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Before everyone gets up and leaves, allow me to explain. Traction engines are only as safe as the operator. For this reason, it is highly desirable that traction engine operators be very knowledgeable in the production of steam. We've all heard of and read tragic accounts of boiler failures and the untimely deaths of the unfortunate souls operating these boilers. What we don't hear about is why these boilers failed. Human error accounts for 99.9% of these failures. In other words, the boiler doesn't fail the operator - the operator fails the boiler.
For example, consider a typical 25 horsepower locomotive style boiler fired to 150 pounds per square inch. There is enough energy contained in the hot water in the boiler that if coupled to a large rifle, it could shoot a one-pound ball 7500 miles straight up. If this power were applied to the lifting of a steam engine weighing 25,000 pounds it would raise it to a height of 1700 feet. If we were working with a cannonball weighing one ton this projectile could be shot straight up to a height of 3 ½ miles. These figures should impress on the engineer the need to exercise all due precautions when operating a boiler under pressure.
Anytime water is boiled there is a potential for explosion. Ever wondered why your water heater at home has a relief valve? The same reason a boiler has a safety or “pop” valve. Both your water heater and a boiler are built to withstand certain pressures. Repeated operation above these pressures can cause metal stress and fatigue leading to weak/leaking joints that pose potential problems. Pop valves open at a pre-set pressure and then close when the pressure decays to another pre-set point. This is done to ensure the boiler pressure never goes above design. The pop valve is one safety device that should NEVER be bypassed in any manner. A pop valve should be tested daily under pressure to ensure that it pops and resets as per design pressure.
Anytime there is a fire in a boiler, there must be water in the boiler. The water level in the boiler is seen in the gage glass either on the side of the boiler or at the rear of the boiler on the operator's platform. Depending on how hard the engine is operating, this level should be kept midway of the glass to one inch above the bottom fitting on the glass in order to protect the crown sheet in the boiler. The crown sheet is the metal part of the boiler immediately over the top of the firebox. This area is exposed to the most intense part of the fire, and therefore needs water over it for cooling purposes. The Frick that I operate has a built in safety feature here. When the water level is at the bottom fitting on the gage glass, there is still 4 inches of water over the crown sheet.
The water glass should be checked daily for proper operation. Prior to building a fire in the boiler, open the gage glass drains while watching the water level. It should drain out the bottom, and the bounce back into the glass when the drain is closed. This provides the operator with a very important piece of safety information - the glass is working and not plugged causing a false level indication. Correct water level is the absolute most important thing that a boiler operator should be aware of at all times. Be sure your gage is active every time you steam up a boiler.
Another means of indicating water level in a boiler are the tri-cocks. These are 3 small valves placed at different heights on the boiler. They are usually found on the operator's deck, however some are found on the side of the boiler near the gage glass. The tri-cocks serve as a back up water level indication to the gage glass. Opening these one at a time will result in releasing steam, steam and water combined or simply water. When opened, if steam is released the water level is below that tri-cock. If water/steam are released, the water level is approximately at the open tri-cock. If water is released, the water level is above the open tri-cock. These should be checked daily under pressure to ensure their proper operation.
As the boiler begins to build steam pressure, it is a good idea to be sure water can be added. It is prudent to have 2 means of water addition on any boiler. Most traction engines have a steam operated feed pump and an injector. Some have only 2 injectors. The steam operated feed pump is exactly that - a steam operated reciprocating boiler feed pump. An injector operates by using boiler pressure and a venturi nozzle to pick up water and deliver it to the boiler. Here, redundancy is simply for back-up purposes. If one means fails, there is another to fall back on. Should both means fail, proceed immediately to remove the fire from the boiler and allow the boiler to cool. The purpose for this is explained in the next paragraph.
The operator should know at all times where the water level is in his boiler. Should the level go low and the operator does not know how low his level is or how long it has been there, STOP! DO NOT ADD WATER. Pull the fire out of the boiler using whatever means available. The idea here is to get the fire out of the boiler and let it cool naturally rather than putting water in the boiler. If the crown sheet has come uncovered and is hot, adding water will quickly quench the hot crown sheet and possibly cause it to crack and fail. If this happens the remaining water in the boiler will escape, flashing to steam as it returns to atmospheric pressure. One gallon of water will expand to 1646 cubic feet of steam, so you can easily imagine what will happen when approximately 300 gallons of water at roughly 350 degrees Fahrenheit instantly turn to steam.
Should you lose sight of your water level and have to pull your fire, before firing the boiler again you should check the fusible plug. The fusible plug is device placed in the highest part of the crown sheet to allow escape of steam and water into the firebox if the crown sheet overheats due to low water. It is made of brass and has a hole drilled through it. This hole is filled with an alloy, which melts at 445 to 450 degrees Fahrenheit. The plug is located either in the back or the front of the firebox, just below the top of the highest tube. The plug will melt when it loses contact with the water and the fire is put out by water and steam. It should be checked periodically (according to state law) to make sure there is no aggregation of scale over the top of the plug, which could cause it to malfunction in an emergency. It is very important to ensure the fusible plug is scale free. Also check the amount of alloy in the end of the plug. If it is partially melted, you may consider replacing the plug. It is a good idea to consider replacing the fusible plug once a year to ensure proper operation.
The traction engine should never be left unattended. Minnesota for example requires that a licensed operator be on the deck of a traction engine at all times when in operation. If you must leave your engine unattended, you should make the following a practice: (this is the law in Minnesota and Virginia )
Water level should be at least 1/3 glass
The header or dome valve is closed
The draft doors are closed
The fire is banked or extinguished
The boiler pressure is at least 20 psi below the pop valve setting.
When all these conditions are met, the traction engine is considered as not being in operation.
Each time you leave and return to a traction engine, it is good practice to check the position of every valve on it. By doing this, you ensure that all valves are correctly lined up open or closed. This is vital in determining correct water level as well as being able to add water to the boiler.
When moving about on a traction engine, you should have 2 people on the operator's deck. The 2nd person serves as an extra set of eyes for tending the engine/boiler and most importantly for watching out for people. It is advisable in heavy crowds that you move about slowly and responsibly. Traction engines have no brakes, and only quick operator action can prevent the darting child from becoming a fatality.
A traction engine is only as safe as the operator. Careless operators have no business in this hobby as they could quickly bring it to an end for everyone. Know your engine/boiler, have it inspected as per state law, manage your water level prudently and be alert for spectators. Being safety conscious when operating traction engines ensures the hobby will be carried on responsibly for future generations.
Written by Tim Wade, EDGE&TA Advisor