Tank Immersion Heating Coil Assembly

Function

Bitumen must be held between 150 °C and 185 °C (302–365 °F) for effective spraying. The coil provides the thermal mass to raise a full cold charge from ambient to working temperature — typically 3–5 hours for a 6,000 L (1,585 gal) tank — and to compensate for heat loss to the ambient environment during extended site operations in cold weather. Damaged or scaled coil sections produce cold zones where bitumen viscosity rises, restricting pump suction, reducing delivery pressure and causing uneven spray application. A leaking coil section contaminates the bitumen charge with heat-transfer oil, which alters binder properties and requires full tank purge and clean-out.

Construction & quality

Tube: seamless carbon steel, 38 mm or 50 mm OD (1½ in or 2 in), schedule 40 wall, ASTM A106 Gr. B or equivalent. Bends: socket-welded or butt-welded, 1.5D radius to avoid stress concentration. Headers: heavy-wall carbon steel with flanged external connections. Tank wall penetration: reinforced by backing ring welds. Internal surface: bare carbon steel — bitumen provides cathodic protection against corrosion in service. Support brackets: carbon steel saddles welded to tank floor, allowing longitudinal thermal expansion. Each assembly is fully hydrostatically tested at 1.5× working pressure before despatch.

When to replace

• Heat-transfer oil visible in the bitumen charge — milky appearance or abnormal behaviour — indicating a coil tube leak
• Bitumen temperature fails to reach or hold the setpoint despite the burner running at full output
• A localised cold zone at one end of the tank detected with a surface contact thermometer
• Thermal oil circuit pressure drops consistently between pump cycles without a visible external leak
• Sludge or scale accumulation on coil outer surface reducing heat transfer, visible on internal tank inspection