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 be viewed 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