A heat trace cable is installed on a line that will be insulated. When will the cable be megged?

Megger testing, or insulation resistance testing, is an important procedure performed on heat trace cables to ensure their integrity and safety. Performing this test before insulation is applied allows for the detection of any insulation failures or damages that may have occurred during the installation process. By verifying the condition of the cable beforehand, any issues can be addressed prior to sealing it away with insulation, which would make troubleshooting more difficult later.

Additionally, conducting a megged test after the insulation is applied provides a second layer of assurance that the insulation remains intact and that the cable has not been compromised during the insulation process or from external factors once in service. This dual testing method—before and after insulation—is key in the maintenance and reliability of the heat trace system, ensuring that it functions correctly in preventing freezing or structural damage due to temperature variations.

In contrast, only testing before insulation may miss any potential later damage, while testing strictly after may overlook any pre-existing conditions. Testing during decommissioning serves a different purpose, mainly to establish safety before removal or maintenance rather than ongoing operational readiness. Thus, conducting the test in both scenarios maximizes safety, efficiency, and peace of mind regarding the cable's operational capacity.