rivonia
Well-Known Member
Well this is where we differ as the gas produced from DIESEL is VERY volatile and is an EXPLOSIVE substance. I was taught this during my demolition days in the Forces.
As I said Nuff said
Peter
can a diesel tank explode?
- Thread starter cumbrian
- Start date
Well this is where we differ as the gas produced from DIESEL is VERY volatile and is an EXPLOSIVE substance. I was taught this during my demolition days in the Forces.
As I said Nuff said
Peter
PaulJS
Well-Known Member
Safety first
As a marine engineer I was always told not to carry out hot work on any tank which contains or has contained hydrocarbons unless it has been certified "gas free" or, in exceptional cases where this is impractical, "fully inerted". Even then there have been well documented instances where enough heat has been generated to vapourise liquid residue which has subsequently exploded.
Therefore I think it much safer to err on the side of caution and do what you can to purge the tank before cold cutting it.
It's true that you would probably be very unlucky to have an explosion if you angle ground the tank, but you could still be dead, or injured. I was going to say "maimed", but i think that "injured" conveys the point.
Take care.
Paul
EDIT Maybe worth considering temporarily enlarging the locker opening? ENDEDIT
As a marine engineer I was always told not to carry out hot work on any tank which contains or has contained hydrocarbons unless it has been certified "gas free" or, in exceptional cases where this is impractical, "fully inerted". Even then there have been well documented instances where enough heat has been generated to vapourise liquid residue which has subsequently exploded.
Therefore I think it much safer to err on the side of caution and do what you can to purge the tank before cold cutting it.
It's true that you would probably be very unlucky to have an explosion if you angle ground the tank, but you could still be dead, or injured. I was going to say "maimed", but i think that "injured" conveys the point.
Take care.
Paul
EDIT Maybe worth considering temporarily enlarging the locker opening? ENDEDIT
Last edited:
vyv_cox
Well-Known Member
Sorry, diesel has low volatility. Don't take my word for it, put some in a dish and leave it lying around for a few days, when it will still be there. Do the same with gasoline and it will almost all be gone. The flash point of diesel is above 55C, below which very little vapour will be produced. Obviously if you heat a can of diesel enough it could explode, but as has been said, at ambient temperatures you can throw matches in it all day and it won't ignite.
sarabande
Well-Known Member
whillst you can throw matches into a pan of diesel, and not be blown up, it only needs a bit of rubbish (cloth, leaf, old heap of dead diesel bug crud) to hold diesel in contact with lots of air (think sponge) for a spark to settle on the material, heat it up, and then catch fire.
Quite simply the risk of an angle grinder is not acceptable when you think of the probability and the consequences.
Quite simply the risk of an angle grinder is not acceptable when you think of the probability and the consequences.
vyv_cox
Well-Known Member
As I said earlier, give the tank a flush with water and detergent and it can be welded quite safely. I've done it a sufficient number of times to know that it's safe. Using your analogy, a candle is dangerous!
P4Paul
Well-Known Member
I think I would be more concerned about where the sparks from the angle grinder would end up and the damage they may cause rather than worrying about the tank heading off into orbit.
I haven’t seen the installation nor the size, shape or thickness of the tank, so I am only guessing but perhaps another option could be to use a nibbler.
One here for hire
Or buy one to fit a drill
Some absorbent material might be useful to soak up any latent diesel which may escape.
Reusable absorbant pad
Hope it goes well whatever the OP decides to do.
I haven’t seen the installation nor the size, shape or thickness of the tank, so I am only guessing but perhaps another option could be to use a nibbler.
One here for hire
Or buy one to fit a drill
Some absorbent material might be useful to soak up any latent diesel which may escape.
Reusable absorbant pad
Hope it goes well whatever the OP decides to do.
Mandarin331
Well-Known Member
why take the risk?
The extent of the argument seems to indicate that the answer is not clear - Therefore it's a risk. Certainly when I recall enormous precautions used when working on ships with heavy fuel oil in tanks - and that's a lot less volatile than diesel.
Incidentally I also heard that working on a full tank is a lot safer than an empty tank - its the fumes which explode, not the liquid. Personally I wouldn't do either.
Since the moment you find out who's right will be the moment when it catches fire or blows up I would take the easy precaution of flushing it first.
