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Petroleum and gas safety alert no. 45 | 01 July 2010 | Version 1

Purging gas piping

What happened?

A number of incidents have occurred either during commissioning or re-connection of gas pipe work after maintenance work, where purge gas has been released to an uncontrolled environment and ignited. The February 2010 incident in Middle town (Connecticut – USA) highlighted this issue, where six workers died and a number of others were seriously injured. This was a gas power plant under construction, and near the final completion stage of construction/commissioning.

A series of purges of the gas pipes had been undertaken a week earlier without incident. A week later, another series of gas purges were conducted and on the final gas purge, an explosion occurred with tragic results.

The US Chemical Safety and Hazard Investigation Board have approved 18 urgent recommendations http://www.csb.gov/newsroom/detail.aspx?nid=330 While the legislative framework and practice in US is significantly different to Queensland, these incidents and this safety alert are a reminder to all operators, staff, their employees and contractors to take particular care when purging systems with gas.

Safety issues identified

  • Lack of risk assessment and hazard identification
  • Limited or no gas monitoring
  • Multiple ignition sources in the vicinity
  • Procedures not adequately documented and or implemented
  • Lack of sufficient/competent supervision—ad-hoc coordination of personnel/contractors
  • No communication of tasks/planned events. Workers unaware purging taking place


Compliance/regulatory issues

  • Identify the regulatory framework.
  • Identify related Australian Standards or industry codes of practice for purging requirements for pipe installation appliance e.g. AS2885, AS5601, AS NZS 4645, AS NZS 1596 etc (See Table 1 – this list is not exhaustive).
  • Ensure local authorities e.g. EPA / Councils are consulted or and approvals sought where applicable.

Understand the risks

  • Conduct a risk assessment to identify all the hazards especially potential ignition sources and develop adequate control and or mitigation measures.
  • Ensure gas type/properties identified, e.g. density, static electricity issues.
  • Consider if non-flammable/inert gases can/should be used in the purge process.

Implementation issues

  • Ensure purge gas is directed away in such a manner that it can be adequately ventilated e.g. vent pipes are used, with minimum pre determined exclusion zones from the outlet (based on risk and hazard assessments).
  • Ensure gas release area is clear with adequate ventilation, wind direction identified, and ignition free exclusion zone established with appropriate signage.
  • Ensure burning/ flare stacks are approved equipment for the specific tasks.
  • Ensure a system/s of work is employed (for example, work permitting).
  • Ensure adequate resources (personnel & equipment) are in place for tasks.
  • Ensure competently trained staff for continuous gas monitoring are in place.
  • Ensure emergency plans are developed, in place and communicated.
  • Ensure communication plan is in place.

Appliance installation types and relevant standards and legislation

  • This was originally published as a separate notice called 'Additional information'.
Appliance installation Standard/s Legislation comments General comments
Commercial AS5601

AS/NZS ISO 31000-2009 (formerly AS4360)
Industrial AS3814

AS/NZS ISO 31000-2009 (formerly AS4360)
Piping AS2885
AS2885 is a
Standard in P&G
AS/NZS ISO 31000-2009 (formerly AS4360)


AS/NZS ISO 31000-2009 (formerly AS4360)
Other/vehicle workshops AS2746

AS/NZS ISO 31000-2009 (formerly AS4360)

Other standards

This is not meant to be a definitive list of all the standards (Australian and or International).

  • AS1375 – 1985 Industrial fuel fired appliances code
  • AS/NZS 1425 – 2007 LP Gas fuel systems for vehicle engines
  • AS/NZS 1596 – 2008 Storage and handling of LP gas
  • AS1668 – 2005 The use of ventilation and air conditioning in buildings
  • AS1697 – 2005 Installation and maintenance of steel pipe systems for gas
  • AS2746 – 2008 Working areas for gas fuelled vehicles
  • AS2865 – 2001 Confined spaces
  • AS2885 – 2007 Pipelines – Gas and liquid petroleum - Design and construction
  • AS3645 – 2010 Essential requirements for gas equipment
  • AS3814 - 2009 Industrial and commercial gas-fired appliances
  • AS 3961-2005 Liquefied natural gas - Storage and handling
  • AS4645 – 2008 Gas distribution network management
  • AS5601 – 2008 Gas Installations
  • AS/NZS ISO 31000-2009 (Formerly AS4360) – Risk management – Principles and guidelines
  • AS/NZS 60079.10.1:2009 (Formerly AS/NZS 2430.3.5:2004 Classification of hazardous zones)
  • Explosive atmospheres - Classification of areas

Consider also

Investigations are ongoing and further information may be published as it becomes available. The information in this publication is what is known at the time of writing.

We issue Safety Notices to draw attention to the occurrence of a serious incident, raise awareness of risks, and prompt assessment of your existing controls.

Authorised by Chief Inspector, Petroleum and Gas

Contact: Chief Inspector, Petroleum and Gas

Issued by Queensland Department of Employment, Economic Development and Innovation