EXNAL 8859: Trafag’s Ex Submersible Pressure Transmitter for Hazardous Areas (2026 Guide)

Introduction

Where hazardous atmospheres, explosive gases, and challenging environments are part of everyday working life, it is essential to choose the appropriate instrumentation. Trafag AG, Switzerland’s EXNAL 8859 is now one of the most reliable solutions for level measurement in explosive areas. The advanced Ex certified submersible pressure transmitter will provide reliable performance, long term stability and industry leading safety certifications for Zone 0, Zone 1 and Zone 2 hazardous areas.

The EXNAL 8859 is used in oil and gas facilities, wastewater treatment plants, marine applications, mining installations and chemical storage systems, and offers accurate pressure and level measurements that meets all international hazardous area standards. This 2026 Guide presents all of the specifications, certifications, applications, installation requirements and benefits of the EXNAL 8859 as compared to standard submersible transmitters for the engineer, plant manager and system integrator.

What Is the EXNAL 8859? Core Product Overview

What Is the EXNAL 8859? Core Product Overview

Trafag AG has developed a special Ex immersion/submersible pressure transmitter for continuous pressure and liquid level measurement in hazardous areas, the EXNAL 8859. Uses a very reliable piezoresistive measuring principle to translate pressure generated by a liquid column into a standard 4-20 mA output signal, which can be used with modern PLC, DCS and SCADA systems.

Key Product Identifiers

• Product Name: EXNAL
• Product Code: 8859
• Manufacturer: Trafag AG, Switzerland
• Ex Submersible Pressure Transmitter
• Measuring Principle: Piezoresistive
• Feedback Signal: 4–20 mA, 2-wire loop powered

The EXNAL 8859 is designed to operate in a safe area compared to standard submersible transmitters, which are only suitable for safe area use. It is designed and built to withstand the rigors of permanent submersion in harsh industrial settings.

ATEX & IECEx Certifications for Zone 0, Zone 1, Zone 2 Applications

The EXNAL 8859’s distinguishing characteristic is its broad hazardous area certification portfolio. In industries like wastewater treatment, chemical manufacturing, and offshore drilling, where a small ignition source can result in devastating consequences, safety is a primary concern.

Certifications and Compliance

The EXNAL 8859 carries:

• For information, please contact ATEX Certification: Ex ia IIC T3 to T6
• IECEx Certification: SEV 12.0007X 003
• DNV-GL Marine Approval

Compliance with:

• IEC/EN 60079-0
• IEC/EN 60079-11
• IEC/EN 60079-26
• EN 50303

The Ex ia intrinsic safety rating means that the device can be operated in Zone 0, the most severe area of classification where explosive atmosphere may exist continuously or for prolonged periods.

Its temperature class 3-6 makes it suitable for installation in areas where gases with ignition temperatures as low as 85°C are present, further increasing its application range in various different industries.

Connecting with the real world: technical specifications and performance capabilities.

Tech specs and performance: connecting with the real world.

The EXNAL 8859 can be used in extreme industrial environments and offers outstanding measurement accuracy and stability.

Measure and Electrical Specifications

Parameter

• Pressure Range: 0–0.1 bar to 0–25 bar
• PSI Range: 0–1.5 psi to 0–360 psi
• Starting Range: 100 mbar
• Output Signal: 4–20 mA
• Accuracy: ≤ ±0.5% FS Typical
• Power Configuration: 2-wire loop powered

Temperature Ratings

• The temperature range for the media is -5°C to +80°C.
• Freezer Temperature: -15°C to +30°C
• T4/T6 Classification: -5°C to +50°C

Mechanical Design Features

The transmitter comes in these options:

• Open pressure connection
• Closed pressure connection
• G1/4″ male
• G1/2″ male

One of the key engineering benefits is a completely welded stainless-steel design, which avoids the use of o-ring seals. This design also minimizes potential paths for leakage and drift in long-term measurements.

Here are some of the features of EXNAL 8859 that make it stand out.

EXNAL 8859

Some of the salient features of EXNAL 8859 are:

The EXNAL 8859 is a special solution for instrumentation engineers and hazardous-area specialists, thanks to several design innovations.

Intrinsically Safe Construction

The transmitter is Ex ia IIC T3-T6 certified to be deployed directly in hazardous areas without explosion proof housing.

A pressure measurement is taken to begin at 100 mbar.

It is particularly useful to measure very low pressures such as:

• Shallow tanks
• Lift stations
• Wells
• Small process vessels

O-Ring-Free Welded Design

The EXNAL 8859 is different from standard transmitters, in that there are no o-ring seals within the instrument, which means this type of transmitter will have less maintenance and higher long-term reliability.

Advanced Cable Options

Users have the option of:

• PUR Cable – Excellent for water and wastewater use.
• FEP Cable – For fuels, chemicals, solvents and aggressive media.

Optional Titanium Construction

For applications involving:

• Hydrogen sulfide (H₂S)
• Chlorides
• Aggressive wastewater
• Chemical storage

The optional titanium casing offers outstanding corrosion protection.

Lightning Protection

To ensure the reliability of operation in outdoor installations, an optional lightning protection system with IEC 61000-4-5 rating is available, which provides surge protection up to 10kA (8/20 μs).

Uses and applications in various industries.

The EXNAL 8859 is used by a wide variety of industries that require level measurement in hazardous environments.