Either way if this is a mild steel tank I would not use any tool which created swarf or filings, you'll be dealing with the rust spots for years to come!
The extent of the argument seems to indicate that the answer is not clear - Therefore it's a risk. Certainly when I recall enormous precautions used when working on ships with heavy fuel oil in tanks - and that's a lot less volatile than diesel.
Incidentally I also heard that working on a full tank is a lot safer than an empty tank - its the fumes which explode, not the liquid. Personally I wouldn't do either.
Since the moment you find out who's right will be the moment when it catches fire or blows up I would take the easy precaution of flushing it first.
Either way if this is a mild steel tank I would not use any tool which created swarf or filings, you'll be dealing with the rust spots for years to come!
sarabande
Well-Known Member
I am not disagreeing about the method of removing raw diesel from the tank, at all. (see my earlier post)
The common feature with diesel and candles is that they are both fuel sources. I was making the point, perhaps badly, that diesel MAY not catch fire if you chuck a match in it, but soaking something in the physical format of a sponge (i.e. with lots of air: surface ratio) with diesel, and then chucking a match WILL almost certainly result in inflammation.
www.nfpa.org/assets/files/PDF/Candlereport.pdf
Factors contributing to ignition in 1999-2002:
• Half (50%) of the home candle fires occurred when some form of combustible material was left or came too close to the candle.
The potential for a diesel fire is greatly increased when diesel is contained in some combustible material which exposes the soaked surface area to air.
I have never welded diesel tanks, but I have managed to set fire to all kinds of things (on purpose) using diesel contaminated by bugs or water.
The common feature with diesel and candles is that they are both fuel sources. I was making the point, perhaps badly, that diesel MAY not catch fire if you chuck a match in it, but soaking something in the physical format of a sponge (i.e. with lots of air: surface ratio) with diesel, and then chucking a match WILL almost certainly result in inflammation.
www.nfpa.org/assets/files/PDF/Candlereport.pdf
Factors contributing to ignition in 1999-2002:
• Half (50%) of the home candle fires occurred when some form of combustible material was left or came too close to the candle.
The potential for a diesel fire is greatly increased when diesel is contained in some combustible material which exposes the soaked surface area to air.
I have never welded diesel tanks, but I have managed to set fire to all kinds of things (on purpose) using diesel contaminated by bugs or water.
vyv_cox
Well-Known Member
Fair enough, but there is a huge difference between things catching fire and things exploding. Most people who have carried out gas welding repairs on e.g cars will be very familiar with starting small fires when underseal, paint, and possibly even carpets(!) ignite. My wife used to stand by with a squeezy bottle of water to put out these small fires as required.
An explosion in a fuel tank is a completely different matter. I would never even attempt to weld a gasoline tank but I am well aware that high flash point fuels like diesel or central heating oil pose an extremely small risk even if not flushed out first. Someone made the good point that partially filling the tank with water cuts down the air space and reduces the risk of explosion. The first time I welded a diesel tank I did the same thing, relaxing this practice when I realised it was not necessary.
An explosion in a fuel tank is a completely different matter. I would never even attempt to weld a gasoline tank but I am well aware that high flash point fuels like diesel or central heating oil pose an extremely small risk even if not flushed out first. Someone made the good point that partially filling the tank with water cuts down the air space and reduces the risk of explosion. The first time I welded a diesel tank I did the same thing, relaxing this practice when I realised it was not necessary.
Scotty_Tradewind
Well-Known Member
Yes but surely only if compressed..... as in a combustion chamber of a diesel engine?
Refueler
Well-Known Member
I've read through and I can say this ....
Some people talk a load of old codswallop .... and some posts are spot on.
So what's right ?
Diesel tank can be cut up as you wish after basically overfilling with water .... adding detergent later is a "let's make sure" item. Despite some post above - the same works with petrol tanks.
Diesel will explode but only when highly compressed or heated to extreme - two cases that are highly unlikely in the above tank cutting exercise.
People who go on about vapours and air mixtures - it is unlikely that Diesel in ambient form will create an LEL or UEL mix sufficient to be a problem. Petrol, Kerosine and other LIGHT distilates will though. Diesel is the light end of middle distilate.
