×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

What is 'It' of an impeller of centrifugal compressor

What is 'It' of an impeller of centrifugal compressor

What is 'It' of an impeller of centrifugal compressor

(OP)

I am an intern in a rotating equipment company.
Can i know what 'It' of an impeller is?

I know it is some kind of inertia. Ip is different and it is Polar moment of inertia. Ip in a solidmodelling software like UG is Iz.

Please advise on 'It'

RE: What is 'It' of an impeller of centrifugal compressor

Hi,
already saw this as referred to "Inertia - T-orsional" instead of "Ip". But who knows, maybe it's the right explanation: are you dealing with foreign-country equipment, where for example the terms "It" and "Ib" (for Inertia - B-ending) could be used? Note that in some cases the "calculation men" use even more cryptical denominations depending on the conventions they use for shaftline analyses: for example, I1, I2 and I3 where generally "direction 1" is the shaftline axis (so I1 = Ip = Izz)... As a further example, for me-myself, direction-1 is the machine-axis regardless of if it's vertical or horizontal... I use Izz when I interface with the designers, and Ip when I "speak" with externals... I use Ib when speaking about bending inertia of axi-symmetric shapes (so that Ixx and Iyy are exactly the same), but I'm very far from knowing if these are standard terminologies or not!

Regards

RE: What is 'It' of an impeller of centrifugal compressor

(OP)
Hi cbrn

Actually we are buying a high speed motor from a supplier in UK. the acceptable specifications for the impeller for that motor are
Ip = .00123 kgm2
It = .000xyz kgm2
and CG lies t mm from back end of impeller

here we use Ip=Izz, but have no idea about "It"

so we have to design the impeller within these...
I can contact supplier to know what is It, but I am afraid to hear ..."you dont know this"..you know I am just an intern ....you can just tell me what you would assume if somebdy sends this to you...i will then have some idea before i talk to the supplier..

RE: What is 'It' of an impeller of centrifugal compressor

Hi,

if I were you and if I hadn't anybody else to ask to, I wouldn't be too worried about asking the motor manufacturer: you can always "hide" behind the fact that the terminology you are used to is completely different (and nobody can argue, since it's a matter of fact that every company has its own terminology: try to compare Alstom, Siemens, GE, Andritz,...).

To return to your question: the "xyz" you have written after the ".000" in "It" is a bit misleading: in fact, if you considered the impeller as a thin disc, the bending inertia would be half the value of the polar inertia, so it would be interesting to see WHICH are the numbers written for this "It"; it could easily be "Inertia, T-ilting", no? - a specification like this would have to do with bending critical speeds, just like the polar one certainly has to do with torsional eigenfrequencies. Strange they don't specify a maximum residual unbalance (which would be in units of [force*distance])... If vibrations are a design point for you, then you will have to check this by yourself.

Another thing about terminology: what do you mean by the fact that "you're only an internal"? (Sorry, I'm not a native speaker...)

Regards

RE: What is 'It' of an impeller of centrifugal compressor

(OP)
Dear cbrn
Thanks a lot for guidance. I will get back to you after I talk to supplier.
---- by "intern" I mean, I am a Graduate Mechanical Engineering Intern at my present company. I am pursuing this internship and hope it turns into a full time job after I am done with my MS degree. hope so!!!!!!!

Again thanks a lot for your help.....

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources