cold draw

[Gunner77]

I have a thermal insulation spec that asks for cold draw to be prevented around supporting bracketry on pipework supports. My interpretation of this is that due to the fact that part of the bracket is outside of the thermal insulation the intention would be to keep the bracket from actually contacting the pipework section by useing a foil face hard wood block support and running the insulation up to the block and foil tape the joint. This would be for Chilled Water but what about for Hot Water - LTHW. Does cold draw come into place here, I would say so, but not to the extent of Chilled Water. Whats the alternative to the Hard Wood Block for Hot Water. I would assume the Phenolic Block with a Steel Shell to take the weight of the pipework in the bracket.

 

[ChrisConley]

I've never heard the expression 'cold draw', but I agree that avoiding having the support of cold pipe drop below dewpoint temperature is important. Our standard detail includes a thermal block and insulation a distance up the hanger.

My thought is that 'cold draw' would only apply to pipes that operate below dewpoint, but without actually knowing the intent of the phrase I'd hestitate to guess.

 

[sailcat753]

If the insulation is completely surrounding the pipe and an aluminum jacket is used around the pipe with a pipe roller, cold draw would be eliminated because there is no direct contact between the pipe and the pipe support in my opinion.

 

[Whoops]

Cold draw refers to thermal expansion bellows on heating pipework.

The bellows is installed cold and is usually stretched on tightening the bolts. Cold draw is usually 50%; the bellows never has to expand by 100%, but is under tension for 50% and in compression for 50%.

 

[walkes]

From the description it would appear that they are just avoiding a thermal bridging scenario. Our specs always call for pipe hangers on chilled water piping to be large enough to go around the insulation, there would be an insulation saddle such that the insulation doesn't get crushed at the support point. So the hanger isn't in contact with the cold pipe causing condensation on the hanger.

It doesn't happen on hot piping.

The thermal expansion Whoops seems to be referring to is more "cold springing" of the pipe.