Lessons Learned from the Rupture of a Steam Superheater Header

Abstract

A 110 barg (1,595 psi) stainless steel superheated steam coil outlet header ruptured, producing an instantaneous release of high-pressure steam. The failure occurred at a methanol plant after eight years in service, and without any prior indications. The failure mechanism was determined to be stress relaxation cracking adjacent to the longitudinal seam weld, which resulted in a large “window” torn out of the side of the header. The initial investigation focused on the materials and fabrication of the header, but deeper analysis highlighted that code compliance does not always equate to fit for service. This article walks the reader through the header specification, design, fabrication, and inspection processes to identify where opportunities were available to question and act to proactively address the vulnerabilities that resulted in the header rupture.

Introduction

One of the biggest fears for any executive leader in the chemical and energy industry is a loss of primary containment event, which brings with it the potential for fatalities, significant equipment damage, and downtime.

Methanex experienced such an event in April 2019. Fortunately, the rupture occurred at shift change so all on-site personnel were in the control room and there were no injuries, but given the energy release associated with the event, there was potential for far greater consequences than what was experienced.

This case study suggests how the strategic, systematic approach to technical knowledge acquisition/assimilation, management, and utilization in the design, fabrication, maintenance, and operation of assets should evolve.