I ask again!!  What is/does cause a gas explosion in a van??

Seems to be too many recently and I'm sure in the past.

Helen

The gas itself is odourless and colourless and heavier than air so settles low down. Very slow leaks can settle without being sniffed so as Stoney says a good detector is essential.

Just as an aside I lived in Scotland for a couple of years near a place that manufactured the "Smell" that was added to the gas.

They had a major leak and the emergency services were activated. Police Firies ambos. the whole shebang.Police touring with loudspeakers telling people to turn off pilot lights have no naked flames.

Seems the plant didn't inform the authorities that it was just a smell and not inflammable in itself.

The name of the Plant was "Lurgie" as in the dreaded.

I kid you not

adreamer wrote:

---

I ask again!!  What is/does cause a gas explosion in a van??

Seems to be too many recently and I'm sure in the past.

Helen

---

Hello adreamer

I will assume that no Gas Fitters have seen this thread, therefore from a layman point of view, I will attempt to answer your question

There are many areas inside the van the gas could accidently start leaking from, such as a hairline crack on the supply pipe, any joins along the gas pipe which are inside the van, the control switches of the gas appliances, etc.

The leaking gas is heavier than air, it will accumulate in the lowest area it can find
The smallest leak, over time, will result in a large enough accumulation of gas to explode when it comes into contact with a spark or flame

In a van with a three way fridge, while it is working on gas, there is always a flame burning, which will cause any accumulated leaking gas to explode

The manufactures put in a smelling agent (Ethyl Mercaptan).
To ensure that a person will be able to smell leaking gas
Unfortunately when a person is asleep, or has the sniffles, there is a good chance that they will not smell leaking gas

There are many gas detectors a person can buy. This is a link to just one of them

Sometimes there is not much left of the van after a gas explosion, to pinpoint exactly what happened
This is why we sometimes just have to guess, how did it happen

Some people I know, have decided that as they do not open their fridge at night, they will turn it off, to save gas
I will assume that if the gas bottle is also turned off, there would be no chance of a gas explosion

Some of my remarks have already been posted and I am not intending to disregard them.

There is a difference between an explosion from the ignition of gas and a gas cylinder exploding. If there is insufficient ventilation when there is a leak then as stated previously the gas will pool from the lowest point and rise. When the gas/oxygen mixture comes into contact with an ignition sauce you will get an explosion due to the confinement whether it be in a house, caravan or car. Ignition sauce could be the pilot light or any device that has an electrical switch that that is turned on and off as a function of an appliances operation. If this incident occurred outside the caravan then there would be a sudden fire but not an explosion. VENTILATION IS THE KEY WORD and one should also be vigilant with maintenance and periodically check for leaks. ALWAYS check for a seal when replacing a gas cylinders by using a small spray bottle with soapy water.

For a gas cylinder to explode it has to be punctured or involved in a fire where the heat is sufficient to weaken the cylinder wall. A cylinder when heated will breach the safety valve and the escaping gas will ignite if there is an ignition sauce otherwise it will dissipate into the atmosphere. If the cylinder wall is breached and there is an ignition sauce then a BLEVE will occur and the resulting fire ball will depend on the size of the cylinder. (Bulk Liquid Expanded Vapour Explosion) Gas is compressed into a liquid form in the cylinder and expands to a vapour on release and conveyed to your appliance through a regulator to ensure a safe flow. Gas is an efficient, low cost fuel and is only dangerous when not maintained as is electrical and fuel appliances.

If you smell gas immediately turn off the cylinder and move clear until it is checked by a licensed operator which is the same if you have a fuel leak or an electrical short involving high voltage.

I hope I have not rattled on too much but attempted to answer the original question a simple way. Sometimes when we answer questions we forget that not everybody has our particular understanding of what we are explaining and are afraid to seek clarification for fear of following postings.

Moorey

Moorey wrote:

---

Some of my remarks have already been posted and I am not intending to disregard them.

 

 

 

There is a difference between an explosion from the ignition of gas and a gas cylinder exploding. If there is insufficient ventilation when there is a leak then as stated previously the gas will pool from the lowest point and rise. When the gas/oxygen mixture comes into contact with an ignition sauce you will get an explosion due to the confinement whether it be in a house, caravan or car. Ignition sauce could be the pilot light or any device that has an electrical switch that that is turned on and off as a function of an appliances operation. If this incident occurred outside the caravan then there would be a sudden fire but not an explosion. VENTILATION IS THE KEY WORD and one should also be vigilant with maintenance and periodically check for leaks. ALWAYS check for a seal when replacing a gas cylinders by using a small spray bottle with soapy water.

For a gas cylinder to explode it has to be punctured or involved in a fire where the heat is sufficient to weaken the cylinder wall. A cylinder when heated will breach the safety valve and the escaping gas will ignite if there is an ignition sauce otherwise it will dissipate into the atmosphere. If the cylinder wall is breached and there is an ignition sauce then a BLEVE will occur and the resulting fire ball will depend on the size of the cylinder. (Bulk Liquid Expanded Vapour Explosion) Gas is compressed into a liquid form in the cylinder and expands to a vapour on release and conveyed to your appliance through a regulator to ensure a safe flow. Gas is an efficient, low cost fuel and is only dangerous when not maintained as is electrical and fuel appliances.

