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

Recommendations

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 AS4645 AS1596 AS1668		AS/NZS ISO 31000-2009 (formerly AS4360)
Industrial	AS3814 AS5601 AS2885 AS4645 AS1375		AS/NZS ISO 31000-2009 (formerly AS4360)
Piping	AS2885 AS1697	AS2885 is a mandatory Standard in P&G Regulation	AS/NZS ISO 31000-2009 (formerly AS4360)
Flares	AS3814		AS/NZS ISO 31000-2009 (formerly AS4360)
Other/vehicle workshops	AS2746 AS1425 AS1668		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

IGEM IGE/UP/1, Edition 2, Communication 1716, Strength testing, tightness testing and direct purging of industrial and commercial gas installations
IGEM IGE/SR/23, Communication 1623, Venting of natural gas

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.