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External nozzle loads 2

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farhad2474

farhad2474

Mechanical
Joined
Sep 15, 2007
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Is any body Know how I can find external nozzle loads and moments for nozzle’s pump . I need those for stress analysing program. I found those in in API610 but there are in force unit(pound) I need stress(F/A)psi .
thanks
 
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What you found is what you're going to get. External loads are always in units of force (lb) and moment (in*lb).

Why do you need them in units of stress? And why would you think that it is an F/A stress and not a Mc/I stress? or maybe a combination of both? What "stress analysing" (sic.) program requires a stress for nozzle loads?
 
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I DONT WHY YOU NEED STRESS TO QUALIFY THE NOZZLES.
If you are using Caeser as Piping stress program, then in the output ,your pump nozzle node should be within the allowables.(As per table 2-1A in code API 610).
 
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Are you confused and loads and stress ? API 610 appendix F2 deals with vertical in-line pumps and does express the allowable in terms of stress.
 
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Actually, I am going to calculate pipe stress analyze for a pipe that connect to
a pump so I start first node with flange so the program asked me following question for flange
1-flange type
2-flange weight
3-gasket diameter
4-allowable pressure.
I don’t know what does the programs means for allowable pressure at flange

thank you
farhad
 
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Allowable pressure for a flange is based on material, temperature, and class. If it is an ASME B16.5 flange, look up the allowable pressure (allowable internal pressure) in the B16.5 code. The reason your program is asking for the allowable pressure is that it is calculating the flange loading, hence the request for gasket diameter. Your program probably coverts flange external loads to an equivalent pressure and added that to the operating pressure to calculate the total flange pressure. It then would compare the equivalent pressure + operating pressure to your input of allowable pressure.
 
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Banu.....

1) Is this the first piping stress analysis that you have ver done ? If so, it may be beneficial to read the manual

2) Qualification of pump nozzles typically means evaluating the nozzle loads generated by the piping via a stress analysis program (such as CAESAR-II)and comparing the loads generated with those allowed by the pump manufacturer. If the loads are excessive, eith a re-rout of the piping or reconfiguration of the supprt scheme is usually done

3) Not all pumps are built to API-610 requirements. It has been my expereince that the pumps built to ANSI B73.1 ( or the ISO equivalent) have lower allowables.

My opinion only....

-MJC

 
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Start with Zero, Zero, Zero, Zero, Zero, Zero. Keep playing with the pipe configuration, slides, guides and anchors until you get those values (or something less than the actual flange allowables) as a final result too. Most pump flange allowables are pretty close to Zero anyway, so that's about what you'll have to hit in the end.



 
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BigInch, that's some pretty poor advice. No connection will ever see zero loads, especially on a pump. We have allowable load tables (such as API-610) for a reason.

Guides and anchors in the area close to a pump are mathematical solutions only that won't do you a bit of good in the real world. You typically have an 1/8" gap on a guide or anchor. By the time the pipe deflects that much, your nozzle is grossly overloaded. You need a flexible piping layout to get pump systems to work.

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

"All the world is a Spring"

All opinions expressed here are my own and not my company's.
 
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Dear Edward

Please tell me how can I use allowable load tables (in API-610 ) in stress analyses .when a pipe connect to the pump.

best regard
farhad
 
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farhad2474 (Mechanical)

If you have BOSS FLUID by Paulin Research Group use as a check in piping stress analysis for Pump Nozzle Loads.
 
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StressGuy. I don't think its bad advice. The table allowables for pumps are so low in relation to what most any pipe can give with just 1º temp change, the practicality is that the "allowables" are effectively zero anyway. And since Zero flange load is the ideal target. Why not start there?

 
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This is getting a bit complex. Surely BOSS FLUIDS is a fluid dynamics program and has nothing whatever to do with mechanical / structural loads on a pump nozzle.

Most refinery pumps are API type, agreed there are others, but API 610 is pretty clear in what is required. Most manufacturers allow 2x API loads, and if you cannot extract calcualted loads for comparison from a computer output, you should not be attempting the analysis.

I agree with Mr Klein, flexibility, decent support and realistic restraint are key to a successful pump hook-up.
 
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API 610 allowable loads are often difficult to obtain. It is my understanding that one underlying problem with excessive loads is the associated problems with shaft misalignment. I have seen some folks try to avoid the whole issue by installing expansion joints on pump suctions and discharges flanges.

Example:
API 610 Table 2-1B allows an 1800 lb axial load on a 12” side nozzle. With an expansion joint in place, there is an equivalent hydraulic load on the pump with 16 psig of pressure. So how can a pump engineered for API 610 maximum flange loads work with an expansion joint??? Perhaps shaft alignment is less important when expansion joints are used. NOT

BigInch is correct, It is difficult if not impossible to design a piping system that has the flexibility to allow significant temperate changes and still meet the requirements of API 610.
 
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Biginch,

I second the comments by Mr. Edward L. Klein, whom has performed piping stress analysis, knows how the programs work and the limitations of the real world.

Stating that the allowable reactions are "Zero, zero, zero," is the typical MBA solution ....... not practical in the real world.

All pumps see some reaction loads from the piping system, ...even those with rubber or SS "flex joints" at the nozzles. Most manufacturers give such small allowable loads, that they are impossible to meet in the real world, and require an expensive "review" by the pump vendor before they are acceptable. The clients usually are enraged at these kinds of costs

BI, the only way for a pump to see "zero" loads is to leave it on the truck and not attach any piping........!!!!!

My opinion only

-MJC

 
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A 6" pipe can easily give loads of 75,000 lbs and when I compare an allowable of 75 lbs to that, I still get zero after 2 decimal places.

Its not only your opinion, its mine too. I don't disagree with Klein, other than he is implying that allowable nozzle loads are high. I am well aware of API limits and in relation to those that any pipe bigger than 4" can reach with less than 1º F temperature change, if anchored in a poor location, they're nothing. 0,0,0 is my way of saying "real world style" that the allowables are so low, why begin the analysis with anything higher than 0. It only makes the support placement iterations and reruns that much harder. If you begin an analysis thinking you will be allowed to have higher loads, you'll really have a lot of work to do. Think in your mind, "How do I get zero loads" and you just might come in under the allowables, eventually.

PS, I began doing pipe stress on an IBM360. Its not like I discovered it yesterday. In fact I feel like it was almost as far back as CEASAR-Agustus. The only difference is that back then I didn't believe the allowables could be so low. After seeing the results of misalignments and other problems caused by piping, I believe.

 
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"If anchored in a poor location" being the key phrase.

I don't say meeting the API-610 allowables is easy, especially as I'm facing more and more systems where the suction piping can be twice the diameter of the pump nozzle.

Now, trying to hit 0 force and 0 moment, that's tough.

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

"All the world is a Spring"

All opinions expressed here are my own and not my company's.
 
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