Safety notes on old steam models.

While boiling water is quite common in the 21st century, live steam under pressure is not. Consequently, most people are unaware of it’s basic nature, or how dangerous it can be. The potential hazards of live steam were common knowledge around 1900, when most of these old models were made, so the manufacturers assumed that the buyer was familiar with the nature of steam. Such is not the case today. What follows here is NOT a full explanation of how to inspect a 100 year old model for safety defects. Instead, I hope to offer up some of the reasons that one should seek out and familiarize themselves with the potential danger of small scale live steam if you have one of these old models and want to fire them. These little models are fascinating, but they can also bite you or set your house on fire if not handled properly. 

The older live steam models were built at a time when there was no Consumer Product Safety Commission, no Underwriter’s Laboratories testing, no CE certification, no Good Housekeeping Seal of Approval, and product liability lawsuits were not nearly as prevalent as they are today. Consequently, the dangers inherent in operating a steam model are not outlined in large red labels on the outside of the model, or even in the instruction sheet if you are fortunate enough to find one. When you enter the world of 19th century models, you also enter the world of 19th century safety, where a great deal more responsibility was placed upon the operator.

In particular, the Nuremburg models are very delicately constructed. The primary focus of the makers was art, not strength. Consequently, despite their high price these days, the Nuremburg models are more prone to failure from damage or age related decay than the more robustly built models, such as older Jensen or Bowman engines.

But, I digress – back to steam in general. There are actually two basic forms of steam. There is the steam that comes off of a pan of boiling water or out of a hot steam iron, which our old high school chemistry class taught us was 212 degrees F, or 100 degrees C. And then, there is live steam, capable of driving machinery. Live steam is a different beast altogether. It packs quite a punch – has to, in order to move machinery. In its highest form, live steam could produce a six thousand horsepower engine, in the form of the ALCO 4000 series Big Boy locomotives, or 250,000 horsepower, in the form of the four geared steam turbines used to propel the 1,000 foot long passenger ship SS United States to over 42 knots top speed. Imagine a large office building moving at 50 mph. Theoretically, live steam power plants are capable of even greater amounts of energy, but somehow a power plant generating electricity just doesn’t conjure up the majestic image of a Big Boy pulling a 1 mile long coal train over the Wasatch mountain range, or the Big U with a bone in her teeth.

In order to generate that sort of massive power, you don’t just boil water. You put it under pressure so that it can contain even more energy. Under pressure, steam rises to a much higher temperature than 212 degrees. It rises to a temperature of 300 to 800 degrees F, under a pressure of anywhere from the simple 15psi/1atm of the model steam engines, to the over 300psi/20atm used in the Big Boy. Live steam contains tremendous energy, in the form of pressure and heat. 400 degree air is merely your hair dryer on low setting. 400 degree steam, on the other hand, will burn you, in an instant. You see, for an equivalent volume, live steam packs a lot more heat than simple air. Up to fifty times the amount of heat, if my old physics textbooks are accurate. It is at this point that the causal observer should recognize that there’s something serious going on with pressurized steam. Indeed there is, live steam is dangerous stuff. In the late 1800’s, when locomotive crashes were not uncommon, many of the fatalities that occurred with the locomotive’s crew came not from the impact, but the release of superheated steam from a ruptured line. The boiler room ‘black gang’ in ships hit by torpedoes usually met the same fate, when the impact broke delivery lines to the ship’s engines. This fate was generally referred to as death by scalding. Death by being cooked would be more accurate. It was a horrible way to die.

Fortunately, the Nuremburg model engines do not develop near that sort of potential. They usually operate in the 15psi or 1 atmosphere pressure range, with fairly small boilers, but they can still produce serious injury or present a fire hazard if mishandled, or in poor condition.

