Materials mostly used in boilers are steel or wrought iron. Certain small size boilers are also made of copper and brass. Because of the high thermal conductivity copper was used for fire boxes. A high quality of wrought material was used earlier in most of the boilers. These materials were used in almost all the boilers with high pressure. Steel was much stronger and cheaper material compared to wrought iron and it was easy to install with a lower labor. The material which was mostly used in domestic water heaters were cast iron. They normally require low pressure and were used for the purpose of hot water and not steam. This was not a good material when the boiler required high pressure steam. Many types of fuel are used to heat the boilers such as coal, wood, natural gas etc. In the 18th century pot boilers were used where a container filled with water is heated by wood or coal. This required more wood and coal for heating and the steam produced had very little pressure. These pot boilers provided a very little efficiency. In fire tube boilers only half the water is filled in the barell and left space is for steam accommodation.
Most of the steam producing locomotives used this type of boilers. In this the temperature should be kept below the boiling point so it is usually kept surrounded by water. The capacity of storing steam is more in fire tube boilers than its steam production. Solid fuels are mostly used in fire tube boilers but are also adaptable to liquid and gas variety. Another boiler was water tube boilers in which a large drum is connected to a water tube. In monotube boilers a pump circulates the water with the help of a coil. The storage capacity is less in this type of boilers but the steam production is much more. This type of boiler is used where a high pressure of steam is required. Due to poor welding and thin metal shells many destruction have happened in the early days. Due to poor engineering work these high pressurized steam come out and huge accidents can happen. Steam travels much faster and many times more than the original volume of water so good precautions should be taken in order to avoid accidents. These are high flowing energy so the steam plant should be regularly inspected without any failure.