Failure of a Wrought Iron Firebox Stay-Bolt from the Soo Line 1003 Locomotive

Engine 1003 is a steam locomotive that was operated by the Minneapolis, St. Paul, and Sault Saint Marie Railroad (known as the Soo Line), which had a railroad network that extended across the upper-Midwest. Manufactured by American Locomotive (ALCO) in 1913, engine 1003 was officially retired from the railroad in 1959. In the mid 1990’s, 1003 was partially restored in accordance with Federal Railway Administration (FRA), allowing it to operate on the nation’s railroad system again. In 2011, as part of an FRA 1472 inspection, it was noted that some of the tell-tale stay-bolts around the boiler were expelling small quantities of water when the boiler was under pressure; this is an intentional function of the tell-tale feature of the bolt to indicate if the stay-bolt has been internally compromised. Upon disassembly of the boiler, it was observed that the tell-tale stay-bolts that indicated failure were not fractured or corroded in a manner that would enable egress of boiler water through the tell-tale hole; the stay-bolts were heavily corroded but did not visually appear to be compromised upon inspection. Recently, an analysis of the original wrought iron stay-bolts from the 1003 has provided additional context on how these aged bolts may have indicated failure during operation while appearing functionally sound upon later inspection. The present talk delves into a brief history of the Soo Line and engine 1003, as well as the technology for producing wrought iron at the turn of the 20^th century. Microstructural characterization from optical and scanning electron microscopy with energy dispersive X‑ray spectroscopy of a stay‑bolt from engine 1003 showcase the wrought iron microstructure of the bolts and support a proposed failure mechanism of tell-tale stay‑bolts.