I am looking at a used tank someone has .I looked up how to find all the tank markings and decipher what they mean, however I am really confused on the year of manufacture for this tank as well as other information. Here are some photos of the tank:
Help needed with this tanks markings
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February 1975 according to the stamp
Boarderguy
Chief Narctopus Wrangler
You'll need to find a shop that will do an eddy current and visual on these old tanks. It adds $10-15 each year for inspections. The other problem is finding a shop to fill them since so many consider anything from the last millennium to be voodoo and untouchable. I'm lucky to have a shop 10 minutes from my house that doesn't care so long as they pass and I get my VIP done at another location.
I'd pass on buying anything this old since the added cost equals a new tank that didn't require the VE stamp pretty quick.
I'd pass on buying anything this old since the added cost equals a new tank that didn't require the VE stamp pretty quick.
Attachments
Scared Silly
Contributor
DOT = Dept of Transportation
SP 6498 == Special Permit 6498
3000 == 3000 psi working pressure
P69831 == Serial number
2^75 == first hydrostatic test date aka born date.
It is a very old cylinder made from AL6351. Though it can be requalified many shops will not fill it. See this thread for more details on cylinders made from AL6351.
My suggestion - scrap metal.
SP 6498 == Special Permit 6498
3000 == 3000 psi working pressure
P69831 == Serial number
2^75 == first hydrostatic test date aka born date.
It is a very old cylinder made from AL6351. Though it can be requalified many shops will not fill it. See this thread for more details on cylinders made from AL6351.
My suggestion - scrap metal.
I'm impressed that someplace in Redwood City has a 415 area code.
Cthippo
Contributor
How can you determine the alloy from the markings? Do you have to look up the SP number in a database somewhere?
Scared Silly
Contributor
Jimchris
Support your local dive center
SP6498 was grandfathered in with DOT3AL, Prior to 1982 they were stamped with the SP6498 or E6498. Luxfer also has a published list of when they changed from 6351 to 6061.
Dates when Luxfer changed its aluminum alloy from 6351 to 6061
Bob DBF
Contributor
A good reference for reading cylinders:
Cylinder Markings — XS Scuba - Everything For The Perfect Dive
That's an old sticker, since then the 415 code has been split into 7 different area codes. The stamp was probably from the last hydro, decades ago. Wallin's moved to Palo Alto (650 area code) and I believe are now gone.
Cylinder Markings — XS Scuba - Everything For The Perfect Dive
That's an old sticker, since then the 415 code has been split into 7 different area codes. The stamp was probably from the last hydro, decades ago. Wallin's moved to Palo Alto (650 area code) and I believe are now gone.
richerso
Contributor
All of the information above is accurate. No worries.
About the SP6498 number.... SP6498 is a U.S. PHMSA special permit number to manufacture and offer for sale a "special" pressure vessel. The SP6498 number can be referenced through the Pipeline Hazardous Material Safety Administration (PHMSA) web site. For this particular special number, see link: Hazardous Materials Special Permits Lists | PHMSA
Here you can find information about SP6498. The PHMSA web site will reference to a lot of literature about SP6498 to include an alloy composition of AA-6351. It also references a number of reports that speak to explosive ruptures of these cylinders; albeit, the rupture numbers are small quantities, ie. 13 tanks total.
The funny thing is everyone talks about 6351 as the bad alloy and everyone yammers on about "Sustained Load Cracking". I can't find any reference to SLC in the engineering databases of the American Society of Materials (formerly Metals) or the American Society of Mechanical Engineers (the design authority for pressure vessels). Funny thing, if you reference this document: https://www.luxfercylinders.com/img...uminium_scuba_cylinders_safety_alert_2217.pdf
front and center is a pretty clear picture of a ruptured AA-6351 tank. Look closely at that picture. That picture showcases a classic "brittle fracture" failure mode..... Hmmmm..... brittle fracture? Just my opinion, but that speaks to a bad heat treatment process on that particular tank. Is there a lot or two of 6351 tanks floating around with a bad heat treatment ?? Inquisitive minds wonder.
About the SP6498 number.... SP6498 is a U.S. PHMSA special permit number to manufacture and offer for sale a "special" pressure vessel. The SP6498 number can be referenced through the Pipeline Hazardous Material Safety Administration (PHMSA) web site. For this particular special number, see link: Hazardous Materials Special Permits Lists | PHMSA
Here you can find information about SP6498. The PHMSA web site will reference to a lot of literature about SP6498 to include an alloy composition of AA-6351. It also references a number of reports that speak to explosive ruptures of these cylinders; albeit, the rupture numbers are small quantities, ie. 13 tanks total.
The funny thing is everyone talks about 6351 as the bad alloy and everyone yammers on about "Sustained Load Cracking". I can't find any reference to SLC in the engineering databases of the American Society of Materials (formerly Metals) or the American Society of Mechanical Engineers (the design authority for pressure vessels). Funny thing, if you reference this document: https://www.luxfercylinders.com/img...uminium_scuba_cylinders_safety_alert_2217.pdf
front and center is a pretty clear picture of a ruptured AA-6351 tank. Look closely at that picture. That picture showcases a classic "brittle fracture" failure mode..... Hmmmm..... brittle fracture? Just my opinion, but that speaks to a bad heat treatment process on that particular tank. Is there a lot or two of 6351 tanks floating around with a bad heat treatment ?? Inquisitive minds wonder.
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