Apparatus, system and method for monitoring external properties of plant equipment and/or pipe work

A method of evaluating a corrosion condition of plant equipment and/or pipe work surrounded by an insulating material, the method comprising:

• providing a sensor system comprising:
• a plurality of sensors located in and spatially distributed over the insulating material, each sensor being operable to provide a sensor output indicative of a presence of water in an insulating material;
• at least one reference sensor operable to provide a reference sensor output indicative of the presence of water in an ambient environment in a vicinity of the plurality of sensors;
• and
• a processor configured to receive the sensor outputs from the plurality of sensors and the reference sensor output;
• using the processor to correlate the sensor outputs from the plurality of sensors and the reference sensor to identify whether one or more of the plurality of sensors has a sensor output which closely correlates to or deviates from the reference sensor output to determine whether one or more of the plurality of sensors is located in a substantially dry portion of the insulating material or a substantially wet portion of the insulating material and provide a correlation data output;
• and
• using the correlation data output in the evaluation of a corrosion condition.