Exelon PowerLabs has been performing failure analysis services for half a century, helping businesses across various industries get to the root cause of the failure. When a component fails its routine function, it is important to find out why it failed by identifying the physical cause of the failure to prevent recurrence.
After a thorough investigation, Exelon PowerLabs’ engineers provide an in-depth failure analysis report that shares a broad scope of testing and analysis to customers. While the level of detail on a report is dependent on the failure analysis case, Exelon PowerLabs is determined to help customers identify the contributing potential causes of the failure through a variety of examinations. Such examinations may include:

• Documentation of Part in As-Received Condition
• Visible Inspection
• Test Functionality (PQI testing based on the categorical component)
• X-ray if Necessary
• Disassembly if Necessary, for Further Inspection
• Component Analysis – stemming from an electrical failure
• Cross-Section Capabilities to the Points of Interest
• Metallurgical Testing if Necessary
• Discovery and Determination of the Cause of the Failure
• Corrective Action Recommendations
• Extent of Condition Recommendations

It’s essential that businesses are proactive with the report results and take preventative maintenance measures to ensure the safety of their employees, equipment reliability and continue daily operation performances. As new failure analysis cases come into the laboratory daily, Exelon PowerLabs recently received a failure found to be problematic due to a manufacturing issue.

Just Another Day in the Labs

A remote sensor for a valve was sent in for failure analysis for further investigation to determine why the component failed. This instrument is fastened to a valve and senses the position of the valve. The readings falsely reported the valve was 100% open when it was closed. While this component was only installed in early 2018, it started having problems a few months after installation giving the customer false readings when the problem was detected.

Failure Analysis Inspection Process

Once the item arrived at the lab, the engineers first inspected the component in its received condition. Careful review of the component’s external view of the shaft and port view were first performed, which did not reveal evidence of any problems.

Testing the Functionality

The remote sensor valve was connected to a system where the valve changes state at certain intervals, remaining closed when the system is running. The remote sensor was in a different state than it should have been and gave a false reading. After enough information was gathered in the initial inspection, a functional test was performed.
The remote sensor has a potentiometer inside a robust, industrial housing which is mounted on the valve. The potentiometer itself has three wires including a wiper that rotates similar to a radio dial and the valve movement changes the potentiometer’s resistance. As the shaft of the sensor turns the potentiometer, the wiper provides the signal voltage corresponding to the valve’s position.

After performing the initial testing, the problem did not reveal itself. The engineers continued to perform more extensive testing. The device was temperature cycled while the output was continuously monitored. At elevated temperatures, a position in the potentiometer rotation was found where the output voltage was discontinuous and would have given a false valve position. Once the bad position was found, it was very repeatable even at room temperature.

Disassemble the Component

The team disassembled the remote sensor as well as the potentiometer itself to microscopically examine the potentiometer. At the position where the discontinuity occurred, a defect was found in the potentiometer’s resistor which caused the wiper to lose contact with the resistor. There were no cracks found to compromise the other wiper positions. The depression in the resistor was found to be a manufacturing issue.

The Key Reason for Failure

After the failure mode was determined, Exelon PowerLabs contacted the manufacturer regarding the potentiometer’s flaw. The manufacturer acknowledged the defect and had recently selected a new potentiometer for their remote sensors. After acknowledging the issue, the manufacturer offered to replace the old remote sensors with the newly designed ones.

Upholding Quality with Failure Analysis

Through rigorous investigation and thorough examination, Exelon PowerLabs was able to determine the failure mode of the remote sensor. Not only were the engineers able to find the reason behind the failure, they also took action in reaching out to the manufacturer to ensure the design flaw was corrected. Failure Analysis is not only beneficial to customers, but to the community as manufacturers are held accountable for their quality.