Boiler Refractory are heat resistant material which is used in the lining of boilers and other equipment like furnace. When it comes to Marine boilers refractory materials are used to contain the heat, which is generated from the furnace of the boiler.

Boiler Refractory which are selected for marine boiler should have sufficient strength for :

  • ‌High temperature
  • ‌Rapid Change in temperature
  • ‌ Heat load at boiler running condition
  • ‌From Flue dust
  • ‌Not to get contamination by the impurities.
  • ‌From adjacent brickwork weight(Firebrick)

Boiler Refractory material are classified into 3 types mainly :

  • ‌Base/Alkaline type material - Lime, Zirconia, Magnesia
  • ‌Neutral type material - Graphite, Chromite, Alumina
  • ‌ Acid type material - Clay, Quartz, Silica ,sandstone

IMPORTANT : Proper installation, Startup and maintainence are always needed to get the maximum boiler efficiency and also to prevent other damage of refractory material. Select proper material for the specific boiler and while taking a Refractory material check whether the reactions during operation and non operational condition should be less.

As we have got a basic idea on Refractory material and it's applications now we can move on to the installation part. The installation of a Refractory material are of 2 types :

  1. ‌ Firebricks
  2. ‌Monolithic Refractory

FIREBRICKS

  This is an older practice of installation of refractory materials, but practiced for many years earlier. Refractory material are made into a shape of bricks shape by firing the material at high temperature in special insulated chamber. The installation time and manpower are more in case of Firebrick, so this method is not economically feasible compared to monolithic refractory.

MONOLITHIC REFRACTORY

     This refractory materials are unshaped, so we can make it into different shape in accordance with the boiler. Due to the rapid installation time, lower cost of raw material, and less manpower this monolithic refractory is preferred over 2 decades. The main properties of monolithic material are :
  • ‌Abrasion resistant
  • ‌ Chemical inertness
  • ‌ Mechanical integrity
  • ‌Thermal stock resistance at hight temperature
There are 5 different forms of monolithic Refractory :
  1. ‌ Castable Refractory - The material consist of fine grains and precision graded coarse which are mixed with water and applied to the boiler surface
  2. ‌ Plastic Refractory - The material can me made into any shape and it is mainly applied is a liner to the boiler.
  3. ‌ Ramming Refractory - This is similar to plastic but are more stiffer than plastic.
  4. ‌ Gunning Refractory - Granular materials are sprayed using air placement guns for maintainence purpose.
  5. ‌ Coating Refractory - Protect refractory lining against any forms of chemical attacks.

Precautions to be taken during and after Refractory installation.

  • ‌ Provide adequate space for expansion of the boiler Refractory.
  • ‌ The amount of Refractory material applied will tell how slowly the temperature is raised.
  • ‌ After shutdown close the air dampers because it prevent entry of cold  gas inside the furnace to sudden cooling off the refractory material, which leads to Refractory spalling, causing reduction of thickness.
  • ‌ Impurity like sodium or vanadium entering to the boiler should be avoided because it can cause reaction in the refractory material which leads to reduction of thickness.

So we have explained in detail of boiler Refractory, materials used, type of installation, Property of materials, and precautions during and after Refractory installation. If you have any doubt regarding this topic or any marine topics please comment below and we will clear it soon as possible.