Someone suggested air tools ..... have you ever been in a confined area with a kango hammer or other air tool ? I have and it's not an experience I wish to repeat. As a teenager I used to help out with a trucking company. They bought up old road tankers and we used to cut holes in the bulkheads to get free-flow and create a single tank but still with bulkheads providing baffling. Some were ex Bitumen wagons ... others were petrol or diesel wagons. Bitumen wagons were 'hot-washed' with rubbish diesel and then flushed before 'gas-axeing' the holes into bulkheads. The petrol wagons we flushed out with water .... we tried air cutters on one tanker from Esso Shoreham depot ... never ever did that again ... ears were ringing for weeks after even with ear defenders on.
The beauty of overfilling with water is not only do you flush out residual fuel - but on emptying - you put in clean air. Must say that when we were cutting - we had fans pushing air in to tanker and bottom drains open to get throughput. Not a job I would repeat now !!
Some people talk a load of old codswallop .... and some posts are spot on.
So what's right ?
Diesel tank can be cut up as you wish after basically overfilling with water .... adding detergent later is a "let's make sure" item. Despite some post above - the same works with petrol tanks.
Diesel will explode but only when highly compressed or heated to extreme - two cases that are highly unlikely in the above tank cutting exercise.
People who go on about vapours and air mixtures - it is unlikely that Diesel in ambient form will create an LEL or UEL mix sufficient to be a problem. Petrol, Kerosine and other LIGHT distilates will though. Diesel is the light end of middle distilate.
Someone suggested air tools ..... have you ever been in a confined area with a kango hammer or other air tool ? I have and it's not an experience I wish to repeat. As a teenager I used to help out with a trucking company. They bought up old road tankers and we used to cut holes in the bulkheads to get free-flow and create a single tank but still with bulkheads providing baffling. Some were ex Bitumen wagons ... others were petrol or diesel wagons. Bitumen wagons were 'hot-washed' with rubbish diesel and then flushed before 'gas-axeing' the holes into bulkheads. The petrol wagons we flushed out with water .... we tried air cutters on one tanker from Esso Shoreham depot ... never ever did that again ... ears were ringing for weeks after even with ear defenders on.
The beauty of overfilling with water is not only do you flush out residual fuel - but on emptying - you put in clean air. Must say that when we were cutting - we had fans pushing air in to tanker and bottom drains open to get throughput. Not a job I would repeat now !!
H
halfway
Guest
I know you hid the bit about emptying, but I can just picture a diesel tank full of water and a person cutting through the side with an electric angle grinder!
At least the explosion would not be IN the tank.
Any closed tank can explode. No one really knows what is in it. The key is never to weld/cut any enclosed space. The first step is always to open up the tank.
If you are not sure about explosions using fine mists of diesel look up " Thermobaric bomb".
At least the explosion would not be IN the tank.
Any closed tank can explode. No one really knows what is in it. The key is never to weld/cut any enclosed space. The first step is always to open up the tank.
If you are not sure about explosions using fine mists of diesel look up " Thermobaric bomb".
cumbrian
Well-Known Member
can a thread explode!
delighted as ever to see volatile opinions on this one - but the forum always gets there in the end - clearly caution needs to prevail - there is a risk but sounds like its manageable
its not a big tank and can be completely drained, flushed and re-flushed via a lower drain hole so i'm not too worried about residue - will look to get hold of the suggested tools and will watch out for those steel fragments in the bilge
thanks to all
(if i don't post again you know it went horribly wrong)
delighted as ever to see volatile opinions on this one - but the forum always gets there in the end - clearly caution needs to prevail - there is a risk but sounds like its manageable
its not a big tank and can be completely drained, flushed and re-flushed via a lower drain hole so i'm not too worried about residue - will look to get hold of the suggested tools and will watch out for those steel fragments in the bilge
thanks to all
(if i don't post again you know it went horribly wrong)
misterg
Well-Known Member
Sorry for the diversion, but just in case:
The above is true(ish) for petrol engine exhaust, but *not* for diesel engine exhaust (which will still contain almost as much oxygen as the ambient air unless the engine is running under a heavy load).
