water purification and the RR

[NW Mailing List]

Pardon me for appearing to be the purist (no pun intended,) but I think the proper term for the railroad's treatment of boiler water is "softening," not "purification." 

Locomotive boiler water was not "purified" to kill malevolent micro organisms (shucks, the heat in the boiler would take care of that!) Rather, boiler water was treated to remove (by sedimentation, frequently chemically enhanced) calcium, silica and other dissolved minerals which, during the evaporation of the water, would precipitate and build up a calcified scale. Scale has an insulating effect on the inside of a boiler and prevents the transfer of heat from the firebox sheets to the water being evaporated. A heavy scale condition can result in overheating of the firebox sheets and premature metalurgical failure of the firebox components. Railroads "washed" boilers periodically to remove scale build-up. 

This treatment of locomotive boiler water was informally called "softening" (not purification,) and the facilities which did the treating were generally referred to as "water softeners." 

-- abram burnett 
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