Maximum Length? Flexible LPG pipe.

[Dustydog]

I’ve used 3 metres of flexi hose from caravan to BBQ for years.
The reality is I could do with 5 metres. Is there any Law that dictates the safe allowable length?

 

[bertieboy1]

Hello, don't know about law but I found the pressure drop on a 3m length of flexible gas piping to be quite high.When I reduced the length to 1.5m the flame greatly improved and the lava rock started to glow (it didn't when pipe was 3m long)

 

[Sproket]

I can't find anything regarding maximum flexible pipe length, only the age of pipe but for instance a roofer using a blow torch may not wish to take a bottle onto a roof hmy: so they would do a risk assessment as they may require the bottle to be more than 3m from the appliance / torch

Now isn't that the same type of pipe as you use on your bbq ?

As for lack of gas pressure i suggest having the gas flow checked on your regulator.

 

[Anseo]

I guess pressure drop relative to the length of hose is a factor depending on the final output device being used.

(Hi Sprocket it was good to meet you in Lincolnshire recently - best wishes to you )

We use torch-on-felt roofing contractors regularly, some use less and some use greater hose lengths than others, however, the propane torches that are used differ very much from say a gas fire, most torches used have broad pattern flame spread as the material being heated requires little heat to softenmelt the backing compound to a bonding grade consistency.

In observation the flame from a roofers blowtorch appears very intense, but in reality it is spread wide producing a reduced overall heat over a broad area, or so it appears to me.

Hope the Prof comes along to clarify (or shoot me down ).

Fire in the hold

 

[ProfJohnL]

As far as I know there is no Law that limits the length of a flexible gas hose, but good sense suggests keeping it as short as is reasonable.

From a practical point of view, the pipe should of course be LPG approved reinforced pipe. This should have a pretty rigid wall so the internal diameter should remain virtually unchanged.

When gas is used the flow of vapour in the tube will be resisted to some extent by the tube. So the longer the tube the greater the total resistance will be.

Roofers mange to run quite large burners using 6.5mm i/d flexible pipe I've seen them with 20M long pipes when doing some jobs - BUT i don't know what pressure they were using, some have a habit of winding up the pressure on their regulators - strictly against HSE of course.

In practice we were able to run a 6.5kW load (approximately 700gms an hour) on propane with a 10M hose with a 6.5mm bore. I would be surprised if any caravan BBQ was anywhere near that powerful so you should not have any real problems with hoses under 10M. Its more likely restrictions in the pipe connector that might cause more pressure drop

 

[Gabsgrandad]

I use that much on mine Dusty and have done for years, (your sausages at Woosiefest were cooked on it.) -- there may be a pressure drop, but hardly noticeable , but it is hardly significant. (ps when I was obtaining the longer length the dealership told me they couldn't sell me longer than 3 metres, so I told them I'd have 2 and join 'em, looked at me 'a bit old fashioned' but sold me the 1 length I required!

 

[Damian]

It never ceases to amaze me that dealers and some outlets say that they cannot supply LPG hose in greater lengths than 2 mtrs. It is absolute nonsense and has no legal standing whatsoever.

The rules (guidelines actually) say that the hose should be long enough to operate the appliance taking into consideration trip hazards of longer pipes, security of cylinders from interference, terrain the hose is in contact with and the avoidance of the hose being driven over.

The longer the pipe the more chance of pressure drop which is why caravans have a quite complicated system of pipe sizing maths taking length, needs of the various appliances, number of bends, number of fittings etc as each has a value which affects what size pipe is fitted where.
If you are plugging in to the van system via the outlet you are already limited by the size of the pipe to the outlet.