Drum Insulation

Function

By minimising radiant and convective heat loss through the drum shell, the insulation system reduces specific fuel consumption — litres of fuel per tonne of mix — and allows the drum to maintain mix discharge temperature within specification even in cold or windy ambient conditions. This directly affects mix quality: asphalt placed below approximately 145 °C may not compact to the required void content. The insulation also dampens shell temperature excursions during start-up, reducing the rate of thermal fatigue cycling on the shell plate and riding-ring weld zones, directly extending the service interval of those components.

Construction & quality

Primary layer (hot zone near burner end): high-density ceramic fibre blanket, 25–50 mm thick, rated to 1,000 °C continuous. Secondary and outer layers: mineral wool (rock wool), density 96–128 kg/m³, 50–75 mm per layer, rated to 600–750 °C. Total installed thickness: 100–175 mm. Blankets are pre-cut to drum circumference and supplied with stainless-steel tie wire and ceramic-button fasteners. Circumferential banding: 25 mm × 0.7 mm stainless-steel banding at 400–600 mm pitch to resist centrifugal displacement at operating RPM. All insulation materials are supplied with batch certificates for temperature rating and density. Each kit is pre-cut per drum model and packaged to prevent moisture damage in transit.

When to replace

• Visible hot spots or discolouration through the outer cladding indicating missing or compressed insulation beneath
• Increased fuel consumption at constant throughput shifting more than 5% from established baseline
• Cladding outer surface temperature exceeding 80 °C measured by infrared thermometer during operation
• Tearing, displacement, or bunching of blanket sections visible when cladding panels are removed for inspection
• Moisture condensation or steam on the drum outer surface during cold-weather start-up, indicating gaps in coverage