Nonferrous nozzles in a carbon steel water tank?

[numberfive]

We are looking at designing and fabricating a "U" stamped hot water heater vessel as a replacement vessel for a 40+ year old unit installed at one of our customer's facilities. The existing vessel consists of an SA-515-70 shell, 5/16" thick with SB-111 (copper nickel) nozzles for attachment of the 3" copper tube cold water inlet & hot water outlet lines. The vessel has a 1" thick cement liner that has broken down over the years and has allowed the vessel to corode from the inside out.

Question - What is the purpose of the copper nickel nozzles? Obviously the first thing that came to my mind was corosion but could it have anything to do with electrolysis? This is not for a salt water service - potable water only.

Any ideas?

 

[metengr]

Most likely, the copper nickel was used because of weldability to the steel tank versus threaded fittings. In most potable water piping systems, threaded brass connections are used to bridge between copper and steel piping components because of galvanic concerns.