piping and equipment insulation

A quick Google will reveal numerous resources on the topic.

A few things to consider:
-Is insulation for personnel protection or for process?
-What temperatures do your proccess(es) need to maintain? What are worst case ambient temperatures?
-Does the equipment insulation need to be fire-rated?

For a process that needs insulation, you determine the required process temperatures and ambient area temperatures, and perform calculations to determine the size of the insulation based on a given material. If multiple insulation materials are applicable for your service(s), you can do this for multiple materials.

If the insulation is for personnel protection, it may end up be a smaller thickness since it's not concerned with keeping heat/cold in, but rather just that someone won't be burned by touching it.

Then you can decide what kind of cladding/jacket materials you want, pipe labeling, and so on.