Faber tank question

[Peter69_56]

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

I understand your point and agree based on your comment "reputable dive shop", "should have" "as long as the compressor is being maintained properly" etc etc. My concern is to make a blanket statement saying blanking off bursting discs is OK, without providing information on assumptions and increased risks. Its always a risk, however as you state, if the users understand, fill operators understand the increased risk etc and don't unwittingly add to or increase that risk, then it can be a risk that to many may be acceptable. To the untrained person, however they may accept it on face value and not realise the added risk this imposes, coupled with a back yard compressor and a blasé approach, its a time bomb in the making.

I think we just have to be a little careful and not assume we are always talking to people who have experience and knowledge that we may have. Thus sometimes we need to put riders on our statements so we don't unintentionally lead those with less knowledge or understanding into an unintended trap.

For the inexperienced the following may apply "You don't know what you don't know until you get there, and often its far too late"

---------- Post added December 15th, 2014 at 06:29 PM ----------

I might also point out the additional risk of on-selling a tank which is inadvertently fitted with blanking disks. This was the situation I found myself with a set of 300 BAR 7 litre faber steels. Sold to me on ebay and the previous owner being an "Instructor".

The first indication I had was a leaking bursting disc (or so I thought), so took it in and had it checked and hydroed. One disc was a blank, and the other 2 disc's. Now couple this with the crappy chinese compressor I bought, this had the potential to be a bomb.


Hence my concern for us all to explain our comments if they deviate from the norm.

 

[tbone1004]

true, and this is why burst discs need to be replaced every year at vip time with the appropriate burst discs that you want. Whether that is a blanking plug, high pressure, low pressure, middle of the road whatever pressure, they are a consumable and are supposed to be replaced.

I fill on non commercial compressors all the time, they all have opv's, and every commercial compressor I've ever used does as well. The commercial ones all have fourth stages that control the output pressure of the lines. The compressor will also only every compress so much, a 3500psi Rix simply can't compressor much higher than that due to the compression of the bottle. Some of the guys using SCBA compressors that can run to 6k have issues, but most scuba compressors are generally 4500-5000psi max which isn't enough to blow most steel tanks, it's hydro pressure, but shouldn't cause them to blow. Something else in the system will likely fail before the tank gets that high.

That all being said, the norm in cave country is to either double disc at 4000-4500psi on the burst discs or to plug them completely and leave the liability to the shop who is supposed to have at least 3 points of relief prior to a burst disc going.

 

[abnfrog]

sorry to hijack ...but if any body has a tank that failed because of visible thread cracks im looking foe some for training ill pay more than scrap value (other defects wanted too ) thx steve