Heat Tracing Tank Sizing
Tank heat tracing is often sized from a pipe calculation with a generous safety factor — and then under-performs. Tanks lose heat through walls, roof, bottom and appurtenances in different proportions, and the tank's own thermal mass changes the answer. This guide covers the practical sizing approach.
Where a tank loses heat
- Walls: the largest area; heat loss depends on product level, insulation and ambient.
- Roof: exposed to wind and sky radiation; often less insulated than the walls.
- Bottom: heat loss to the foundation or ground; sometimes ignored entirely.
- Appurtenances: nozzles, manways, ladders, platforms — thermal bridges that bypass insulation.
- Vapour space: for tanks with a gas space, condensation and heat loss through the roof.
Sizing approach
1. Calculate per surface, then sum
Do not use a single "tank factor". Calculate wall, roof and bottom separately with their own insulation and boundary conditions, then add appurtenance allowances.
2. Account for product level
Heat loss depends on wetted area; a half-full tank has less wall heat loss but more vapour space. Design for the worst credible operating case, not the nominal level.
3. Heat-up versus maintain
Maintaining temperature needs only the steady-state loss. Heating a cold product to temperature requires extra power for the thermal mass — often several times the maintain load. Decide which case applies; do not size for maintain and then expect heat-up.
4. Ground and foundation
For tanks on concrete or ground, the bottom loss depends on the foundation temperature, which is not ambient. Use a realistic ground temperature.
5. Appurtenances
Nozzles and manways are thermal bridges. Add an allowance (often 10–20 %) rather than trying to trace every small item.
6. Cable selection and distribution
Tank tracing is usually distributed across several circuits around the shell. Circuit layout should follow the tank's geometry and avoid long single runs that create voltage drop.
Typical calculation inputs
| Input | Note |
|---|---|
| Product maintain temperature | From process, with margin |
| Minimum ambient | Design value, with wind for exposed tanks |
| Insulation | Thickness and conductivity; roof may differ |
| Dimensions | Diameter, shell height, roof type, bottom |
| Product level | Design worst case |
| Heat-up requirement | Time and starting temperature, if any |
| Ground temperature | For bottom loss |
Common mistakes
- Sizing from a pipe formula with a blanket safety factor.
- Ignoring roof and bottom losses.
- Ignoring appurtenance thermal bridges.
- Designing for maintain but requiring heat-up.
- One long circuit around a large tank instead of distributed circuits.
Tank heating project?
Send the tank dimensions, insulation and temperature requirements. We calculate wall, roof and bottom losses and size the tracing.
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