pipe insulation calculation

I'm assuming you mean the losses with and without pipe insulation.

You can use a simple heat transfer equation if you want to calculate it by hand

Q=U*A*dT

The U value can be tricky if you have moving fluids whcih i assume you do in a pipe.

You can use an easy and free software program built by the National Insulation association. The US DOE also uses this program in it's Industrial technology best practices (ITP) program. There are several calculators available for energy consumption and energy efficiency for different systems.

http://www.pipeinsulation.org/

Remember that the program will give you the loss from the pipe. To calculate the energy consumption, you have to account for the efficiency of the boiler or cooling equipment.

A rough estimate would be to use the k value(thermal conductivity coeff.) You know the thickness of your pipe and the length of it gaining heat. You should know the temperature of fluid / gas in and allowable temp out. Calculate the amount of heat gained per length of pipe and adjust the thicknesses of your insulating material to suit.

Another factor with very low (or very high) temperatures might be a safety issue from the outer skin temperature. In addition to economic factor of cost of energy lost is the safety of the workers who may come in contact with the hot or cold surface.