Visual inspection is usually good enough for under roof insulation that is accessible, as in boiler rooms, pipe chases, and steam tunnels. If the insulation is intact, fits snugly, and remains dry, it is almost certainly doing its job. Damage that is serious enough to reduce the effectiveness of insulation is usually obvious. The only subtle case is where insulation may become wet from a leak in the equipment it surrounds.
You can use infrared cameras and other types of thermal scanners to survey large areas of insulation and inaccessible equipment. See Reference Note 15, Infrared Thermal Scanning, for details.
In a buried steam distribution system, you can estimate the rate of heat loss from the pipe insulation by measuring the rate of condensate flow from the drip traps. Each pound of condensate represents a conductive energy loss of about 1,000 BTU. If the system has an intact condensate return, pick a time when all the end user equipment can be turned off, so the condensate flow is returning only from the drip traps. Alternatively, drain the drip traps into containers and time how fast they fill.
This test method works only if the steam in the lines is saturated. Some facilities superheat the steam to keep it from condensing in the lines. To get around this, turn off the boiler’s superheaters during the test, or use the desuperheater.
Steam becomes superheated in passing through a pressure reducing valve. If the line is fed from a pressure reducing valve, reduce the boiler pressure enough to allow you to bypass the pressure reducing valves for test purposes.
You can localize defects in boiler insulation by using the same methods used to find leaks.
