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Old 02-18-2020, 02:30 PM   #17
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Join Date: Jan 2008
Location: Massachusetts
Posts: 2,185

Originally Posted by JimThias View Post
I have no idea what a "boiler jacket" is and when I look at that photo, it looks like a regular old steam engine to me. [shrug]
Hi Jim,

A boiler jacket an insulating layer placed around the boiler shell to minimize heat loss to the atmosphere and improve the thermal efficiency of the engine. Generally, it consists of a layer of insulation material, surrounded by a protective, sheet metal jacket, which is usually painted black. In park engines, the jacket is often removed for a lot of reasons. First, the ones from back in the day contain asbestos insulation, and are a health hazard. Second, when left outside for a long time, water tends to get under the jacket and into the insulation, which then holds the moisture against the boiler shell, promoting corrosion. Removing them actually helps preserve the steel. Unfortunately, to the purist, it doesn’t look right. A boiler jacket looks smooth, and when clean, it also looks shiny. Without the boiler jacket, you can see the raw boiler steel, including the rivets and seams. It’s a dead giveaway that the engine is cold and dead.

BTW, most steam engines in service today use a modern insulation such as calcium silicate blocks. Asbestos is no longer used.

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