Welding New Outlet Headers with Old Bullhead Tees in a Steam Methane Reformer Furnace: Lessons Learned

Introduction

In this article, we will primarily cover the key learnings from welding existing bullhead tees to the new outlet headers of the primary reformer in a 1965 vintage, two-tier, two-cell, terrace wall Foster Wheeler design primary reformer (F-101) installed at the Fauji Fertilizer Bin Qasim Limited (FFBL) plant in Karachi, Pakistan. Background information on the requirements to replace the outlet headers and the execution strategy that was followed during the installation of the outlet headers are provided, along with remedial actions taken for the successful completion of the job.

This reformer was also discussed in a previous article, “Multiple Degradation Mechanisms in 1965 Vintage Primary Reformer: Failure Analysis, Inspection Methods, And Remedial Actions,” published in the March/April 2024 issue of Inspectioneering Journal.

Background

The primary reformer’s outlet headers were replaced in 2000. The bullhead tees were replaced during the replacement of the transfer line in the 2017 turnaround (TA-2017). However, during the transfer line and bullhead tees replacement activity in TA-2017, severe cracking occurred during the grinding and welding of the new bullhead tees to the old outlet headers. Cracks were found mainly at bevel ends and at weld toes towards the old outlet header side, which were repaired with a specialized welding procedure developed in consultation with the original equipment manufacturer (OEM) representative who was on-site at FFBL to oversee the transfer line and bullhead tees replacement job.

In view of the above cracking issue, segments of the outlet headers removed during TA-2017 were sent to a laboratory for metallurgical evaluation and remaining life assessment (RLA). The lab reported that 70% to 90 % of the operational life of the header had been consumed after 17 years of operation, causing creep ductility exhaustion. Accordingly, replacement of the headers was recommended. The OEM of the primary reformer concurred with the metallographic evaluation and remaining life assessment performed by the laboratory and agreed with the recommendation to replace outlet headers in one to two years. Procurement of new outlet headers was carried out in 2020, followed by replacement during the 2021 turnaround (TA-2021).