tank on car roof

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fostertom
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tank on car roof

#1 Post by fostertom » Thu Aug 13, 2020 5:22 pm

Just bought a 1998 Honda Stepwagon - a van-type 8 seater, Jap import not sold in UK - which has LPG conversion (as well a three large solar panels!).

It has a 65l (fill capacity) donut tank, and used to have a supplementary bullet tank, also 65l (80l actual), wobbly mounted on the floor right at rear, so it's been taken out.

Now seeing how LPG outlets seem to be closing (Shell, BP), that extra LPG capacity looks essential - nothing in Cornwall west of Truro. So I'm thinking to mount the bullet tank crosswise on the roof. It can be made very secure and would be well forward from the rear. Pipework would be completely external - I can see how to do it to look OK and not be exposed to damage. The bullet tank is a TMS 300/1020, 'Internal Cylindrical Tank'.

Question is - would that be legal?

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Re: tank on car roof

#2 Post by Gilbertd » Thu Aug 13, 2020 7:54 pm

In a word, yes. The code of practice specifically mentions tanks on roofs:

2.3.4 Fuel tanks mounted on rooftops
Fuel tanks may be mounted on the rooftops of vehicles, subject to the following:
Section 2: LPG Fuel Tank or Tanks
(i) the vehicle manufacturer confirms that the location will not affect the ability of the vehicle to meet statutory requirements. See Section 6 for buses and PSVs;
(ii) crash-bars and/or roll-over protection are provided where necessary, taking into account the type of vehicle and its duty. See also 2.4.3;
(iii) tank valves, fittings and extended pipework are housed in a gas-tight housing as described in 2.3.2 (a) unless a suitable protected roof compartment as described in 2.3.2 (b) is provided;
(iv) the ventilation from the gas-tight housing or compartment takes account of the heavier than air density of LPG vapour, and ensures no discharge can enter the interior of the vehicle.
2.4 Fuel Tank Mounting
2.4.1 Means should be provided for attaching the fuel tank(s) securely to the vehicle. This provision may take the form of fixed lugs welded to the fuel tank during manufacture or the provision of cradles, metal straps, or bonds attached to the vehicle. In order to prevent distortion of the fixing area or the tank(s) breaking loose in the event of impact, reinforcement of floors, body panels etc should be provided by suitable means which are designed to equally distribute the weight of the tank and its contents.
Mountings should be designed to meet the requirements of ECE 67.01.

For example, for cars and light goods vehicles the tank must be securely mounted to withstand acceleration of 20 g in the direction of travel and 8 g horizontally and at right angles to the direction of travel.
Straps, bolts and spreader plates should be designed bearing in mind the material, profile and thickness of the mounting panel to ensure an adequate contact area.
Straps should be of corrosion protected steel having a minimum tensile strength of grade E 235-B to ISO 630. Bolts and spreader plates should be of appropriate corrosion resistant materials or subsequently protected against corrosion.
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Re: tank on car roof

#3 Post by LPGC » Thu Aug 13, 2020 9:22 pm

The 'code of practice' isn't law anyway, it is just a trade body's self imposed stuff, frankly it mostly refers to nuts and bolts common sense type stuff... A vehicle could pass a 'code of practice' test yet be totally undriveable (and dangerous to drive) on LPG. The BSEN Standard (if anything) is more likely to be considered 'law' but strictly speaking even that isn't law.

The code of practice says hidden / adaptor type fillers should not be used but it seems the most recent factory LPG converted vehicle available in the UK has a hidden/adaptor type filler - If we listened to the trade body this factory converted vehicle isn't fit for the roads yet we know it will be. Might think DVSA would listen to a trade body, instead DVSA seem to know the score and ask me if they want to know anything about vehicles running on LPG. Trade body's can be ignored.. Imo trade body's that profiteer from ineffective supposed safety schemes should be ignored (for want of a better scheme / system). I got my own way with how the MOT approaches LPG converted vehicles, against what the trade body wanted/advised.

