Thread: Addional LPG Tanks

Originally Posted by Lotz-A-Landies

I think that most people refer to a pair of APA H66 tanks as scuba tanks. But now you've let us know I won't use them for spear fishing.

And I have a fridge full of scuba tanks, 'cept they contain beer and soft drink and stuff.

Originally Posted by Lotz-A-Landies

Also Bee Utey, just for my understanding.

1. You can have two tanks fitted with a single filler/AFL, but not three?
2. On the fuel supply side all tanks must have a non-return valve between the common supply line and each tank?
3. If you have two individual fillers connected to one or more tanks each, can you use the "automatic fuel shut-off" connected to one filler as an effective reserve switch as long as all tanks connected to that filler are switched together?

AFL refers to the maximum liquid level float valve installed into each tank, set at a maximum 80% +/- 1% of the cylinder volume, with the cylinder at its correct orientation. They have specified performances in the flow rate to the tank after they shut off the inlet flow. This is to allow the valve to reset. This is why you can trickle a tank fulller than 80% in some cases as the bypass lets a bit of gas through. This is why you are supposed to stop at the "clunk" of the valve operating, unlike what the dood did with the 100 series Toy with fumigation.

1. Theoretically you can have 3 tanks, each with its own AFL, running off a single filler. In practice, many AFL's will not shut off under a certain flow rate, which can be hard to achieve with two tanks. Axiom brand AFL's are particularly troublesome in this regard (fitted to later style APA tanks) Older Robertshaw screw-in AFL's would shut off at a much lower flow rate. Filler manufacturers (AMR especially) now make higher flow filler valves to cope with this problem, especially the D1 and RRC fillers. Together with 10mm fill hose they are generally reliable. Ford uses 1/2 inch steel filler pipes on their twin tank ute set-ups. Personally I wouldn't have 3 tanks on one filler as the risk of overfilling is way too high.

2. Correct. Twin tank installs usually have a unified dual non-return valve/relief valve on the supply side. Extra tanks can be plumbed in with single non-return valves or another dual valve if suitably arranged (cascaded). Ford factory tanks have the non-return valve fitted directly to the tank outlet. It can be raided and fitted to any extra tank with a suitable outlet thread.

3. Tanks filled off individual filler points can be controlled electrically via a selector switch which takes the safety cut-out output and switches it to either tank or both, as required. It is the electric solenoid on the service valve on the outlet that you are switching, not the inlet. "Automatic fuel shut-off" refers to the operation of this solenoid on the service valve, in conjunction with the safety cut-out. Together they automatically close off any tank connected to the engine in the event of the engine stalling, within a couple of seconds.