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70-30 COPPER NICKEL PIPING AND 90-10 CU-NI FITTINGS

70-30 COPPER NICKEL PIPING AND 90-10 CU-NI FITTINGS

70-30 COPPER NICKEL PIPING AND 90-10 CU-NI FITTINGS

(OP)
I  work  as  QA  SPECIALIST  on  US NAVY  destroyers. The firemain  and sea  water  piping  was recently   changed
from   90-10  copper nickel  to  70-30   copper  nickel  but  some of the fiittings are still  90-10 cu-ni as per the
drawings.The pipefitters in this shipyard have at  different times installed  valves backwards,strainers  backwards,
and installed  wrong  material piping.
    I  think that by picking  and choosing  where you are going to use 90-10  fittings  or   70-30 fittings there will   be  confusion  and mistakes  made.Is  a  70-30  fitting that much more expensive than 90-10 fitting?
    Any opinions  out  there  on  this?   DON  KUMPUNEN

RE: 70-30 COPPER NICKEL PIPING AND 90-10 CU-NI FITTINGS

Is this sil-braze piping, or flanged, or threaded piping??

Might have a bearing on the cost and selection.

rmw

RE: 70-30 COPPER NICKEL PIPING AND 90-10 CU-NI FITTINGS

(OP)
THIS IS SILVER BRAZED PIPING WE ARE TALKING ABOUT.
   DON KUMPUNEN

RE: 70-30 COPPER NICKEL PIPING AND 90-10 CU-NI FITTINGS

OK,  As to the pricing, someone else will have to advise you on that.  It has been too many years for me to be able to remember that.

However, I can comment on the technical merits of your questions.

The thermal expansion of both metalurgies are the same at 9.5 X 10^-6 in/in/F, so there won't be undue stress on the braze joints with temperature changes.

The hardness of the 90/10 is Rb 30, compared to Rb 20 for 70/30, so the 90/10 will be more resistant to erosive wear in the elbows and any fittings subject to erosive flow patterns.

The ultimate strengths are the same, but the 70/30 has a higher yield than the 90/10.

I don't have a problem with it, however, I would refer your question back to whoever it was that initiated the change in the piping alloy or shipyard engineer, or someone with technical overview of the project.

rmw

RE: 70-30 COPPER NICKEL PIPING AND 90-10 CU-NI FITTINGS

DONKUMPKIN,
The price on these alloys varies hour by hour. A month a go the 70-30 would have been higher due to the nickel content, but with what’s happening the metal business, especially copper at this time only a quote could give the price. Prices increases,  surcharges, allotments and back orders are in place on every metal.
It is bad enough that a pipe supplier I'm acquainted with could sell his inventory of copper pipe at scrap prices and recover his investment.

A good website to monitor the nickel side of the metal market is.

www.marfas.com

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