70-30 COPPER NICKEL PIPING AND 90-10 CU-NI FITTINGS 1

[DONKUMPUNEN]

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

 

[rmw]

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

Might have a bearing on the cost and selection.

rmw

 

[DONKUMPUNEN]

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

 

[rmw]

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

 

[unclesyd]

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.

http://www.marfas.com