Mark 15 Tavco Spheres

jimaqua

Need information on aquiring new Tavco spheres for Mark 15 that are DOT approved here in the states. Is there any other manufactures that are making replacements for the spheres or can new spheres be purchased from a Tavco distributor serving the gas cylinder/NASA industry.

caveseeker7

My information may not be up to date as it's 4 years old, but when Steam Machines build up the SM1600 the spheres were available through Tavco in Chatsworth, CA. Problem is that they required a minimum order of 50 spheres, and quoted prices were only good for 30 days due to the fluctiating inconnel price. The last quote was $1,045.- for each. And those were, AFAIK, not DOT approved.

IIRC, Steam Machines sold a bunch of their stock to Colkan in Australia.
Colin Wilcox still builds up MK15.5s in small numbers and is probably your best bet for them. Search the forums for those names, there should be a contact somewhere.

Others who have done plenty of work on MK series rigs are Divematics here on the West Coast and Juergensen Marine on the East Coast. They may be able to point you in the right direction, contacts are in the links section.

Good luck.

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Stefan



"Political Correctness is a doctrine, fostered by a delusional, illogical minority,
and rabidly promoted by an unscrupulous mainstream media,
which holds forth the proposition that it is entirely possible
to pick up a turd by the clean end.'!"

divetheworld

What about the Drager spheres used on this one. http://www.ebay.com.sg/viItem?ItemId=7221619662

Phi knows something about them.

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caveseeker7

Composite spheres, from what I understand neither much less expensive nor much easier to come by. Don't know if they're the same size or if they were/are available with DOT markings. Military hardware is usually excempt from stuff like that.

A third option are the steel tanks used on the original CCR1000 from which the MK15 was derived. Since they were build for the civilian market those tanks might have DOT aproval, but I think the spheres are welded and hence they don't.

Edited: Just looked at the old thread, it was Phi that commented on the prices. Metal (inconnel or steel) pretty much keep their value as they're hard to come by, composites still cost over $500 each.

__________________
Cheers
Stefan



"Political Correctness is a doctrine, fostered by a delusional, illogical minority,
and rabidly promoted by an unscrupulous mainstream media,
which holds forth the proposition that it is entirely possible
to pick up a turd by the clean end.'!"

iain-hsm

At work we have a current project to supply similar small pressure vessels at 3.2 ltr water capacity and 250 bar working pressure but the main problem for recreational diving use is the rational of the cylinder design. At present the only customers for this type of vessel are military with immunity from commercial or legislative standards i.e. DOT.

The design calculations for life span, safety standards, inspection and test procedures are based on a limited pressure cycle use of around 15K cycles of expected life with x-ray and dye pen tests on the welds at years 3, 6, and 9. The working life of the vessel is 12 years from manufacture.

Basically to make the cylinders lighter, the calculations for allowable design stress of the particular inconel alloy used is increased over what would normally be used on a commercial pressure vessel design. This thin wall makes a much lighter cylinder but with an increased risk. The reduced wall risk is compensated for by increasing the testing cycle and criteria. Note the original spheres for the mark 16 UBA were 1.9 ltrs water capacity and 207 barg working pressure.

The question of these items ever being available is unlikely. The wall calculations and design codes for one preclude there use outside of the military. Further although projects of this nature require additional quantity from each batch to be made for testing etc the bottles left over are normally destroyed.

For an example on cost, add to each batch destructive testing of sample cylinders and to this the kiln cost of a 19 hour pre and then post manufacture heat treatment process. With the quantity per batch being dependant of the size of the kiln used just pity the poor sod who has bought the last one left out!! lol. Iain Middlebrook

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diverrob

You might want to check with Carleton Lifesupport, they supply us (Canadian Millitary) with Tavco flasks that we use in our Rebreather. The cost is quite high I think. http://www.carltech.com/diving/default.html

not to rub it in but we are currently getting rid of 15 - 20 flasks because they have reached their life cycle end (time not pressure cycles)

Rob