In my 20 years of working with these old models, I have had two failures under pressure. Both were very small models, a Bing 130/272, and a Carette 108. The Carette blew out a sight glass plug (my fault, I shouldn't have fired it until I had put a proper sight glass in place), and sent a jet of hot water squirting out about a foot. The little Bing blew off it's steam feed line on top of the boiler. It sent a jet of hot steam out about three feet, and the steam continued to vent for about ten seconds. That was a lot of steam from a very small boiler. If I had been standing over that model when the steam line let go, I would have hit in the face with 300 degree steam. Not good, that could have resulted in serious eye damage. Both failures were first firings of models that had been dormant for a long time. And both failures came without any warning.

If you have your heart set on seeing a live steam model run, and don't know much about them, my recommendation is that you purchase a new model that can be operated without difficulty, and learn about live steam in relative safety. I highly recommend Jensen models, they are very stoutly built. Learning how to run a live steam model using an antique is not a good idea.

The chief causes of danger that I have encountered :

General age of the models. Most of the Nuremburg steam models are close to, or over, 100 years old. After many years, solder joints can become weak from repeated thermal cycling, the heating up and cooling down as the engine is fired. Pressure relief valves can jam from calcified deposits, or corrosion from sitting unused. These engines can run, but one has to respect their age, and the various forms of mechanical illness that age and use can bring. Don't assume that a model can run, just because it looks nice.

Periods of inactivity. Quite often, these models were packed away in an attic in the 1930’s, and have only recently been rediscovered. During that time, seals can rot or dry out, pressure valves can corrode, dust can accumulate where it shouldn’t be. Any engine that has been sitting for an unknown period of time needs an inspection by a knowledgeable person to insure that no safety related decomposition has occurred. If a sight glasss seal dries out, the sight glass can pop off when the boiler is pressurized – many sight glasses are held in place only by a compression seal. And that will result in a jet of superheated steam shooting out of the boiler.

External damage. This includes dented boilers, or bent steam lines. Many of these old models began life as the treasured possession of an adult, but were later handed to a child when they were no longer state of the art. Children, sadly, can be rough on models, and the boilers and steam lines suffer accordingly. Dented boilers should be considered suspect – they can fail along the dent line, or if the dent is on the end of the boiler, the end cap can fail. For that reason, I generally do not fire boilers that have obvious dents in them – too much chance of failure. I have disassembled and repaired three boilers, only because they were on particularly fine models. I do not recommend this procedure to anyone who does not have extensive experience with live steam models – the consequence of error is a burst boiler.

Joints on the steam lines. It has been my experience that this is the most common failure – a steam line whose solder joint has become weak. Quite often, this failure is brought on by a stuck pressure relief valve, or sometimes just age and repeated firing of the engine and the thermal cycling of the joint. Often, an amateur has 'repaired' a loose steam line with electrical solder. That is a real no-no, electrical solder has a melting point close to the operating temperature of the engine, and solder becomes weak long before it actually melts. It requires special equipment to solder steam lines and boilers on these models, specifically a micro oxy/acetylene torch. A plumber's torch does not produce the very hot, very focused flame needed to safely solder a steam line. Unfortunately, most amateurs don't know this, and typically use a plumber's torch and low temp solder for repairs, creating a potentially dangerous condition.

Heat or pressure damaged boilers. If a boiler is heated when it is dry, the solder joints on the ends of the boiler will become weak. They may not fail on that run, but it leaves the boiler prone to failure upon successive firings. Boilers can also be damaged by a stuck pressure valve, in which case the end caps on the boiler usually bulge out. These conditions can lead to a boiler explosion. Even on these small models, an exploding boiler can blast shreds of brass at considerable velocity. I have one large Doll overtype that has a pressure damaged boiler – serves me right for buying based on a fuzzy ebay photo. Needless to say, that engine has never been fired, and never will, unless I can find another boiler.

