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Why Failure Analysis Services and PQI are Crucial to Streamlined Workflow

April 13, 2022

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When a small section of an electrical component is damaged, the entire device can fail. This interruption in signal flow can have an exponentially negative effect on workflow, as it can cause an entire assembly of automation to be disabled indefinitely.

Failure analysis services are designed to determine this flaw after the fact, yet there is a preemptive program known as Parts Quality Initiative (PQI) which pinpoints equipment failures and potential defects before installation. This practice can assure a continuous workflow that enables an organization to streamline its operations and consistently meet production goals.

Small Flaws can Equate Big Delays

Circuitry controllers such as time delay relays are used in many applications including military, nuclear, pharmaceutical, aerospace and commercial manufacturing. While these instruments are routinely bench tested before installation, miniscule manufacturing flaws are not always detected.

Minute inconsistencies do not always render a piece of equipment inoperable, and undetected defects can result in a faulty component going to market, being sold and implemented in a manufacturing facility. Moreover, defects and flaws can worsen during the shipping or installation phases, so that soon after being energized, the relay can fail altogether.

Once a system is disabled by a failed relay, considerable time can elapse while management and technical personnel work to locate the point of failure and replace the faulty component.

Diagnosing a Failed Relay

Recently, the engineers in the failure analysis department at Constellation PowerLabs received a faulty time delay relay requiring thorough analysis. Specifically, when energized, it was noted that not all contacts were changing state causing the control circuit to never energize.

The initial examination determined that the component was properly assembled and in good condition. Upon closer inspection, however, a slight discoloration was noted on one corner of the circuit board. This led to the suspicion that a potential heat event may have occurred during manufacturing or service. Initial resistance measurements determined that the time delay coil was in good condition. Yet, when subsequently energized, the relay did not change state, meaning that the normally open contacts did not close, making it impossible for current to flow through their respective circuits.

Closer inspection of the resistor revealed surface discoloration near the center point as well as a brittle ceramic coating that cracked easily at one end point. This was the only resistor, or any component within the relay for that matter, which displayed signs of damage. The resistor was removed by a meticulous de-soldering process for closer inspection. This step revealed a lateral crack at the end opposite the chipped ceramic coating.

The resistor was replaced with a comparable part of similar manufacture, which restored function to the entire relay assembly. The relay was energized multiple times and found to have good repeatable timing. This led the analysis team to determine that this connection was the sole defect within the time delay relay.

Hypothetical Analysis of the Findings

Investigative diagnosis determined that the heat event which caused discoloration to the circuit board was responsible for the failed resistor and thus, for the defective relay. It could not be determined, however, if the heat event occurred during the relay’s manufacturing, installation or in-use/service phase.

Constellation PowerLabs failure analysis records show that numerous time delay relays from this specific manufacturer had been previously analyzed. Over a period of 18 years, a total of 12 similar failed components were submitted. In three of these cases, heat damage to the circuit board due to a damaged resistor was found to be the cause of failure. In two other cases, failure was shown to have originated in a similar area of the circuit card where this component failed.

There is some speculation that the resistor in question had a manufacturer defect which caused it to have a lower power dissipation rating than required. The only way to be sure of this, however, would have been to subject the component to PQI testing before installation.

Why Failure Analysis Provides Front-End Assurance

A thorough front-end PQI testing of components is necessary for facilities to better avoid downtime or delays from a failed part. Constellation PowerLabs offers PQI testing which assures that by the time a part is inventoried or installed into a production configuration, it has passed no less than seven (7) thorough and rigorous tests to assure the part is in proper working order. For time delay relays, these include an initial energizing and de-energizing to confirm the relay engages at the manufacturer rated voltage level. Then, there are three (3) subsequent tests at minimum time setting and three (3) more tests at the maximum time setting.

There are short- and long-term, company-wide benefits of PQI testing. This practice can keep operating costs low by reducing unplanned maintenance shutdowns while keeping production on track with market demand.

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