We don't see many vehicles with LPG tanks installed on the roof but I know of a few (and who fitted them). Iirc I believe Dai Classicswede fitted a tank on the roof of a VW camper a lot of years ago. It might look unusual but in the real world what would be the safety concerns that should prevent fitting a tank on the roof?
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fostertom
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Re: tank on car roof

#4 Post by fostertom » Fri Aug 14, 2020 11:16 am

Thanks to both - that is very helpful.
I have searched for info, pics etc incl Dai Classicswede, but nothing, just transporting loose gas bottles on roof rack. Can anyone point to fixed installation pics?
Gilbertd wrote:
Thu Aug 13, 2020 7:54 pm
(iii) tank valves, fittings and extended pipework are housed in a gas-tight housing as described in 2.3.2 (a) unless a suitable protected roof compartment as described in 2.3.2 (b) is provided;
(iv) the ventilation from the gas-tight housing or compartment takes account of the heavier than air density of LPG vapour, and ensures no discharge can enter the interior of the vehicle.
How would it be if all pipework runs externally, in the fresh air, i.e. securely clipped down the rear outside to join the existing underfloor system? then no need for protected roof compartment or sleeved ventilation of the valve etc housing that's already on the tank?

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Re: tank on car roof

#5 Post by LPGC » Sun Aug 16, 2020 9:51 pm

If you had it inspected I expect the inspector wouldn't know what to make of it! It would probably be the first tank on a roof they'd seen...

Their gut instinct may be 'Doubt this will/should be allowed, I dare not pass it'. They could think that the externally clipped pipe isn't sufficiently protected hence fail it but I'd disagree with that because pipes under the vehicle don't have to be protected either. Just that external pipes running down (say) the back of a vehicle are 'in your face' and the tester could think/say 'in a rear-ender those pipes will definitely be hit and aren't protected.

The main problem with running the pipes 'in your face' may be the external venting factor. An inspector could say that if there's a leak at the tank then since gas is heavier than air and since the van has windows/doors/tailgate that can be opened/broekn gas from a leak/venting could enter the vehicle. And if you're going to run external venting down to below vehicle floor level why not run gas pipes through that venting... And then they could think 'And hmm that venting containing gas pipe should be run inside the vehicle where it's all protected in a crash'. I wouldn't agree but that's probably how a lot would see it.

If they wanted to fail such a conversion and couldn't find another definite reason to fail it they might see the 20G/8G stress limits as an easy cop out. Make sure you fit it well with big spreader plates and that the roof panel isn't just spot welded on at a few points - If you have (say) an 60L tank on the roof the tank itself might way 30kg and 60L of gas will weight approx 30kg for total of 60kg. 60kg at 20G is 1.2 tonnes (momentary in a crash with stationary heavy object).
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fostertom
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Re: tank on car roof

#6 Post by fostertom » Mon Aug 17, 2020 7:18 pm

Very good pointers - thanks v much.

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Re: tank on car roof

#7 Post by Gilbertd » Mon Aug 17, 2020 10:20 pm

While only a Code of Practice, it is based on the EN standard so some of it would be enforceable and if there was an accident, whoever did the install could be held liable. It is contradictory in places though. Pipework shall be visible over it's full length so it can be checked for damage but equally, it should be protected from damage. So on the one hand, having the pipes open and visible running up the back of the car would be correct, but at the same time having it covered would also be correct.
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Re: tank on car roof

#8 Post by LPGC » Tue Aug 18, 2020 12:19 am

A lot of the bulk gas supply company trade body's code of practice and indeed the BS/EN standard is outdated anyway. E.g. Faro pipe is very different to copper pipe yet installers who fit Faro pipe still often approach fitting Faro pipe as though it were copper.

