Cylinders in Fires

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Background

Like all closed metal containers, gas cylinders present an explosion risk if exposed to fire. Fire and Rescue Services (FRS) are aware of this and have safe methods for dealing with cylinders involved in fires.

If the contained gas is flammable, or is oxygen, this can considerably increase fire loads. But dissolved Acetylene (DA) has distinct properties which require special precautions. The direct heat of a fire may, in extreme circumstances, initiate decomposition of Acetylene. This is an exothermic (heat creating) reaction, which can cause a DA cylinder to reheat after the fire is extinguished.

From 2003 until recently, and only in the UK, FRS had what has since proven to be a somewhat excessive precaution for DA cylinders, which involved water cooling them for at least 24 hours, during which a hazard zone of 200 metres radius was usually maintained throughout. Whilst very safe, this often lead to major disruption, which, in turn, prejudiced safety away from the incident. The UK protocol had been at odds with what previously operated safely in the UK prior to 2003 and still operated safely in other countries.

Acetylene is the most flexible oxy-fuel gas and is used across multiple welding and metal cutting applications.

Put simply, there is no replacement for it and when handled, stored and transported correctly, Acetylene is perfectly safe and has been invaluable to industry for over one hundred and fifty years.

What could be done about the disruption?
In 2006 the BCGA joined senior representatives from the Fire Service, Health and Safety Executive (HSE), Department for Transport (DfT), Department for Communities and Local Government (DCLG), Highways Agency, Police, Network Rail, Transport for London (TFL) and others, to form a National Stakeholder Group (NSG) to work together on the issue.

What could Acetylene suppliers do?
BCGA members offered various initiatives to help:-

An advice leaflet was prepared for DA users - BCGA Leaflet L6. Download this document for free.

Special retro-reflective marking tape is being applied to DA cylinders, to help the FRS identify DA more easily.

The UK's DSEAR (Dangerous Substances Explosive Atmospheres) Regulations require users to undertake a comprehensive risk assessment that mandates the use of flashback arrestors (it is not clear that all users are fully aware of DSEAR). BCGA fully endorses the mandatory use of flashback arrestors.

BCGA has developed a simple risk assessment model for oxy-acetylene users - available free to download as TIS15

Click here to download the document.

A full DSEAR risk assessment model is summarized in BCGA Guidance Note GN13.

Members :
click here to download the document.
Non-members: click here to purchase.

BCGA has made agreement with EBAY to ban the sale of DA cylinders through their site as a way of restricting access to the product by untrained and unskilled individuals.

BCGA will continue to help the Fire Service through training and provision of training material to hazmat officers within the Fire Service. In addition, BCGA members offer the emergency services expert help at incidents through our Competent Person Scheme.

BCGA has also advised on the potential effects of mechanical impact to DA cylinders, which will help police and Highways agency staff when dealing with road traffic incidents.

In summary cold impact alone to an acetylene cylinder CANNOT initiate decomposition.

 

Acetylene Regulations

The new Acetylene Safety (England and Wales and Scotland) Regulations - SI 2014 No. 1639 - came into force on 1 October 2014.

The Health & Safety Executive (HSE) provide guidance on the safe use of acetylene, along with a range of additional information, on their website.

A copy of the regulations can be downloaded here.

 

Research

Five Stakeholder parties, namely BCGA, DfT, HSE ,TFL and, latterly, CFOA co-funded major research conducted over a period from 2008 and 2009, by BAM, the German Federal Institute for Materials Research and Testing. BAM is world renowned in Acetylene science and research.

Their task was to find out, with certainty - after how many hours of realistic cooling can we be sure that no decomposition can be ongoing and therefore that it is safe to close out an incident completely?

The results from the BAM work may be summarised as follows:-

  • Mechanical impact alone CANNOT initiate acetylene decomposition.
  • A robust combination of heat transfer experimentation and computer modelling has produced a model which could be questioned for various "what if?" scenarios, eg cooling rates etc. The modelling conclusions were then confirmed through small and full scale fire tests.
  • Decomposition of acetylene cannot be initiated until at least 350°C, meaning that only a cylinder which has been exposed to direct flame impingement can be at any risk.
  • Polymerization reactions of acetylene can occur at temperatures below 300°C, but these are pressure-reducing reactions and therefore not of concern to FRS.

And finally, the BAM work confirmed that the 24 hour precautionary cooling period had been very significantly excessive.

The scope and validity of the BAM work was discussed extensively with the Fire Service and with DCLG's expert panel of consultant Professors and a recommendation was accepted that just 1 hour cooling followed by a further 1 hour monitoring precaution would be more than prudent. It is no coincidence that the findings of the BAM research agreed exactly with the empirical evidence found at real incidents.

The Executive Summary report on BAM's work may be viewed by clicking here.

And BAM's Opinion on the proposed 1+1 hour protocol may be viewed by clicking here.

The conclusions of the BAM work were incorporated into new UK FRS HazMat guidance published in November 2012. The gases section of this guidance may be viewed by clicking here.

The findings of the BAM Research is of Global significance to both Fire and Rescue Services and others alike and we trust that the new UK protocol may be adopted in other countries too and thereby mitigate needless disruption.

Download the full document from the government website.