The primary purpose of the boiler is to supply energy to the facility's operations – for comfort heating, manufacturing process, laundry, kitchen, etc. The nature of the facility's operation will dictate whether a steam or hot water boiler should be used. Hot water is commonly used in heating applications, with the boiler supplying water to the system at 120°F to 220°F. The operating pressure for hot water heating systems usually is 30 psig to 125 psig (hydrostatic). Under these conditions, there is a wide range of hot water boiler products available. If system requirements are for hot water of more than 250°F, a high-temperature water boiler should be considered.
This is because, under normal circumstances, the exhaust temperature of the boiler cannot completely condense the water in the flue gas, and the difference between the low calorific value and the high calorific value is mainly in the part of the latent heat of vaporization, so the low heat is used. The value is calculated to reflect the true efficiency of the boiler. However, there will be some special circumstances. For example, if the boiler is a condensing boiler, the calculation of the condensed water portion should be calculated using the high calorific value.
In order to improve the combustion efficiency of the boiler, in a large boiler, the combustion air is not supplied all at once, but is supplied in two times, one is supplied with the fuel that controls the rate of combustion as well as the amount of fuel that can be burned,and the other is directly supplied to the combustion process that that improves combustion efficiency. The primary air rate of the boiler refers to the proportion of the primary air. If the total air volume is 100% and the primary air rate is 70%, the secondary air rate is 30%.
In a boiler, energy from the fuel is transferred to liquid water in order to create steam. Once the water is heated to boiling point, it is vaporized and turned into saturated steam. When saturated steam is heated above boiling point, dry steam is created and all traces of moisture are erased. This is called superheated steam.
A fire tube steam boiler is a boiler where the combustion gases from the burner are channeled through tubes that are surrounded by the fluid to be heated. The boiler body is the pressure vessel and contains the fluid. In most cases, this fluid is water that will circulate for heating purposes or become steam for use in processing.
Each set of tubes through which the combustion gas passes, before making a turn, is considered a "step". Consequently, a three-step boiler will have three sets of pipes with the outlet located at the rear of the boiler.
