The Basics of Boiler Inspection

an engineer inspecting a boiler at a work place

The Basics of Boiler Inspection

What They Are, What They Do, and the Type of Industries that Use Them

Before we take a closer look at how boiler inspections are conducted, let’s start at the beginning and answer some basic questions about boilers.


A boiler is a closed vessel whose purpose is the creation of hot water or steam. This steam is then used as a power source for various purposes (see the next section for some examples).

Typically, in order to create steam in a boiler, coal, oil or gas is converted into heat by combustion. That heat is then applied to the water contained in the boiler and, as the water is heated, it turns into steam.


The steam produced by a boiler is used as an energy source for various types of needs, including:

  • Power generation. Steam can be used to power components within various facilities, such as pumps, blowers, or turbines for generating electricity.
  • Production. Steam-driven power can help a company in making a product by providing power, the extreme heat needed for production, or sterilization.
  • Climate control. Steam can also be used to power a.c. and heating units, either to maintain the temperature needed for equipment or to create a comfortable working environment for employees.


Boilers are designed to transfer the maximum amount of heat from combustion into the water in the boiler using conduction, convection, and radiation. 

The more efficient this process is, the greater the savings will be for the company.

But boilers don’t simply heat water in order to produce steam. Conditions within a boiler are also optimized to increase the boiling point of water through pressurization. This works the same way in a pressure cooker, where an airtight seal speeds up the time it takes to boil water, or to cook in general.

Through the combination of pressure, an efficient fuel source, and an efficient mechanism for transferring heat to the water, boilers are able to create huge amount of energy in the form of steam.

Boilers use various kinds of fuel to create heat, and thereby generate steam:

  • Coal. This is a common fuel source for boilers
  • Gas. Gas refers to either propane or natural gas (LPG)
  • Oil. Oil refers to either gasoline or petroleum-based fluids
  • Wood chips or pellets. Only biomass boilers can use wood pellets for fuel.


There are many different types of boilers out there. The difference between them has to do with the way heat is conveyed to or through the water in order to turn it into steam.

Here are some of the most common types of boilers:

  • Fire-Tube BoilerIn a fire-tube boiler, fuel is burned inside the furnace and then the heat produced is transferred by tubes through the water in the tank to generate steam. Fire-tube boilers are one of the cheapest types of boilers to create since their design and construction is fairly straightforward. For the same reason, they are typically limited to low and medium pressure applications because their shell is not thick enough for higher pressures.
  • Recovery Boiler. Recovery boilers are used in the pulp and paper industry. They burn black liquor (a pulping byproduct) and recover inorganic elements in order to generate superheated steam.
  • Water-Tube Boilers. Water-tube boilers are similar to fire-tube boilers, but in water-tube boilers water tubes are heated inside the furnace to create steam instead of heating fire tubes that then transfer heat to the water inside of a tank. Water-tube boilers are more efficient than fire-tube boilers, but also more complex and therefore more expensive.
  • Biomass Boiler. Biomass boilers are similar to gas-fueled boilers except that they use bio fuel, such as wood chips, wood pellets, logs, or other forms of biomass to create heat instead of using fossil fuels.
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