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#42177 - 04/05/11 05:15 AM Steam Turbine Data
micvanzil Offline
Member

Registered: 05/11/09
Posts: 57
Loc: South Africa
Dear All,
I'm evaluating the vendor data required for pipe connections to turbine nozzles.
Each page contains to tables.
The upper table (In the bottom right hndd corner) there are summations for applied moments. I don't know what Z*Fy or y*Fz mean in the following:

SIGMA(z*Fy) + SIGMA(y*Fz) + SIGMA(Mx)

The lower table includes values for Actual pipe actions which I don't know the reason for stating them ( I know they are probabely paseted in wrong columns).

Please let me know any other general data I shall check to preform this job.
I've attached the preliminary information I've got to have your ideas.


Thank you
Mic


Attachments
Layout.TIF (774 downloads)
Load Data.PDF (769 downloads)


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#42182 - 04/05/11 08:32 AM Re: Steam Turbine Data [Re: micvanzil]
MoverZ Offline
Member

Registered: 11/22/06
Posts: 1195
Loc: Hants, UK
Mic,

Look at just the X axis: The X axis moment acting at the resolution point consists of three elements from each nozzle ... Mx +(Fy.Dz)+ (Fz.Dy)
Where Fy and Z are forces at the nozzle
Dy and Dz are the distance from nozzle to resolution point.
Together each F and D represents a moment couple.
Of course 'sigma' is jus the 'sum of ...'

The tabulation is similar to a NEMA calculation, but not quite the same.


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#42186 - 04/05/11 08:45 AM Re: Steam Turbine Data [Re: MoverZ]
Edward Klein Offline
Member

Registered: 10/24/00
Posts: 334
Loc: Houston, Texas, USA
I'll link to the response I gave to your post on the eng-tips forum.

http://www.eng-tips.com/viewthread.cfm?qid=295997&page=1
_________________________
Edward L. Klein
Pipe Stress Engineer

All the world is a Spring

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#42194 - 04/05/11 11:07 AM Re: Steam Turbine Data [Re: Edward Klein]
danb Offline
Member

Registered: 04/22/05
Posts: 1453
Loc: ...
Welcome back Edward.
_________________________
Dan

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#42205 - 04/05/11 09:33 PM Re: Steam Turbine Data [Re: danb]
micvanzil Offline
Member

Registered: 05/11/09
Posts: 57
Loc: South Africa
Thank you MoverZ, Thank you Edward,
That would be great if anyone could help me with dynamic analysis considerations.
Any advice, practice, book...

Regards
Mic

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#42211 - 04/06/11 02:47 AM Re: Steam Turbine Data [Re: micvanzil]
MoverZ Offline
Member

Registered: 11/22/06
Posts: 1195
Loc: Hants, UK
Mic,

To deal with piping dynamics in Caesar II you really need to think about a training course. Refer to (Coade) Intergraph for this.

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#42319 - 04/09/11 11:47 PM Re: Steam Turbine Data [Re: MoverZ]
micvanzil Offline
Member

Registered: 05/11/09
Posts: 57
Loc: South Africa
Dear all,
I have some problems regarding this steam turbine data:
Please look at the attachments in my first post for more information

1- In the part of the exlanations, I have the following staement:

The displacement dX, dY of the connections with the pipe connected for overhaulting the turbine in cold condition (room temperature 20 C)

I don't know what are dx and dy in cold condition. The displacement values suplied by vendor arefor hot condition I think. Should I ask for more informaion ir there is sth I don't know?
What does "overhaulting " mean? is that overhauling?

2- In other part of the exlanations I have the following staement:
Warm, i.e. at operating temperature during initial startup; the cold spring considered in the calculation may be inserted with only 0.67
Does anybody know how should I treat this? Is it normal to have the piping system prestressed (using cold spring for instance) for this kind of system?

Best


Edited by micvanzil (04/09/11 11:50 PM)

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#42323 - 04/10/11 09:32 PM Re: Steam Turbine Data [Re: micvanzil]
micvanzil Offline
Member

Registered: 05/11/09
Posts: 57
Loc: South Africa
Guys,
Would you let me know your ideas?

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#42336 - 04/11/11 07:43 AM Re: Steam Turbine Data [Re: micvanzil]
Edward Klein Offline
Member

Registered: 10/24/00
Posts: 334
Loc: Houston, Texas, USA
From those notes, I'm afraid I can't make sense of what they are trying to say. I think you are going to have to go back to the vendor on those and request some clarification. I think the vendor has got some translation issues with their phrasing.
_________________________
Edward L. Klein
Pipe Stress Engineer

All the world is a Spring

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#42344 - 04/11/11 11:30 PM Re: Steam Turbine Data [Re: Edward Klein]
micvanzil Offline
Member

Registered: 05/11/09
Posts: 57
Loc: South Africa
Dear all,
Would you please share your experience if you've done such thing before?
In the attached file, you can see some allowable nozzle loads for a steam turbine. I'm having problem with the highlighted one; it's for the low pressure steam outlet duct coming out from the turbine.
As you can see the load amounts are much higher than the other connections making me doubtful if they are quoted by vendor correctly!! Do you know how this connection should be connected to the steam outlet duct (The steam pressure inside the duct is negative)? Are there options like flexible joints available? I don't know the reason for such high loads.
I cannot understand the +/- signs for this row of the table as the load directions are not important if they are considered individually.
The load/moment combination constraints are not easy to satisfy as the maximum limit for them is much lower than the loads for the highlighted connection itself.

