Basic Elements

An in-house program can be developed by many different approaches. A program that is limited to the use of only qualitative thermal imaging instruments (as compared to radiometric/quantitative) is likely to be less comprehensive. Assuming that a program was created to make full use of a radiometric/quantitative imager and image processing software, the following topics would need to be addressed:

• Qualification of personnel

• Scheduling

• Equipment matrix

• References

6.1.1 Introduction

This section provides a discussion of the purpose and goal of the IR survey.

6.1.2 Definitions

In order to put the program in the proper context, the definitions should be at the front. This will allow the reader or reviewer to have an easy reference for the terminology that follows.

6.1.3 Scope

The scope of the program should be very specific as to what is covered and what is not. The applications for infrared thermography are very broad. Inspections of roofs and buildings should not be addressed in a document that has inspections of safety-related equipment as its main purpose. An addendum to the main procedure should be used to avoid confusion.

6.1.4 Responsibilities

This section should clearly delineate who is responsible for the various aspects of the program from administration through corrective action. The main areas of responsibility are

administration, inspection (Infrared Thermographer), and corrective action. Most of the difficulty in applying this technology is in image interpretation and diagnosis. It might be necessary to use others in this effort and, if so, their role should be specifically identified.

6.1.5 Precautions

Many of the infrared inspections necessitate that panels be removed from energized electrical equipment. Precautions as to electrical and personnel safety should be included.

6.1.6 Prerequisites

All of the prerequisites for conducting the survey should be identified here. This should include the qualification of personnel, calibration of equipment, approvals needed from Operations and/or Management, and the required resources (equipment and personnel).

6.1.7 Conduct of the Survey

This section could reference or include specific procedures for inspections. Specific techniques and a suggested sequence of inspections could also be included.

6.1.8 Acceptance Criteria

All survey results should be compared to either a baseline thermogram or other industry accepted standards. Problems or anomalies should then be reviewed for determination of which corrective action, if any, should be undertaken. The following acceptance criteria provide a generic

example but would need adaptation for component-specific use.

Advisory 1°F to 15°F rise above a reference (0.5°C–8°C) Intermediate 16°F to 50°F rise above a reference (9°C–28°C) Serious 51°F to 100°F rise above a reference (29°C–56°C) Critical in excess of 100°F rise above a reference (56°C)

An alternative to the above classification is that used in Military Standard MIL-STD-2194 (1988). The MIL Standard uses four categories as follows:

Desirable Component is 10°C (18°F) to 24°C (44°F) above ambient Important Component is 25°C (45°F) to 39°C (71°F) above ambient Mandatory Component is 40°C (72°F) to 69°C (125°F) above ambient Immediate Component is 70°C (126°F) or more above ambient

The main difference between the two methods of problem classification is that the MIL Standard references temperature rise above ambient and the guide classification relates to a temperature rise above a reference value. That reference value could be ambient or, in the case of three-phase electrical circuits, a temperature rise above an adjacent phase.

Each facility should adopt criteria that provide a balance between maintenance requirements and operational considerations.

6.1.9 Reporting Criteria

A rigid process should be established when reporting the results of infrared inspections. This rigidity is necessary due to the ease of misinterpretation of the thermograms by untrained

personnel. A typical quarterly survey of electrical equipment might result in 25 to 50 problems in 200 pieces of inspected equipment. The vast majority of these problems might be minor in nature and require corrective action on a low priority. The process that works best, based on industry responses, is one that keeps the report distribution and decision-making in the hands of the right people (operations, maintenance, and/or program managers).

The format for the report should also be consistent. At a minimum, it should include the following:

• Time/date

• Equipment identification

• Specific problem

• Corrective action recommended

• Problem action criteria

• Visible photograph

• Infrared photograph

• Inspector’s name and signature 6.1.10 Qualification of Personnel

Personnel responsible for conducting the surveys and interpreting the results should be trained in the use of the equipment and certified by their employer. The training and certification criteria, established by the American Society for Nondestructive Testing (ASNT), should be adapted and incorporated into the program. These criteria are outlined in their document SNT-TC-1A and will be discussed in more detail in Section 7.

6.1.11 Scheduling

The documentation requirements and listing of equipment to be evaluated during the survey should be established in advance so that trends in equipment operation can be translated easily into predictions of future results. This is the key to predictive maintenance. The program must also be flexible enough to accommodate emergency inspections and inspections during

unplanned outages. Typically, the administrator of the IR program provides this interface.

6.1.12 Equipment Matrix

The equipment to be surveyed, the selection criteria, and the locations and frequency of inspection should be compiled in a matrix. Typically, the electrical equipment is grouped together, as are the other major component groups. An alternate approach would be to list the equipment in a route of survey-format, which might save time for the infrared thermographer.

6.1.13 References

References to any helpful information should be provided. These typically include training materials, textbooks on the subject, and equipment operation manuals.