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Author: Subject: Anyone know about LPG?
ChrisW

posted on 27/12/17 at 07:31 PM Reply With Quote
Anyone know about LPG?

Or more specifically, pumping it from one tank to another?

Scenario is this: I bought an LPG-powered Jeep. I wanted a cheap runabout that could pull a decent sized trailer and deal with the odd bit of mild off-roading (mainly dragging said trailer through a field) and it fits the bill nicely. OK it only does 15-ish mpg but with LPG being about half the price of petrol I get the equivalent cost of about 30mpg whilst still being able to drive about in a 4.7 v8.

What is getting on my nerves however is having to fill it up. It only has a 70l tank which, once you take into account only being able to fill it to 80% (standard practice to leave expansion room) means only 55l of LPG available and therefore about 150-160 miles between trips to the only LPG supplier around which just happens to be completely the opposite end of town to where I live.

Clearly if I had some way of buying in bulk and filling the car up myself life would be a lot easier. The gas is the same stuff as used for heating, and there is a process with HMRC (Google C&E930B if you are interested) for declaring that you have used heating gas as road fuel and paying the difference in duty, the issue is one of getting the LPG from a bulk tank into the car.

I have managed to acquire a 1000l tank with a bottom outlet (required to get the contents out as liquid) I now just need some method of pumping the gas from there into the car. Has anyone attempted something like this before?

As I understand it, I need a positive displacement pump. The commercial installations use a gear type pump but 'proper' LPG ones (eg from Smith pumps in the US) are expensive. I have also heard of DIY'ers using sliding vane type although apparently there is some issue of cavitation at the tips of the vanes causing the liquid to turn to gas and massively reducing the efficiency of the pump (I don't profess to understand the physics behind that).

Would a gear type hydraulic pump do the job? If so, will the LPG act as a lubricant or am I going to either have to make some other arrangements to lubricate or just accept that the pump will die over a period of time?

What about a car air-con pump? These are usually piston type pumps with a non-return valve at each end. I hesitate here as I was taught when I did my F-gas certificate that allowing liquid in to AC pumps was the most common way of killing them but I have no idea why that is. My only guess is that it is something to do with the non-return valves.

Anyone got any experiences or advice they can offer?

Chris





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BenB

posted on 27/12/17 at 07:52 PM Reply With Quote
Can't help with the original question but is there such a thing as "red" LPG? IE what's to stop people using heating LPG for cars? Or do they just assume the number of LPG cars is quite low and the number of people who have the knowledge to transfer LPG without flame-throwering themselves even less so???
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luke2152

posted on 27/12/17 at 07:54 PM Reply With Quote
Loads of forklifts run on LPG and I assume they get filled on site so I guess smallish bulk equipment must be available. Also some of the small LPG filling stations look like they have pretty basic equipment.

Couldn't you just connect the tanks without a pump and have a bit more pressure in the external tank to force it to the car tank. Or pressurise it with welding gas. I'm sure the pressure in the car tank is pretty low (2bar rings a bell).

I don't think LPG is taxed at all so not sure buying heating gas will be any cheaper although I guess buying in bulk is.

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ChrisW

posted on 27/12/17 at 09:25 PM Reply With Quote
quote:
Originally posted by BenB
Can't help with the original question but is there such a thing as "red" LPG? IE what's to stop people using heating LPG for cars? Or do they just assume the number of LPG cars is quite low and the number of people who have the knowledge to transfer LPG without flame-throwering themselves even less so???


Answer was in my original post.

quote:
Originally posted by ChrisW
The gas is the same stuff as used for heating, and there is a process with HMRC (Google C&E930B if you are interested) for declaring that you have used heating gas as road fuel and paying the difference in duty, the issue is one of getting the LPG from a bulk tank into the car.



