I have seen a table for the freezing time of water in pipe for various diameters, insulation thickness, and external temperatures but I cannot find the reference. Does anyone know where to find it or an appropriate calculation?
I do not have a specific address for online information, but I have found vendor calculation guides to be helpful in the past. If you perform a search on "surge tank" or "hydropneumatic tank" you should get a lot of hits. You might also try AWWA, ASHRAE, and ASPE.