fire bricks

[emuchops]

I have a multi fuel burner-like a wood burner but takes coal too-cast iron. The fire bricks are wearing out. Before replacing them i'm wondering what they actually do and whether they are necessary?
Can anyone enlighten me?

[woodchopper]

They are necessary - if you dont put them back in the wear that occured on the fire bricks will happen to the inside of your burner and eventually burn through the casing.

[heathfield]

They also act as a kind of insulation, and stop the casing becoming red hot. If that happened, it just migh be a fire risk to anything inflammable close by.

[emuchops]

Many thanks Woodchopper and Heathfield-I am enlightened!

[PatriciaH]

Wilkinsons sell them -roughly �1.99 when i last bought them