So yes, all heating LPG is 'red', but unlike red diesel you can declare your usage in order to be legit with HMRC, and of course there is no way to dip an LPG tank.

quote:
Originally posted by luke2152
Loads of forklifts run on LPG and I assume they get filled on site so I guess smallish bulk equipment must be available. Also some of the small LPG filling stations look like they have pretty basic equipment.



I have not seen or heard of a DIY refilling machine for fork lifts. If such a thing exists I would certainly be interested to hear about it!

quote:
Originally posted by luke2152
Couldn't you just connect the tanks without a pump and have a bit more pressure in the external tank to force it to the car tank. Or pressurise it with welding gas. I'm sure the pressure in the car tank is pretty low (2bar rings a bell).



I believe you could, but as the volume in the bulk tank decreases so does the maximum you could fill the car. Also the time taken to transfer will increase. Pressure in an LPG tank is roughly 100psi (about 7 bar) I believe. This is based on the vapour pressure and varies with temperature.

quote:
Originally posted by luke2152
I don't think LPG is taxed at all so not sure buying heating gas will be any cheaper although I guess buying in bulk is.


Price for heating LPG is about 32p/litre, then you have to pay 10p/litre duty on top (I believe) so should save me about a third on the local place (currently 62.9p/litre).

[Edited on 27/12/2017 by ChrisW]





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rash12

posted on 27/12/17 at 09:38 PM Reply With Quote


might not be for you but i used to get lpg from an upturned 47kg cyl using one of these made your arm ache i suppose you could motorise it mine was on a hand lever

[Edited on 27/12/17 by rash12]

[Edited on 27/12/17 by rash12]

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ChrisW

posted on 27/12/17 at 09:51 PM Reply With Quote
That looks like the one on the DIY-LPG site here.

Tinley Tech sell them pre-made here but not sure I want to hand pump it each time. You are right though I could potentially motorise it.

I was thinking of buying something like this: eBay Item. OK it will be slow (4 litres per minute) but I can just hook it up and leave it running for ~15 mins. It is a gear type pump like the 'proper' ones. Has anyone got any comments on whether this will work or not?

Chris





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rash12

posted on 27/12/17 at 10:09 PM Reply With Quote
thats where i got the plans from worked well used it for a couple of years
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02GF74

posted on 27/12/17 at 10:30 PM Reply With Quote
Is fitting a larger or second lpg tank not an option?






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ChrisW

posted on 27/12/17 at 11:22 PM Reply With Quote
quote:
Originally posted by 02GF74
Is fitting a larger or second lpg tank not an option?


It's possible, but I would lose even more boot space, even doubling the tank size (which would be a push) would only half the number of trips to fill up, and would mean I had to throw the idea of saving money on the gas out of the window.





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llionellis

posted on 28/12/17 at 11:02 AM Reply With Quote
I have never pumped LPG, but have been involved with liquid transfer many times over the years. My first point of call for a positive displacement pump
with known reliability would be an air operated diaphragm pump and my choice of manufacturer would be Blagdon. They are not cheap and would probably eat into the cost saving between LPG and other fuels.

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trextr7monkey

posted on 28/12/17 at 02:16 PM Reply With Quote
Once read an article in some Cumbria mag about an Estate agent who worked around Coniston running a massive engined Range Rover and he had a tank at home to top it up so it can be done. We use lpg for heating but tank belongs to Shell. If you are buying bulk could you not get a free tank and pump from a supplier?
Atb
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mark chandler

posted on 28/12/17 at 05:50 PM Reply With Quote
I used to invert 47kg cylinders and pump them into my Range Rover, less than 25p per litre, used to go through 4 a month.

I started off with a vane type pump, slow and fell apart so moved onto a quality diapham pump that was pretty quick although cost maybe £250 at the time, it was a quality bit of kit.

Looked like this. Lpg Transfer Pump
The problem is LPG rotting the seals.