Falling over, or a leaky burner. This sounds silly, but it happens. The model steam engines usually vibrate and shake while they are running. If they are not secured to a steady base, the vibration can cause them to move to the edge of a table and fall off. The primary reason that modern model steam engines use solid fuel and not alcohol burners comes directly from what will happen next – the burner will tilt over, the alcohol will run out and ignite, and you have a fairly large and very persistent fire to deal with. With age, the burners themselves can develop leaks, the alcohol can leak out onto the base of the model, and you have yet another fire. Remember that alcohol vapors can communicate flame, so fire doesn’t have to touch the liquid alcohol – it can ignite the vapor that comes from evaporating alcohol.

Out of control engine. Not a common event, but a potential hazard nonetheless. These engines were designed to run at a specific speed, with a  specific amount of heat to fuel them. If a leaky burner creates a large flame, or the wrong burner is used, the engine will get too much heat, and create too much steam. Normally, the pressure valve should let go and vent the excess steam, but you will now have too much flame, a wildly gyrating engine, and a geyser of very hot steam to deal with. It is at this point you realize that the only way to shut down the engine is to put out the fire, but you don’t want to get anywhere near that thing when it’s spouting flames and hot steam. Yes, having a fire extinguisher handy would have been a wise thing to do. I keep a small, car sized unit nearby.

Running the boiler dry. The single greatest hazard of operating a model steam engine. Water in the boiler serves two purposes: it conducts energy from the flame to the operating machinery, and it keeps the boiler cool. Without water, the boiler can heat far beyond it’s design capacity of 300-400 degrees, and the joints that hold it together will be weakened to the point of failure. If the pressure valve does not function (or is jammed by melted solder from the excess heat), the boiler can burst. At the very least, an overheated boiler is ruined, and cannot be safely reused. Boilers MUST HAVE WATER IN THEM!  This gets back to the ‘situational awareness’ necessary to safely operate a model steam engine. There are no alarms to tell you that the boiler is getting low, just a sight glass. The smaller engines don’t even have a sight glass, just a burner that is designed to run dry before the boiler does – if you started with a full boiler, and if you have the correct burner for that particular model. And if the boiler gets low, you must be prepared to extinguish the flame to shut down the heat. 

Sight glass or whistle holes covered with solder. A fairly common occurrence on abused models, and very dangerous. The sight glass breaks, and someone plugs the holes with chunks of melted solder. Under no circumstances should an engine with solder plugs be run. These plugs can pop out and send a jet of scalding steam shooting out.

These are not the only pitfalls, just a sampling of the things that can go wrong. The point of this is – these small models can decay from mishandling, from neglect, from improper operation, or just plain old age. There is absolutely no guarantee that a 100 year old model, designed to burn alcohol and create hot steam, will hold together after remaining dormant for decades. While these engines can be restored to running condition and operated in a trouble free fashion, it does take some special knowledge and awareness of the potential hazards. If you have found one of these models, and don’t know much about them, it is not a good idea to just fill it with water and fire it. You can get hurt. A ruptured steam line can burn exposed skin instantly. A burner can leak alcohol out and set your house on fire. A damaged boiler can burst. The experienced steam operator keeps a situational awareness – how much flame is present, how much water is in the boiler, the speed that the engine should be expected to be at given the fire being put into the engine and the load that has been placed on it, the lubrication status of the bearings and cylinder, and a few other things. There is more to this than just firing it up and watching.

Contemporary engines. If you have purchased a new model, such as one from Wilesco, Jensen, or Mamod, the age and condition related problems will not be a factor. The modern engines are well designed, and if purchased new, are in perfect operating condition. However, you will still need to insure that water is in the boiler, the engine is well lubricated, a fire extinguisher is close at hand, and the model is secured. And beware of any engine, old or new, that has visible damage to the boiler or steam lines.

How can you avoid trouble? Seek out an expert in person. I can’t possibly cover all of the potential failures to look for, and am not foolish enough to open myself up to that sort of liability. Where can you find an expert? Best place to start is a local railroad model club. Inevitably such clubs have one or two live steam modelers, or know of them. Most live steam modelers are glad to share their knowledge – it is so unusual to find anyone with an interest in live steam these days.

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