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Mechanical engineering

Application of the directive 94/9/EC to Gas Turbines - revised version

  1. It was accepted by all concerned that:

- Gas turbines on their own are not normally placed on the market as a single functional unit but are generally incorporated with other machinery before they can function, and will only function as intended once they are properly installed.

- Since 30 June 2003, manufacturers and users of gas turbines need to comply, in addition to the machinery directive, as appropriate with the requirements of both ATEX Directives 94/9/EC and 1999/92/EC respectively - relating to design and manufacture of such equipment and the health and safety of workers potentially at risk of explosive atmospheres.

- Gas turbine fuel supplies may give rise to a potentially explosive atmosphere in the vicinity of the turbine. Additionally, other sources of a potentially explosive atmosphere may also exist, e.g. lubricating oils. Equipment in category 3 of equipment-group II would usually be required in such areas.

- In normal circumstances, a gas turbine could have hot surfaces above the auto ignition temperature of the fluids used. Operation under fault conditions may increase surface temperatures.

- A gas turbine which has surface temperatures that can lead to the ignition of a potentially explosive atmosphere cannot comply with the relevant provisions of directive 94/9/EC. In such circumstances additional measures are required.

  1. It should be noted that in all instances of the following guidance the general concepts described in chapters and of the Guidelines on the application of directive 94/9/EC will apply (e.g. ATEX compliant equipment must be used, where applicable, inside machinery).

- Although manufacturers must, to the state of the art, eliminate or control sources of ignition, it may not be technically possible to reduce the temperature of all hot surfaces to comply with the Essential Health and Safety Requirements of the ATEX Directive 94/9/EC(1).

- A number of alternatives are available for selection as a basis for safety, e.g. limitation of the volume of the explosive atmosphere by dilution ventilation(2), explosion relief, explosion suppression or a combination of these techniques.

- A supplier (this may be the turbine manufacturer, packager, installer, final supplier, etc. and in some cases the end user) delivering gas turbine machinery and associated safety devices is responsible for risk assessment and implementation of the chosen basis of safety under Directive 94/9/EC. Irrespective of the chosen basis of safety there is the potential for an explosive atmosphere to arise near the turbine, and proper consideration should be given to minimising the risk of ignition. The supplier as described above is also responsible for the communication of instructions for safe use and any residual risk to the end user sufficient for the completion of risk assessments under the relevant work place directives.

- Interested parties should consider Chapter 3 of the Commission guidance on the ATEX Directive 94/9/EC, which provides further information on the relevant responsibilities.

  1. a gas turbine as a complete machine the ignition sources of which have no interface to a potentially explosive atmosphere outside the enclosure does, however, not fall under scope of the ATEX Directive 94/9/EC and as such cannot be affixed with the special marking for explosion protection and other marking detailed at Annex II, EHSR 1.0.5. of the Directive.
  1. intended to be used in a potentially explosive atmosphere.

(1) Annex II, EHSR 1.3.1 "Potential ignition sources such as …, high surface temperatures, ..must not occur".

(2) Dilution ventilation reduces the size of any flammable cloud to below that which would result in a hazardous explosion if ignited. In order that the dilution ventilation ensures a negligible risk of an explosive atmosphere at all times, the ventilation system should have additional safety features such as e.g.: a 100% standby fan; an uninterruptible power supply to the ventilation fans; interlocks so that the gas turbine cannot start without sufficient ventilation; proven automatic isolation of fuel supply if ventilation fails.

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