Failure Analysis To Improve Reliability Of Production Equipment
Failure analysis is a crucial tool in identifying the root causes of equipment failures and devising strategies to improve the reliability of production equipment. Let’s consider an example of how failure analysis was used to enhance the reliability of a manufacturing machine.
Improving Reliability Through Analyzing Past Failures
This case illustrates how a metallurgical failure analysis helped pinpoint the source of a problem and establish a plan to prevent future occurrences.
Evaluation of Defeat
In my last piece, I wrote about how metallurgical failure analysis can be used to increase product dependability. The cause of a failure can be pinpointed with the help of data gleaned from a component’s failure analysis. Once the cause has been determined, the failure analysis data and conclusions are used to determine what preventative measures must be taken.
Negative Model
The stainless steel paddles in our industrial mixers kept cracking. A stem (machined bar) was welded to a plate to create the paddles. The paddles were fastened to a shaft that extended through the length of the apparatus by screwing the paddle’s stem into the shaft. The paddles stirred the processed material as the shaft turned.
Broken paddle
The paddles were subjected to cyclic stresses that caused bending in both directions, as revealed by the failure analysis. The failures were localized to the very end of the weld connecting the paddle shaft and the plate. Higher stresses were found at the weld compared to the rest of the paddle because the weld was a stress concentration. The microstructure and chemical makeup of the paddle materials and the weld joint were up to par.
Weld failure
Since the equipment shaft only rotated in one direction, the failure to bend in the opposite direction seemed strange. It turns out that transient acceleration and deceleration in motors can be traced back to power supply fluctuations. After looking into the issue, it was discovered that the power supply to the motor that rotated the equipment shaft had a few issues, which caused large voltage spikes and erratic motor behavior.
Two Problems and Their Solutions
A stressed-out paddle design and a shaky power source for the motor both played a role in this accident. The stress on the paddles was reduced after modifications were made to the power supply, which eliminated the large voltage spikes and improved the motor’s behaviour. The number of failures and the average time between failures dropped drastically as a result of the adjustment, but they were not eliminated.
The entire paddle was cast in one piece, and the design was altered to remove the stress concentration. The modification eliminated all previous failures in operation.
