Omega Owners Forum

Chat Area => General Car Chat => Topic started by: mrgreen on 31 March 2011, 12:02:24

Title: cng vs lpg
Post by: mrgreen on 31 March 2011, 12:02:24
in austria the big way to go (as in more tankstations) is cng is this a better fuel than lpg? i have also read that the pressures involed are alot bigger as in by the thousands! so if so is the stag system also designed to run cng? and does anyone know what tanks (makes, names) i should search for as i can find the stag front kits in germany but no tanks! any help would be greatly appreciated TIA Rich.
Title: Re: cng vs lpg
Post by: Lazydocker on 31 March 2011, 12:41:43
Stag software has CNG as an option so I guess it will control it :-/

I would think that pretty much everything will be different though... Certainly the tanks are.

Don't know if they do tanks for CNG but Stako and GZWM(?) are the main brands of LPG tank
Title: Re: cng vs lpg
Post by: TheBoy on 31 March 2011, 13:14:29
The Stag site seems to imply CNG, worth a look to confirm though www.ac.com.pl
Title: Re: cng vs lpg
Post by: JamesV6CDX on 31 March 2011, 13:28:48
Read something not long ago, where someone filled an LPG tank with CNG, (not sure how that's possible, I think a DIY'er cobbled the kit together)

The tank exploded - can't remember if it caused serious injury  :-/
Title: Re: cng vs lpg
Post by: Lazydocker on 31 March 2011, 13:37:29
Quote
Read something not long ago, where someone filled an LPG tank with CNG, (not sure how that's possible, I think a DIY'er cobbled the kit together)

The tank exploded - can't remember if it caused serious injury  :-/

Yes, yes (although not particularly cobbled TBH) and fairly.

Was banded around as a scare tactic by some LPG installers for a while... One tried it on me when he found out mine was DIY converted until I suggested he show me some of his work :-X ::)

CNG is at a considerably higher pressure and, in the UK, an impractical choice due to lack of filling stations IMO

[edit]Oh... And the incident was in Northern Europe some 2 years or so ago[/edit]
Title: Re: cng vs lpg
Post by: Sir Tigger KC on 31 March 2011, 22:26:20
There was a company converting trucks to CNG a while back and they had a few filling stations at motorway service stations.  There was one at the services just before the old Severn bridge on the M48. 

Not sure if they're still about, but they did a package deal ie convert the trucks and install a CNG tank in the yard. They also sold converted trucks and I remember that they had a few ERF's on their website  ::)

If I remember rightly the difference in price between diesel and CNG was considerable, but in my trucking days I only ever spotted one converted truck! and that was an old ERF before they were rebadged MAN's!

I'd have thought if it was worth doing then the likes of Stobarts would have been all over it  :-/  Maybe with todays inflated fuel prices it might be worthwhile and it's greener than diesel :y
Title: Re: cng vs lpg
Post by: albitz on 31 March 2011, 22:44:51
What is CNG ? Ive never heard of it tbh. :-/
Title: Re: cng vs lpg
Post by: Lazydocker on 31 March 2011, 22:55:45
Quote
What is CNG ? Ive never heard of it tbh. :-/

Compressed Natural Gas

instead of Liquid Petroleum Gas ;) :y
Title: Re: cng vs lpg
Post by: albitz on 01 April 2011, 05:25:19
Cheers.LF. :y
Title: Re: cng vs lpg
Post by: Kevin Wood on 01 April 2011, 12:03:48
There's very little difference between the kits for CNG and LPG apart from the high pressure components - tank, feed / filler lines and vapouriser. Just a few tweaks to the fuelling calculations.

CNG is predominantly Methane gas which has a much higher vapour pressure than the propane and butane present in LPG so we're talking tank pressures up to 250 bar. :o

So, yes, you need a slightly higher wall thickness on the tank. ;D

Kevin
Title: Re: cng vs lpg
Post by: TheBoy on 01 April 2011, 12:10:41
Quote
There's very little difference between the kits for CNG and LPG apart from the high pressure components - tank, feed / filler lines and vapouriser. Just a few tweaks to the fuelling calculations.

