Oversized Electric Motor

that this set up is not efficient in its design, But bottom line it will work.

He is right. The motor works most efficiently at near rated value but at anything less than that it will work.

However you must be sure that the system has enough protection. since again in case of any problem on load side, where earlier the motor had tripped due to overload and saved the pump, now it will try to rise to its full rated power and the resulting almost 1.5 times torque may break the pump drive shaft.

Yu can save it through either current protection at motor or mechanical protection through coupling.

I'd give it a green light. Do as your boss says.

Good luck.

Oh yea I want to go with a green light and do as the Electrical Engineer says, however the job is bogged down in doubts and un-founded finger pointing at the moment. Basicaly it is at the stage below, names of course XXXX for the purpose of attaching this letter that I have sent, still no favorable reply.

These guys in the possition to hold the job up obviously cant grasp whats going on and I cant figure out how to open there eyes....

I am grasping at straws at the moment, hoping that one of you guys may have an idea or better way for me to explain my case...

"

XXXXXXX,

Let me first say that when coming on board this hitch I would have been perfectly happy never even speaking about or working with the SW Service pumps this hitch in lieu of the conversation you and I had in your office. Then the Stbd SW Service failed forcing me into this unpleasant situation once more looking for a solution to our problem.

I had hoped that there would be a solution that we could agree upon in way of fitting our pump with an off the shelf standard motor of a lower power rating but upon consultation with XXXXXX regarding suppliers standard stock and also researching the ABB site we find that this is not a standard off the shelf application to have a lower rated motor with the same frame size as our ABB M2CA-280MD motor. It is possible to do this, but certainly the quicker solution would be to UAF the old pump parts at this point if using our current new set is not a viable option. While working with XXXX on the replacement motor option, he also pointed out that there is no reason that our current new pump/motor can not be used. He did also verify that our existing soft starter that is in place for the SW Service will work with no problems.

The following and also the attached is an explanation of why I do feel somewhat put off to think that there may be some quick assumption that I in any way done something wrong or did not follow proper procedures in regards to the pumps we have on board currently in question;

1. When I found these pumps were here on the rig with no RES I did in fact get one started ASAP and addressed the situation of the 185 Kw rating, the rating was determined not to be a problem by applying common electrical and physic laws as applied to hydraulic circuits and centrifugal pumps by our AME Team.
2. I also immediately contacted Hamworthy to better specify all remaining pump packages to better match actual requirements and not oversize the motors as someone previous to I had done on the pumps in question here today.
3. I had also made it a point that all pumps exactly matched the rigs advertised performance to avoid later discrepancies with client or regulatory authorities.
4. Every effort was made to standardize our package; S.W. Service and Bilge/Ballast are same other than the impellers and the motors.

There are many things that took place regarding the pumps that I do not understand, and do not find sufficient explanation on here in the files;

1. I find that there is a completely new quote on all the pumps that appears to have been generated by CE XXXXXXX?
2. I am told from my CM that there was an idea that there was no approved RES regarding our pumps on board?
3. The approval to install these pumps was sent to your attention on Thursday 3/11/2010 from XXXX XXXXXXX that states among other things the following; "Calculation of the pump horsepower requirement indicates that based upon the TDH (total head) and flow requirements the 112kW motor (accounting for 4% mechanical loss through coupling and 65% pump efficiency - referred to attached for calculation); whereas motor furnished with pump is rated 185kW (motor is sized to allow system operating at approximately 30% - over rated but essentially met the flow requirements)" At that time nothing further was mentioned regarding these pumps?

If you maintain the pump will not be installed, I understand as that is certainly your call and I will respect that.But I feel it would be irresponsible on my part to not make this situation 100% clear so I am certain an informed decision has been made in regards to not installing this pump as it is needed badly by the Marine Department.

I hope you do not take this as in any way being dis-respectful, because that is certainly not my intention."

Ok, what you have here is a couple of plays at work here.

You've correctly identified that this new motor is not an identical motor to the old motor to be replaced. You've brought this to the attention of the authorized engineers (electrical and hydraulic) for them to evaluate the suitability of this much more robust motor. They've done their jobs (presumably) and approved the installation of this new motor. You should now have the motor installed.