If you smell gas immediately turn off the cylinder and move clear until it is checked by a licensed operator which is the same if you have a fuel leak or an electrical short involving high voltage.

I hope I have not rattled on too much but attempted to answer the original question a simple way. Sometimes when we answer questions we forget that not everybody has our particular understanding of what we are explaining and are afraid to seek clarification for fear of following postings.

 

Moorey

---

 Thank you Morrey, Correct I am a mere female, you made it very clear for me.

Helen

This belief that leaking gas does not mix with air but settles to the lowest level and remains there is just plain wrong. For a gas "explosion" to occur the gas MUST be mixed intimately with air in the correct proportions to burn. All gases mix together in all proportions and do not remain separate as in oil floating on water. The only time LPG will settle and flow to the lowest point is when the leak is massive and there is insufficient time for it to mix with air. Have a look at the Elgas web site for further info on the properties of propane and the air gas ratios required for combustion to occur. Also gas cylinder "explosions" are very very rare and only occur under extreme heat when the pressure relief valve on the cylinder cant dump the contents quick enough and the cylinder bursts . Almost all reports of gas cylinder explosions are in fact not and the cylinders are undamaged. Just poor reporting.

Brenda and Alan wrote:

---

This belief that leaking gas does not mix with air but settles to the lowest level and remains there is just plain wrong. For a gas "explosion" to occur the gas MUST be mixed intimately with air in the correct proportions to burn. All gases mix together in all proportions and do not remain separate as in oil floating on water. The only time LPG will settle and flow to the lowest point is when the leak is massive and there is insufficient time for it to mix with air. Have a look at the Elgas web site for further info on the properties of propane and the air gas ratios required for combustion to occur. Also gas cylinder "explosions" are very very rare and only occur under extreme heat when the pressure relief valve on the cylinder cant dump the contents quick enough and the cylinder bursts . Almost all reports of gas cylinder explosions are in fact not and the cylinders are undamaged. Just poor reporting.

---

 Hi Brenda and Alan

If you read my original post, I never mentioned gas bottle.  Just gas explosion and you answered my question pretty much as did the other contributors.

Guess Gas can be deadly if not respected as it should be.

Sorry, I did say GAS BOTTLES in the subject line.

But I know, you know the bottles do not explode by themselves.

Helen

stoney123 wrote:

---

get a gas leak detector. also have to watch for carbon monoxide poisoning from gas heater.

old hoses, valves, old cylinder, leaks ie oven,stove,heater,fridge...hence need for detector.

---

 One should not be using a flueless gas heater in a caravan.

Moorey wrote:

---

................... (Bulk Liquid Expanded Vapour Explosion) ...................................

Actually, the correct term is Boiling Liquid Expanding Vapour Explosion - I was in the engineering design office of a major National Fire Protection company for over 3 years.

BLEVE's were mostly due to overturned road tankers or rail tankers totally surrounded by fire, which 'boiled' the contents, greatly expanding the vapour inside until a tank seam ruptured, then BAM !

brickies wrote:

---

How many on this forum cover the vents on their RV to kept the cold out , I have read lots of post on the forum from member who do so .

---

 Not I

Unlike natural gas, propane is denser than air. It may accumulate in low spaces and near the  floor

It does have to mix with air in the right proportions for an explosion to occur, but that mix must be within range of ignition source

It can separate out from the air & settle, if no ignition source is in proximity to the correct mix

Any explosion must be due to a gas leak of some form,

The leak could be from:

faulty joints

Cracked pipes or perished hoses

faulty control taps /valves

burners not completely turned off or accidently slightly turned on.

Equipment not fitted with or a faulty flame  cutout, which  for what ever reason are allowing gas flow but no flame.

The work that NON licenced gas fitters can legally do ,is very limited for good reasons

Gas & electricity are highly regulated as both DO cause deaths & severe injuries.

All vans /motor homes etc  shall, by design , have a degree of fixed  through ventilation ,especially one at floor level [which should not be covered] &roof level & the areas are determine by the gas burning devices in the van.[That does not include the 3way fridge whose rear shall be sealed from the van interior & shall have it's own ventilation]

The floor level one is often in the step well ,that being the lowest point 

Most 4 Season hatchs do not fully seal ,& can give the required area of  roof ventilation to allow through ventilation

Those areas should never be sealed!!!

Any smell of raw gas should be quickly investigated

-

-- Edited by oldtrack123 on Saturday 27th of August 2016 04:25:56 PM

Sorry oldtrack123 but once gasses are mixed they do not separate and settle in different layers. It takes very expensive equipment to separate different gasses as gasses. {not as liquids}

Alan

99% of Gas explosions are the gas leaking.

I've seen two actual bottle explosions.
Both in mid '60's early '70's on construction sites.
One was a "tea room in old wartime bomb shelter in UK Winter.
ALSo bottle storage for site (100lb bottles.)

