Spotting electrical problems with IR thermography

There is perhaps no industry that requires zero room for error than nuclear power generation. Exelon Nuclear, part of Exelon Corp., one of the nation’s largest electric utilities, uses infrared thermography as a key component – along with other technologies such as vibration and lubrication analysis – in its extremely successful predictive maintenance program.

06/01/2009


There is perhaps no industry that requires zero room for error than nuclear power generation. Exelon Nuclear, part of Exelon Corp., one of the nation’s largest electric utilities, uses infrared thermography as a key component %%MDASSML%% along with other technologies such as vibration and lubrication analysis %%MDASSML%% in its extremely successful predictive maintenance program. Thermography makes it possible to measure the temperature of each part of an entire assembly %%MDASSML%% including parts that are inaccessible or at high voltage %%MDASSML%% and do it rapidly and without touching anything. Temperature anomalies often reveal otherwise-undetectable problems.

Once a problem is identified and diagnosed, a comprehensive approach eliminates the possibility of recurrence and improves future maintenance efficiency. The following examples are taken from the component health database, with thermographic data gathered with a FLIR ThermaCAM PM 695.

Chiller control panel hot spot

During routine thermography, a potentially serious hot spot was identified on the main power supply, “B” phase connection in the control panel of a large commercial chiller. The delta-T between phases trended up to 57 F (Fig. 1A), which turned it yellow or in “alert” range in the component health-tracking program. We assumed that the temperature was higher given the insulating wrap installed on the connection. Since the hot spot was on the supply side, the breaker may not have tripped to prevent failure.

An analysis of the bolted connection indicated that there was RTV-type sealant between the areas of contact, causing a high resistance connection and the subsequent heating. Repair procedures were adjusted to prevent a recurrence. Figure 1B shows the result.

Hot spot in distribution panel

During routine thermography, a 244 F hot spot was identified on a lug to the busbar for multiple control power breakers inside a critical panel. The delta-T from similar connections was around 165 F, making this a red component requiring immediate action. As shown in Fig. 2A, some covers on the front of the panel had to be removed to see the connection more clearly (Fig. 2B).

The bolt that holds the lug to the copper bus bar, and carries most of the current, appeared to be visibly loose. This was detected about one month prior to a refueling outage. Making the repair while online would have been risky, so after assessing the risk we decided to complete the repair during the upcoming outage.

This connection would not fail at or below measured temperatures of 600 F, so we did a thermal test every day until the scheduled outage. Fortunately, the temperature remained stable until repairs were completed. Electrical maintenance technicians removed the degraded hardware, cleaned the connection and installed a new bolt on the lug assembly.

Minor hot spot?

In many cases, the control instrumentation of large circuit breakers is just as important as the breaker itself. A terminal board connection in a control panel for a switchgear breaker is a good example of a problem that on the surface, appeared to be minor %%MDASSML%% and indeed had a low risk of failure %%MDASSML%% but whose possible consequences were high. During an annual inspection, we found a hot spot on the terminal board connection for a circuit that provides amp indication in the panel and plant control room. The connection was 5.5 F hotter than other terminal board connections, most likely because of a loose terminal screw or inadequate lug crimp connection. Failure of this connection would cause a loss of amp indication and could affect the trip function of the breaker. The trip function of the breaker not only protects the load but also the bus.

Electricians investigated and found the terminal screw loose approximately one-quarter turn. Temperature on the connection returned to normal after corrective maintenance was completed.


Author Information

Mike Ralph is program coordinator for the LaSalle (IL) Station Vibration, Thermography and Lubrication Program for Exelon Nuclear. He is a Level II thermographer, Level II vibration analyst and Level II lubrication analyst, and has been using these technologies for nearly 18 years. For more information, go to www.goinfrared.com/electricalproblems .




No comments
The Top Plant program honors outstanding manufacturing facilities in North America. View the 2015 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
2016 Product of the Year; Diagnose bearing failures; Asset performance management; Testing dust collector performance measures
Safety for 18 years, warehouse maintenance tips, Ethernet and the IIoT, GAMS 2016 recap
2016 Engineering Leaders Under 40; Future vision: Where is manufacturing headed?; Electrical distribution, redefined
SCADA at the junction, Managing risk through maintenance, Moving at the speed of data
Safety at every angle, Big Data's impact on operations, bridging the skills gap
The digital oilfield: Utilizing Big Data can yield big savings; Virtualization a real solution; Tracking SIS performance
Applying network redundancy; Overcoming loop tuning challenges; PID control and networks
Driving motor efficiency; Preventing arc flash in mission critical facilities; Integrating alternative power and existing electrical systems
Package boilers; Natural gas infrared heating; Thermal treasure; Standby generation; Natural gas supports green efforts

Annual Salary Survey

Before the calendar turned, 2016 already had the makings of a pivotal year for manufacturing, and for the world.

There were the big events for the year, including the United States as Partner Country at Hannover Messe in April and the 2016 International Manufacturing Technology Show in Chicago in September. There's also the matter of the U.S. presidential elections in November, which promise to shape policy in manufacturing for years to come.

But the year started with global economic turmoil, as a slowdown in Chinese manufacturing triggered a worldwide stock hiccup that sent values plummeting. The continued plunge in world oil prices has resulted in a slowdown in exploration and, by extension, the manufacture of exploration equipment.

Read more: 2015 Salary Survey

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.
This article collection contains several articles on the vital role of plant safety and offers advice on best practices.
This article collection contains several articles on the Industrial Internet of Things (IIoT) and how it is transforming manufacturing.
This article collection contains several articles on strategic maintenance and understanding all the parts of your plant.
click me