Standards and Nickel Aluminium Bronze

The standards tend to regard NAB as bronze, treating it in the same way. As has been discussed earlier, there are significant differences in the mechanical properties of the two materials. The valve and flange standards do not recognise these differences. In general there are two main streams of flange and valve standards. These are shown below:





(CWP, bar)




ASME B16.24



(ISO 7005-3)


B62, B61



Various Cu alloy


Class 150,300 FF
150: 12” max
300:   8” max

B16.5     R/F

Class 150,300 FF
to DN900 (150)
or DN600 (300)


Cl150=15.5 bar,300=34.5


Cl150=13.4 bar, 300=35.5

Cl150=15.5 bar,300=34.5
Cl150, >DN350 14 bar
Cl300, >DN250 20 bar




EN 1092-3:2003
(ISO 7005-3)


Various Cu alloy


PN6 – PN40 Flat
or raised face
DN500 (PN16)
DN400 (PN40)


PN x = x bar,
PN16 = 16 bar etc

The EN standards have a pressure temperature rating for NAB (CC333G), but apart from extending the high temperature performance beyond that of the bronzes, no recognition is made of the yield strength being over double that of the bronzes.

The American standard, B16.24 does have an aluminium bronze with dimensions to B16.5. This is still weaker than NAB (40%) and stronger than B62 (80%). However the dimensions in this instance require B16.5 dimensions with the raised face, explaining the reduction in the cold working pressure. The clause that allows bronze flange faces to be raised, provided that the extra dimension is added to the thickness appears to be inconsistent with these two ratings.

The European “PN” standards allow both raised and flat face dimensions and a full PN rating irrespective of the material. Due to the weak material and bending moments involved, extreme caution is required for all “bronze” materials with raised face flanges, particularly when bolting-up. Choice of gasket and assembly procedure using controlled bolt loads is critical. The author recommends that bronze flanges with raised faces are avoided wherever possible.

None of the standards recognise the high yield strength of NAB. However, the appendices of B16.34 and B16.5 do give a method for determining the pressure-temperature ratings. If this is used, a cold working pressure of NAB of 19 bar results (see Appendix III). To calculate the pressures at higher temperatures, data on material properties is required. The rating, “SPT01” (Shipham pressure-temperature rating) is presented below in Figure 6.

This rating has been in use at Shipham for many years without any issues, is consistent with the B16.34 rules and enables the full potential of NAB to be safely maximised. It is conceivable that the high temperature ratings could be extended, but NAB is not generally used where this is a requirement and from experience has not found to be necessary.

A similar approach is also required for other materials, particularly titanium. The data is more readily available as titanium is listed within ASME II, which NAB is not.

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