What is Lagging in Boilers ?

Lagging in Boilers refers to the covering over the boiler.  The principal function of the lagging is to cover the insulation and prevent heat loss from the boiler.  It also provides a cool surface over the boiler for fitment of accessories.  It provides a formal shape to the boiler after the insulation has been fitted.


Lagging is a essential part of boiler design.  Lagging is usually made of aluminium or steel.  The Lagging should be adequately supported so that it maintains its shape. 

The surface of the Lagging should also be provided with drainage so as to drain the excess water in case of rain or other water leakage.  This is important particularly in outdoor design. 

Adequate allowance should be made in the design for expansion and contraction of the lagging during operation as the temperature varies. 

The expected lifetime of the insulation and lagging is 15 years.