Communicating in hazardous areas

Radio communication has become a part of daily life in the UK, with a proliferation of new applications for voice and data appearing every year. But what if you need to use radio for communicating in a defined hazardous area? Mark Heaven offers some guidance on the raft of stringent legislation that apply.

ATEX approved intrinsically safe radios are essential for communicating in hazardous areas and when designed for this purpose and compliant with all relevant standards are among the best regulated products within the CE marking regime for the European Union. Radio communications are required everyday in a wide variety of hazardous situations and play a key role in the oil and gas industry, the utilities and emergency services.

The types of radio that can find their way into hazardous areas will include, but not be limited to, private mobile radio, security and site radios or terrestrial trunked radio. Operators may also find tri services voice and data communications, mobile telephones, speech and general packet radio services. Bluetooth is in common use for short range data and speech, headsets and other equipment for hands free radio operation. Then there are laptop computers with wireless internet access and other Wi-Fi connected equipment so it becomes clear that it is not prudent to rely on all radio users entering hazardous areas switching off at the right time. They may not even be aware they are carrying such a device, or that it might be dangerous in a particular set of circumstances that have developed, for example during an emergency.

To ensure safety, a radio communication system itself must meet or exceed standards defined in a variety of EU directives.

ATEX approval and radios

Compliance with the ATEX Product Directive 94/9/EC is crucial and mandatory, and is linked to the ATEX User Directive 1999/92/EC, which is applicable to hazardous locations and the people responsible for them.

In the directives, a radio device is defined as an intentional transmitter of RF energy to provide communication and as such must also comply with the requirements of the Radio and Telecommunications Terminal Equipment Directive 1999/5/EC known as the RTTE Directive. This encompasses four areas: Radio, Electromagnetic Compatibility (EMC), The Low Voltage Directive (LVD) and Telecoms.

A radio system of any description for use in a hazardous area must meet the mandatory requirements of two CE marking directives (with reference to five in total) and demonstrate compliance in four technically different areas. It is important to note that CE marking, and all its implications, is the responsibility of the manufacturer or the importer of the equipment. In the UK, HM Customs and Revenue, the Health and Safety Executive (HSE) Trading Standards and the end user are responsible for enforcing the regulations. Non-compliance may result in a hefty fine, withdraw of products from the market or in some extreme cases, for impeding an investigation, imprisonment for up to three months.

As an example, the reader could consider the requirements for a hand held, battery powered, walkie-talkie type site radio transceiver – a transmitter and receiver in one unit. The RTTE Directive will require the radio to meet a European Telecommunications Standard Institute (ETSI) electromagnetic compatibility and radio spectrum Matters (ERM) standard applicable to its operation and use as a radio device, including an Electromagnetic Compatibility (EMC) standard and a Low voltage Safety standard.

Radio approvals (1999/5/EC)

The typical Radio ERM standard is ETSI EN 300 086 for the Land Mobile Service intended primarily for analogue speech, covers the parameters in Table 1.

In our example, the areas covered by ETSI EN 301 489-5 Electromagnetic Compatibility (EMC) standard for radio equipment and services; Part 5: Specific conditions for Private land Mobile Radio are listed in table 2.

The Low Voltage Safety Approvals are set out in two standards. The user will select EN60065:2002/A1:2006 Audio, video and similar electronic apparatus - Safety requirements, or: EN60950-1:2006 Information technology Equipment - Safety - Part 1 general requirements. Whichever is chosen, there are five compliance tests to be met. These are listed in Table 3.

The radio transceiver must undergo all relevant tests for the RTTE Directive to enable it to be placed on the European Market and taken into service with a mandatory CE mark.

ATEX approvals product directive

To meet the requirements for use under the ATEX Product Directive 94/9/EC, the radio transceiver must be additionally assessed against the Essential Health and Safety requirements of Annex II, which usually involves the use of relevant sections of comprehensive and demanding standards. EN 60079-0: 2007 describes the general requirements for electrical apparatus for explosive gas atmospheres. Table 4 outlines the requirements for an intrinsically safe transceiver.

Part 11 of the standard (EN 60079-11: 2007) deals with requirements for intrinsic safety in equipment destine for use in potentially explosive gas atmospheres.

In addition the guide PD CLC/TR 50427:2004 Assessment of inadvertent ignition of flammable atmospheres by radio-frequency radiation, will require the radio transceiver to be reviewed under the headings of Transmitters and transmitter output parameters and Ignition of flammable atmospheres.

Designing intrinsically safe radios

In order to render a CE marked radio transceiver suitable for use in hazardous areas, certain features should be designed into it at the outset. Retrofitting later on is costly and not always feasible. Firstly, ensure that it is incapable of igniting volatile gases or particles. Secondly, eliminate the chances of various energy hazards, including high levels of Radio Frequency Energy, sparking, short circuits and heat generation. In order to do this, various design actions could be taken in accordance with the requirements of EN60079-0 and EN60079-11.

Ensuring that all the relevant parameters have been met, and that the radio is suitable for use in all hazardous areas, requires extensive knowledge of a variety of approval and certification requirements. As failure in a hazardous environment is too costly to take any chances, it pays to seek expert help and use approved laboratories for compliance testing, such as those of TRaC.

(source: HazardEx - The journal for hazardous area environments - July 2008)

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