Creep Strength of Welds in Hydrogen Reformer Outlet Manifolds

This paper reviews the creep strength of welds of the type typically used in hot outlet manifolds of hydrogen reformers. These manifolds can be visualized as a high-temperature piping system that collects the reformed gas from the outlets of the catalyst tubes. The catalyst tube outlet usually is connected to the manifold by means of a flexible pigtail. The pigtail is connected to the manifold via welded fittings, and the components of the manifold assembly are connected by welded joints. These hot manifolds operate under internal pressures in the range of 2000 to 3500 kPa and at temperatures in the range of 800 to 900 °C. The components are typically made of wrought Alloy 800, 800H or 800HT or similar cast 20Cr-32Ni-1Nb alloys. The welds are made using filler metals or electrodes of similar compositions or high-nickel alloy compositions. Creep-rupture data that have been developed for weld metals are reviewed and compared. Problems that have been encountered with failures of welds in this application are discussed. The current recommended materials for welding these manifolds are outlined.Copyright © 2009 by ASME