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SOLUTIONS: Copper and Copper Alloys Aluminium brass (Yorcalbro) Copper sea water piping on board ships has increasingly been replaced by Yorcalbro pipes. Yorcalbro (aluminium brass) is an alloy with the following chemical composition and mechanical specification:
Some years ago, numerous welding tests were carried out on Yorcalbro pipes using the TIG (GTAW) process. The results were very satisfactory. Both small and large size pipes were welded in these tests, and the conclusions were as follows:
Alloy: . . . . . . . . . . . . . . . . . . . . . . . . . Cu 76%, Al 2%, Zn 21,96%, As 0.04% Tensile strength: . . . . . . . . . . . . . . . Hard (untreated) . . . . . . . . Heat treated . . . . . . . . . . . Annealed . . . . . . . . . . . . . . . . . . . . . 310–370 N/mm2 Hardness: . . . . . . . . . . . . . . . . . . . . . Hard (untreated) . . . . . . . . Heat treated . . . . . . . . . . . Annealed . . . . . . . . . . . . . . Elongation: . . . . . . . . . . . . . . . . . . . . Hard (untreated) . . . . . . . . Heat treated . . . . . . . . . . . Annealed . . . . . . . . . . . . . .
580–700 N/mm2 360–470 N/mm2 165–194 HB 83–111 HB 63–78 HB 8–15% 55–65% 65–75%
2.08
Specific weight: . . . . . . . . . . . . . . . . 8.34 Outside coefficient per °C: . . . . . . 000013. The use of Yorcalbro piping allows a higher flow rate in the pipe than possible with copper piping. A flow rate up to 3.5m/s is permitted in Yorcalbro pipes compared to 1.52 m/s in copper pipes.
Aluminium brass pipes are more durable than copper pipes. Aluminium brass pipes have a widespread use in cooling water installations, sanitary installations, oil coolers, heat exchangers, heat coils etc. In view of the widespread use of aluminium brass piping on ships, maintenance is inevitable. Common repairs include welding of leakages and replacement of pipe lengths subjected to corrosion. The most serious problems appear to arise in connection with the repair of leakages in large-dimension Yorcalbro pipes.
– Pipes with diameters less than 4'' where the repair can take the form of an overlapped joint should be silver brazed using Unitor AG 60 and Unitor ALBRO flux.
– Pipes with diameters exceeding 4'' should be TIG welded using Unitor IALBRO-237MF and the special flux, IFLUX-238PF.
Wire welding: IALBRO-W-237. – Pipes should be unstressed before welding takes place, and cold bended piping should be annealed at 400–500°C for approximately 20–30 min. Finished welds, and an area covering approx. 15 cm to either side of the bead should be annealed. Annealing temperature 300–400°C for 30–40 min.
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