valve design code- fatigue analysis req'd?

[davefitz]

Can anyone advise if the valve design code ( B16.34 for example) defers to the associated piping code ( B31.1 for example) insofar as requiring the valve vendor to demonstrate the valve is suitable for the service defined in the specification?

The case of interest is : we purchased a steam turbine bypass control valve for installation in power piping ( B31.1), and specifed cycling service. The valve designed and supplied is grossly inadequate for the massive thermal shocks imposed on the valve ( shocks caused by the valve design which used an integral spray without thermal sleeves). When the vendor replied to our request for a fatigue review of the valve, we were shocked to find such an analysis has never been conducted by this valve vendor on any valve they supply!

B31.1 references section VIII for piping components, and section VIII div 2 app 5 has simplified rules for fatigue analysis. However, there seems to be a massive loophole, in that the valves being designed by B16.34 have no requirement for fatigue analysis yet are permited to be specified as piping components in a system which does require a fatigue analysis.