BRC problem

[brianm]

I've bought a BMW fitted with a BRC Flygas system, which had two 90 litre tanks filling the whole of the boot. All performed flawlessly on the 90 mile drive home.
I decided I don't need 180 litres of tank, but do need a boot, so I've taken the rearmost tank out, and reconnected all the pipework, etc.
The only problem is, it will no longer run on gas!!
I've traced the problem to the BRC multivalve on the remaining tank, by slackening off the outlet pipe and powering up the solenoid (which gives a healthy click). Gauge/level sender on the tank reads 3/4 full, but no gas comes out.
I've discovered that the screw in the centre of the solenoid valve is a manual shut off, and is in the full on position. I've also assaulted the multivalve with the end of a 10" x 1/2" socket extension
I've fitted the solenoid coil to the multivalve on the tank I've removed, and that vents LPG when powered.
Anyone familiar with these particular BRC mutivalves, and any idea as to what might have gone wrong? And what to do about it?
I could swap the multivalve over with the other tank, but the problem with that idea is that both tanks are nearly full.
I have a LPG pump, and, with a bit of effort, could transfer the gas from the spare tank into a couple of toroidals that I have, but that still leaves the tank in the car. I'm reluctant to just loosen the multivalve and vent it, as there's about £30's worth in it

[SimonHobson]

When I did my course the problem of faulty valves was mentioned. It's a bit of a catch 22, you can't safely remove the valve with gas in the tank and you can't get the gas out without changing the faulty valve

One option they said works fairly well is to put the tank in the coldest freezer you can find overnight - they have their own big fish freezer so no problems finding one for their use. The cold drops the pressure and boiling point of the gas significantly, and if you insulate the tank (wrap it in old blankets or similar) to minimise heat ingress, then you can (carefully) remove the valve and replace it. The tank will still be pressurised so care is needed, and the gas will start to boil off when you release the pressure, but apparently you can look in and see the gas gently bubbling away It will only stop boiling when it gets itself down to -40˚ so you do need to be careful to avoid cold burns.

I'll stress that I haven't tried this myself !

<a**e covering mode>I'll also stress that you'll be unscrewing the valve from a pressurised tank, AND that the gas will flash boil once the pressure is released (until it lowers it's temperature by the boiling off). You really, really need to consider the personal protection required for this - a minimum would be eye protection and thick rubber gloves.

And you must work in a very well ventilated environment, you'll be releasing propane with is a) explosive, and b) an anaesthetic that will knock you out by breathing a fairly small amount, and c) if you do put yourself out, you'll fall to the floor where the propane will kill you by excluding all the oxygen.</a**e covering mode>

[jayc]

The above sounds right as I had to vent over 100L from a tank I had in a boat. After about 30 mins of so of venting it I thought it was empty as the pressure had dropped right off. The tank had a thick layer of ice all over it from it cooling off and when I removed the valve there was little pressure left in the tank so I assumed it was empty.

When I rolled the tank over to remove it I found it still had plenty of liquid gas in it which almost instantly vaporised when it flowed out the valve opening and fit the floor!

I think in the end I replaced the valve whilst leaving about 10L of LPG in the tank.

[SimonHobson]

The above sounds right as I had to vent over 100L from a tank I had in a boat

That must have been painful, watching all those beer tokens floating away

Yet another use for my hand pump built from a pneumatic cylinder

[brianm]

Thanks for the replies so far!
There's definitely power at the solenoid coil - I've powered it direct from a battery, using the cable I removed with the other tank, and even tried the coil from the other tank.
It's also quite correct that the problem could have been present when I bought the car, although I topped the tanks up at a cheap gas outlet on the way home, and the gauge shows this tank as being not quite full, as if I used some on the journey.
The tank in the deep freeze sounds like a possible plan - better than my idea to wait for a realy cold winter's night.
I've already had some experience of boiling propane when I cracked off the pipes to the tank I've removed. There was a good three metres of flexible filler hose in the system, and the pipe to the front of the car is a fairly large bore flexible green plastic tube. I had liquid propane filling the bottom of the airtight box, running over and forming puddles in the spare wheel well (which I can now use). The amount that came out was quite spectacular - I was seriously beginning to think that one of the non return valves in the multivalve had failed. It didn't boil off quickly either - there was still plenty left after twenty minutes, when I decided to help it on its way by squirting it with water from a spray bottle.

[brianm]

Well, as you all say,no way of sorting the problem without taking the tank out, so I got stuck in. Tank was so close to the roof of the boot that it had to come our complete with cradle, which caused a few problems, as a couple of the bolts weren't exactly accesable under the car (petrol tank and exhaust shield), but eventually it was out.
I then checked the width of the space where the tank sat, and could see that it might be just possible to fit the tank I removed first in place of the failed one.
Both tanks are of 90 litre capacity, but the failed one is narrower and of a greater diameter than the other one. The smaller diameter would make it possible to (just) roll it into the ready fixed cradle, but it was going to be extremely tight at the ends, at least with the boot side liners in place.
I modified the cradle from the failed tank to fit the second, bolted it back into the car, then just managed to force the good tank into place and strap it down.
Pipes back on, crack off the connection to the vapouriser at the front, apply power to the gas solenoids, and I'm rewarded with a nice hissing and liquid from the loose joint.
I've still got a 90 litre tank full of gas and no easy way of getting it out, but I'll worry about that some other time.