Cylinders Flashcards
(17 cards)
A cylinder can be defined as
any vessel containing a gas or liquid under pressure
In what form are gases stored within cylinders
Gases are stored in either a liquefied form (e.g. LPG), as a compressed gas (e.g. oxygen), or, in the case of acetylene dissolved in a solvent and stored in special cylinders containing a porous mass within the steel shell
What are the four types of cylinder construction
- Welded cylinders: two steel halves welded together around the centre.
- Drawn steel: a single steel skin containing no weld.
- Aluminium cylinders: lighter in weight than steel cylinders and used to contain specialist gases.
- Composite cylinders: a woven “fabric” jacket impregnated with resin and protected by a hardened plastic outer cage. This type of cylinder is mainly used for LPG but can be found with various contents. Occasionally these cylinders can have an aluminium inner lining.
During the risk assessment carried out by the IC who else will provide assistance to him?
ICs will be supported in this decision making process by the hazardous materials and environmental protection officer (HMEPO) attending the incident. They, in turn, may be supported by the British Compressed Gas Association (BCGA) competent person (BCGA CP) and/or the Scientific Adviser - where appropriate
Are HMEPOs mobilised to all cylinder incidents?
HMEPOs are mobilised to all cylinder incidents and have received specific training for dealing with acetylene cylinders and hazard zone (HZ) management.
What happens to cylinders are they are heated
As a cylinder is heated the steel or aluminium shell loses its tensile strength (300oC for steel, 200 – 250oC for aluminium)
All cylinders ultimately fail because the shell reaches a point where its tensile strength weakens and can no longer contain the increasing internal pressure. In the case of composite cylinders the resin will begin to break down and becomes porous.
What happens to a composite cylinders that are involved in direct flame?
Where a composite cylinder is involved in direct flame impingement the cylinder may become porous, this will be evident by a substantial increase in the size of the fire as it will be fed by the gas from inside the cylinder.
How can you deal with composite cylinder that is involved in a direct flame impingement and the cylinder has not yet become porous?
the fire can be extinguished and the cylinder cooled. However, caution should be taken when moving any composite cylinder as the resin may have become weakened to an extent where it may begin to leak when handled. In these situations it is best to leave the cylinder in situ and consult the HMEPO
How do you treat an unidentifiable cylinder?
If a cylinder could potentially be acetylene, but it is not possible to confirm the contents, then it must be treated as being an acetylene cylinder
If a steel cylinder fails what is the potential distance fragments may be projected?
up to 200 metres
what is the potential effect of a cylinder failing
When a cylinder fails this causes the contents to escape and may ignite causing a fireball of up to 25m in diameter and throw debris up to a distance of 200m
How are acettylene cylinders designed to fail
Acetylene cylinders are designed to fail in ductile mode and split along their entire length. However, if a partial split occurs the cylinder itself can be propelled up to 200m
Actions en route,
Once an IC becomes aware that cylinders may be involved in a fire, either by additional information supplied by Brigade Control or by the nature of the premises, what considerations should be given?
A safe route of approach and the subsequent positioning of appliances.
• The possibility of acetylene cylinders being involved.
• The use of the initial hazard zone overlay
The surrounding risks that may become involved if a HZ is implemented – railway lines, major roads or public buildings etc.
• Early notification to Brigade Control of an appropriate RVP.
• Any additional information received from Brigade Control or locally.
What actions should be carried out on discovering a cylinders at a fire?
As soon as a cylinder is discovered at a fire, regardless of the contents, ICs should make every effort to extinguish any fire affecting the cylinder and apply a cooling spray directly onto any affected cylinders. This will immediately begin to restore the tensile strength of the cylinder and reduce the likelihood of cylinder failure. (In the case of composite cylinders the application of the cooling water will prevent further breakdown of the resin). This needs to be carried out from behind substantial cover such as suitably constructed double skin brick wall HMEPOs have been given additional training in determining the suitability of substantial cover. Where the cylinder(s) is currently not being affected by the fire and has not been affected prior to arrival, then the IC should consider protecting the cylinder(s) by the use of covering jets or having the cylinder(s) moved to a safe location
How do you deal with a composit cylnder that has failed?
Where a composite cylinder is involved and has failed, the contents should be allowed to burn off before extinguishing the fire. The extinguishing of the fire prior to this will allow a potential build up of un-burnt gases. ICs should ensure they protect the surrounding risks whilst allowing the contents of the cylinder to burn off.
What should the IC do where cylinders that have been confirmed as not containing acetylene are involved in a fire,
Where cylinders that have been confirmed as not containing acetylene are involved in a fire, the IC should consider implementing a HZ of 200m (See appendix 3 for further details of HZ management). However, the time to do this compared to the time taken to cool the cylinder will need to be taken into account.
what does the CAP (Cylinder Assessment Process) consists of
Stopping the application of cooling water after one hour:
• Monitor the cylinder with a thermal imaging camera (TIC) and record temperature.
• Observe for any violent steaming* or rapid drying out of the cylinder surface.
• Leave cooling water off for 15 minutes.
Apply a momentary spray of water to the cylinder then shut off.
The above process must be completed 4 times (a total of 1 hour).
*Violent steaming – It should be noted that this steaming would be the equivalent of when red hot metal is plunged into cold water and not a gradual drying out consistent with the atmospheric conditions of the day. The critical temperature is around 300° centigrade. At these temperatures any water will violently react and boil off the surface.
