3-phase motor failure

[Bestboy]

I wish to share some learning with you guys about this failure.It sounds basic but it may help someone.
A week did not go by after posting a question on thread237-176733 about an upgrade I am intending to do of a 40 years old system.
An operator and a mechanical fitter were changing over fans from A to B as a weekly routine. The fitter was in the plant and the operator was in the switch room. When the operator pressed the start button, the off-line motor accelerated to speed as normal and then poooof…fire and huge smoke. The 15 kW, 2pole, 3-phase induction motor caught fire. The operator did not notice anything because the amp meter was still indicating healthy. The fitter in the field could not reach to the emergency-stop button next to the motor so he ran 12 meters into the switch room to stop the motor. He pressed a stop button but the current was still high. Then he ran out again to the subs station to isolate and then the motor stopped. After that they dosed the fire. Then without proper isolation fitters and electricians were on top of the motor coupling and terminal box getting the motor to the rewinders as soon as possible. Then a root course analyses was done and it was established that: -
1.There was no records of this motor ever been rewound but a bearing change had been done 5 years ago
2.It is an open motor and it’s very dusty around the motor. Not abnormally hot and there is fair amount of ventilation.
3.There is no emergency-stop button in the control room but there is one in the field.
4.The contractor welded in hence pressing the E/S could not stop the motor.
5.The overload did tripped but late.
6.Only isolating fuses and no circuit breakers protects the power circuit. Two of the three fuses popped.
7.We could only suspect that the motor caught fire due to a spark in the windings possibly due to insulation failure.
8.In the endeavours to get the job done quickly, the artisans worked on the equipment without proper isolation/lock-out and a getting the necessary permit-to-work documentation.
9.And lastly a question on work ethics.The motor was brought back a day later when it was realised that the electricians concentrated on the burnt motor and never checked checked and repared the gear.This resulted to time wasting and increase in risk.

 

[waross]

It sounds as if your lockout procedure is in need of an overhaul as well. Do you have a lot of MBA influence in upper management?
If every worker has a set of locks, and permission to install them when he sees the need, they probably will be used when needed. There are sometimes problems with a man forgetting to remove a lock when he goes off shift. There are procedures to address this.
The MBA paragdim seems to be to concentrate on avoiding this nuisance at the expense of safety.
I worked on a project where I was reprimanded for leaving a lock on overnight on equipment that was still in an unsafe condition.
Operating personnel were doing equipment checks every night and this equipment was not ready to be energized. Procedures said that All LOCKS MUST BE REMOVED WHEN GOING OFF SHIFT, regardless of the potential risk involved.
I was on a project recently where the project manager objected to the manner in which a worker was working on a ladder in a stairwell. The manager made such a fool of himself that none of his staff were going to risk their jobs by explaining to him that the worker was following the proper documented procedures. The subcontractor involved thought that the issue was resolved and sent another worker to complete the work, in acordance with the new procedures, only to have the project manager again display his unique combination of an ignorance of his own procedures and an astonishing hubris.
I think that the issue was finally resolved by scheduling the work between 7:00 AM and 8:00 AM., a time frame when the manager was never on the job site.
And, by the way, the final agreed upon procedure would have allowed the first worker to continue his work unmolested.
Too often safety procedures and lockout procedures loose sight of safety and are concentrated on the convenience of management and "Cover Your ASSets" with written procedures.
Sorry for the rant, but my experience is that if lockout procedures arn't followed it is often because the system is flawed.
Sorry for the Rant, but unsafe conditions in the name of safety are one of my peeves.
respectfully

 

[wrsharper]

Here Here, You can lead a horse to water but you cannot make it drink, that is what my grandmother used to say. I am one of the few that uses lock out consistantly, even if the disconnect is only three feet away. We have people putting their hands in all kinds of places that, would appear to a resonable and sane person, is idotic and some of these people have missing digits, etc. I constantly chastise mechanics and then lock it out for them. I get the "light in the deers eye" look. I just try and do it like the little dutch boy who would put his fingers in the holes in the dike. Thanks for listening to my rant.

 

[Bestboy]

Thank you for the comments.
These guys know the procedures and they have been trained over and over again but sometimes proper work ethics fall through the cracks and this can be disastrous. One stupid action can easily jeopardise the plant or people’s lives. In this particular incident no one was hurt but the parties concerned were warned