Rules / regulations never did address the most common safety issues anyway, the most common safety issues are drive-ability issues which can include engine cutting out with loss of power steering etc type scenarios. The E67 standard for components would prevent most risks being realised even in the case of most dodgy jobs of fitting (with few exceptions, one of which is internal tanks not being externally vented - though external venting is seldom going to happen and even on an install with a tank free floating in the back the occupants are more at risk of something nasty happening due to drive-ability issues). Anyone can follow nuts and bolts type advice to meet a code of practice or BS EN but on some vehicles it takes more in-depth skills to ensure correct mixture and good drive-ability. I find most pro installers who whittle on about nuts and bolts aspects can't cut it when it comes to getting good driveability especially on demanding vehicles.
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fostertom
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Re: tank on car roof

#9 Post by fostertom » Wed Aug 19, 2020 5:39 pm

Really grateful for educating me - hope it's OK to keep asking questions.
LPGC wrote:
Sun Aug 16, 2020 9:51 pm
They could think that the externally clipped pipe isn't sufficiently protected hence fail it but I'd disagree with that because pipes under the vehicle don't have to be protected either. Just that external pipes running down (say) the back of a vehicle are 'in your face' and the tester could think/say 'in a rear-ender those pipes will definitely be hit and aren't protected.
I see on http://www.go-lpg.co.uk/Filler.html under 'Fixed Bayonet Filler' (like mine - actually Towbar mounted):
"A coil is put in the pipe to prevent it rupturing during a rear - end shunt, but even if it pipe where completely severed the multi valve would stop any significant (large scale) leakage. All that can happen in that case is the escape of pipe content since the last fill, rarely more than 30 or 40 millilitres".

Wouldn't similar apply to my external pipes? I belive I'd need two of them?

The attached pics show how pipe could surface-run through P-clips fixed into the joint line between body side and tail lights, or hidden inside the door shut, or behind the tail lights if there's space. At bottom, pipe would pass through the plastic bumper top, to underneath; at top it would curve in and forward over the roof top. Pipe could be half-hard (rigid) copper, or stainless, or mild steel say 1.5mm wall for real rupture-strength.

I am contacting Thule for strength info; load shared between three roof bars locked into the Stepwagon's fore-aft channels, to resist 60kg x 20G = 400kg momentary force per bar.
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Re: tank on car roof

#10 Post by LPGC » Thu Aug 20, 2020 3:02 pm

Your tank should (will) have a one way valve on the inlet and electronic solenoid controlled outlet, in which case the only gas that could escape in event of a pipe being ruptured would be gas in the pipes. Some older tank multi-valves only feature manual valves, some 4 hole tank fill valves are installed so tight that the internals are crushed and the one way fill valve doesn't work.

Still it could be considered one thing to mount a tank solidly to the roof, another to mount the tank to a roof bars that are usually considered not permanent, and still there's the point about externally venting (at least gas from an automatic opening PRV) to a position where it can't enter the vehicle. I don't see much of a problem if the roof bars are strong enough but others will have different takes on it. There are loads of aspects that anyone who wanted to fail it could fail it on, e.g. The tank has to be bolted to the car using bolts that will withstand the impact forces of a crash, usually meaning 3 / 4 or more (for a large cylinder tank) M10 bolts, if the roof bars are held together with smaller bolts it could be considered they're not strong enough unless there are a lot of them in relevant positions. Info provided by Thule might help argue your case, or might prompt someone who had concerns about strength of the roof bars to ask you to provide info from the vehicle manufacturer that the mounting points for roof bars are strong enough.

Are you trying to set this up so the tank can easily be removed (maybe along with roof bars) or just looking for the easiest way to mount the tank?
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fostertom
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Re: tank on car roof

#11 Post by fostertom » Thu Aug 20, 2020 8:33 pm

Easiest way, thinking that roof bars (two already fitted, a third to be added) locked to Honda's longitudinal presumably strong roof channels will have a calculated strength, which I hope Thule will be able to give me, tho not answering emails at present. I would not expect to remove any of it. If welding etc to roof were involved, I'd forget about the whole thing.

The bullet tank's steel angle subframe could easily be bolted to the two longitudinal RHS bearers with M10s; each bearer in turn bolted to the three roof bars' RHSs. Drawings would be done.

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