had one today ,and i had to put in what looked like liquid nitrogen gas into a socket just infront of the rear wheels on the unit , says something on a sticker about hybrid , it was a 55 reg so i wondered whats the gas do 
I hope you had the proper cryogenic insulated gloves and close fitting goggles when refuelling!
ady1:
had one today ,and i had to put in what looked like liquid nitrogen gas into a socket just infront of the rear wheels on the unit , says something on a sticker about hybrid , it was a 55 reg so i wondered whats the gas do
Hi Ady !!! Its all technical bumf, but basically it makes the engine go !!!
IT MIGHT BE TECHNICAL BUMF BUT THE DIFFERENCE IS YOU GRAB A DIESEL NOZZLE WITH BARE HANDS YOU JUST GET SMELLY HANDS, WITH LIQUID NITROGEN OR LPG YOU GET FROST BITE! sorry about the caps!
had riggers on but no goggles but must admit you should have them on as when i took hose off gas didnt half come out with a whoosh , made me jump 
was the test driver on a lpg conversion (danger money job) they had trouble getting it just right thing kept exploding going bang that much smoke i couldnt see out my mirrors car drivers keeping a respectful distance said had enough off this put it back on diesal fulltime 
lpg factoid its minus44 and compressed 250 litres to 1 litre a leak is a big problem as it spreads quickly at ground level
scania245:
lpg factoid its minus44 and compressed 250 litres to 1 litre
That’s very interesting scania245. I’m not sure about “lpg” and “minus44.”
Do you know what kind of LPG it is?
Do you know where you got the “minus 44?”
scania245:
a leak is a big problem as it spreads quickly at ground level
That’s a fire-risk for sure- very dangerous.
its at minus 44 can cause severe cold burn s tissue damage hence the need for goggles and gauntlets as for what type ? propane/butane and i came up with the minus 44 because thats what the company told me if ive been misinformed im sure you let me know 
why do gas cylinders frost over ?
mikermhh:
I hope you had the proper cryogenic insulated gloves and close fitting goggles when refuelling!
Well obviously. otherwise he wouldnt be typing this 
Is the LPG you speak of CNG
scania245:
why do gas cylinders frost over ?
Melchett puts geek head on:
To liquefy a gas needs either refrigeration &/or pressure. Either way the gas molecules are slowed & forced closer together dissipating heat. The resulting liquid/compressed gas is then stored under pressure.
As soon as the pressure is released the gas wants to return to it’s natural state but to do this it has to re-absorb the heat lost during the intial process… the only place to get this heat is from the atmosphere. So the outside of the cylinder gets extremely cold & water vapour condenses to form frost.
Full cylinders that are not in use are usually at ambient temp, only those in use get frosted.
Sorry 
A company I worked for converted it’s Fodens (Cat engines) to run on LNG. it took some time (& quite a few engine blowups) to get the diesel/gas ratio right.
I think they ended up running a 75/25% diesel gas mix, great for cruising on motorways but useless on hills. Luckily there was a switch in the cab to run on full diesel.
melchett are you related to dieasal dave
5 years ago I bought a V8 land-Rover with an LPG conversion. The LPG is taken from the tank in liquid form and evaporated on demand in a vapouriser. The vapouriser was heated by the engine cooling system to stop it getting too cold and once running well it worked fine. Trouble was if you started on gas, drove a mile down the road, then stopped the engine before it had warmed up it would feeze solid before you could start it again. switching to petrol rarely helped because the inlet manifold was now so cold it just condensed the fuel vapour. This was the main reason for starting on Petrol, then switching to gas when warmed up a little.
scania245:
melchett are you related to dieasal dave
I don’t believe he is, however, this bit is ok:
Melchett:
To liquefy a gas needs either refrigeration &/or pressure. Either way the gas molecules are slowed & forced closer together dissipating heat. The resulting liquid/compressed gas is then stored under pressure.
Melchett, could you review the (bold) wording of this, I think I’m missing something:
Melchett:
As soon as the pressure is released the gas wants to return to it’s natural state but to do this it has to re-absorb the heat lost during the intial process. the only place to get this heat is from the atmosphere. So the outside of the cylinder gets extremely cold & water vapour condenses to form frost.
I might have misunderstood you, but if the bold part were true, how would frost form on a warm cylinder??
scania245 This kind of info is presumably from the the product sheet:
scania245:
lpg factoid its minus44 and compressed 250 litres to 1 litre
I’m ok with the compression of 250 litres to 1 litre, but I’m wondering about the “minus44,” so do you remember the name of this “LPG?”
