Curing boiler ache

The Museum's curator cuts out around
the stay bolts that secure the inside
sheet to the outside sheet.  During
operation, water between the sheets
is heated by combustion in the firebox.

Rehabilitation and restoration of a steam locomotive that is more than 115 years old can present many challenges, sometimes even when components appear to be in great shape.  Take the boiler for instance.  It's a pressure vessel designed to operate at up to 180 pounds per square inch. It represents a discipline that saw continuous change throughout the first half of the 20th Century as new techniques were developed, and older practices were sometimes found deficient.  Fast forward to the 21st Century and the best practices and regulations of the past have been combined with the knowledge and scholarship of the present to form the "new" regulations that govern the eventual certification of locomotive 924. 

The lower portion of the side sheet on

the right side of the firebox has been

removed allowing the back side of the

wrapper sheet to be inspected.  Several

small cracks were found radiating from

stay bolt holes.

With today's regulations - and the genuine desire to operate in a safe and efficient manner - there are some parts of the locomotive boiler that are being replaced.  Inside the firebox, the side sheets were repaired with a mixture of gas and early electric welding techniques, perhaps as many as 90 years ago.  Unfortunately, this presents challenges for the certification and sustainable operation of the locomotive.  Even if these repairs could be dissected and the boiler approved for operation, these repairs of unverifiable workmanship could present a problem during the next 1,492 days of operation, and require remedial repairs in the middle of an operating season.

The new side sheet sections are welded

into the boiler.  The holes will soon be
tapped for new stay bolts.

So in December 2014 the lower portion of the side sheets on both sides of the locomotive - together incorporating at least two prior repairs - were cut out.  This work required each individual stay bolt to be cut out so the sections of side sheet could be removed.  Inside, the outer sheet or wrapper was found to be in good condition, though several small cracks were found radiating from the stay bolt holes. Thanks to the added efforts of more than a dozen volunteers, the surfaces were cleaned up in preparation for new sheets.

Brand new sheets were purchase, fitted, drilled, and installed.  A modern electric welding machine was used to install the plate and the holes are being tapped for new stay bolts.  While working inside the firebox, some of the rear sheet seams were welded to improve performance and reliability when the locomotive is converted from coal to oil.

Replacing the lower portions of the side sheets inside the boiler is just one of many tasks required in the process of rehabilitating and restoring former Northern Pacific Railway steam locomotive 924.  This intensive process will take approximately two years of effort.  Already, dozens of volunteers have contributed more than 750 hours, and the Museum's curator is committing 85% or more of his work day to the project.  It is just the beginning, but a measurable effort for a project that began less than four months ago.