Infrared (IR) Thermography Program

 

Thermography is a valuable diagnostic tool for predictive maintenance. By detecting anomalies often invisible to the naked eye, thermography allows corrective actions to be taken before electrical, mechanical, or process equipment fails. Infrared radiation is emitted by all objects based on their temperatures, according to Planck’s black body radiation law. Thermography makes it possible to "see" the subject environment with or without visible illumination. The amount of radiation emitted by an object increases with temperature; therefore, thermography allows one to see variations in temperature.

As temperature in a conductor rises, so does its resistance. Conversely, as resistance increases (in most conductors) temperature rises. The majority of thermal electrical problems involve improper torque specifications or improper installation at the junction points. A loosely torqued connector effectively reduces the surface area in which current can flow and consequently an increase in the contact resistance. Oxidation build up at the connection point can also cause a rise in resistance. The origin of most conductor, insulation, and component problems can be traced to a poor connection using an infrared camera.

The IR Thermography program is a mandatory maintenance for the appropriate types of equipment.

 

Program Goal


The performance of the IR Thermography program has three primary goals:

• Increase equipment and system availability,

• Improve equipment operating condition, and

• Reduce unnecessary energy expenditures through reduction in inefficiencies.

 

The IR Thermography program will increase critical equipment reliability and extend equipment lifespan, reducing overall equipment lifecycle costs.

 

IR Thermography Services


EPIC shall provide scheduled collection of equipment temperature conditions and analysis of collected data and trending.

Typical equipment includes:

• Chillers, generators, pumps, and other rotating machinery that directly supports the mission-critical equipment;

• Mechanical equipment driven by belts or gears including motors and critical exhaust and/or ventilation fans, and similar;

• Main electrical distribution equipment including medium-voltage transformers, main bus systems, transfer switches, motor control centers, and main distribution panels;

• Component-level electrical distribution equipment including mechanical and solid-state circuit breakers;

• Circuit breaker panels and all subcomponents supporting critical functions, including PDUs, RPPs, and lighting control panels; and,

• Uninterruptible power supply (UPS) equipment and related systems including static switches and battery strings.

 

Safety

 

All electrical work (including but not limited to IR Thermography conducted on energized equipment and systems) shall follow the guidance in the NFPA 70E Program. All work shall be supported by an “Energized Electrical Work Permit” signed by the site Director (or his/her appointed designee) prior to any energized work.

For facilities that do not currently have IR viewing windows for high-energy equipment to reduce technician exposure to electrical hazards EPIC will provide the correct PPE. As individual site IR Thermography programs develop, some equipment may be identified as being too hazardous for inclusion in the program. Decisions regarding which equipment to be left out of the program are reserved for the Chief of Facilities Engineering.

 

IR Thermography Equipment

 

Technical requirements for the infrared camera to be used to perform this service include:

• Minimum resolution for the camera equipment shall be 320x240 pixels.

• Minimum temperature measurement accuracy requirement: ± 2% or 3.6° F.

• Ability to input variable emissivity parameter on camera.

• User-replaceable, rechargeable battery system.

• Visual camera mode to capture visible light image of target simultaneously with IR image.

• Laser target identifier and visual light illuminator.

 

Surface Temperature


The surface temperature rise limits for surfaces subject to user contact during normal operation or maintenance (including incidental contact) are 140⁰ F (60 ⁰C) for non-metallic surfaces and 95⁰ F (35 ⁰C) for metallic ones (included painted metal). These are the maximum allowable surface temperatures for exposed equipment above ambient. (For example, if the ambient temperature is 80⁰ F (27 ⁰C), the exterior of a metal motor casing should not exceed 175⁰ F (79 ⁰C) to be within the specification.)

 

Maximum Allowable Operating Temperature

 

The maximum allowable operating temperature for equipment is based on a maximum ambient temperature of 104⁰F (40⁰C). Here are a few items and the allowable temperatures.

 

Equipment

Allowable Temp. Above Ambient

Max Allowable at Max Ambient (104⁰F)

Air Cooled/Dry Power Transformer

239⁰F (145⁰C)

343⁰F (185⁰C)

Control Transformer

122⁰F (50⁰C)

226⁰F (90⁰C)

Molded Circuit Breaker

149⁰F (60⁰C)

253⁰F (100⁰C)

Wire (Type THHN)

194⁰F (90⁰C)

298⁰F (130⁰C)