Gas bottles and the euro train.

[T_5064313]

We are taking the train this year instead of the ferry, and one of the conditions is that the gas bottles must be less than 75% full and that we may be asked to verify this. Has anyone been asked to verify the contents of their bottle(s) and if so how did you do it to their satisfaction?

Regards,

Tillman

http://www.tkimages.co.uk

 

[ProfJohnL]

Hello T

I am intrigued by your posting. I can think of no good technical reason for such a stipulation. LPG bottles as used in caravans are Vapour Phase Take Off, and as such they are never completely filled with liquid, there is always some vapour space left at the top. I do wonder if they are referring to Liquid Phase Take Off bottles where the liquefied gas is taken of. This is usually used on things like fork lift trucks or other internal combustion engined devices where you need the highly concentrated fuel to get the necessary performance. These bottles should also have some vapour space to allow for the change of volume of the liquid with temperature.

I have requested clarification from Euro-star, if I get a coherent answer I will pass it on.

 

[T_5064313]

This is the relevant text from the caravan page.

Please help us by keeping gas cylinders (hydro-carbon gas) and their appliances switched off before boarding and whilst travelling on board. In addition, no more than 50kg of gas (maximum cylinder size 47kg) can be transported in a vehicle. Leaking or inadequately secured cylinders will not be accepted on the shuttle.

They must not exceed 80% capacity, this will need to be demonstrated before travel.

Tillman

 

[ProfJohnL]

Thank you Tilman for the text,

Their stipulation of maximum size (47Kg) is understandable, as in the event of an incident, the inertia of one of these bottles (1.2M tall) is considerable and it could do a lot of physical damage if it not secured properly. The reference to leaking bottles is also a very sensible precaution. Just in case you were not aware, LPG is heavier than air and will collect at the lowest point, which clearly in a tunnel under the sea would not be a good thing.

But the 80% figure bemuses me. I have asked Euro-star for a technical response, but I did use you previously quoted figure of 75%, so there could be some confusion, as the calor recommended maximum fill would leave about 20% volume free of liquid in the bottles/tanks.

 

[Zbungle]

If it helps, I have used the EuroTunnel on many occasions with my caravan in tow. I have always been asked to go over to a special checking area where the car and caravan have been politely scrutinized for aliens, ground to air missiles and hard drugs. But nobody has ever checked the contents of my gas bottles. They simply ask me if I have any LPG on board, I say yes, they take a look (just in case I am telling porkies?) and then wave me on.

Because they are polite and efficient, and because I recognise that all security personnel are doing an important job, I don't really mind. But like you, I don't understand the 80% rule, especially with John L's very detailed explanation.

 

[Nidge1]

Hi,The rule you are talking about is not realavant to caravan gas bottles.The rule is for motorhomes with a fixed gas tank for leisure use only(not as a alternative dual fuel) as this rule is still in force)You are still limited to 2- 7kg bottles which must be turned off and the regulator disconected.

I have travelled on the shuttle numerous times and think it is brilliant.The staff are very helpfull and the on/off time is fantastic.

Have a great journey

Regards Nidge

 

[ProfJohnL]

Thanks Nidge,

What you add to our discussion has some merit, but even a fixed tank requires a vapour space, and so even these should not be filled above about 80%.

It seems ludicrous not to include LPG tanks for motive power as they are constructed in just the same way as bottles. The primary difference is the valve stem draws the liquefied gas from the tank rather than the vapour and and potentially will leak liquid gas rather than vapour if the valve or pipework is damaged.

Incidentally Euro-star have not yet responded to my enquiry.

For your information a litre of leaked liquefied gas will expand at atmospheric pressure to about 250 litres of 100% saturated vapour. To create a combustible mixture it needs to mix at a ratio of about 1:10 gas to air this gives us about 2.5 cubic meters(the internal volume of a large estate car). If burnt it will about 25KwH of energy, and if burnt explosively it would certainly rip the roof and sides of a car or caravan.

 

[jacky3]

have a look here it tells you about regulations

http://www.motorcaravanners.org.uk/TEXT/matinfo.htm

 

[jacky3]

http://www.eurotunnel.com/ukcMain/ukcBoarding/ukpBoardCaravan

 

[ProfJohnL]

Thanks again Klarky

It seems that LPG tanks for traction is not permitted.

I note that ES also require a capacity gauge to be fitted. This could be a problem for Calor, as the only two ways of adequately confirming the content of a bottle is either a liquid level float/sight glass, or by the difference between the bottles weight and the Tare weight.

I would guess that the ES inspectors are omitting to check for this feature for most caravans.

Neither of the sites you give addresses for explains the reason behind the stated 80% capacity.

It now occurs to me do they mean 80% of the bottles volume capacity, or 80% of the permitted fill capacity?

And ES still have not responded to my email.

 

[gary]

Hi John, When I first read this and the 75% rule it confused me but 80% is the stated maximum LPG for all tanks to allow for normal expansion and more important abnormal pressure build up in the case of superheating in a fire.

Obviously the tank has been designed to withstand overheating for a time and this design will be based on the maximum of 80% full, any overfilling will rapidly increase the point the tank reaches bursting point in a fire so any predictability due to the design will be gone.