[Edited on 28/12/17 by mark chandler]

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Angel Acevedo

posted on 28/12/17 at 10:53 PM Reply With Quote
Back in the days working as an interpreter I remember a Video about an accident involving propane and Liquid transfer in Ghent, W.Va.
Shouldn´t be that hard to google.
Not to discourage you, but to make sure you review and heed all safety procedures before attempting such transfers.





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Angel Acevedo

posted on 28/12/17 at 10:55 PM Reply With Quote
Found the page and video of the accident recap...
http://www.csb.gov/csb-safety-recommendations-from-ghent-west-virginia-propane-explosion-largely-adopted-effecting-life-saving-change/
Link to video on page...





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coozer

posted on 29/12/17 at 10:47 AM Reply With Quote
A few of the rdcs I go with my truck have a big tank and the forklift drivers fill the cylinders from it. Not sure how it works but next time I'm there I'll take a picture of the pump arrangement.

Might be while yet like cause I'm sunning mesell in Tenerife atm...





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sebastiaan

posted on 29/12/17 at 12:15 PM Reply With Quote
Having worked with LPG professionally for years (decade and a half) I only have one advice: don't do what you are planning. Transferring LPG from one tank to another regularly, safely and reliably isn't a DIY proposition. Having a modified 1000L tank at home also isn't. Just think what will happen if one of your fittings fail.

Sorry to be the bearer of bad news. I'm usually all for doing stuff yourself, but this is just a bad idea and possibly lethal...

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ChrisW

posted on 3/1/18 at 05:45 PM Reply With Quote
First off, thanks for the comments everyone.

quote:
Originally posted by mark chandler
I used to invert 47kg cylinders and pump them into my Range Rover, less than 25p per litre, used to go through 4 a month.



I'm going to give that a shot first to prove that my pump set up works and, if all successful, will look at getting the bulk tank filled up. Picked up the correct hose today to connect to a 47kg cylinder.

quote:
Originally posted by mark chandler
I started off with a vane type pump, slow and fell apart so moved onto a quality diapham pump that was pretty quick although cost maybe £250 at the time, it was a quality bit of kit.



I have heard that the vane type pumps work ok as long as the liquid keeps flowing at reasonable speed to carry the heat away. Not heard of anyone using a diaphragm pump up to now but you are right, that one you linked on eBay certainly is that.

quote:
Originally posted by coozer
A few of the rdcs I go with my truck have a big tank and the forklift drivers fill the cylinders from it. Not sure how it works but next time I'm there I'll take a picture of the pump arrangement.


I believe this is a fairly common thing to do. Also a mate who does hot air ballooning says that it is common for pilots to refill their own tanks. I have not managed to find a rig for sale yet though or even a picture of one. My only source of reference at the moment is the local LPG retailer (an independent shop as opposed to a filling station). They have a 1000l tank with Smith's pump feeding a pressure relief valve that feeds back to the tank. I had a look today and the valve is set to 75psi which I assume is relative to tank pressure.

quote:
Originally posted by sebastiaan
Having worked with LPG professionally for years (decade and a half) I only have one advice: don't do what you are planning. Transferring LPG from one tank to another regularly, safely and reliably isn't a DIY proposition. Having a modified 1000L tank at home also isn't. Just think what will happen if one of your fittings fail.


I appreciate your concerns, but on the other hand I am confident that I can come up with something that is safe. The rig will be on a farm in the middle of nowhere, not in an enclosed back garden or with people in close proximity, so if there was a problem it will only be myself in trouble.

The tank already has a bottom outlet, it will not need to be modified. I intend to fit a ball valve directly to the tank with some kind of remote lever to ensure that I can turn it off without having to get too close in the event that something nasty did happen. Yes a fitting could fail, but as long as the isolation tap is a quality part and I switch it off when not in use I do not see any more of a risk than at the local filling place which, incidentally, is amongst a busy industrial estate.

I understand that you might not want to give advise, but surely it would be better to help me find a suitable method for doing this than withholding information that would help me avoid making safety mistakes?

