A boiler is a container for heating water and other fluids, but it does not necessarily boil them. North Americans use the term “furnace” for vessels that do not heat fluids to the boiling point. Heated water has various applications such as central heating, power generation, cooking and sanitation.
Most boilers have pressure vessels made of steel, but the older ones were made of wrought iron. Stainless steel, which can crack and corrode, is not used in wet parts of a boiler. However, it often appears in heater sections that are not exposed to water.
Live steam models often use copper or brass, which are easier to fabricate in smaller boilers. Copper was once used for fireboxes in steam locomotives due to better thermal conductivity. The high price of copper makes steel a more practical choice today.
Boilers are classified into different configurations. Pot boilers or Haycock boilers, fire-tube boilers, water-tube boilers, flash boilers, and sectional or “pork chop” boilers are some examples. Boilers have dozens of fittings and accessories that keep them operational.
Several types of fuel can heat a boiler or furnace. Coal, wood, oil and natural gas are the most common fuels. Electric steam boilers use immersion- or resistance-type heating elements. Nuclear fission is another source of steam generation.
Historically, boiler accidents caused serious injuries and property damage due to misunderstood engineering concepts. Boiler operation and maintenance still pose safety concerns, and organizations like the American Society of Mechanical Engineers (ASME) have developed regulation codes and safety standards.
Boiler training from American Trainco and similar companies offer seminars and training courses on boiler operation, maintenance and safety. The courses are designed to teach maintenance personnel how to service boilers safely and effectively. They often include optional certification exams and personalized continuing education (CE) certificates.