Regular equipment inspection serves many important purposes. For example, it:
- Helps districts or users determine the current condition of the equipment and also allows comparison of results with previous inspections.
- Helps spot trends and predict life cycles.
- Can uncover defects and deficiencies that must be corrected before a catastrophic breakdown occurs.
- Can prevent major losses due to equipment breakdown and/or failure.
Equipment must be inspected and tested at the frequency recommended by the manufacturer or mandated by an authority having jurisdiction. After equipment has been accepted and placed in service, it should be tested within its designed parameters to prevent damage (except when required by the manufacturer or an authority having jurisdiction).
Common Inspection Methods
Four commonly used methods of inspection are visual, ultrasonic, eddy current and thermographic. A visual inspection should be performed in conjunction with any other type of inspection. These four methods are considered Non-Destructive Examination (NDE) or Non-Destructive Testing (NDT).
Meaningful results can only be achieved when the equipment and instruments used are suitable for the material being tested and when the inspectors are trained and qualified in the procedures used.
Visual Inspection
Visual inspection includes looking at the equipment that is in direct view. Equipment that is not in direct view can be inspected by using mirrors, cameras, flexible optical tubing, or other similar devices. Visual inspection can only determine the surface condition of the object and surrounding area. Some conditions to be considered:
Ultrasonic Inspection
Ultrasonic inspection measures the thickness and detects flaws on different types of materials, including metals, ceramic, plastics, glass, and rubber. Ultrasonic testing can be accomplished in a relatively short period of time and is used extensively to measure the wall thickness of pipe, tubing and other pressure-retaining parts. High frequency and highly directional sound waves pass through and bounce back to the instrument that monitors, records, and analyzes the wave patterns to document the test results.
Eddy Current
Eddy current testing locates surface cracks, near-surface cracks, pitting, and corrosion on inner surfaces. It can determine metal thickness by measuring the change in an induced magnetic field caused by discontinuities of the material being tested. The eddy current test is most commonly used to inspect exchanger tubing on air conditioning and refrigeration chiller systems for thickness, cracks and corrosion. The magnetic field is created by a device that is pushed inside the tube. The instrument monitors and processes the intensity of the magnetic filed as the probe is pushed through the full length of the tube to display and record the test results.
Thermography
Thermography is performed using an infrared camera that detects the intensity of heat waves. It processes this information to create an image of the object in different colors that represents a temperature scale. The outer surface of the equipment is scanned at a distance, and there is no contact with the object being tested.
Typical equipment that is surveyed includes electrical switchgear and panels, electrical wiring, transformers, cable and bus, motors, bearings, and insulation. Through this testing, you can spot the hidden factor of heat being generated by defective electrical wiring.
With regularly-scheduled inspections, you can help ensure awareness of the equipment’s condition so that maintenance and replacement can be planned without interrupting the normal operation of your business.
