Flare and Digestors

Unodourised Gas Risk Assessments

Safety within the Queensland gas industry is regulated under the Petroleum and Gas (Production and Safety) Act 2004 (Act) and the Petroleum and Gas (Production and Safety) Regulation 2004 (Regulation).

Where a person is supplying fuel gas to a consumer, section 628 of the Act requires that the gas has the prescribed odour or where the supply is to an industrial installation, the installation must have appropriate gas detectors and shut-down system, and a risk analysis that has been carried out by an appropriately qualified person showing the supply is safe.

Commonly a prescribed concentration of odourant is added to fuel gas, providing a distinctive and unpleasant odour to ensure its presence is readily detectable to a person without the use of gas detectors. Where un-odourised gas is present there is an elevated level of risk, and alternative or additional controls may be required. Any risk is further elevated where the gas is supplied into a plant room, where people are required to access plant and equipment as part of their duties.

Biogas is produced at the facility and is considered to be unodourised as the prescribed odourant is not added. It would be impractical and beyond economic viability to install and maintain odourising equipment at the plant due to the size, operational needs and location of the gas system.

Bluefield’s Technical Report and Risk Assessment addresses the risks associated with unodourised gas and meets the requirements of the ACT to ensure the risks are as low as reasonably practical for both people and plant.

Assessment guidance

The person undertaking the assessment should consider:

  1. The use of unodourised gas would normally not be accepted where equipment is located in an enclosure unprotected by an interlocked forced ventilation and equipment shutdown facility.
  2. Gas detection and shut down systems are to be appropriately designed, installed, commissioned and operational prior to the introduction of un-odourised gas to pipe work, fittings and gas devices on the site. The purpose is to ensure that wherever gas leaks are detected the installed detection and shut down system will remove the potential for an incident to occur. Such system(s) should be designed by experts in the field of gas detection.
  3. Where pipes, fittings containing unodourised gas and gas devices are enclosed and personal are required to access the plant the following applies:
  4. Forced ventilation through the enclosure is required with proof of ventilation airflow required prior to permitting an unodourised gas supply to the device. Ventilation must comply with AS5601:2005 sections 4.15-16, 5.4 and 5.5.
  5. AS/NZS 60079.10.1:2009 ‘Classification of areas – Explosive gas atmospheres’ (IEC 60079-10-1, Ed.1.0 (2008) MOD), must also be considered when a hazardous area under this standard or under AS2430: 2004 exists. Further AS1482:1985 ‘Electrical equipment for explosives atmospheres – Protection by ventilation – type of protection v’ specifically section 1 can also be considered in relation to electrical equipment.
  6. Activation of the gas alarm system at any level above 20 per cent of the LEL which is monitored at all times when a hazardous area under AS2430:2004 exists. Activation of the alarm/monitoring system at 40 per cent LEL shall cause the gas supply to automatically shut down, depressurise all enclosed pipe work and equipment and initiate requirements for evacuation procedures.
  7. Induction and training of relevant staff shall ensure that they are fully cognisant of the dangers of unodourised gas.
  8. Safety warning signs shall be placed at appropriate locations on the site including on pipe work to warn of the possible presence of unodourised gas.
  9. Written procedures for commissioning, maintenance and ongoing operation of the gas supply system must reflect the unodourised nature of the gas and be made available to all relevant staff.
  10. The installer, commissioning and or maintenance personnel shall have suitable equipment and the necessary training to ensure safety in dealing with the unodorised nature of the gas during the construction, commissioning, operational and maintenance phases of the project.
  11. Maintenance, testing and recording procedures are established to ensure the functional integrity of the gas detection system.
  12. A scheduled system and record of manual leak surveys is to be followed, requiring discovered leaks to be repaired immediately and a ‘close out’ audit process implemented.