Steam Pressure Transmitters with 4-20mA Output

Explore pressure transmitters specifically designed for high-temperature steam with 4-20mA output. Integral cooling & diaphragm seal options for reliable measurement.

Specialized pressure transmitters engineered specifically for measuring steam pressure in high-temperature industrial and research applications, such as autoclaves, power generation cycles, and food processing systems. These instruments typically provide a robust 4-20mA current output and incorporate essential design features like integral cooling elements or compatibility with external cooling accessories (e.g., pigtail siphons, diaphragm seals) to protect the sensing electronics from heat damage, ensuring reliable and accurate measurements where standard transmitters would fail. Selecting the appropriate configuration based on maximum steam temperature and pressure is crucial for operational safety and efficiency.

16 bar, 200°C steam pressure transmitter and gauge - Combined pressure transmitter and indicator in one package with the option for use with high temperature media such as steam at 200°C
Autoclave pressure sensor and display with 10 bar range - We are looking for a autoclave pressure sensor and display for connecting to a laboratory steam sterilising autoclave and operates at about 10 bar @160°C

20 barg 4-20mA output 200degC steam pressure sensor for process control use - A hi-temp media 200°C/392°F max gauge pressure sensor for process control use to measure pressure of steam over a range of 0 to 20 bar g from the 1/2 BSP flush diaphragm male process connection, and sending the corresponding 4-20mA signal through the M12 connector electrical connection.
10 bar g steam pressure transmitter, indicator and PNP switch - Steam pressure transmitter with LED display indicator for measuring 0 to 10 bars with in-built temperature reducer
10 bar g steam pressure transmitter - High temperature pressure transmitter for use with steam pressures up to 10 bar gauge.

Find out more about Steam Pressure Transmitters to determine which product options and capabilities will best meet your application requirements.

Steam pressure transmitters with current output capabilities are specifically engineered measurement devices designed for reliable operation in demanding high-temperature steam applications. These instruments provide a standard 4-20mA signal, ideal for integration into industrial control systems, and are crucial where standard pressure transmitters would rapidly fail due to excessive heat exposure. Typical applications include sterilizing autoclaves, various food and beverage processing stages, and critical monitoring points within power generation facilities.

The primary challenge in measuring steam pressure is the direct correlation between pressure and temperature; as steam pressure rises, its temperature increases significantly beyond the boiling point of water at atmospheric pressure (100°C / 212°F). For instance, steam at 10 bar gauge reaches 184°C (363°F), a temperature far exceeding the typical operating limits of 100-125°C found in many standard industrial pressure transmitters. Accurately determining the maximum steam temperature expected in the process, using steam tables or calculations based on the maximum operating pressure, is therefore a critical first step in selecting an appropriate instrument. Failure to account for this can lead to sensor damage, inaccurate readings, costly downtime, and potentially compromised processes, especially in critical applications like sterilization or power plant safety systems.

To withstand these elevated temperatures, steam pressure transmitters often incorporate integral cooling elements directly into their design. These features are engineered to dissipate heat before it reaches the sensitive internal electronics and sensing element. Common integral cooling designs include extended neck tubes, specialized cooling fins providing a larger surface area for heat exchange with the ambient air, or internal pathways designed to thermally isolate the sensor body. The advantage of such integrated solutions is a more compact installation, potentially eliminating the need for additional cooling accessories in some scenarios.

Alternatively, when integral cooling is insufficient or not available, external protection components must be installed between the hot steam line and the pressure transmitter. A common and effective accessory is the pigtail siphon, typically made of steel or stainless steel piping. The loop or coil in the siphon traps condensate, creating a water barrier that prevents live steam from directly contacting the transmitter’s diaphragm while still accurately transmitting the pressure. The trapped condensate and the siphon’s material dissipate heat to the surrounding environment.

