Steel boilers, as their name implies, are made of steel and are usually made of horizontal cylinders. Steel boilers have a combustion chamber in which pipes are placed around this chamber. The pipes that are installed around the combustion chamber of steel boilers are made of a special alloy so that they do not burn or damage in the face of a direct flame. These pipes are called (fire pipes). Steel boilers are divided into friends from the point of view of heat transfer, which are as follows.

Engine room boilers have capabilities that have made them the main and common part of buildings. Boilers have a long life, and boiler efficiencies can achieve efficiencies of % and above, provide effective methods for heating buildings, and require very little or zero pumping energy in steam systems. But fuel can be significant, and regular maintenance is required by the facility engineer, and if it is delayed, the cost of repairing the engine room can be high.

Cast iron boilers are very useful because they can be collected in the basement and passed through smaller doors and gates. The most important drawback is that they are prone to leakage due to the connection of the parts by the washer when the washer becomes old or damaged by chemical reactions. Among the famous cast iron boilers in Iran, we can mention the boiler cast iron boiler and M.I. cast iron boiler made by Iran Pipe and Machine Building Company.

If a building has multiple boilers, you may be able to use the boilers in sequence to prevent repeated cycles. If you use boilers that do not adjust, it is better to use the next boiler when the capacity of one boiler is full, instead of disconnecting and connecting several boilers that are loaded. On the other hand, in regulating boilers, the efficiency of the boiler increases in the load-sharing situation. Therefore, using several boilers at the same time in load sharing mode is more beneficial than using one boiler with % efficiency. Figure shows the relationship between ignition rate and efficiency in boilers with adjustable air and fuel flow utilization.

The pressure difference between the combustion chamber of the boiler and the ventilator (also called the exhaust chimney) creates a suction that carries the products of combustion along with the boiler and directs it to the chimney. The natural suction of boilers depends on the natural buoyancy of hot gases to remove combustion products through the aerator and direct fresh air into the combustion chamber. Mechanical suction of engine room boilers includes compressed air, where the air is forced into the combustion chamber by a fan or blower to maintain positive pressure. Induction suction, where the air is drawn through the combustion chamber by a fan or blower to maintain negative pressure.