Regarding the max capacity of the reheater relief valves, some unusual scenarios can arise for the case of multiple HRSG's on a header system:
a) If the STG has tripped and the HRSG is on a bypass system , the max steam flow to the reheater may need to include the add'l steam flow from the HP bypass spary attemporator
b) Such a reheater could be considered as a "separately fired superheater" in that it has isolation valves at both inlet and outlet ( since it is downstream of the IP boiler bank on a HRSG, it cannot avoid code inclusion). The code clause that proportions the relief valve capacity to the "separately fired superheater" surface area has been interpreted to mean all the steam the reheater can generate if it is blocked, and there may be a code case or interpretation that formalizes this.
c) some plants have included an "overload valve", bypassing some HP main steam directly to the hot reheater, to avoid overpressuring the GE STG that has a low throttle pressure limit. This design must add add'l releif capactiy in the hot reheater piping near the intercept valve to account for the max casualty flow thru the overload valve.
