A class or B1 class insulation for a jacket
The insulating fill decides both heat loss and combustion class. A class is non-combustible; B1 is flame retardant and stops burning when the source is removed.
In a removable jacket the fill is the functional core: it sets thermal performance and the combustion class of the finished part. Under GB 8624, the fills in common use divide into class A non-combustible and class B1 flame retardant materials.
B1 fills are mainly organic polymers with flame retardants added. They resist ignition in air under flame or high temperature and stop burning when the source is removed. Common types in jacket production include flame-retardant elastomeric foam and modified organic foams, with conductivity in the range of 0.03 to 0.045 W/(m K).
How the choice is actually made
Class A fills are inorganic, non-combustible and stable at higher temperature, at a cost in weight and handling. Where the jacket sits near a hot surface, in a plant with fire requirements, or on equipment that must keep working during a fire event, the non-combustible fill is the defensible choice. Where the duty is low temperature and the fire load is remote, B1 fills are lighter and cheaper.
- Surface temperature of the equipment, and the fire case it sits in
- Whether the jacket is indoors, outdoors or in a classified area
- Weight and handling, given the same operator removes it
Reference note. Figures and standard references are indicative and do not replace the project specification, the current edition of the standard, or product test reports for the specific supply.