HP vs. LP
- Thread starter VTWarrenG
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The preceived problem of getting full fills with HP 3500 PSI tanks has not cause me any grief. On the East coast, most dive boats simply do not have compressors (or they simpy state they are for "emergency fills" only). You simply have to take whatever gasses you expect to use. That includes live aboard diving.
I have recently completed two drive trips to the West coast. In Ventura, CA. I was able to rent a steel 120 and get full fills with nitrox on the boat. We did four dive on the Channel Islands. I just finished another trip to Monterey Bay and that boat also could fill to 3500 PSI with nitrox. Unfortunately, not one dive shop in town rented HP tanks!
I get full fills at the local Quarry too. I DO NOT get full fills in the Florida Keys except at one IANTD dive shop. Obviously, that is where I go to get my HP's filled.
Yes, HP's are more negative. As a dry suit user this is a very good thing. It takes weight off me and makes a better balanced diving rig.
HP's are more expensive. You get in this case (PST, Inc.) what you pay for. I have seen HP 120 on sale for as little as $250 each. So look around for the good deals.
HP's are more suseptable to corrosion. The reason they can hold higher pressure and still be phyically small is the steel used has a higher carbon content. That makes them strong but you have to be extremely careful so as not to allow any moisture in them. I have owned my HP's for 3 years now and the inside still looks like a mirror.
I have recently completed two drive trips to the West coast. In Ventura, CA. I was able to rent a steel 120 and get full fills with nitrox on the boat. We did four dive on the Channel Islands. I just finished another trip to Monterey Bay and that boat also could fill to 3500 PSI with nitrox. Unfortunately, not one dive shop in town rented HP tanks!
I get full fills at the local Quarry too. I DO NOT get full fills in the Florida Keys except at one IANTD dive shop. Obviously, that is where I go to get my HP's filled.
Yes, HP's are more negative. As a dry suit user this is a very good thing. It takes weight off me and makes a better balanced diving rig.
HP's are more expensive. You get in this case (PST, Inc.) what you pay for. I have seen HP 120 on sale for as little as $250 each. So look around for the good deals.
HP's are more suseptable to corrosion. The reason they can hold higher pressure and still be phyically small is the steel used has a higher carbon content. That makes them strong but you have to be extremely careful so as not to allow any moisture in them. I have owned my HP's for 3 years now and the inside still looks like a mirror.
Bill and Neal, those were good posts. Times are changing, and the capabilities of Scuba equipment and boat facilities to handle HP are moving right with them.
Bill, I'm curious about the comment on corrosion and carbon steel. Traditionally, alloys known as carbon steels were only used for tanks rated up to 2015 psi. These were designated 3A whereas chrome vanadium or chrome molybdenum steel tanks were labeled 3AA and contained pressures in excess of 3000 psi. Are you saying that PST is using high carbon in the E9791 steel tank(the light weight HP tank) and that this is related to alleged higher corrosion?
Just curious.TIA
Bill, I'm curious about the comment on corrosion and carbon steel. Traditionally, alloys known as carbon steels were only used for tanks rated up to 2015 psi. These were designated 3A whereas chrome vanadium or chrome molybdenum steel tanks were labeled 3AA and contained pressures in excess of 3000 psi. Are you saying that PST is using high carbon in the E9791 steel tank(the light weight HP tank) and that this is related to alleged higher corrosion?
Just curious.TIA
Sorry guys! I am not that familair with metals and how they corrode. What did interest me was how PST made the HP tanks so light and HP. My LDS is also a company called Compressed Air Systems. They deal in all kinds of HP things. So when I posed this question to the owner of the LDS, the statement I made was actually their explanation of the differences with PST tanks and others. They also said that the reason for the hot dip galvanized exterior was because the higher carbon alloy steel is prone to corrossion.
If you visit the PST web site they do not give out any manufacturing secrets! If you want a better explanation simply call Bill or John Allen at Northeast Scuba Supply. Tell them I sent you there!
If you visit the PST web site they do not give out any manufacturing secrets! If you want a better explanation simply call Bill or John Allen at Northeast Scuba Supply. Tell them I sent you there!
I am not a rocket scientist either. Yes, my LDS has some really nice people. They also tell me when they do not know the answer.
I was probably a little soft on myself replying to the post about carbon steel and corrosion. I do have some experience in this field but not as a metallurgist. I was in the Navy Air program for 23 years and besides being an Avionics specialist I was also on the corrosion control team for many years. I do understand what makes metals corrode. I know how to treat them and prevent corrosion. Unfortunately my metals were alumimnum, titanium and stainless steel.
The explanation given to me by the LDS did make sense to me knowing what I do know about corrosion processes of some types of metals and alloys.
It is my hope we can get a real rocket scientist on this board and then make a really good presentation on tanks and the alloys used.
I was probably a little soft on myself replying to the post about carbon steel and corrosion. I do have some experience in this field but not as a metallurgist. I was in the Navy Air program for 23 years and besides being an Avionics specialist I was also on the corrosion control team for many years. I do understand what makes metals corrode. I know how to treat them and prevent corrosion. Unfortunately my metals were alumimnum, titanium and stainless steel.
The explanation given to me by the LDS did make sense to me knowing what I do know about corrosion processes of some types of metals and alloys.
It is my hope we can get a real rocket scientist on this board and then make a really good presentation on tanks and the alloys used.
The guys at NE Scuba Supply are good guys. John is a retired cop from NY. And, this is my opinion, he will stretch the facts some what. Even so I will still do business with them. I just take everything with a grain of salt from most shop owners.
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