Another prevalent method for protecting the transmitter involves using a diaphragm seal assembly. This configuration physically isolates the transmitter from the steam using a flexible diaphragm (often made from stainless steel or specialized alloys) exposed to the process pressure. The pressure exerted by the steam on this diaphragm displaces a stable, high-temperature fill fluid through a capillary tube connected to the transmitter’s pressure port. This hydraulic system ensures the transmitter’s sensor only interacts with the fill fluid at a significantly reduced temperature, effectively protecting it from direct steam contact. Careful selection of the fill fluid is necessary based on the maximum temperature and vacuum conditions expected.

The materials used for wetted parts – those components in direct contact with the steam or condensate, such as the process connection, any isolation diaphragm, and the transmitter diaphragm itself – must be carefully chosen for compatibility with high temperatures and potential corrosivity. Stainless steel grades like 316L are common, but more demanding applications might necessitate Hastelloy or other exotic alloys.

These specialized transmitters predominantly utilize a 4-20mA current loop output signal. This industry-standard signal offers high noise immunity, allows for long-distance transmission without signal degradation, and often enables the device to be loop-powered, simplifying wiring requirements in industrial environments. While other outputs exist, the 4-20mA signal remains the most common for process control integration in steam applications.

In sterilizing autoclaves, used widely in medical, pharmaceutical, and laboratory settings, precise steam pressure control is essential for ensuring effective sterilization cycles and meeting regulatory compliance standards. In food processing plants, steam pressure measurement is vital for cooking, pasteurization, evaporation, and cleaning-in-place (CIP) systems, directly impacting product quality and food safety. Within power generation plants, monitoring steam pressure is critical at numerous points, including boiler drums, superheaters, turbine inlets and outlets, and condenser systems, ensuring both operational efficiency and plant safety. Other applications include chemical reactors, rubber vulcanization presses, district heating systems, and pulp and paper production lines.

When specifying a pressure transmitter for steam service, engineers and technicians must consider several key factors beyond the basic pressure range. The absolute maximum steam temperature is paramount, followed by required accuracy, the choice between integral cooling or external accessories like siphons or diaphragm seals, the process connection size and type, material compatibility with the steam conditions, the required output signal, and any necessary certifications for hazardous locations or specific industry standards. Selecting the correct configuration ensures long-term reliability and safety in challenging high-temperature steam environments.

Contents

Product Help

Steam temperature

Is steam temperature always the same value?

Under standard atmospheric conditions water turns to a gas and produces steam at a temperature of 100 degC / 212 degF, however this boiling point temperature is dependent on the pressure. As the pressure increases, the point at which water turns to a gas is a higher temperature. For example at a pressure of 10 bar gauge, the temperature at which steam is produced is 184 degC / 363.2 degF.

Maximum operating temperature

What is the highest operating temperature limit of the pressure transmitter?

When specifying a pressure transmitter for use on steam, it is important to determine the steam temperature by using a published table, online calculator or formula. At higher pressures it will become increasingly difficult to find suitable pressure transmitters because many will not have a sufficiently high enough maximum operating temperature.

Higher temperature steam protection

How are pressure transmitters protected from steam at higher temperatures?

Many of the pressure transmitter technologies that are widely used by manufacturers are not suitable for direct contact with high temperature steam, with typical operating limits from 100 to 125 degC / 212 to 363.2 degF. Therefore it is necessary to add protection components between the pressure transmitter and steam to act as a heat sink to cool the media in close proximity to the transmitter.

The high temperature protection components vary in mechanical design; some allow the steam to pass through, whilst others will isolate the steam using an oil filled isolation diaphragm seal. The majority of these design concepts rely on providing sufficient surface area of thermally conductive material to make contact with the surrounding cooler ambient air, and a restriction to reduce steam volume or a membrane to block it altogether, to increase the cooling effect.

Checklist for steam pressure transmitter requirements

Define your steam pressure transmitter requirements using this checklist:

Pressure range?
Current output type?
Accuracy?
Electrical connection?
Media type? Steam
Maximum media temperature?
Maximum ambient temperature?
Process connection?