Investigation of in-service damage accumulation of Alloy 800HT methanol reformer outlet tubes

Abstract

Methanol outlet reformer tubes, or pigtails, transport reformed syngas from reformer tubes to outlet manifolds at high temperature (800–900°C). These outlet tubes tend to have a convoluted geometry to accommodate thermal expansion of the reformer tubes, outlet tubes and manifolds, hence the term pigtails. The industry standard material for reformer outlet tubes is Alloy 800HT, a creep resistant austenitic Ni–Cr steel. A number of anomalous in-service failures of Alloy 800HT reformer outlet tubes have occurred at lower than expected service life and at low creep deformation. A discussion of the failures is presented in this paper, covering the parameters which affect potential damage mechanisms.