Steam boilers are very complex, but we’ve tried to explain how they work in an easy to understand way.
There are two main designs of steam boilers: water tube and flame tube/smoke tube (otherwise known as a shell boiler). In a water tube boiler, water is contained in tubes that are surrounded by hot gas. In a shell boiler, hot gas flows through tubes that are surrounded by water. In both cases, the hot gas is able to heat the water. A water tube boiler is able to reach a pressure of about 200 bar, whereas a shell boiler will reach a maximum pressure of around 25 bar. A shell boiler can produce up to 26 tonnes of steam per hour, making it sufficient for industrial use.
The boiler itself is a large horizontal cylinder which has insulation all around it. The boiler will be 75 per cent full of water, allowing a 25 per cent gap for the steam. Both water tube and shell boilers work via a three-pass system, however the following information is only applicable to shell boilers.
Within the boiler, the flame tubes sit in the water. Hot gas enters the flame tubes (first pass) and continues through an internal reversing chamber that reverses the flue gases, leading them into the smoke tube (second pass). An external reversing chamber reverses the flue gas a second time, leading it into another smoke tube (third pass). It’s as if the gas is passing backwards and forwards through the boiler, heating the water as it moves. Once the gas has moved through the third pass, it exits through a chimney. The heated water then turns into steam.
The steam can be transported around the system via pipes and hot water will be pumped to taps. Any steam that condenses within the pipes will be returned to the boiler, where it is heated again. Some water may be lost over time and will need to be re-added.
You can find a cross section illustration of a three-pass shell boiler below:
Want more information on industrial steam boiler corporation, steam boiler, steam boiler supplier? Click the link below to contact us.