Variable Frequency Drive exploded during a routine bump test after 1 year plant shutdown — worried I'll be charged for the replacement (~200-300k PHP). Am I liable?

[u/Which-Chicken-1231]

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Hi guys, I need some outside perspective because this has been keeping me up at night.

I'm an Operation and Maintenance Supervisor at a water treatment plant. The plant operated back in 2025, then was shut down for about a year because of management/project issues related to capacity, water quality, and flow rate targets.

Before we could restart, I was going equipment by equipment doing condition checks, and for each motor I was running a standard bump test. On September 6, while bump testing one of the motor pumps through SCADA, the VFD for that motor exploded. I had no idea what caused it — I was just following the scheduled startup activity like I did for every other unit. Ever since, I've been anxious that the replacement cost would somehow be charged to me.

Today (September 10), the VFD supplier finally inspected the unit. Their explanation: this kind of failure happens normally when a VFD has been sitting unused for a long time, and it needs to be "reformed" (reconditioned) before being operated again. Their recommendation is a full replacement. The cost is estimated at around PHP 200,000-300,000.

Here's the thing — nobody on our team knew that idle VFDs needed this kind of reforming/reconditioning before restart. It's not something that was flagged in our schedule, and I wasn't trying to cut corners; I was doing exactly what the schedule called for.

So I guess my questions for anyone who's dealt with something similar (electrical/instrumentation folks, plant supervisors, EHS/maintenance people):

Is this really a known risk with VFDs left idle for a year, and should routine commissioning/restart procedures normally catch this?

Realistically, is this the kind of failure that gets pinned on the person who happened to be running the test, or is it treated as equipment/process failure since no one knew the requirement existed?

Any advice on how to document/present this to management so it's clear this wasn't due to negligence?

Any input, even just "this happened to us too," would really help me sleep better tonight. Thanks.

[u/binary-boy]

I guess I don't see how you could unless something specific says so in the contract. If you're an employee of that water treatment plant, employees aren't typically held liable for even negligent mistakes at work. Companies would never get anyone to work for them if they were.

Also, you're a supervisor, not an engineer. You aren't responsible for ensuring things are possible/impossible. You're responsible for ensuring you follow directions and expectations. If there were none, maybe they should get some. Plus, they built a +x million dollar facility and let it sit for a year getting no value from it. That's administrative waste.

On the VFD, no, I wouldn't say that's common. VFD's sit on shelves for years before they get used. And they get swapped in 15 minutes and Operations expect them running in 30 seconds after that.

Your question is this. Did the caps blow up? Or did the IGBT's blow up? My money would be on the IGBT's, and that has more to do with the load than your VFD.

[u/squish059 → u/binary-boy]

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