Faber tank question

[Dnaber]

Simple question...... is a Faber LP95 actually a HP117 if filled to 3000? I'm being told yes. Need some input.

Thanks

 

[tbone1004]

it holds 108cf at 3000psi..... It doesn't make it a HP117 though....
Holds 124cf at 3442, and 130cf at 3600psi which is where most of the cave shops will fill them to

It holds 118cf at 3000psi if you do the math wrong and run the number by being 95cf at 2400psi, but they don't hit their rated capacities until they get their 10% overfill, so if you're only getting a 2400psi fill it is only holding 86cf of gas.

This is obviously linear math and gas at these pressures doesn't follow a pure linear trend, but it's close enough.

 

[Scared Silly]

As said above LP cylinders are only at their rated capacity with filled with their + rated pressure (+10% over fill).

LP 95 @ 2640 psi == 95 cuft

Correct : 95 * 3000/2640 = 108 cuft
Wrong : 95 * 3000/2400 = 118 cuft


Now the other myth that has been out there for a long time is LP cylinders in the USA are the same HP cylinders in Europe. This notion is pure BS. The cylinders have the same form factor but are made from different materials.

 

[C Dub]

it holds 108cf at 3000psi..... It doesn't make it a HP117 though....
Holds 124cf at 3442, and 130cf at 3600psi which is where most of the cave shops will fill them to

It holds 118cf at 3000psi if you do the math wrong and run the number by being 95cf at 2400psi, but they don't hit their rated capacities until they get their 10% overfill, so if you're only getting a 2400psi fill it is only holding 86cf of gas.

This is obviously linear math and gas at these pressures doesn't follow a pure linear trend, but it's close enough.

Hey Tbone,

In cave country, do they replace the LP burst disks with the 5250 HP ones?

 

[tbone1004]

mine are 4500psi burst discs, some double disc them, some plug them permanently since the odds of you hooking up to a compressor able to pump up above 4500psi are pretty limted there really isn't a whole lot of point in using them imho.

 

[C Dub]

Thanks!

 

[Peter69_56]

mine are 4500psi burst discs, some double disc them, some plug them permanently since the odds of you hooking up to a compressor able to pump up above 4500psi are pretty limted there really isn't a whole lot of point in using them imho.

This of course is based on the assumption that the compressor safety valve is set correctly and has not failed closed. Many compressors are quite capable of pumping to much higher pressures than their safety valve setting.

To relate a story told to me when I was doing my recent Dive Technician course. A Thai dive company used to fill their cylinders at night. Left to a young guy on the dive boat while the clients and owner slept. Apparently the fill boy used to sleep and wait for the safety to operate before changing cylinders. This lead to failure of a couple of safety valves on the compressor over time so the owner plugged the safety valve port. The fill boy still slept during fills, and so inevitably bursting discs would go on the tanks. The owner then blanked some of the discs. Now what's the odds that you get all 4 filling tanks with blanks fitted, being filled at the same time (in a stock of some 30 tanks). It only takes time. All the odds lined up one night (4 tanks being filled all with blanks, compressor with no safety valve operating) and the ensuing explosion (when the filling lines reached some 6000-8000 psi) drove a cylinder through the bottom of the wooden boat and sunk it at anchor in the harbour.

So people should be aware that yes you can blank off a bursting disc, but there is always the potential for failure from things you may not be aware of at the time.

 

[NAM001]

I think themath says 108 at 3k. havnt done it for a while. 3000/2640*95.

Simple question...... is a Faber LP95 actually a HP117 if filled to 3000? I'm being told yes. Need some input.

Thanks

 

[Roman_66]

Correct : 95 * 3000/2640 = 108 cuft
Wrong : 95 * 3000/2400 = 118 cuft

This is why I more like to use metric.
See how it simple to compare.

 

[tbone1004]

I agree Peter, but there are still other safety valves that are supposed to blow prior to the tank and in a properly maintained shop it is pretty much a nonissue. The compressor should have a kill switch, the filtration stacks will sometimes have an OPV to keep them from bursting, the fourth stages on the good fill stations are set to a max pressure with opv's, etc etc. If you're at a reputable fill station which that Thai operation clearly was not, and you are diving cylinders either rated to high pressure or intentionally being filled that high, then there really isn't a point. AL80's, and the old 2250 cylinders that are regularly being filled at stations accustomed to filling to 3600+ should have the appropriate burst discs in them for safety, but the high pressure steels and the LP ones being filled that high don't really need them as long as the compressor is being maintained properly