It strikes me that owners of refillable bottles faced with a time abroad might be tempted to overfill their bottle in the hope of lasting the holiday and this stipulation by ES is more aimed at them than those with the proprietary filled bottles.

The two small sizes of bottle commonly used for camping are designed to a higher standard than the larger sizes and will stand more pressure, it surprises me then that ES allow anything but these on it's service.

 

[ProfJohnL]

Thanks for you input Gary,

Your thoughts agree with my understanding of LPG bottle filling in the UK, however bottles that comply with UK regulations also carry an over pressure relief valve that will begin to vent excess pressure. The professional view is it's better to have a controlled vent of vapour that can then burn off, rather than a burst. Also the venting of the vapour will cause the bottle to drop its pressure (latent heat of vapourisation) which actually reduces the danger (Though I agree with the Fire Brigade - keep well away and dowse with lots of cold water)IN extreme cases the brass valve will melt (and shoot of like cannon ball) and allow the content to vent. Bottles must be secured in an upright position to ensure that the valve is in the vapour space above the LPG. The fire brigade will evacuate who areas if LPG tanks are not secured or are observed to be on their side.

I quite agree that privately owned refillable bottles could present a danger if over filled by their owners, but in doing so they automatically invalidate their insurance and endanger themselves. It is also possible that some refillable bottles acquired abroad or from some locations in the UK may not meet the UK standards for construction - some do not have over pressure relief valves, and some are made from plastics which may have sufficient strength when cold but become pliable and more likely to rupture at only modest elevated temperatures.

As to the strength of the different sizes of steel bottle, I am not aware of a different standard of construction, all should meet and exceed the test pressure which will be significantly greater than pressure relief valve setting, but by simple physics, the greater surface area of a larger tank means that the pressure inside will have greater potential energy in a large tank compared to a smaller one.

PS - ES have still not replied!

 

[ProfJohnL]

Thanks for you input Gary,

Your thoughts agree with my understanding of LPG bottle filling in the UK, however bottles that comply with UK regulations also carry an over pressure relief valve that will begin to vent excess pressure. The professional view is it's better to have a controlled vent of vapour that can then burn off, rather than a burst. Also the venting of the vapour will cause the bottle to drop its pressure (latent heat of vapourisation) which actually reduces the danger (Though I agree with the Fire Brigade - keep well away and dowse with lots of cold water)IN extreme cases the brass valve will melt (and shoot of like cannon ball) and allow the content to vent. Bottles must be secured in an upright position to ensure that the valve is in the vapour space above the LPG. The fire brigade will evacuate who areas if LPG tanks are not secured or are observed to be on their side.

I quite agree that privately owned refillable bottles could present a danger if over filled by their owners, but in doing so they automatically invalidate their insurance and endanger themselves. It is also possible that some refillable bottles acquired abroad or from some locations in the UK may not meet the UK standards for construction - some do not have over pressure relief valves, and some are made from plastics which may have sufficient strength when cold but become pliable and more likely to rupture at only modest elevated temperatures.

As to the strength of the different sizes of steel bottle, I am not aware of a different standard of construction, all should meet and exceed the test pressure which will be significantly greater than pressure relief valve setting, but by simple physics, the greater surface area of a larger tank means that the pressure inside will have greater potential energy in a large tank compared to a smaller one.

PS - ES have still not replied!

 

[ProfJohnL]

Thanks for you input Gary,

Your thoughts agree with my understanding of LPG bottle filling in the UK, however bottles that comply with UK regulations also carry an over pressure relief valve that will begin to vent excess pressure. The professional view is it's better to have a controlled vent of vapour that can then burn off, rather than a burst. Also the venting of the vapour will cause the bottle to drop its pressure (latent heat of vapourisation) which actually reduces the danger (Though I agree with the Fire Brigade - keep well away and dowse with lots of cold water)IN extreme cases the brass valve will melt (and shoot of like cannon ball) and allow the content to vent. Bottles must be secured in an upright position to ensure that the valve is in the vapour space above the LPG. The fire brigade will evacuate who areas if LPG tanks are not secured or are observed to be on their side.

I quite agree that privately owned refillable bottles could present a danger if over filled by their owners, but in doing so they automatically invalidate their insurance and endanger themselves. It is also possible that some refillable bottles acquired abroad or from some locations in the UK may not meet the UK standards for construction - some do not have over pressure relief valves, and some are made from plastics which may have sufficient strength when cold but become pliable and more likely to rupture at only modest elevated temperatures.

As to the strength of the different sizes of steel bottle, I am not aware of a different standard of construction, all should meet and exceed the test pressure which will be significantly greater than pressure relief valve setting, but by simple physics, the greater surface area of a larger tank means that the pressure inside will have greater potential energy in a large tank compared to a smaller one.

PS - ES have still not replied!

At last ES have replied I repeat their answer for you.

The reason for this limitation is of course safety. Effectively, the correct and safe level of filling a tank is 80%. This allows for the natural expansion in the tank of the LPG, which will occur in case of an increase in the outside temperature. Should this not be respected then excessive pressure might develop in the container, hence carrying a risk of explosion. Eurotunnel therefore requires its customers to respect this safety procedure.

For the second part of your question, the 80% applies to the total capacity of the tank, not to the permitted net fill (this permitted net fill corresponds in fact generally to the above mentioned 80% of the total capacity of the tank for the very same reason).