Bourdon tube pressure gauges in stainless steel with a metric G1/4 connection monitor static and dynamic test pressure cycles up to 400 bar. Mounting is done via angle brackets with vibration-damping rubber inserts; measuring devices are designed in accuracy class 1.0. For test reports, digital transmitters with 4–20 mA output are used, connected to the data logger system. The seals are made of FKM (Viton) for chemical resistance to hydraulic oil additives. Corrosive process media in the chemical industry: Diaphragm pressure gauges with Hastelloy measuring cell inserts and PTFE coating separate corrosive media from the mechanics. The connections are flanged to easily connect with pipelines made of special materials. For high process temperatures, metal bellows are used; the gauges are supplied in explosion-proof versions. For remote monitoring, a HART-enabled pressure transmitter is additionally installed.

Maintenance, Calibration, and Service Life

Regular calibration at operationally relevant intervals is necessary to ensure process safety. Visual inspection for damage, leak testing of connection points, and functional testing of switching contacts are part of the maintenance plan. Mechanical gauges with glycerin filling require less frequent adjustments but may show changes in filling pressure during strong temperature fluctuations; interval checks are provided accordingly. Replaceable measuring modules or complete measuring cells simplify repair and reduce downtime.

Selection Criteria for Purchasing

Accurate selection is based on defined specifications: medium, temperature range, maximum pressure, permissible leakages, accuracy requirements, connection type, and environmental influences such as vibration, humidity, or explosion protection. Documentation such as material certificates, Pressure Equipment Directive conformity, calibration certificates, and ATEX/IECEx certificates are often mandatory for procurement. Create specifications with the mentioned parameters to easily derive suitable variants. Further technical information and application examples can be found on our technology page at https://maku-industrie.de/technik and in our practical examples at https://maku-industrie.de/anwendungsbeispiele.

Compatibility with Functional Fittings

Pressure gauges are often part of complete functional fittings. Pay attention to material and thread coordination between the fitting and the measuring device to avoid galvanic corrosion and leaks. Compression fittings and hard metal seat constructions offer repeatability for frequent assembly. For modular concepts, standardized interfaces are recommended to exchange measuring devices without adaptation.

List: Selection Check before Ordering

* Medium / Temperature range / Maximum pressure / Desired accuracy class * Connection type / Mounting position / Protection class (IP, Ex) * Materials (housing, measuring cell, seals) and documentation requirements

FAQs

1. Which measuring range should I choose?

Choose a measuring range where the normal operating pressure ideally lies between 25 and 75% of the scale. For fluctuating or pulsating pressure peaks, choose a range with sufficient reserve, typically 1.5–2 times the expected maximum pressure.

2. Which sealing materials are suitable for aggressive media?

PTFE and FFKM (perfluoroelastomer) offer broad chemical resistance; for higher temperatures and abrasive media, metal-graphite seals or metal bellows are preferred. The material combination of measuring cell and seal must be checked based on the specific medium.

3. How often should pressure gauges be calibrated?

Calibration intervals depend on operating conditions and safety requirements; in critical processes, typical intervals are between 6 and 12 months. Shorter intervals are advisable for heavy loads, high temperatures, or after shocks.