Hello, Would like feedback on this statement. I have read in many places that this can be used as a control measure and also reduces the zoning to 21 instead of 20. However on the other hand i have had people saying to me that there is still a chance to have an explosion in the remaining 30% it's just a matter of getting right concentration. Feedback on this would be appreciated Katie

Katie, Logic would suggest that if you have a smaller volume of whatever to explode then you get a smaller explosion. You still get an explosion though... A

I was led to believe (depending on the flashpoint of the product)that an empty receptacle i.e. nominally empty / still residue left within, is as dangerous as a full receptacle, sometimes more so, take a 205 litre drum of petrol, the less petrol there is in the drum then the more vapour/air mixture will be produced, which as mentioned depending on LEL & UEL could ignite on the introduction of an ignition source. If the drum is full less vapour air mixture will be present so would reduce the possible likelihood of explosion or ignition.

The guidance relating to Dangersous Substances and Explosive Atmospheres Regulation (DSEAR) suggests various ways to reduce risks from explosions. One of the suggestions is that you avoid ctreating an explosive atmosphere. For an explosive atmosphere to be present you would need air therefore it would follow that the more a silo was filled the less air it would contain and the less likely the risk would be, so in theory it could work as a control measure but only as ONE of a number of control measures. As I am sure you are aware that there are numerous other factors to consider and not just this one in isolation.

quote=Brian Hagyard]Katie Not sure I fully understand your question, but I had a similar understanding to phargreaves. For me the example is a nominally empty bottle of lpg where the gas and air mixture could be such that the explosive limit is reached and if a spark or other ignition source is applied the consequences could be worse than with a full bottle of lpg.

quote=Holbrook42275]The guidance relating to Dangerous Substances and Explosive Atmospheres Regulation (DSEAR) suggests various ways to reduce risks from explosions. One of the suggestions is that you avoid creating an explosive atmosphere. For an explosive atmosphere to be present you would need air therefore it would follow that the more a silo was filled the less air it would contain and the less likely the risk would be, so in theory it could work as a control measure but only as ONE of a number of control measures. As I am sure you are aware that there are numerous other factors to consider and not just this one in isolation.

Belive I was not aware that lpg cylinders were in a vacuum state before being filled - so there must be some level of air in them at all times? As the amount of LPG falls the explosive limits can be met. Say for example in a fire situation a full bottle of lpg may become damaged and the gas be expelled and burn, my understanding was a nominally empty cylinder could explode. If this information is incorrect I would welcome advice. There only appeared to be 1 question in your post why the extra 9 question marks?

jj you are correct that in reading the thread I had forgotten the reference to the zones at the very beginning and that it was reference to dust, I apologise if I have confused the original poster. However as with all threads the theme often develops and expands, and as for what people know or don't know it is often only by asking supplementary questions that we expand our knowledge and learn. I have not yet learned everything there is to know about everything and I doubt I ever will.

PVE At the risk of being accused of hijacking this thread thank you for that information. I accept that in an intact cylinder the conditions for an explosion are unlikely. However people may be interested in the following hse information. http://www.hse.gov.uk/fo...d/oc/200-299/286_102.pdf Clearly there are situations were residuary LPG and air can mix and the LEL be reached.

Well thank you for the advice. Yes sorry to confuse anyone, it was regarding dust. Thanks again, Katie

Katie The fuller the cylinder the less chance of a hot (as against cold caused by e.g. impact) Boiling Liquid Evaporating Vapour Explosion ('BLEVE" - lots of dramatic footage if google search). A hot BLEVE is initiated by the heating of a vessel containing a liquefied gas e.g. by flame impingement or a pool fire. This leads to the liquid boiling, vapourising the gas and increasing the pressure in the vessel. This results in a pressure release valve venting and the release of vapour. If this, like LPG, is flammable, it is likely to be ignited, either in a second fire or by adding to the fuel for the original fire. Continued heating of the tank, particularly of any unwetted part leads to failure of the vessel with resultant BLEVE. HSE assess on the basis of the fuel representing 90% of the contents of a vertical container such as a cylinder, or 50% of the contents of a horizontal container such as most LPG tanks. It's about having enough bare unwetted metal to heat up. www.hse.gov.uk/landuseplanning/failure-rates.pdf In the Netherlands they assume that you can have a 100% BLEVE and they assign probabilities of hot BLEVE on the basis of 100%, 66% and 33%. The emptier the vessel the more probable a BLEVE, but conversely with less consequence than for a fuller vessel. www.rivm.nl/milieuportaa...-CONCEPT-20-okt-2009.pdf - how's your Dutch!!