You are not convinced that this is a good idea. You come to us instead of these engineers with your reservations but cannot explain to us your concerns other than to say that this motor is capable of more power than the previous model. That's a little short sighted of me. You may have repeated your concerns to these engineers but they either did not have enough time and patience to explain their reasoning to you or they did explain it but you still did not grasp their explanation. Regardless of all of these scenarios, install the new motor.

Right or wrong these engineers have the authority and presumably the documentation to ascertain if this motor is suitable for the installation. Now none of us here at CR4 have access to this documentation. So we cannot say specifically why these engineers have approved this replacement. Likely there is either an energy release device like a pressure relief valve or a feedback system that keeps the whole thing in check. It may even be that this is just a designed in upgrade to your system.

So, install the new motor and don't make a big corporate fuss over it. If you do make a fuss and the engineers are right, you will do serious damage to your own credibility. I would consider discussing you concerns with your safety officer. Make sure that you point out that the engineers already approved the upgrade. Suggest that maybe a suitable added precaution be taken on initial startup. I'd bring up the point that the system worked well with the smaller power but has yet to see all of this new available power. Follow the recommendations of the safety officer and do your job.

If something breaks, don't gloat.

I appreciate your position, but it is now quite obvious that I a having great difficulty getting my point across!

I am the one, along with the engineers who wants to install the new unit imediatly....

I am being faced with BS from people who obviously do not see things the way we do!

I hope you now understand my position.

You see my company recently put in place an AME group and an Asset Manager over my geographic area of operation. Quite obviously not very well "tuned in" or even basically versed in this area we are referring to...

Listen... I would like nothing better to install this pump, but I am soliciting your help in finding a way to get my point across to a superior who does not understand why I am saying this pump/motor set up will operate just fine. Actually, I would think that the motor, operating in this condition, would probably outlast the drilling rig.

Thank you for pointing out clearly that there might very well be a mis-understanding at play here as you quite obviously did mis-understand my position in this thread.

Yes, there are multiple misunderstandings at play here. Removing the misunderstanding is your objective here. The key I think still lies in what I wrote earlier but obviously with you on the side for installation instead of against it. Demonstrate to your superior(s) the multiple points in your system where various safety systems will prevent any catastrophic conditions from happening. Show them that your power supply to this motor can provide the additional electric power it will draw. (Likely this is an AC induction motor at these power levels. It will then draw more current but at a lower power factor, unless you compensate with a different matching capacitor bank.) Write up a commissioning procedure that will include personnel and machine safety concerns will be mitigated.

If you demonstrate to your superior(s) that you are listening to their concerns and your goal is to improve the system, not just grabbing something that might work then you will be doing exactly what they hired you for. It maybe that this individual is just playing a devil's advocate role and is testing your thoroughness in making a design change.

If I am to understand correctly, this "superior" is an asset manager? Are you alone in you argument (apparently with this asset manager and/or the managers department) for utilization of this oversized motor? Is his argument against driven by standardization policies?

It appears the outcome will depend on who has the strongest argument/politic. You have illustrated that the motor can be applied, but the reason for opposition is not clear, considering the urgency you convey.

Thats it in a nut shell my friend.

I however will never know who or for what reason have gotten my Superior against this installation?

I was actually looking for some form of justification in his (there) reasoning to better understand there firm position, but it is becoming obvious that it can not be justified. As I have thought all along....

Ahhh the joys of political correctness huh?

Is the motor starter being changed also? The old starter and wiring might not be enough for the new motor.

Has anyone asked why the new pump has been supplied with a 185kw motor in the first place? Who specified it, who quoted it and who ordered it? It's unlikely the supplier would fit an oversized motor on a whim, so there must be a reason.

Could someone somewhere have deemed that all pumps, or pumps on certain services, should be fitted with motors sized for end-of-curve power? If so, you would have no choice but to install the unit. What is the pump's EOC power?

