In Tom Marshall’s teachings to the Steam Team he often talked of more rare issues that can affect a Stanley’s performance. The issue of boiler foaming and priming is rare and involves only the water on board a Stanley and not the vehicle itself. This author has experienced boiler foaming involving a Wilmington & Western Railroad locomotive that had excess boiler treatment added to the water. In that case, the problem was quickly visible in the glass boiler sight gauge as instead of the glass tube 2/3rds full of water, when the engineer opened the throttle, the glass quickly turned milky white, an indication of boiler foaming. Ignored, such a problem might quickly become dangerous for continued operation of the locomotive or steam car. In the case of a condensing Stanley, the boiler gauges are of an actual gauge construction, and unless the the steam car has been retrofitted with a glass sight gauge, a foaming issue must be recognized through other clues.Tom Marshall advocated a tablespoon of Arm & Hammer Super Washing Soda be added to the water tank every three or four tankfuls of water. Arm & Hammer Super Washing Soda, Tom’s favorite, is pure sodium carbonate (Na2CO3). Washing soda is also known as soda ash and soda crystals and is primarily used to manufacture glass, paper, rayon, soaps, detergents, and as a water softening agent. Since the start of the 20th century, boiler operators have experimented with the addition of sodium carbonate to boiler water to provide alkalinity to the water. In the late 1800s and early 1900s, a treatment of washing soda was employed by land and marine boiler operators as the best means to prevent scaling and corrosion. Use of washing soda as boiler water treatment resulted in dramatically reducing boiler maintenance and associated costs. For Stanleys it does seem to “wash” the water system of impurities and keep the pumps, check valves, and other components free of mineral buildup.
Too much washing soda, however, can create a condition known as “foaming,” which leads to “priming” occurring. Inside the boiler, the heat of the fire generates steam bubbles within the water. The steam bubbles, which originate on the boiler tubes and internal boiler surfaces, float and burst when they reach the water surface, releasing their encapsulated steam. As a boiler generates steam, any impurities that are in the boiler supply water and that do not boil away with the steam will concentrate in the remaining boiler water. Likewise, having too much washing soda in the water supply causes the concentration of washing soda in the boiler to increase over time. The supply water containing washing soda boils away and leaves the boiler as steam. Replacement water making up for the steam used contains washing soda, which effectively increases the boiler’s washing soda concentration. When Stanleys return from a day’s use, boilers are blown down (cleared of all water, leaving only pure steam behind), which clears the boiler of the higher concentration of washing soda and other impurities and thus foaming and priming should not occur.
If the boiler water is not cleared of an increasing concentration of washing soda, the dissolved solids and sodium carbonate becomes more and more concentrated, which results in the steam bubbles becoming more stable. The bubbles of steam fail to burst as they reach the water surface of the boiler, and miniature steam bubbles are created throughout the boiler water, which represent the foaming condition. The bubbles actually start to form on the impurities within the water in addition to the boiler surfaces. The water in the boiler, when foaming occurs, becomes very similar to the foam on beer or what happens when a warm liter bottle of soda is violently shaken and the cap removed quickly. There comes a point (depending on boiler pressure, size, and steam load) where a substantial part of the steam space in the boiler becomes filled with miniature bubbles. The resulting foam of bubbles is carried along with the steam exiting the boiler, which flows to the steam engine. This is the condition known as “priming.” Due to the small spaces at the end of a piston’s travel in a cylinder, it doesn’t take a lot of “primed steam” to damage the engine. The boiler water turning to foam also can quickly lead to a low water condition in the boiler, which might result in boiler failure.
The boiler water level, upon reaching the Hagley Car Show, was “full” on the gauge as the boiler was intentionally filled above nominal operating level in preparation for sitting all day at Hagley. However, within 10 minutes of parking the car and extinguishing the pilot, the boiler water level gauge indicated a boiler half-full of water. The search for a large water leak uncovered nothing that might cause the quick loss of a half boiler’s worth of water. The gauge reaction pretty much pointed to the problem — high water when boiling, low to middle water level when not boiling. In diagnosing the problem, it was soon realized that this year, unlike previous years, the car has been making quite a number of short trips, all of which only used a quarter to a half of the supply tank’s capacity. However, Tom’s recommendation of the addition of washing soda has been followed religiously, and not realizing it, the concentration of washing soda in the supply water tank has been increasing over the summer months. Our foaming problem wasn’t caused by lack of boiler blow-downs but because we’ve not been running through multiple tanks of supply water on any given use of the steamer, thus allowing the concentration of washing soda to increase in the water tank supplying the boiler.
Beginning next year, we’ll start logging water tank fillings to ensure the concentration of washing soda in the supply water remains minimal.