Support spacing and compensation of thermal expansion
Spacing tables for DN 15–108. Calculating thermal expansion.
Maximum support spacing
Support spacing for the TAVINOX PRESS system in accordance with the technical manual (horizontal runs, pipework full of water):
- OD 15 mm: 1.5 m
- OD 18 mm: 1.8 m
- OD 22 mm: 2.0 m
- OD 28 mm: 2.5 m
- OD 35 mm: 2.8 m
- OD 42 mm: 3.0 m
- OD 54 mm: 3.5 m
- OD 76.1 mm: 4.0 m
- OD 88.9 mm: 4.5 m
- OD 108 mm: 5.0 m
On vertical runs the spacing may be increased by 20%. Always place a support close to a fitting (within 200 mm).
Thermal expansion of stainless steel
The coefficient of thermal expansion of austenitic stainless steel is 16.0 x 10^-6 /K — roughly 1.5 times that of carbon steel and similar to that of copper (approx. 16–17 x 10^-6 /K).
Calculating the change in length: dL = L x alpha x dT
Example: a 10 m tube, a temperature change of 60 °C: dL = 10 x 16 x 10^-6 x 60 = 9.6 mm
This change in length MUST be compensated — otherwise stresses build up in the fittings and the supports.
Compensation of thermal expansion
Ways of compensating:
Natural changes of direction — elbows and bends absorb the expansion
Expansion loops (U, Z and L shapes) — always design one into straight runs longer than 6 m
Axial expansion joints — where space is limited
Anchor points — place one at each end of the compensated run
Key rule: there MUST be at least one compensating element between two anchor points.
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