The new pump was specified with a 185 Kw due to the wiring configuration someone well before me had specified. As I do not have those details in front of me, I can not go into great detail on that end.

The existing cables and Soft Starter has in fact been confirmed to be suitable by one of our Electrical Supervisors (a very sharp Danish fellow). Who then goes on to say that it is completely irresponsible of any one to feel it is necessary to replace the 185 Kw motor and it should be installed immediately.

BUT then I always fall right back to square one... Someone has poisoned the thoughts of our Asset Manager and he feels there will be problems if this new pump/motor is installed.

Well if nothing else, I now know that I am correct by wanting to install the new equipment based on your replies

If anyone knows of a paper or a study done that I could make available to Asset Management, this may help to open his eyes?

(a very sharp Danish fellow)

Indeed, they often are, as is evidenced by their Viking forbears (I thought it was three bears, and who said they were vikings?!), although I find it hard to connect the affable Danes I know with stories of the Danes of yore. Must be down to Hygge (ask him!).

It's a shame your asset manager won't heed the advice of the competent experts you clearly have. If I find anything that will help you I'll let you know.

Thanks in advance

I concur with the electrical engineer who gave his advice.

Bill Willis, PE (electrical engineer)

Indeed. The EE Manager has not only given the green-light, but apparently has also explained in detail how and why it is OK to install the new motor. He clearly knows his stuff, and is employed there for a reason. Why should anyone argue with this, and who there is qualified to contradict him?

I must have missed something. Don't you have a pump curve?

Tim stated that the pump curves match well.

So, the issue must be one of the ability of the existing electrical service to provide sufficient energy? Which I believe is resolved.

The curve exists and can be understood by ASS MAN?

What else does can he want?

Haaaa that my friend is the 1,000,000.00 question..... What else do they require? Its been driving me nuts as I need to somehow get my point across to Asset Management while still being the humble, respectful Technical Coordinator who is SUSPOSED to respect my superiors decisions and not question them as I often do.

In my mind this is just one step away from an argument that the world is flat or somthing. Unless I could produce enough information to make the parties come to the conclusion on there own that it is round, it will stay flat end of story...

Would it help to show the AM a curve of the pump that the motor could support?

And the difference in energy consumption between the two impeller diameters?

Have to go swim with the kids now. Happy Holiday.

Yes there certainly are curves, and engineering studies that include friction losses through out the rig etc. They are spot on and match well, unfortunately I do not have this data with me at the hotel as I am on time off at the moment.

Big task here is simply finding a way to properly state the basic Motor Theory to those who cant seem to grasp the fact that the 185Kw motor will function fine once I follow the engineers recommendations to make minor adjustments to the circuit protection to handle the start up spike.

At the end of the day, we know the 185 Kw motor will draw no more current than the motor we currently have in place due to the fact that the 185Kw motor is driving a pump that is designed and has its impeller cut for 111.7 Kw absorbed power.

You can take the horse to the pond but can't make him drink water. It is a sort of mystery that even Agatha Christie's curious mind can't unravel. After going through the entire thread, it appears to me that the person who has originally ordered the motor has fallen from grace with the powers that be. They know in the heart of their hearts that the new motor can be installed and successfully commissioned, but by not allowing it to be installed they want to escalate the situation to higher mangement thereby bringing the person down to his heels. It may also be that AM group have developed cold feet lest they be held accountable and could be questioned for allowing to run an asset (new oversized motor) in an inefficient manner thereby bringing financial loss to the company. You may just be undergoing collateral damage due to their personal insecurities or some politics behind it. Do what your boss tells you to do and do not break your head on it.

BB Raina

I have not read all the replies so excuse me if I repeat what has been said before.

• The pump has no idea how big the motor is, so it don't care.
• The motor will only produce enough power to satisfy the pump, so it don't care.
• The Electrical Engineer is happy so asset manager should not care.
• The motor will have been sized by an enthusiastic pump OEM probably for water at 120% of BEP plus a 10 or so percent safety margin - so the OEM don't care.
• The motor will not be working at its best efficiency, but the difference will be small so who cares.

Fit the damn thing, it is fit for purpose.

AMEN