First one.
Line to "being used" bottle split. Flame travelled to bottle. blew valve off.
This BOTTLE explosion blew off a solid reinforced concrete bomb proof roof and landed it 10 ft away.
Only 2 other bottles blew.Rest were ok and still full.

Those other 2 bottles, closest to blast. blew of top valves. gas jetted out and mixed. Boom.
There were 2 separate distinct explosions.
I was there but not in shelter.

This was findings for experts afterwards.

Other one.
fire in storeroom. Small bottle overheated.
Boom.
Instant NO storeroom,and steel shrapnel pieces found up to 100 yds away.
embedded in whatever.

Leaking gas. an overall explosion in all directions. then gone.

Bottle explosion. Primarily from one end of bottle in that direction with some lethal shrapnel from source..
and doesn't that remaining part of bottle travel at a rate of knots in opposite direction.

Gas leaks are a mix of oxy and gas to dangerous proportions then boom all gone..

Bottle leak is a progressive 'expanding" type of explosion as more gas eats more oxxy and prolongs the boom.
(in a microsecond)
Compressed and expanding/mixing. rather than one premix at air pressure

all going off in one hit.

One an instant flash and damage caused.  finished.
T'other a more prolonged flash/pressure wave with a lot more damaging effect overall.

One of the courses I did in army on armoured recovery.(ARV/BARV)
was controlled explosives and HOW to hopefully control the different types of materials used..
Using whatever was avail.

And DON'T hold the sealed end of ANY det(onator) for more than a few seconds.

instant finger loss.

Some should read up on these things. Very interesting.
Just for increasing your knowledge.

Hi Allan
Without trying to start a bunfight I suggest you do a little research on Propane
I am sure you will find many sites that state:
Propane is heavier than air
If there is a leak it will tend to accumulate in the lowest spot.
You will also that is the prime reason for all vans & motor homes etc to have a PERMANENT vent at the lowest point

You will also find that the area of the permanent vents is determined by the combined possible gas output of ALL gas appliances installed

Perhaps others with doubts should do the same.

Of course if there is sufficient air turbulence in the situation , all the propane may not settle,

You will also find that many explosions on boats are due to the propane settling.

I am well aware of how all the gases in air for example  are separated out  .

Compressed to extremely high pressure  to form a liquid, then boiled off @ different temps& collected[including the rarer gases , such as argon ] the method works because each gas has it's own point at which it changes from liquid to gas

Propane is not heavier than air, a Kgm of propane is the same weight as a Kgm of air. The specific gravity of propane is higher than air, but this does not change the fact that all gasses mix together in all ratios.

Propane will only burn in air if the gas concentration in the air MIXTURE is within the range of 2.15 to 9.6 %. If the concentration is outside these limits it will not burn. So if your propane is sitting on the floor only the surface in contact with air will burn, hence no explosion. For an explosion to occur requires a propane air mixture within the above ratios not gas on the floor and air above. This is more likely to occur due to a small gas leak in an enclosed space such as a caravan rather than a major than from a major leak.

As a safety measure a smelling agent is added to the gas which can be detected by the nose long before the concentration of the gas air mixture reaches flammability levels. Detecting this smell under normal operation is an indicator the gas system needs attention and should not be ignored.

Alan

Brenda and Alan wrote:

---

Propane is not heavier than air, a Kgm of propane is the same weight as a Kgm of air. The specific gravity of propane is higher than air, but this does not change the fact that all gasses mix together in all ratios.

Propane will only burn in air if the gas concentration in the air MIXTURE is within the range of 2.15 to 9.6 %. If the concentration is outside these limits it will not burn. So if your propane is sitting on the floor only the surface in contact with air will burn, hence no explosion. For an explosion to occur requires a propane air mixture within the above ratios not gas on the floor and air above. This is more likely to occur due to a small gas leak in an enclosed space such as a caravan rather than a major than from a major leak.

As a safety measure a smelling agent is added to the gas which can be detected by the nose long before the concentration of the gas air mixture reaches flammability levels. Detecting this smell under normal operation is an indicator the gas system needs attention and should not be ignored.

Alan

---

OK , Allan , All the sites that say other wise must be wrong

A long post telling most of us facts we already know

All those vans & motor homes with the mandatory vent at the lowest point should just seal them off ,that will save dust getting in

Did you bother to do a bit of googling???

For those who want FACTS ,this should be classed as a reputable site & there are many others along the same lines if you do a good search.

http://www.elgas.com.au/blog/453-the-science-a-properties-of-lpg

There are other AUSTRALIAN   sites, & I know one ,specifically refers to slow leaks ,as from a cracked pipe , in enclosed spaces

 ALL make the clear statement that PROPANE gas is heavier than air!!

But make sure you are reading about AUSTRALIAN PROPANE

 Do not just go to Wiki

My data did come from Elgas web site and it and the others are wrong to say propane is heavier than air. The correct terminology is specific gravity not weight.

Alan

iana wrote:

---

A parachutist jumps out of an aircraft way up there, and finds his parachute won't open, he passes another guy going up, do you know anything about parachutes he calls out, no said the other guy, do you know anything about gas leaks in caravans.

---