Gas Regulator Blockage Again

[ProfJohnL]

Hello Damian,

With respect of ruprtured diaphragms let me assure it is not nonsense.

I agree that a rupture that destroys the total integrity of the diaphragm will allow gas at a significantly higher pressure through, but the small oroface area of the regulators needle valve will limit the ultimate mass gas flow. With such a catestophic failure the gas pressure in the low pressure side and pipe work is unlikely to climb to the levels you suggest becuase of the gross leak through the ruptured diaphram which is then vented to atmosphere. I am in no way claiming this is a safe or satisfactory situation.

Some symptoms came to light when a client company (I cannot name for reasons of confidentiality) were contemplating importing a regulator manuafctured in the Far East for sale in the EU.

Various test regimes were set up including those where water could collect in the area of the breather vent. It was known that under certain conditions water could gain addmitance to the atmospheric side of the regulator. These units were left on long term test, and it was noted that after some particulary frosty weather LPG could be smelt around the regulators, but the smell deminished as the as the appliance demand increased.

Investigation of the internal working found about a teaspoon full of water, and that the diaphragms had been damaged around the edge where the water had collected. The damage to the diaphram indicated it and been locally stretched and due to the form of the clamping ring and bottom casting it seemed to have cause fissure type stretch marks which proved to be penetrating These would allow varying amounts of gas to vent to atmosphere depending on the position of the diaphragm due to throughput. The fact the damage was localised to the area where the water had collected discounted general aging of the diaphragm and pointed to so relation to the water. Other tests discounted any checmical reaction with the water, which left mechanical stress induced by the expansion of freezing water

The company decided that due to this and a number of of other design and manufacturing isssues it was not possible to obtain EU approvals for the product as it stood, so it was never adopted.

However I cannot categorically say that other makes and designs will or wont suffer in exactly the same way but the possibility is there.

 

[Surfer]

Is there anything preventing you from fitting a regulator on the cyclinder in addition to the bulkhead regulator. After all which is cheaper to replace?

 

[JohnGriffiths]

Quote : "The notion that John L put forward of a ruptured diaphragm is nonsense, quite simply because you would, with Propane, have 6Bar of gas pressure through your system which you WOULD notice as the flames would be about 6 feet high!!!!!!!"

Now surely that would be nonsense. I was complaining that venting of the gas from the reg. if the diaphram ruptured was a safety hazard, you're saying it hadn't ruptured because the flames would be 6 feet high! That would be a enormous safety issue and I can't believe that could happen.

Quote : "This will never happen , quite simply because LPG is a by product of oil, and odd as it may seem, the residue causing the damage is ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,oil.
Fitting a filter is not practical as there is no way of draining such a filter safely, and it would reduce the pressure available to the appliances, causing them to malfunction."

As someone who spent 25 years working as a scientist in first an industrial laboratory and then medical biochemistry I can assure you it is possible to completely separate components like LPG and oil, maybe not with a filter, but it is possible.

 

[JohnGriffiths]

Anyway, some very good news from my POV. I wrote an e-mail to Swift Monday evening, Yesterday morning they asked for the reciept, the dealer e-mailed me an electronic one within minutes and yesterday afternoon Swift promised to send me a cheque for the whole amount. So my thanks and appreciation to Swift and the dealer (Canwell Caravans) for prompt action. There was no discussion of what they thought the problem was or where the fault lay but you can't have everything.

 

[Dustydog]

This makes an interesting read

http://www.nationalcaravan.co.uk/images/news/gas_regulator_blockages_rev1.pdf

 

[Gafferbill]

If anyone is to blame it is the British Government for taking the EU directive and actually implementing it, instead of just ignoring it as Germany, France and other countries have, and still fit 30mb cylinder mounted regulators.

............and there you have it.
You hit the nail right on the head Damian.

 

[ProfJohnL]

Hello John,
Damian's last post does seem particularly terse, and uncharateristically contains some failry glaring errors or inappropriate assumptions.

I do have to defend Damian's point about filtering. Scientifically you may be able to reduce all the undesirable fractions, but I suspect he was was trying to point out that the equipment needed to achieve it is quite extensive, expensive, and probably quite deleicate, consequently it is most likely to be impractical to implement it in a caravan.

I know that some filtering systems are used, becasue gas appliance manufactures when developing and testing appliances have to use high purity gasses of known characteristics. for checking combustion efficecencies, and conformance to the gas catagories applicable for the regions the applaicnes are to be sold in. These bottles of near pure Propane, Butane and Propolene cost a small fortune and can only be produced in relatively small quantities under laboritory conditions.

However I cant accept Damians next point about it necesarily causing a drop in pressure to the appliances, For the filter to be of any use to protect the regulator it would have to be on the high pressure side before the regulator. And as we don't know what form of filtering may be necessary it may not have any effect of delivery pressure at all.

I thank Dusty for digging out yet another document, unfortunately it is not assigned so we don't who actually produced it and what if any axe they may have to grind. We also have no reference to be able to gauge its accuracy. However it does seem to be failry well balanced, and it does present cogent and believeable points.

 

[JohnGriffiths]

John L , Agreed on all points. I don't know where the idea came from about fitting caravan filters. All I said was :
Quote:
I'm suprised an enterprising saleman from the opposition hasn't come up with a "buy your guaranteed clean, uncontaminated gas from XXXXX" campaign.
End Quote.
Some car fuel suppliers have claimed their fuel is "cleaner" than others, I'm just surprised LPG suppliers haven'ty tried the same approach.