Fishkiller
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Is there an advantage using a 7 thread DIN on a 120HP compared to a normal K valve?
a question for the GODS.
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When dealing with HP tanks, DIN fittings are preferable due to the inceased psi in the tank. For example, my HP steel 80 usually has about 3500 psi in it. When it was new, dive shops routinely filled it to 3750. AL 80s usually hover between 3000-3200 psi.
A DIN 1st stage actually screws INTO the tank, while with the traditional yoke, it's held on the tank by the thumbscrew and air pressure. IMHO the DIN is a stronger fitting.
~SubMariner~
A DIN 1st stage actually screws INTO the tank, while with the traditional yoke, it's held on the tank by the thumbscrew and air pressure. IMHO the DIN is a stronger fitting.
~SubMariner~
Clearly the DIN is a much stronger connection - which is what theyare sold for - but also be advised that most K-valves are not rated for much more than 3000 PSI - I certainly would not want to put one on a HP tank.
If you are geting your own tanks I would go with DIN in a sec - you can have your first stage converted to DIN and get an adapter for use in trips where only K is available (Assuming here that the trips are not where you will do the most of your diving - that makes sense to me).
Terkel
If you are geting your own tanks I would go with DIN in a sec - you can have your first stage converted to DIN and get an adapter for use in trips where only K is available (Assuming here that the trips are not where you will do the most of your diving - that makes sense to me).
Terkel
Correct me if I'm wrong, but tanks etc... have to be certified in the US by the DoT, don't they??
Surely, in the tank regs, there are regulations for the valves fitted and their maximum pressures.
In the UK, tanks upto 230 (or so) bar can be fitted either with A-clamp, or 5 thread DIN, as they are both suitable for this pressure. However, pressures above this have to have different threads, for scuba diving the 7 thread DIN is what is used, although there are several other fitting allowed (the 1 inch BSP 9 thread for example found on industrial gas cylinders) but don't get fitted.
For the clinically sad, in the UK it is (as far as I can remember) BS5045 part 3 that deals with valves (part one is steal tank construction and testing, part 2 is aluminium tank construction and testing, and I think that part 3 is the fitting of suitable valves)
Surely the US DoT as well as certifying tanks has some specification for what valve can be fitted to what tank?
Jon T
Surely, in the tank regs, there are regulations for the valves fitted and their maximum pressures.
In the UK, tanks upto 230 (or so) bar can be fitted either with A-clamp, or 5 thread DIN, as they are both suitable for this pressure. However, pressures above this have to have different threads, for scuba diving the 7 thread DIN is what is used, although there are several other fitting allowed (the 1 inch BSP 9 thread for example found on industrial gas cylinders) but don't get fitted.
For the clinically sad, in the UK it is (as far as I can remember) BS5045 part 3 that deals with valves (part one is steal tank construction and testing, part 2 is aluminium tank construction and testing, and I think that part 3 is the fitting of suitable valves)
Surely the US DoT as well as certifying tanks has some specification for what valve can be fitted to what tank?
Jon T
Yes, you're correct, the US has specifications set forth by the DOT and the CGA and essentially any pressure cylinder out there on public roads must comply with the law.
Yoke type attachments have a recommended pressure limit of (I think, don't have the info here) 3000 psi, but are seen on 3300 psi tanks. 300 bar DIN are seen here, mostly.
Also, according to the Code of Federal Regulations (Title 49? don't hold me to that) it's unlawful to overpressurize pressure cylinders.
People will find all kinds of reasons and rationales to violate law and common sense safety practices; go figure
Be safe,
Neil
Yoke type attachments have a recommended pressure limit of (I think, don't have the info here) 3000 psi, but are seen on 3300 psi tanks. 300 bar DIN are seen here, mostly.
Also, according to the Code of Federal Regulations (Title 49? don't hold me to that) it's unlawful to overpressurize pressure cylinders.
People will find all kinds of reasons and rationales to violate law and common sense safety practices; go figure
Be safe,
Neil
The DIN fitting is a bit stronger inasmuch that it should withstand impacts better. However, the MODERN yoke fitting is safe pressure wise up to 4000 psi. The valve bodies can easily withstand this pressure. In the 1970's, the valve manufacturers changed the design of the O ring face; they reduced the size of the annulus to allow fitting of a thinner O ring. As a result, the regulator/valve lockup is metal to metal, sort of a semi trapped O ring which will not blow out at pressures up to 4000 psi. The regulator yokes were greatly strengthened and if you look at some examples like the SCUBAPRO, they appear strong enough to pull a truck.
Because I have a lot of gear including compressors and did not want to have two specifications, I machined some yoke valves to fit my PST 3500 tanks. Changed the discs, too. No problems at all. The Sherwood type valves look best, particularly the old OMS versions that were sold in the early 90's.
To answer the Britisher, industry standards were effectively set in the US when PST, the tank manufacturer, decided to go with the 7/8 neck size only allowing the DIN valves. Concerns over the specific type of valve are probably driven by liability concerns. However, I notice that your standards are similar; eg, yokes are allowed for pressures up to 230 bar(3300 psi). An interesting case is the Italian Faber HP tank sold here and rated at 3180+ with a fill pressure of 3498 psi. This tank has a 3/4 standard pipe neck and can be fitted with a standard yoke valve. (The European rating for this tank is 244 bar or 3600 psi).
Because I have a lot of gear including compressors and did not want to have two specifications, I machined some yoke valves to fit my PST 3500 tanks. Changed the discs, too. No problems at all. The Sherwood type valves look best, particularly the old OMS versions that were sold in the early 90's.
To answer the Britisher, industry standards were effectively set in the US when PST, the tank manufacturer, decided to go with the 7/8 neck size only allowing the DIN valves. Concerns over the specific type of valve are probably driven by liability concerns. However, I notice that your standards are similar; eg, yokes are allowed for pressures up to 230 bar(3300 psi). An interesting case is the Italian Faber HP tank sold here and rated at 3180+ with a fill pressure of 3498 psi. This tank has a 3/4 standard pipe neck and can be fitted with a standard yoke valve. (The European rating for this tank is 244 bar or 3600 psi).
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