There are several kinds of LPG, so the UN number (four digits) might help if you can get it.
Was there some sort of refrigeration equipment for the tank in the storage area??
dieseldave:
Melchett, could you review the (bold) wording of this, I think I’m missing something:Melchett:
As soon as the pressure is released the gas wants to return to it’s natural state but to do this it has to re-absorb the heat lost during the intial process. the only place to get this heat is from the atmosphere. So the outside of the cylinder gets extremely cold & water vapour condenses to form frost.I might have misunderstood you, but if the bold part were true, how would frost form on a warm cylinder??
Not sure what you mean by a warm cylinder? The liquid gas is stored in the cylinder under pressure to prevent it’s expansion. If the valve remains closed the pressure remains constant(ish) & no work is being done. Therefore the liquid/gas cylinder temperature will remain at the ambient temp of it’s surroundings.
I did find this which probably explains it better than I can…
“This is called ‘sweating’, and is caused by the process of LPG changing from its liquid state to a vapour state. LPG in a stable state consists of both liquid and vapour. When vapour is drawn from the cylinder the vapour pressure in the cylinder is reduced and alters this stability between the vapour pressure and the pressure required maintaining the LPG as a liquid. In this condition, the liquid LPG boils releasing vapour which stabilises the pressure within the cylinder. In order for LPG to boil, it must draw in heat through the cylinder wall. As this happens the wall of the cylinder is cooled and moisture in the air condenses on the wall of the cylinder. In extreme cases, the cylinder may have ice forming on the surface of the cylinder. Interestingly, the top edge of the sweating or ice, reveals the level of the LPG remaining in the cylinder.”
Melchett:
Not sure what you mean by a warm cylinder? The liquid gas is stored in the cylinder under pressure to prevent it’s expansion. If the valve remains closed the pressure remains constant(ish) & no work is being done. Therefore the liquid/gas cylinder temperature will remain at the ambient temp of it’s surroundings.
That’s correct. That’s due to the fact that pressure, temperature and volume are inextricably linked.
Melchett:
I did find this which probably explains it better than I can…“This is called ‘sweating’, and is caused by the process of LPG changing from its liquid state to a vapour state. LPG in a stable state consists of both liquid and vapour. When vapour is drawn from the cylinder the vapour pressure in the cylinder is reduced and alters this stability between the vapour pressure and the pressure required maintaining the LPG as a liquid. In this condition, the liquid LPG boils releasing vapour which stabilises the pressure within the cylinder. In order for LPG to boil, it must draw in heat through the cylinder wall. As this happens the wall of the cylinder is cooled and moisture in the air condenses on the wall of the cylinder. In extreme cases, the cylinder may have ice forming on the surface of the cylinder. Interestingly, the top edge of the sweating or ice, reveals the level [of the liquid phase] of the LPG remaining in the cylinder.”
Also correct. The key word here is “boil.” Most people don’t realise quite how low a temperature is achieved - sometimes as low as three digits minus in degrees C. That piece you found does explain it quite well, but I added four words [in italics] for completeness, nevertheless you clearly have a good understanding of gases. Not an easy subject… Well done!!
That might be where scania245 got the “minus44” from… that info could be from the product sheet.
Here’s the proof that gases go cold when released. (These low temperatures can cause severe cold burns to human tissue, so BEWARE!!!)
This cylinder is CO2:
I let a very small amount out for demonstration purposes.
The frosting appeared within a few seconds.
Cheers for the “Well done”, Dave.
Something I learned during my “A” level days but never got to use.
Strange how some things stick, even through the mists of 20 odd years 
My explanation could have been better but we got there
Melchett:
Cheers for the “Well done”, Dave.Something I learned during my “A” level days but never got to use.
Strange how some things stick, even through the mists of 20 odd years
Swapping my classroom head for a more appropriate one: My understanding could (and should) have been better, but we certainly did get there. 
You guys who understand science truly amaze me, because I’m just about clueless with scientific stuff.
I’d try and pick up the scientific bit if I was bright enough… , but I’d very probably be wasting a tutor’s time.
My angle on all this is legal definitions and ADR stuff, so it comes from a completely different direction.
Fortunately for me I can phone a friendly industrial chemist if needed, and a strange fact is that I don’t actually need any science to requalify on my exams To borrow a member’s signature: "excuse me while I kiss the sky… 