Supporting of dual insulated piping is somewhat different from normal pipe supporting. Here I will describe the supporting philosophy for such piping system when pipe operating temperature is less than 80 degree centigrade.When pipe is having both positive(+) & negative(-) temperature the hot insulation is applied first and cold insulation is applied on it to prevent heat gain from outside the pipe when pipe is operating below zero degree Centigrade.
When pipe is operating in negative temperature range then we have to prevent heat gain by pipe through support from outside in that case we have to provide Craddle support. Note that High Density Urethane craddle support can sustain temperature up to +80 degree Centigrade after which the melting of the material starts.
For supporting please refer the attached drawing. Follow the below mentioned notes along with the figure.
1. Cradle Radius (R) is based on insulation thickness (T1+T2)
2. Bottom of Pipe shall be based on cradle thickness (T)
3. Temperature for HDPE cradle is less than +80 degree centigrade
2. Supporting of hot and cold insulated pipe when pipe operating temperature is more than 80 degree centigrade.
When the piping system faces temperature more than +80 deg. C which Polyurethane block cannot sustain, we have to think of some other arrangement of supporting which allows higher operating temperature in both positive & negative range.If we use metallic shoe/base support in that case we have to protect cold insulation from higher temperature due to its temperature limitations which can be done by carefully checking the temperature drop (Assume temperature drop or gain as 1.1 degree centigrade per mm og length) through the support or by extending the hot insulation layer along the shoe / base support up to extent of cold insulation temperature limitations. Refer below attached figure to see the supporting philosophy for such cases. Follow the below mentioned notes while reading the figure.
Notes for the figure:
1. Shoe width can be increased as per requirement.
2. While using one must check the temperature limitation of the cold support or cradle.
3. No damage to the cold insulation should be made while supporting.