What makes a good ATEX radio?

Published:  05 August, 2015

Mark La Pensee, Head of TETRA Subscribers Product Management, Motorola Solutions, describes the challenge of designing communications for ATEX environments.

Good design is never the product of a single big idea; rather, it is a combination of hundreds of small things being brought together, all driven by a deep understanding of user experience (UX). When it comes to creating new product for high risk industrial sectors the complications, difficulties and potentially dangerous processes a device and the user may come into contact with expand exponentially. This creates a considerable challenge for the designer.

Many industrial and transport facilities encompass large, complex environments, and these require integrated communication systems to facilitate effective and safe operations. Hazardous work areas within those facilities demand highly reliable, easy to use and intrinsically safe communication equipment to enable safe operations. Understanding what constitutes a ‘hazardous environment’ is therefore the first consideration when designing product to meet communications and operational requirements. When three conditions are met: there is a fuel source (a gas, a vapour, or some sort of ignitable dust); oxygen; and an ignition source, then we have a potentially hazardous environment. ATEX/IECEX radios are a prime example of intrinsically safe communication devices that are designed and optimised to meet these challenging working conditions.

When designing an ATEX two-way radio system, in conjunction with the intrinsic safety capabilities, there are five vital considerations to address: audio performance, coverage, ruggedness, accessories and critically usability.

The ATEX environment

Invariably, hazardous environments are loud, dirty, hostile places and these conditions will tend to define the uniqueness of an ATEX communications device. For the predominant user groups – firefighters; oil and gas; chemical; heavy industry; sea port; airport and mine workers - all are different in their deliverables to the market, yet share common environmental operating conditions.

Globally the majority of ATEX environments are found in the extremes, from the heart of the Middle East, where temperatures regularly exceed 45C and are extremely dusty, to Siberia where temperatures can drop below -20C with snow and ice. This drives the need for radios to operate in the most extreme environments, maintaining ATEX performance levels despite exposure to heat shock, dirt, oil, metal dust or chemicals.

For the numerous industrial fire services that deploy ATEX radios the risk of exposure to flammable materials and ignition from their equipment is very real. Their working environment is further exacerbated by the need to withstand exposure to multiple water jets and fire hoses. The result is the need for equipment able to provide multiple levels of IP protection even after thermal cycling, heat shock and drop testing.

Usability and ergonomics

Being tough is only the start of the design process, critically a significant number of user groups operating in ATEX environments will expect to be wearing gloves and possibly masks, helmets and other protective clothing when using their communications equipment. This means the radio and accessories need to be optimised for use by people who may have reduced tactility in their fingers, possibly restricted vision and almost without exception, are working in a loud ambient noise environment. This drives design considerations to ensure users can continue to communicate regardless of potentially major restrictions to their normal senses.

A further aspect of usability is the duration of radio use between charges. Some users will be required to operate long distances from a charger or suitable power source and this encourages a need for extended usage time, beyond an average shift of eight hours.

Audio

Invariably industrial fire response equates to constant and very loud environments, usually in excess of 90dB which is deemed harmful to hearing. The most obvious requirements are that the two-way radio communications equipment be able to operate with clear audio that can overcome the background noise and be sufficiently rugged to withstand daily exposure to all types of dirt and dust. But the equipment must do all this whilst not providing any ignition source to the hazardous environment.

And here we encounter perhaps one of the toughest technical challenges of communications in an ATEX product. The ATEX standards restrict the amount of current that can be used to drive the speakers in the radios and accessories. This in turn directly impacts the loudness and clarity that can be generated.

The challenge is to drive the speakers to the loudest, clearest possible level to overcome the 85-90dB ambient noise levels, all without resulting in the radio becoming an ignition source.

We also find that in certain environments the ambient noise is of a ‘different’ type. The sound of a pump bay on the fire truck will be very different to the sound of a steel plant. The actual noise levels, the loudness, can be very similar, yet the frequencies which are generated can result in very different audio interferences. This requires radios and accessories to be optimised for each particular type of ambient background noise.

Network and radio coverage

Often the networks in which an ATEX radio is used will be privately owned, by the plant or facility, in which the radios are being used. In the case of civil firefighters, they will often operate on a regional or nationwide public safety network. In both of these situations, the communications managers will still want to optimise their network to minimise capital investment whilst maximising coverage.

Receiving a signal in the radio does not necessarily cause any major challenges from an ATEX perspective, however when transmitting voice or data from the radio, some of the internal components can generate heat. This in turn can raise the temperature in outer skin of the radio, and the hotter the skin, the higher the risk of ignition of gas or a dust.

With more efficient radio frequency (RF) design, higher transmission power can be achieved without creating an ignition source. The ETSI standard allows manufacturers to declare their transmission class with a +/- 2dB tolerance. While all manufacturers declare they are Class 4 (1W), when their transmit (TX) power is measured we see it is actually closer to 0.7W. This obviously impacts the ability for a radio to operate in poor coverage areas of a facility and can result in ‘dead spots’ where communication is lost altogether. This is why higher transmission power and a more optimised system design is necessary to provide maximum coverage, ensuring users are always connected, can hear all messages broadcast and can respond in all emergencies.

ATEX accessories

An ATEX radio communications solution does not stop at a radio. There is a wide range of user requirements when it comes to accessories. Most are tailored for use in a particular environment and this has resulted in an array of accessories required by the numerous ATEX users. Alongside physical NEXUS jack connections used to extend an ATEX solution, the addition of classic Bluetooth (2.1) and secure and energy-efficient Smart Ready Bluetooth (4.0) enables further connectivity and new applications via wireless link to a host. This drives the requirement for advanced interoperability across multiple types of accessories: remote speaker mics; skull mics; boom mics; noise cancelling headsets; hardhat solutions; smoke diver face masks; earpieces; and large push-to-talk buttons; data collection tablets and smart devices; biometrics such as heart rate monitors; location sensors; and environmental sensors that can monitor for, and alert the worker when, dangerous gas levels are detected.

Addressing this enhanced flexibility, brought about by wired and wire-free connectivity options, increases the demand for better, forward looking design and, through the addition of greater intelligence is helping to redefine ATEX radio systems. This has the potential to dramatically improve workers’ operational capabilities while ensuring the highest level of personal safety.

These requirements demonstrate the extraordinary technical challenges in delivering communications equipment which not only meet end user needs, but also comply with the ATEX and IECEX standards demanded across the industrial fire sector.

Motorola Solutions offer two TETRA ATEX radios, the MTP8500Ex and MTP8550Ex models.

  • Operation Florian

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