Patent ID: 8085829

Claim:
A furnace insulation, comprising: fibre modules in the form of at least two cylinder segments ( 2 , 3 ; 7 , 8 ) that are placed against one another so as to form a cylinder whose internal volume constitutes a furnace space, the fibre modules being made of a material that shrinks at high temperatures; and an electrical resistance element ( 5 ) configured to lie against and be fastened in an inner surface ( 4 ) of the cylinder, wherein an inner part of the cylinder includes one or more radially extending or generally radially extending openings ( 12 ; 14 ) along a length of the cylinder segments ( 2 , 3 ; 7 , 8 ), and the one or more radially extending openings include at least one notch configured to be at least one crack indicator ( 14 ) and a plurality of radially extending expansion joints ( 12 ).