Please tell me that while calculating nozzle loading thru software, is it considering pressure thrust on nozzle while giving out put of axial force for local loadings?

As i am trying to deal with nozzle of 36" size there is drastic difference in results obtained by the considering pressure thrust in WRC107 than not considering pressure thrust.
In CAESAR I cant able to find out the option for this. Please guide me in this problem.

No, the software does not add a P*A load to the results.

As to whether or not the P*A load should be included in a WRC107 analysis, please review this document for guidance.

Richard;

I did review the document you mention as guide, do you have any other information about when to use it??

Also, I will like to know your opinion on the answer I got from someone. "The Pressure Thrust Load should be use when checking WRC 107 for a vessel under ASME Code Sect VIII Div 2, and not use it for a vessel under ASME Div 1."

I spoke with a couple of people and the discussion was very similar to your document. The gist is that unless there is a anchor at the first direction change, the nozzle will see pressure thrust.

The nozzle will definitely see pressure thrust load unless ( in this case, much less load)we have an untied bellow in front of it ( in that case the thrust will be on the vessel wall and pushing the foundation).This is due to the fact that stiffer members take higher loads.

Regards

The statement is originally based on philosophy of some of organisations based on detailed study,review and understanding between stress and equipment design group.It is not as general as it is written. Note that equipment designer may reduce the allowable stress factor in some cases while designing the vessel for external nozzle loads for Sec VIII Div. 1 vessel if pressure thrust is not considered. Also if pressure thrust is required to be considered in some cases, again the allowable stress for pressure vessel design may have different factor.

So unless there is definate project/organisational philosophy in place to address increased discontinuity stresses due to pressure thrust at stress analysis or at mechanical design of equipment, such conclusion can not be generalised.

Nozzle will definatley see pressure thrust is there is no suitable support to take care of it as shown in COADE document.

Hello,

If I may piggy back on this conversation, to clarify for myself if you have a pump with a vertical discharge, and a few feet above, the pipe turns from vertical to horizontal, that elbow will cause the pressure thrust of the pump to act down on the nozzle? So, say vertical load due to pipe at operating case is 1000 lbs. The pressure thrust of the pump, per the vendor is 1500 lbs. So, I take both and add, to get a result of 2500 lbs. acting vertically on the pump?

What if the elbow is a 45? will that cause only half the thrust to act on the pump?

Thanks,
Gary

gBeals23,

Your statments above are not correct.

The pump NOZZLE will not see the pressure thrust. While the pump casing and support will, the nozzle won't. (Assuming you are hard piped)

Review Richard Ay's link posted above. He calls it "this document."

Whoops, misread.

Perhaps I shouldn't say this but...

In my opinion, if you have 1000 lbf in pipe weight pushing down on your (pump) nozzle (and I am not tying this to the WRC 107 discussion) and you have a pressure times internal pipe area equal to 1500 lbf and discharge is above the pump, then the net load on the nozzle would be 500 lbf UP, not 2500 lbf DOWN. Look at it this way, if you can pressurize a capped column and break the connection at the bottom, won't the column fly up? Wouldn't your pipe shoot up from your pump?

I am addressing the concept, not it's practical application.

Now back to the Div. 1 / Div. 2 issue. Take a manway on a thin-walled vessel - no load other than pressure. Div. 1 rules may show that there is sufficient metal to reinforce an intersection but, should you push these calculations through Div.2, the pressure thrust load will be excessive. That's just the way it is. I'd stick with Div. 1.

Rich,

The "this document" you mentioned in this post has run away. Can you please put that in?

Seems like it really throws some very useful insight on the mysteries of "pressure thrust" in WRC 107 calc.


Thanks.

I second SJ.

Here is the document.

Thanks !!

Hi Richard,

on the attached sheet about Pressure Thrust, in the case n.2, you have not mentioned the deformation of pump's case that could occur and exceed vendor's specifications regarding internal dimensional tollerances.
(Important Note: I remind you that the evaluation of Resultant Moment on pump's axis do not depend on point of application but only from the distance between the Force Vector and the Axis').

In any case, in CII, we also get the Pressure Thrust in the Output report. How can we explain this to the Official Report of our calculation ?

Thank you in advance for your reply
steves

Steves,

I don't understand your question. What do you need to explain?

Hi Richard,

In accordance to the COADE internal note (see file PressureThrust.zip), in case 2, the Pressure Thrust in pumps should not be included into the pump's 'Nozzle Evaluation'.

Regarding my question:

The max allowable values of 'Nozzle Evaluation', which are given by Pump's Vendor, consider that the internal pressure thrust in pump is balanced by the pressure applied on the first Elbow.

Now, in case I decide to apply an axial expansion joint, the internal pressure thrust in pump will not be anymore balanced and as a result, additional "Forces & Moments" will be transferred to the pump's anchorage, through pump's casing.

The above additional "Forces & Momemts", which -in accordance to COADE note- should not be included into Nozzle's Evaluation, could deform pump's casing and be critical for the duration of the mechanical components of the pump, as per Vendor's design standards (e.g. Internal dimensional and geometric tolerances, loads on bearing, vibration etc).

Q: In accordance to your opinion, should the analyst inform Pump's Vendor about the Unbalanced Pressure Thrust and confirm the max allowable values to be used for Nozzle's Evaluation.

Thank you in advance for your reply
steves

Answer: Yes.

In general, the analyst should always inform the vendor (pump, expansion joint, spring hanger) of the analysis performed and any assumptions made.

Sorry, does someone can explain me CASE 1 because it is not clear what it is representing while case 2 yes...

in few words...if I have pump Nozzle + open bellow + fixed point all together aligned the thrust force does not involve the flange connection and it interest the casing of the pump...is it right? can I say the same thing for the pump below?

http://i.imgur.com/AMUugD9.png?1

Did you know that the zip file shows two pages? Your layout description matches Case 4 on page 2, not Case1.

Here's an idea...
Apply a P*A force on each surface perpendicular to the line of sight as you look out of the nozzle to the piping. If this load or set of loads is called F1, the results from an F1-alone analysis will show the distribution of this leg's pressure thrust load throughout the system. (Note: this replaces the program's automatic inclusion of the pressure thrust load on either side of an XJ when the joint's effective diameter is specified.) What is you pressure load on the pump nozzle now?