Industry Applications

Water & Wastewater

• Lift stations
• Digesters
• Sumps

Oil & Gas

• Produced water
• Separators
• Storage tanks

Chemical Processing

• Solvent tanks
• Acid vessels

Marine & Offshore

• Bilge
• Ballast
• Fuel tanks

Mining activities include:

• Tailing ponds
• Dewatering systems

It is also highly functional for its ability to work in an explosive environment without causing any damage to the area and allows for accurate measurements, which is especially important for industrial plants and facilities which are subject to a high level of safety standards.

With ATEX, IECEx and DNV-GL approval, one transmitter design can be used for multiple industries without having to go through multiple paths for certification.

EXNAL 8858 vs EXNAL 8859: Understanding the Differences

Trafag provides two models, EXNAL 8858 and EXNAL 8859, which are similar, but there are key differences to determine product selection.

Feature Comparison

EXNAL 8858

• Hazardous Area Approval: Ex ia IIC T3-T6
• Max Humidity Temperature: +30°C
• Pressure Range: 25 bar Standard
• Solar Powered: Available
• Resistance to Chemicals: Standard

EXNAL 8859

• Hazardous Area Approval: Ex ia IIC T3-T6
• Max Humidity Temperature: +90°C
• Pressure Range: Up to 25 bar
• Solar Powered: Limited
• Resistance to Chemicals: Enhanced

Usually the EXNAL 8859 is used for:

• Higher-temperature processes
• Aggressive chemical applications
• Hydrocarbon environments
• High-pressure level measurement

The EXNAL 8858 is still an economical choice for normal wastewater or water applications up to 50°C.

Install and wire, and document.

To ensure hazardous area compliance and accurate measurement, it is very important that the instrument be installed correctly.

Recommended Installation Practices

• Attach the transmitter upright.
• Hold the cable to avoid mechanical stress.
• Do no avoid sharp bends or abrasion points.
• Provide correct grounding as per the ATEX requirements.
• Fit an intrinsically safe barrier as necessary by system design and local regulations.

Available Documentation

Trafag has a number of important resources available:

• This datasheet provides information on the H72335c EN 8859 EXNAL Ex Submersible Pressure Transmitter.
• Installation instructions: H73227c Montage and Safety information
• ATEX Certificate: SEV 12 ATEX 0164 X
• IECEx Certificate: SEV 12.0007X
• DNVGL Marine Approval Documentation
• CE and UKCA Declarations of Conformity are mandatory.CE and UKCA Declarations of Conformity are required.

These documents facilitate engineers to make sure that the projects meet the requirement of the project and also regulatory requirements.

EXNAL 8859 outperforms standard submersible transmitters for several reasons.

There are several reasons why EXNAL 8859 beats the standard submersible transmitter.

A standard pressure transmitter can be used in a non-hazardous environment, but special equipment must be used for hazardous area applications.

Additional features included a standard submersible and EXNAL 8859.

Hazardous Area Use (HAU)

• Safe Areas Only (SAO)
• Zone 0/1/2 Approved (Z012A)

Max Temperature

• Typically 50°C
• Up to 80°C

Construction

• The material is a fully-welded construction, with O-rings common.It’s fully welded construction with O-rings common.

Material Options

• Stainless steel
• Stainless steel or Titanium

Certifications

• CE Only

Cable Options

• Basic PUR
• PUR or FEP

An uncertified transmitter in a classified HA can be a serious safety hazard and could be a non-compliance with insurance, regulatory and operational requirements. The EXNAL 8859 dispels these worries and offers long-lasting reliability.

Conclusion

Final Thoughts

The Trafag EXNAL 8859 is still one of the most powerfull Ex certified submersible pressure transmitters offered in 2026. ATEX and IECEx certified, hazardous zone 0 rated, pressure range 100 mbar to 25 bar, optional titanium construction, and robust PUR or FEP cable options, it is designed for the industries where reliability and safety are paramount.

The EXNAL 8859 provides accurate hydrostatic level measurement while meeting the strictest international hazardous area requirements in applications such as water treatment, oil and gas production, chemical processing, marine systems or mining operations. It is welded and has a long lifespan, plus a broad array of approvals that make it a favorite among engineers looking for reliable performance in tough conditions.

FAQ

What is the EXNAL 8859?

Trafag AG has developed a special Ex immersion/submersible pressure transmitter for continuous pressure and liquid level measurement in hazardous areas, the EXNAL 8859.

What output signal does the EXNAL 8859 use?

The EXNAL 8859 uses a 4–20 mA, 2-wire loop powered output signal.

What hazardous area certifications does the EXNAL 8859 carry?

The EXNAL 8859 carries:

• ATEX Certification: Ex ia IIC T3 to T6
• IECEx Certification: SEV 12.0007X 003
• DNV-GL Marine Approval

What pressure range is available?

The pressure range is 0–0.1 bar to 0–25 bar.

What industries use the EXNAL 8859?

Industries include:

• Water & Wastewater
• Oil & Gas
• Chemical Processing
• Marine & Offshore
• Mining

What cable options are available?

Users have the option of:

• PUR Cable – Excellent for water and wastewater use.
• FEP Cable – For fuels, chemicals, solvents and aggressive media.

Is titanium construction available?

Yes. The optional titanium casing offers outstanding corrosion protection.

Why does EXNAL 8859 outperform standard submersible transmitters?

The EXNAL 8859 offers hazardous area approvals, higher temperature capability, welded construction, advanced cable options and long-lasting reliability in hazardous environments.