CNG is predominantly Methane gas which has a much higher vapour pressure than the propane and butane present in LPG so we're talking tank pressures up to 250 bar. :o

So, yes, you need a slightly higher wall thickness on the tank. ;D

Kevin
:o :o :o

break me. The hoses must be kevlar ;D
Title: Re: cng vs lpg
Post by: Kevin Wood on 01 April 2011, 12:15:21
Quote
Quote
There's very little difference between the kits for CNG and LPG apart from the high pressure components - tank, feed / filler lines and vapouriser. Just a few tweaks to the fuelling calculations.

CNG is predominantly Methane gas which has a much higher vapour pressure than the propane and butane present in LPG so we're talking tank pressures up to 250 bar. :o

So, yes, you need a slightly higher wall thickness on the tank. ;D

Kevin
:o :o :o

break me. The hoses must be kevlar ;D

It's not even liquid then, hence it's called CNG and not LNG. This also means that you need a much larger tank for the equivalent range, since it's less dense.

Kevin
Title: Re: cng vs lpg
Post by: TheBoy on 01 April 2011, 12:22:17
Quote
Quote
Quote
There's very little difference between the kits for CNG and LPG apart from the high pressure components - tank, feed / filler lines and vapouriser. Just a few tweaks to the fuelling calculations.

CNG is predominantly Methane gas which has a much higher vapour pressure than the propane and butane present in LPG so we're talking tank pressures up to 250 bar. :o

So, yes, you need a slightly higher wall thickness on the tank. ;D

Kevin
:o :o :o

break me. The hoses must be kevlar ;D

It's not even liquid then, hence it's called CNG and not LNG. This also means that you need a much larger tank for the equivalent range, since it's less dense.

Kevin
Glad we use LPG ;D
Title: Re: cng vs lpg
Post by: bigegg on 01 April 2011, 13:11:56
be nice to use it straight from the gas line at 15p/l equivalent from British Gas tho...
Title: Re: cng vs lpg
Post by: dad1uk on 01 April 2011, 20:12:42
This might make interesting reading...... :o :o

http://www.probeinternational.org/files/Auto%20fire%20with%20compressed%20natural%20gas%20fuel%20tank%20explosion.pdf
Title: Re: cng vs lpg
Post by: blackviper90210 on 01 April 2011, 20:27:46
Quote
This might make interesting reading...... :o :o

http://www.probeinternational.org/files/Auto%20fire%20with%20compressed%20natural%20gas%20fuel%20tank%20explosion.pdf

Glad I wasn't a passenger in that car at the time!  :o
Title: Re: cng vs lpg
Post by: Kevin Wood on 01 April 2011, 20:33:42
Quote
This might make interesting reading...... :o :o

http://www.probeinternational.org/files/Auto%20fire%20with%20compressed%20natural%20gas%20fuel%20tank%20explosion.pdf
:o

Bit of a trouser-browner. :-?

Then again, all that pressure in a composite tank? Guess the tank burned through then bang! :o

I guess, being stored as a gas, once the cylinder ruptures, all of the fuel is immediately released whereas with LPG it will remain liquid until it has absorbed enough heat to vapourise.

Kevin
Title: Re: cng vs lpg
Post by: mrgreen on 01 April 2011, 20:53:46
Quote
be nice to use it straight from the gas line at 15p/l equivalent from British Gas tho...


i read on a site somewhere there is a pump you can install at home to pump it straight from your gas line but i don't know how legal that would be avoiding fuel taxes e.t.c :-/

thanks to all for the replies me thinks a little more research is needed!
Title: Re: cng vs lpg
Post by: Grrrrrr on 02 April 2011, 21:52:08
Wow. That really was a case of bad gas!