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We develop and manufacture sensors designed for use in hazardous areas in accordance with ATEX (2014/34/EU) and IECEx, from the standard version through to the custom-built transducer.
Intrinsically safe sensors for hazardous areas: explosion protection ATEX / IECEx
In the chemical industry, in oil and gas production, in mining, in milling operations and in wood and animal feed processing, gases, vapours or dusts can create explosive atmospheres. Electrical equipment — and with it the measuring technology in use — must under no circumstances become a source of ignition there.
The type of protection of choice: intrinsic safety (Ex i)
For sensors based on strain gauges, the type of protection intrinsic safety (Ex i) is the technically most elegant and safest solution.
The principle rests on consistently limiting the electrical energy inside the hazardous area. Voltage, current and power in the sensor are kept so low that even in the event of a fault — a short circuit or a broken wire, for instance — neither ignitable sparks nor impermissibly high surface temperatures can arise.
Depending on the zone required, we supply versions in Ex ia, intrinsically safe even with two independent faults and therefore suitable for zones 0 and 20, or Ex ib for zones 1 and 21.
Flameproof enclosure (Ex d) on request
Intrinsic safety only works as long as the energy inside the device can be limited sufficiently. As soon as more power is needed — for integrated amplifier electronics, a display or a fieldbus connection directly in the hazardous area — the flameproof enclosure comes into play.
With this type of protection the ignition source is not avoided but contained: the housing withstands an internal explosion and, through defined gap dimensions, prevents flames from breaking through to the outside. The advantage for you lies in the connection, because no Ex barrier is needed and standard signals can be transmitted directly. In return the housing is heavier and larger, and it must not be opened during operation.
We supply such versions on request, as well as combinations of the types of protection. Which one is the more economical for your application is something we clarify on the basis of zone, signal type and installation situation.
The zones at a glance
| Explosion hazard | Gases & vapours | Combustible dusts | Description of the atmosphere |
|---|---|---|---|
| Continuously or long-term | Zone 0 | Zone 20 | An explosive atmosphere is present continuously, for long periods or frequently |
| Occasionally | Zone 1 | Zone 21 | Occurs occasionally in normal operation |
| Rarely and briefly | Zone 2 | Zone 22 | Does not occur in normal operation, and if it does, only rarely and briefly |
Ex versions in our range
Explosion protection is not confined to force measurement. Ex-certified versions are available in several product areas:
- Load cells and force transducers with Ex protection, including load pins and special transducers
- Temperature sensors in ATEX and IECEx versions
- Pressure sensors and pressure switches
- Level measurement for tanks and silos holding combustible media or dusts
- Flow measurement
- Measuring electronics for the safe area
Which zone and which equipment category your application calls for is something we clarify together before the selection is made.
What the nameplate says
A complete Ex marking covers more than the zone. These details determine which version you actually need:
- Equipment group and category, for example II 1G for zone 0 or II 2D for zone 21
- Type of protection, with strain-gauge sensors Ex ia or Ex ib
- Explosion group, IIA to IIC for gases and IIIA to IIIC for dusts, with IIC and IIIC the most demanding
- Temperature class T1 to T6 for gases, or the maximum surface temperature for dusts
- Ambient temperature range, which can be narrower on Ex equipment than on the standard product
Give us these details from your explosion protection document and we will propose the matching version. If you do not have them to hand, medium, zone and temperature range will do to start with.
Design features of our Ex sensors
Explosion protection places high demands not only on the electronics but also on the mechanics.
Hermetic sealing. The strain gauge bridge is hermetically sealed by laser or micro-plasma welding. With protection ratings up to IP68, the ingress of the finest dusts and of aggressive gases is permanently prevented. The mechanical production involved is done in house.
Housing materials. We use corrosion-resistant stainless steels that withstand aggressive chemicals, salt water and mechanical damage. Friction sparks from light metals are ruled out by design through the choice of material.
Ex-compliant cabling. The signal is led out through approved PUR, PTFE or silicone cables, strain-relieved and resistant to high temperatures, or alternatively through approved connectors.
Antistatic surfaces. Electrostatic charging is avoided by design, which matters particularly in the dust zones 20 and 21.
System integration: working with the Ex barrier
An intrinsically safe sensor is always only one part of the safety chain. The sensor in the hazardous area must be connected through an associated apparatus — an isolating switching amplifier or a Zener barrier.
- Hazardous area: the sensor in Ex ia or Ex ib
- Boundary to the safe area: the Ex barrier, which limits the energy and separates the potentials
- Safe area: measuring amplifier, indicator or PLC, connected in analogue form or over a fieldbus
On request we supply not only the sensor but design the entire measuring chain with you.
When functional safety is required as well
In practice, explosion protection and safety engineering often meet — in overload cut-outs on lifting gear in chemical plants, for instance, or in silo weighing with limit-value shutdown. The two do not exclude each other: we supply transducers that are intrinsically safe and redundant at the same time. More on this under functional safety to SIL and PL.
Tailor-made explosion protection
Standard products often reach their limits in complex plants. We develop transducers that fit mechanically into your existing design with precision while meeting the standards required for explosion protection. The documentation and the certificates you need for your plant are part of the delivery; further details of our records can be found under quality and certifications.
Talk to our engineering team about your application. Tell us the medium, the zone, the temperature range and the measured quantity, and we will propose the matching sensor together with its connection.