This specification covers molded expanded perlite block, fittings, and pipe thermal insulation intended for use on surfaces with temperatures of certain range. The insulation shall not have visible defects that will adversely affect its service qualities. Different test methods shall be performed in order to determine the properties of the block, fitting, and pipe insulations: density, apparent thermal conductivity, linear shrinkage after heat soaking, flexural strength, compressive strength, weight loss by tumbling, moisture content, water absorption after heat aging, surface bearing characteristics, hot-surface performance, and stress corrosion cracking of austenitic stainless steel.