Thank you


Attachments
Nozzle data.pdf (505 downloads)


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#42347 - 04/12/11 02:33 AM Re: Steam Turbine Data [Re: micvanzil]
mariog Offline
Member

Registered: 09/29/07
Posts: 798
Loc: Romania
I try to give you a more explicit answer.

Short answer: you must refresh your "Mechanics" knowledge. It will help a lot understanding "z*Fy" terms and so on. But I have to recognize also it seems your Vendor doc is not so clear.

Now a long answer. You have a system of space forces and moments that acts on turbine and you are interested to calculate the resultant moment about x axis, because your Vendor has established limits on the resultant moment about x axis.

From "Mechanics" point of view, you have "n" space points and in each of them you have moments and forces. So in a point defined in your coordinate system as (xi,yi ,zi) you have moments and forces (Mxi,Myi,Mzi,Fxi,Fyi,Fzi) which are the "ACTUAL PIPE ACTIONS" transferred to turbine.

You may start observing Myi, Mzi have -of course- no contribution to the moment about x axis. Also the force Fxi has no moment about x axis (because it is parallel with x axis).

You may conclude that to calculate the resultant moment about x axis, you have to count the contribution of (Mxi, Fyi ,Fzi) that act in point (xi,yi ,zi), and after that to sum the results for i=1n points.

The above considerations are valid in any Cartesian coordinate system, but when input data you have to know which is your coordinate system! I may assume it is NEMA SM-23 system- where x is along shaft, y is vertical, etc. see figure 8-15/SM 23. It may be true or not (Mr. Klein already advised you Vendor Z may be the vertical axis system). I mean you have to consider the actual Vendor info about the coordinate system. Maybe it is already shown by Vendor documents...and, BTW, please don't post documents with "Classe di Riservatezza/ confidential class" stamp!

So in Vendor coordinate system you may understand what is the convention by which Mxi, Fyi and Fzi are positive.
(similarly as they are defined in figure 8-15/SM 23)

The resultant moment should be Mrx=Sum(Mxi-zi*Fyi+yi*Fzi) that may be negative or positive, depending the sign and magnitude of each term. Also, if one or more coordinates of points are negative, you have to input the value with sign.

The result must comply with vendor limit, i.e.
|Mrx|< M_limit
or M_limit< Mrx < M_limit

The above written is just my interpretation.
Normally you must ask Vendor to be more specific. At least you have to know your coordinate system before to calculate!


Attachments
Fig 8-15_SM 23.PDF (470 downloads)



Edited by mariog (04/12/11 03:27 AM)

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#42363 - 04/12/11 11:53 PM Re: Steam Turbine Data [Re: mariog]
micvanzil Offline
Member

Registered: 05/11/09
Posts: 57
Loc: South Africa
Dear mariog,
Thank you for your post, however, there was never been a problem on how to calculte resultant moments.
The coordinte system is supplied by vendor and is clear aswell from the nozzle coordinates; as Edward advised, Z axis is vertical and X axis is along turbine shaft.
That would be great if I could know your idea regarding my previous post as there are problems with the highlighted data.
I'm pretty sure there is a "flxible joint" connection for this nozzle; If so, there shouldn't be such a huge allowable loads for it.

Best
P.S. Anybody who has dealth with such equipment, please help me with this


Edited by micvanzil (04/13/11 01:09 AM)

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#42365 - 04/13/11 12:46 AM Re: Steam Turbine Data [Re: micvanzil]
mariog Offline
Member

Registered: 09/29/07
Posts: 798
Loc: Romania
Mic,

I'm happy to hear the calculation is not longer a trouble and your problem understanding "Sigma" is engineering history.
Now, I understand your main concern is about the Vendor "PERMISSIBLE PIPE ACTIONS". About your previous post, I think you have clarified also why they are quoted as + and -.

About the magnitude of "allowables" is your concern that they are too high whereas your "actual" loads are too low? Or you just look to allowable loads and think about?

Eventually, it is LP exhaust under your analysis? At least, can you identify this "nozzle" on vendor drawing?

regards


Edited by mariog (04/13/11 02:10 AM)

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#42366 - 04/13/11 02:35 AM Re: Steam Turbine Data [Re: mariog]
micvanzil Offline
Member

Registered: 05/11/09
Posts: 57
Loc: South Africa
mariog,
I'm evaluating the data and I'm not envovled in running the stress model yet.

Regards

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#42367 - 04/13/11 02:53 AM Re: Steam Turbine Data [Re: micvanzil]
mariog Offline
Member

Registered: 09/29/07
Posts: 798
Loc: Romania
Maybe you can find out a clue comparing the attached sketch
with your Vendor drawing.



Attachments
Steam turbines.PDF (554 downloads)


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#42421 - 04/14/11 12:29 PM Re: Steam Turbine Data [Re: mariog]
micvanzil Offline
Member

Registered: 05/11/09
Posts: 57
Loc: South Africa
Thank you mariog,
That was really helpful
the turbine I'm working on sends used steam down from the nozzle underneath (Same as the first drawing of your sketch)

Regards
Mic

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