The new International Standard on gas turbine safety has been under development for over seven years, originally initiated by EuMIGT (European Manufacturers of Industrial Gas Turbines). The standard was published on 12 February 2009.

The standard grew from concerns over a perceived risk of incidents, and the need for a uniform approach to safety. Desire for the provision of recognised means of compliance with relevant European Directives was also a strong factor in the decision to proceed with the development of the standard.

The standard covers the safety requirements for gas turbine applications using liquid or gaseous fuels and the safety-related control and detection systems and essential auxiliaries for all types of open cycles (simple, combined, regenerative, reheat, etc.) used in onshore and offshore applications including floating production platforms.

It applies to driven machineryonly where it is an integral part of the gas turbine (e.g. a gearboxintegral to the gas turbine), or is located within the gas turbine enclosure and forms part of the enclosure hazardous area classification (e.g. a generator within the gas turbine enclosure), or where the driven machinery has a direct effect on the operational safety of the gas turbine. It excludes gas turbines used primarily for direct and indirect propulsion, special heat source applicationsand in research and development programmes. It also excludes gas turbines for closed-cycleand semi-closed cycle applications, and compressed air energy storage plants. Where appropriate, it may be used to give
general guidance in such applications.

The standard details the anticipated significant hazards associated with gas turbines and specifies the appropriate preventative measures and processes for mitigation or elimination. It addresses the risks of injury or death to humans and risks to the environment. Equipment damage without risk to humans or
the environmentis excluded.

At the beginning of the standard’s development process, very considerable concern was expressed at the restrictions that a prescriptive set of rules would impose on a well established industry with well established procedures. So far as possible, the working group drafted the standard in terms of objectives, often based on risk assessment, and minimised prescriptive clauses except where it was felt that such detail was really necessary to ensure safety, and where agreement could be reached. In this respect, a very high level of agreement was generally reached, beyond the normal level of consensus recommended by ISO.

Risk assessment is increasingly used internationally by safety professionals and in legislation. It has been embedded in ISO 21789 which states that risk assessment is …“the overriding principal that should, where applicable, be applied to all the requirements of this International Standard.‚

The standard deals with every recognised hazard associated with the gas turbine and associated equipment within the limitations of the scope described above. Therefore it deals with mechanical, electrical, noise, thermal, fire, explosion, and environmental hazards etc., including the following:

Crushing, cutting, severing, trapping, entanglement, falling Rotating parts failure Casing failure Contact with live electrical parts Electrostatic, electromagnetic, lightning Thermal radiation, hot & cold burns Asphyxiation Poor ergonomics Vibration, metal fatigue Fire Explosion Control system failures Power supply failure Gravity, seismic, wind effects

The standard is primarily for the use of equipment manufacturers, packagers and suppliers as a means of demonstrating safety for the benefit of purchasers and users. It is not possible to directly include requirements on operation or maintenance in what is essentially a procurement standard such as ISO 21789 since such requirements cannot be verified. However the working group decided that the omission of any such guidance was unacceptable. A substantial section has been included which specifies the minimum information to be included by suppliers in manuals.

It is essential that a procurement standard of this type should contain methods of verification of compliance. This has been achieved in ISO 21789 by means of a detailed four page table which shows verification means against each clause of the standard.

Plans are now in hand to arrange the conversion of the standard into a harmonised European standard as originally planned.

It is to be hoped that the new standard will assist in the improvement of the safety record for new plant and will provide suppliers and users with a benchmark for the review of existing plant.

The standard is available from the ISO website. To view it please click here

Roger Santon, Convenor, ISO TC/192, WG10