Andy
sarabande
Well-Known Member
I really would not fancy a Richtmyer-Meshkov and Kelvin-Helmholtz instabilities on my boat 
I was emergency planning control at a major fire in Somerset when a fuel train caught fire; 14 fuel wagons (kerosene (aviation), petrol and diesel) burned out over two days. The fire spread from one overheated axle to start in one wagon, and then spread to the others in sequence.
Despite the contents, there was no explosion, rather we had sequential fires. But as the tank walls failed there was certainly a lot of 'jetting' out of rather hot flames. It took two days to reduce the fire, and the environmental damage by the foam suppressant was quite extensive. We had to organise the collection and delivery of nearly all the UK stock of suppressant chemical, and ended up borrowing some from the Navy in Plymouth.
The cause of the fire was an overheated axle box (poor maintenance), which failed, so the wheel/axle dropped off and the first wagon fell over and broke, with sparks from metal to metal contact. Thereafter, everything became quite warm and active.
It is clear that there are certain practical procedures in welding or cutting open tanks which reduce the risk of fire either within the tank or in the vicinity. The consequences of an unskilled person carrying out this risky operation without reducing the presence of fuel sources to the absolute minimum do not bear thinking about.
Noise from a nibbler or shears or reciprocating saw is as bad as noise from a grinder. It is a hazardous operation; what one should be trying to do is reduce the primary risk from the cutting activity - that is fire from sparks off a cutting disc.
If you cannot guarantee that all the fuel risks are removed - the film on the tanks walls, the sludge from the bottom of the tank; adjacent combustible material, everything, then no sparks means no grinder; No brainer.
I was emergency planning control at a major fire in Somerset when a fuel train caught fire; 14 fuel wagons (kerosene (aviation), petrol and diesel) burned out over two days. The fire spread from one overheated axle to start in one wagon, and then spread to the others in sequence.
Despite the contents, there was no explosion, rather we had sequential fires. But as the tank walls failed there was certainly a lot of 'jetting' out of rather hot flames. It took two days to reduce the fire, and the environmental damage by the foam suppressant was quite extensive. We had to organise the collection and delivery of nearly all the UK stock of suppressant chemical, and ended up borrowing some from the Navy in Plymouth.
The cause of the fire was an overheated axle box (poor maintenance), which failed, so the wheel/axle dropped off and the first wagon fell over and broke, with sparks from metal to metal contact. Thereafter, everything became quite warm and active.
It is clear that there are certain practical procedures in welding or cutting open tanks which reduce the risk of fire either within the tank or in the vicinity. The consequences of an unskilled person carrying out this risky operation without reducing the presence of fuel sources to the absolute minimum do not bear thinking about.
Noise from a nibbler or shears or reciprocating saw is as bad as noise from a grinder. It is a hazardous operation; what one should be trying to do is reduce the primary risk from the cutting activity - that is fire from sparks off a cutting disc.
If you cannot guarantee that all the fuel risks are removed - the film on the tanks walls, the sludge from the bottom of the tank; adjacent combustible material, everything, then no sparks means no grinder; No brainer.
Last edited:
Marsupial
Well-Known Member
Seal the tank with caps and bungs and attach an air pump to remove the air, the tank will collapse and you can then get it out.
Ubergeekian
Well-Known Member
I'm sitting ten feet away from a device which vaporises diesel and then puts a spark to the gas/air mix. It hasn't exploded yet ... and runs eight radiators very nicely.
Ubergeekian
Well-Known Member
The compression isn't relevant, as far as I know - it's the heat. Incidentally, the diesel/air mix is not compressed in a diesel engine: it's just the air. When that#s nice and hot the diesel is squirted in to burn.
Marsupial
Well-Known Member
No the device has nt exploded BUT THE DIESEL HAS!!!!
Cliveshep
Well-Known Member
Marsupial's idea of a vacuum implosion is a good and safe one. As to explosion risk, I cut once up an old (not purged but empty) central heating tank with a 9 inch grinder. Naturally there was wet sludge in the bottom. Half way through there was a whoosh and I ran, It burnt for two hours. The whoosh sent flame 6ft into the air, imagine that inside a boat. It was clear that fuel oil had been retained in the tank's crevices and the sludge on the bottom and this was acting like a "desert cooker" once the angle grinder sparks got at it.