A rupture occurred in a 24-inch gas line in a reformer. The pipe contained hydrogen and carbon monoxide at a pressure of about 400 psi and a temperature of 930 °C. The ruptured section of pipe had a high-temperature alloy steel outer wall, a refractory liner, and a stainless steel inner liner. The refractory lining had been repaired several times before (including three months prior to the incident) because of localized deterioration and hot spots. The repair procedure consisted of cutting a section of pipe, re-pouring the refractory liner, and patch-welding the outer wall.
The first rupture occurred when the 42-inch-long welded section of the pipe suddenly blew out. On-site employees heard a rumble and observed a flame above the ruptured pipe. Before the torch fire at the rupture site could be extinguished, it eroded the refractory lining in the secondary reformer and most of the remaining pipe. Instrumentation in the secondary reformer was damaged as was piping and vessel insulation in the vicinity of the rupture. The expansion loop between the primary and secondary reformers dropped about 1 inch and cracks were found in two ells on the loop.
After three weeks of repairs, the plant was brought up to production temperature and pressure again. Employees taking readings after startup noticed a flame coming from the same gas line that had just been repaired. When the reformers were shut down, the flame was extinguished, and a 10-inch crack was discovered in the inside radius of an ell in the expansion loop. The ell had apparently cracked on startup and allowed the gas to escape and auto-ignite. The fracture was apparently caused by excess stress on the ell as a result of the 1-inch displacement of the expansion loop during the first incident.
An important lesson to be derived from this incident is the need to carefully engineer and test all repairs and modifications to high-pressure process equipment.