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5. Thermal compensation
As the internal piping is cooled by the cryogenic fluid, it contracts in length. The usual value used for thermal contraction is 3 mm/m for a temperature difference of around 220°C between ambient temperature + 20°C and liquid nitrogen temperature – 196°C. The shrinkage of stainless steels is negligible between – 196 and – 273 °C.
As the outer shell remains at room temperature, this contraction must be compensated for.
The various compensation solutions, in order of preference and simplicity, are :
-
use of the natural flexibility of the internal piping; the minimum length L to compensate for contraction without exceeding the permissible stress is obtained using the simplified formula in the standard NF EN 13480 (metallic...
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Standards and norms
- Tuyauteries en oxygène et systèmes de tuyauterie - EIGA 13/12 -
- Nettoyage des équipements pour le service d'oxygène - EIGA 33/06 -
- Cryogenic containers – Cleanliness - NF EN 12300 - 1999
- Cryogenic containers – Methods for assessing thermal insulation performance - NF EN 12213 - 1999
- Cryogenic containers – Valves for cryogenic use - NF EN 1626 - 2008
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