The Unexpected III -Motors in a Fertilizer Plant

6 kV phase to phase or line to ground, delta or wye internally, improper phase order?

Thanks all of your for your comment well focused but next what really happened

The commercial ruse was as following:

The motor manufacturer change the stator slot design from strainght shape into slope shape to all motors from 250 HP and above.

The problem arose at first start moment, at both end of winding coils due to a high stress developed whend the coils are forced against to slope slot laminated edge, therefore damaging the coil insulation and hence the winding fault to ground. (IT WAS THE TECNICAL MISTAKE).

there were more than 60 motors in the same situation of wrong design.

What the manufacture did ?: Just sold the failured motors to ovesea supposed purchasers with long time scheduled to motors install and meanwhile get enough time to money recovering due to the loss.

They knew that Urea plant is always scheduled for last statrting in fertilizer complex. (IT WAS THE COMMECIAL RUSE).

N.B. this bad design was ignored in the handed motors test certificate which also must stated that motor shoud run about 4 hour as part of test proceeding

Bye

I am unable to understand the OP's English ..........I doubt my abilities of understanding the english.......confused...not able to understnad the head & tail...

Good riddance. Thanks a heap for the fun and games.

What is the problem, I understood what happened! The OP has found that a batch of motors he was sent were improperly manufactured, and the supplier knew it, Yet delivered them to a customer and took the money for the bad product. The supplier knew that they would have to honour their warranty eventually, but the long lead time allowed enough sales to cover the losses over several sales quarters.

Because I cannot imagine a manufacturer actually admitting this, it might be all speculation on the OP's part, but it makes perfect sense. Personally I would never order from that supplier ever again, but who knows who will win the next bidding process. Losses incurred from the delayed start would not be assumed by the manufacturer, but by the engineering firm who signed the testing certificate. One or two engineers thrown to the wolves, and the manufacturing plant is saved.

What exciting drama! Beats the heck out of what we see on TV these days!

Yes, Mr Yusef1 difficult to understand but it was absolutely true, the manufacturer make trick to recovering their invesment in motos bad design (mufacturer no mentioned for ethic reasons) the actually in fact is that the five motors burn out during the first start during precommissionig stage despite declared test cetificate said that the motors were running during four hour at work.

And for other that not undestand my english the failure reason was due to change on the stator slot from strainght shape into sloping configuration as I explained in my first post.

This was part of mutual confessions between buyer and seller at the end of the work whith the plant already at full production where not claim took place.

The five motors were replace in time for start-up the Urea plant so no reasons for any claim.

It's not a lesson but a good experince for some forum members

Bye

In time for start up! Yay!

I can see an entire engineering firm breathing a great sigh of relief! But I would still fire the signators.... or give them golden parachutes for being team players. Its the way the game is played, I guess. I don't have to like it, and I don't.

Glad your plant got up and running in time Juan, and I hope some management weenie did not blame you!

Juan, I will talk in simple English so that you can understand easily.

It is not question of your mutual settlement with motor supplier. It is some thing called Cheating which should never be tolerated no matter where ever you are located.

May be in your country you can forgive supplier for such cheating case but not in the other countries.

I think your company made big mistake in purchasing such high horse power motors from small company which did not have design experience for such motors.

You may clarify the situation in your bad English no problem we would try to understand.

Thank Mr Suresh: You are right this kind of cheating can't be tolerated by anyone but there are some point to be clarify in this issue:

• There was not mutuaul settlement between the motor supplier and my company becouse it was a contract with an EPC which were also deceived
• The motors manufacterer is still a famous firm, not small, I did not named by ethics
• We are small island and with poor experience at that time (1968)
• The EPC paid for that and other mistake a lot more for bad design (5 million of USD in international court)

Like I express before, the motor supplier deceived the EPC and sold the bad design motors just to recover back the money placing the motors in the right market to get enough time. a classic dirty business

that is the history

Bye

Corrosion of the wiring/windings of the motor related to the nitrates/ammonia/urea ?

The load was too heavy.

Just a shot in the dark, but it sounds like you had a dead phase leg. Or the motors were wired for a lower voltage for testing, and someone forgot to rewire them for the higher 6 Kv operation.
Most 3 phase motors will start with only 2 legs active, but will burn out very quickly.
Is there a VFD or soft starter on these motors? if so I would also check the programming on those.

• Water ingress?
• Dirt ingress?
• Output shaft jammed and overload protection devices incorrectly set?

Is there a prize for the correct answer?

You have a common mode failure - something that has hit all of the drives. Its unlikely anything was jammed or full of water because the same thing would have had to have affected all. A common mode would be as one subscriber has mentioned a phase leg down.

Have you run the drives since a shutdown. Are they wired suitable for the voltage.

It will be better if you let us know the name plate data or Test Certificate details so that we can give you detailed comments. For motors to work in chemical plants windings need special treatment against chemical corrosion. What sort of protections were provided?.