So my plan at this point, unless anyone can tell me otherwise, is to buy that gear-type hydraulic pump from eBay. As above, I am aware that it will be slow, but it is priced such that it is not the end of the world if it doesn't work. My concerns are whether the LPG will provide sufficient lubrication and whether the viscosity of the liquid will be too low for the pump to work effectively. The manufacturer states that the pump is suitable for 'Fuels' and 'Petroleum derivatives' and only states a maximum viscosity so I am keeping my fingers crossed that it will work. I have emailed them asking specifically if the pump will work with LPG but am not holding out much hope of a reply.

I will use a pressure valve that vents back to the tank set at 75psi just like the local filling station. I will probably also put an inline filter too just to make sure I am not sucking any debris into the pump.

I will try it going from an 'orange' cylinder first, probably a 19kg one as that should be less than the size of my car tank and therefore no chance of overfilling. If that works and seems to be effective and reliable I will probably try pumping a couple of 47kg cylinders into my bulk tank and then filling from there before I go ahead and get the tank filled right up. 1000 litres is a lot of gas to waste if I can't get it to work!

Anyone care to point out any mistakes or other considerations before I go ahead?





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Mr Whippy

posted on 4/1/18 at 12:38 PM Reply With Quote
I wonder what your house insurance would say if you blew up the place...?

Sure in theory all this is very simple, in concept but I'm sure there is very good reason these things tend to be regulated. I too am looking at LPG for my Landy but will not be making my own filling station at home.






[Edited on 4/1/18 by Mr Whippy]

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ChrisW

posted on 4/1/18 at 01:02 PM Reply With Quote
quote:
Originally posted by ChrisW
The rig will be on a farm in the middle of nowhere, not in an enclosed back garden or with people in close proximity


As above, will be nowhere near my house, or anyone else's for that matter. If anything was to go wrong there would be very limited fall out, it would certainly not be an issue for house insurance to sort out.

Short of a fitting failing as Sebastiaan mentions, the impact of which I feel can be significantly mitigated by making sure there is a remotely accessible emergency shut off valve right on the tank, I really do not see a much of an increased risk over having a domestic LPG tank in the garden to run central heating. The tank itself is, after all, manufactured to be safe for storing LPG.





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Mr Whippy

posted on 4/1/18 at 01:18 PM Reply With Quote
yeah I use to have a LPG tank in the garden too, can't say I was ever trying to connect my car to it though. These things kind of escalate rather quickly if they go wrong. 1000ltrs, that's a lot of gas to go bang if it did, mushroom cloud kind of scale, crater in the ground...

I'm not saying don't do it, just do it very very very carefully. I'd be most concerned if the regulator or valve failed and the full force and volume of the gas in the tank tried to get out. Isn't it like 300psi normally in a tank, more in hot weather? you ain't plugging that with your finger. Tbh I shudder when I see some of the contraptions people make on the web though.

Pity the Jeep has such a huge engine, probably produces very little power for it's size

[Edited on 4/1/18 by Mr Whippy]

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Oddified

posted on 5/1/18 at 11:35 PM Reply With Quote
Whilst i run my van on lpg, i don't have a home filling set-up. I do know a few people that do/have though, and none reported any issues what so ever. The only thing some said was if the big tank is being filled for domestic use (cheaper), they quite often check for a bottom take off pipe/indications someone using it to fill a vehicle. Of course that wouldn't be so easy to check if someone had a top fitting with a dip tube..lol. I never asked them about the transfer/pump so i can't help on that one but reading above it looks like you've done a bit research, crack on

Ian

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ChrisW

posted on 8/1/18 at 10:35 AM Reply With Quote
quote:
Originally posted by Oddified
The only thing some said was if the big tank is being filled for domestic use (cheaper), they quite often check for a bottom take off pipe/indications someone using it to fill a vehicle.


Thanks Ian. Quite happy to tell them that the gas will be for filling vehicles; it is perfectly legal to do so. You can either buy the gas with the road tax pre-paid or buy it as heating gas and declare the usage to HMRC afterwards using the form I reference in the first post.

