Friday, July 5, 2019

Back in the boiler

Steam locomotive 924 is a former Northern Pacific Railway switch engine that operated in the Seattle area from 1901 until 1924.  It is listed on the King County and City of Snoqualmie Landmark Registers, and is a property truly representative of our collective history in the settlement and development of the region.

The 924 has been undergoing a major rehabilitation and restoration inside the Museum's Conservation and Restoration Center in Snoqualmie, WA.  Despite several unanticipated setbacks in the project, it has moved forward and real progress is becoming evident.

This past week, the last major known work on the 924's boiler was performed.  Seattle Boiler Works visited the Museum to remove the portion of the throat sheet that supports the blow down valve.  A patch had been installed here with patch bolts at least 70 years ago, and the "new" material had wasted in places almost 50% of its original thickness.  So replacement was definitely warranted.

The original patch was removed, which also required three rivets in the mud ring to be cut out.  Then the affected area was cut out, and the perimeter was beveled to allow for welding.  A dye penetrant was used to check for cracks and other flaws.

Seattle Boiler Works installed a flush patch and welded a coupling for a new blow down valve.  The process involved a full penetration weld, and preheating of the native material to about 350 degrees.  Repeated passes, grinding, welding, and continual evaluation took a full day, but the results are impressive.

Up next: three replacement rivets, two new stay bolts, and more.