Cylinders in Fires

Background

Gas cylinders are designed and constructed to safely contain a gas under pressure which, dependant on the type of gas and usage from the cylinder, can vary from a low pressure to a very high pressure.  If exposed to extreme heat, all gas cylinders are at risk of failure and may rupture due to a combination of over pressure and changes to the material properties of the cylinder shell.  The presence of flammable or oxidant gases can have a significant effect on the severity of the fire.  The Fire & Rescue Services are aware of this and have safe methods for dealing with gas cylinders involved in fires.

Exceptionally, dissolved acetylene has distinct properties which requires specific post fire actions. 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 dissolved acetylene cylinder to reheat after the initial fire is extinguished.

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

Put simply, there is no direct replacement for acetylene.  When handled, stored and transported correctly, acetylene is perfectly safe and has been invaluable to industry for over one hundred and sixty years.

From 2003 until November 2012, and only in the UK, the Fire & Rescue Services had what has since proven to be a somewhat excessive precaution for dissolved acetylene 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 led to major disruption, which, in turn, prejudiced safety away from the incident.

 

How did BCGA help?

BCGA members were actively involved in various initiatives to help:-

In 2006, BCGA bought together senior members of the Fire & Rescue Service, along with various Government Departments and Agencies, to work towards a solution. This resulted in the BAM research project, as detailed below.

BCGA created a document providing advice on dealing with cylinders in fire - BCGA L6

Acetylene suppliers are fitting special retro-reflective marking tape to dissolved acetylene cylinders to help the Fire & Rescue Service identify these cylinders more easily.

The Dangerous Substances Explosive Atmospheres Regulations (DSEAR) require users to undertake a comprehensive risk assessment to assess the potential risk from gases under pressure.  Flashback arrestors should always be used with flammable gases. The Health and Safety Executive (HSE) and BCGA fully endorse the mandatory use of flashback arrestors.http://www.hse.gov.uk/fireandexplosion/dsear-regulations.htm.

BCGA has developed a simple risk assessment model for oxy-acetylene users - BCGA TIS 15

A full DSEAR risk assessment model is summarized in BCGA GN 13.

BCGA worked with the HSE during the Consultation for the Acetylene Safety Regulations and fully support their requirements.

BCGA worked with The Fire Service College and the Chief Fire Officers Association (CFOA) to produce an acetylene training video.

BCGA has made agreement with online shopping companies, such as eBay, to ban the sale of dissolved acetylene cylinders through their sites as a way of restricting access to the product by untrained and unskilled individuals.

BCGA will continue to help the Fire and Rescue Services by providing expert advice and emergency response on acetylene incidents from member companies Competent Persons.

BCGA will continue to advise the Police and Highways Agency staff when dealing with road traffic incidents which involve gas cylinders.  Significantly, the research identified that mechanical impact to an unheated dissolved acetylene cylinder CANNOT initiate decomposition.

Research

Five stakeholder parties, namely BCGA, HSE, CFOA, the Department for Transport (DfT) and Transport for London (TfL) funded a major research project which was conducted over 2008 and 2009 by the German Federal Institute for Materials Research and Testing (BAM).  BAM is world renowned in acetylene science and research.

Their task was to find out, with certainty - after how many hours of realistic cooling to a dissolved acetylene cylinder 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.
  • Decomposition of acetylene cannot be initiated until at least 350 °C, meaning that only a cylinder which has been exposed to direct fire 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 direct concern to the Fire & Rescue Service.
  • BAM confirmed that the previous 24 hour cooling had been very excessive and that one hour cooling was more than enough in the vast majority of acetylene incidents.

The BAM work was discussed extensively with the Fire & Rescue Service and with the Department for Communities and Local Government's (DCLG) expert panel of consultant Professors.  A recommendation was accepted that one hour cooling, followed by a further one hour monitoring as a precaution would be more than prudent.  This agreed 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 revised one hour plus one hour protocol may be viewed by clicking here. 

The findings of the BAM research is of global significance, providing a scientific basis to the procedures adopted by our Fire and Rescue Service, and we trust that the new UK protocol may be adopted in other countries too and thereby mitigate needless disruption.

Fire & Rescue Service Guidance

The Fire & Rescue Service published their revised guidance, the Fire & Rescue Service, Operational guidance, Incidents involving hazardous materials, in November 2012.  The findings from the BAM research were incorporated into the guidance.

The Class 2 (gases) section of this guidance may beviewed by clicking here

The complete operational guidance is available here.

Acetylene Safety Regulations

The new Acetylene Safety (England and Wales and Scotland) Regulations - SI 2014 No. 1639 - came into force on 1 October 2014.  They include a very important new provision which MANDATES the use of flashback arrestors on oxy-acetylene sets.

The HSE provide guidance on the safe use of acetylene, along with a range of additional information, on their website. 

A copy of the Acetylene Safety Regulations can be downloaded here.

Fire & Rescue Service Acetylene Training Video

And finally, in 2015, BCGA worked with The Fire Service College and CFOA to produce an acetylene training video, which may be viewed below.

Publications

BCGA publish several publications providing advice on managing gas cylinders.  All BCGA publications are accessible via the ‘Publications' page.  The following are of interest:

  • BCGA CP 44 - The storage of gas cylinders
  • BCGA GN 13 - DSEAR Risk assessment
  • BCGA TIS 15 - Model risk assessment for the storage and use of gas cylinders for oxy-fuel applications
  • BCGA TIS 32 - Acetylene or propane (for welding, cutting and allied processes)
  • BCGA  L6 - Cylinders in fire