Either way I believe it adds about 10p/litre to the gas price so roughly 40p/litre total compared with the best local price of 63p/litre that is still a good saving.

The maths for anyone thinking of something similar: I get about 160 miles of town driving from 50 litres of gas. That is 14.5mpg. This is all rough of course because it does a bit better on a run (not generally what it gets used for) or a bit worse if I have a trailer on the back (fairly common) but at least it gives a ball park.

That 50 litres costs me £31.50 at the local place. With petrol at £1.20/litre roughly that's equivalent cost to about 5.7 gallons of petrol, therefore cost wise the equivalent is about 28mpg. Not too bad for what it is.

The same 50 litres from my bulk tank should work out around £20 with the duty paid, equivalent cost to about 3.7 gallons of petrol and therefore pushing my pseudo-mpg to 43mpg. I would be very happy with that for a v8 4x4!

Plus in my case I would save about a gallon (of gas) on say 50% of fills as I won't have to make a special trip to the other side of town where the filling station is.

Brief project update: I have ordered the hydraulic gear pump from eBay as mentioned above and have a hose with the right connector on it to go to connect to an orange cylinder. I need to get hold of one to connect to the car, I think tinleytech stock them, just need to work out which one I need. I also need to order up a 3-phase contactor and rig that up in some kind of enclosure to make it safe.

I can then do some tests to see whether the pump is effective at moving gas between a cylinder and the car. I will use my air con 'charging' scales to monitor the weight of the full cylinder to make sure I don't overfill the car tank. They are designed for the purpose of weighing cylinders of refrigerant whilst charging AC systems so should be perfect for the job.

Will report back!

Chris





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Mr Whippy

posted on 8/1/18 at 12:59 PM Reply With Quote
you seem to be mixing fluids/gasses in different items are you sure the material in the seals etc are all compatible?, propane in ac or hydraulic equipment. Another thought is the effects of cold, O-rings for hydraulics are unlikely to be happy if they are chilled.

might be worth checking....

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chillis

posted on 8/1/18 at 01:21 PM Reply With Quote
I believe you need a licence for filling vehicles with LPG. The LGP 'petrol' station will have one issued by the local fire brigade.
We used to have one for LPG when we ran LPG engines on the test bed. As for transferring from one tank to another its a real headache. You need to ensure the pressure in the bulk tank is greater than the vehicle tank and by some margin or you'll transfer very little and the pressure changes depending on the temperature. Also the bulk tank will be considered a pressure vessel so you made need regular certification. Can you not fit a bigger vehicle tank to reduce the trips to the filling station?





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ChrisW

posted on 8/1/18 at 04:24 PM Reply With Quote
quote:
Originally posted by Mr Whippy
you seem to be mixing fluids/gasses in different items are you sure the material in the seals etc are all compatible?, propane in ac or hydraulic equipment. Another thought is the effects of cold, O-rings for hydraulics are unlikely to be happy if they are chilled.


The AC scales are just that.... weighing scales. They won't have any contact with the gas itself. They just allow you to tare a cylinder weight and then don't auto time out so you can accurately meter an amount of refrigerant gas (by weight) into an AC system.

Propane weighs (give or take) 0.5kg per litre so the first time I do it I will make sure the Jeep is empty (which means at least a 50 litre fill) and then fill it until the cylinder weighs 20kg less than the start weight. That way I know I will be well within tolerances.

The only hydraulic component I am using is the pump, which is a gear type. As far as I know these use the metal casing against the gear teeth to seal so there should be nothing to perish. The manufacturer does not mention LPG specifically but does say that the pumps are suitable for 'Oil, fuel and gasoline' so I am keeping my fingers crossed.

At the end of the day, as long as I keep the tank and fill valves closed when not in use, even if the pump seal was to fail the worst case scenario is that next time I come to use it it won't work.

Chris





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