Nickel-Aluminium Bronze for Seawater: Flattered by ... - Valve World

Figure 7 shows the cold working pressure (CWP) for the various materials. The comparison is not
straightforward because the bronze and cast iron figures relate only to flat-face flanges and all the
other dimensions relate to the ANSI B16.5 raised face dimensions. Additionally, in the absence of
appropriate standards, the NAB and titanium ratings have been specially calculated.
bar
25
20
15
10
5
0
Class 150 Pressure:temperature ratings
Cast Iron
Bronze
NiAlBrnze
Figure 7: Comparative pressure - temperature ratings
Ni-Cu Alloy
C. Steel
Stainless
The differences across all materials are now not as pronounced. The explanation for this is that an
upper limit on the pressure is imposed in order to limit deflection. The materials affected by this
ceiling figure are 6Mo, the duplexes and Ni alloys where the maximum pressure is reduced to 20
bar.
For comparison, the rating at 250 o C is included. The NAB and titanium values are lower than most
of the other materials. The maximum temperature and pressure for each material is given in
Appendix II. The ceiling values at higher pressures further reduce the differences between
materials.
So NAB is not weak: it compares well enough to compete seriously with its rivals. There is a high
temperature limitation but this is not generally an issue for seawater service.
6Mo
Duplex
Super
Duplex
Ni Alloy 625
CWP (bar)
at 250 deg C
Ni Alloy C22
Ti C2
Ti C3