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Boiler Explosion!

The pictures below show what happens when a boiler catastrophically explodes.

boiler1 boiler2 boiler3 boiler4 boiler5

Why do boilers explode?

The principal causes of boiler explosions are:

  1. Boiler was built outside of USA and was not constructed as per ASME construction codes and standards
  2. Failure of the pressure parts of the steam and water sides.
  3. Malfunction of the safety and control devices
  4. Operator error
  5. Furnace gas explosion

The internationally recognized organizations National Board of Boiler Inspectors and American Society of Mechanical Engineers have developed codes and standards for the construction and operation of the boilers.

All of BPC’s inspectors have several years of experience and are certified by NBIC and local Jurisdictions for the inspections of boilers.

During these inspections, our inspectors verify the critical operating condition of the boilers and proper operation of the safety devices by visual inspection and review of records to ensure the boilers are safely operated.

Below are summarized the most important items that our inspectors verify during the inspection visits:

  1. Verify the boiler is constructed in accordance to ASME codes for the designed pressure (Maximum Allowable Working Pressure). The boiler is stamped by the manufacturer and bears the NB registration number.
  2. Verify the pressure parts of the boiler are in sound condition to withstand the maximum allowable pressure of the boiler as designed and operated. The integrity of the pressure parts could be comprised by the following causes:
  • Poor water treatment or contaminated feed water resulting in the corrosion, erosion and scale formation on the water side surfaces of the boiler.

Corrosion and erosion reduces the integrity of the pressure parts to withstand the MAWP of the boiler, resulting in leakage, cracking and rupture of pressure parts. and scale formation.

Scale reduces the heat transfer and results in localized overheating of the metal. The over-heating makes the boiler material softer and weaker and this causes distortion and makes the boiler unsafe to bear the pressure of the steam, especially in high-pressure boilers.

Scales may sometimes deposit in the valves, safety devices connection piping and condensers of the boiler and cause plugging making the devices inoperative.

Scale deposits could sometimes crack and allow direct contact of hot water with the overheated metal plate resulting in uneven metal expansion and sudden formation of a large amount of steam suddenly. This could cause localized steam explosion and damage to the boiler.

3. Malfunction of safety devices – Safety devices are tested to verify their operating parameters.

  • Safety/relief valves are tested as per NBIC/Jurisdictional mandated intervals
  • Low water control devices are tested regularly to ensure these very important controls function as desired.
  • Pressure and temperature regulators are tested to verify they operated as designed.

4. Operator training – There is a documented program for training and verification of competency of the operators.

5. Furnace explosion. This could be caused by malfunction of the burner management system, operating parameters and operator error.

  • Fuel rich mixture – Improper ratio of supplied air and fuel supply for complete combustion.
  • Improper atomization of oil – To prevent this, the oil tips must be clean, the oil temperature must be correct, the oil viscosity must be in spec, and the atomizing steam (or air) pressure and fuel oil pressure must be properly adjusted.
  • Improper purge and repeated attempts by the operator to relight the boiler. The unburnt fuel suddenly ignites after several relight attempts resulting in explosion.

Improper functioning of the burner management system – The programmable logic controllers for both the combustion control system and the burner management system should be tested at least annually to verify they are operating as designed for the application.


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