Could you tell me how to reduce moment in Z axis at nozzle when pipe is connected to pump? Now it is more than nozzle allowable load about three times. Pipe dia is 12", temp is 140 F and pressure is 640 lb/sq in.

Identify the cause of the load - thermal problems are often reduced by adding flexibility and deadweight problems are solved by adding support.

We will not be able to do your work for you without geometry and load information. This is not a request for such data.

Actually, adding supports will help with the live load problems AND the dead weight problems.

Remember that loadings are a function of the force and the distance away from the nozzle. Once you understand what the moment is caused by you can develop a plan to eliminate it. Work with the moment about one axis at a time. For moments caused by thermal expansion you can often provide flexibility away from the nozzle and then position guides and line stops to push the expansion away from the nozzle and into the more flexible area. Sometimes moments caused by weight (live and dead) can be reduced by the clever use of spring hangers. You have to be creative.

Be prepared to do a lot of "cut and try" work until you learn the straighter path for future use.

Regards, John.

Ah, yes.

The essence of 90% of our workload, distilled to 19 words. It doesn't get much clearer than that.

The only competent answer, as Mr. Breen has politely pointed out, comes from a child's saying.

"If at first you don't succeed, try, try again."

Extreme cases can take weeks. Also make sure, if you have multiple pumps, that you analyze for all possible combinations of operating / idle pumps. This can be even harder.

And then there's the issue of making sure that someone can build and maintain the restraint system you finally put in your model. That's a whole new issue, and more important even than finding the answer to the question you posed.

But I disagree with Mr. Breen in one important respect - no matter how many nozzle connections you have designed, the next one might be outside the envelope of anything you have done before. Experience in this field is a great teacher, but I have not yet learned all its answers.

Of course, Mr. Breen has been in the business a lot longer than I have. Maybe I will have the truth finally revealed to me in another decade or so.

Reduce either term... P or L in the equation PXL=M

hi chintaaa

if Z-axes is vertical axis, then moment about Z-axis can be reduced by reducing force in either of y or x directions. or otherwise check for any resting support near by nozzle subjected to more frictional froce, this frictional force may increase the force in x & y directios. resulting in increase in moment about z-direction .

regards
suresh kumar

Chint aaa,

Take a refresher course on Applied Mechanics and a brief overview of structural analysis methods like "stiffness method" etc.I presume you did not have any FEA course in your curriculum.

Pl. don't think I am trying to pull you down or insult you; it is for your betterment only if you take it in good spirit.There is no substitute to learning the hard and methodical way.

Regards

dear sir

you must compare the load and moment in pump nozzle in different load cases such as SUS AND EXP AND OPE and OCC to find the origin of this.
for example suppose that the moment in load case SUS is high and there is no very differnce between moment in load case SUS with load case OPE so the source of this high moment is load such as weight and preload of spring or pressure thrust in expantion joint ,... you must check the span of support or preload of spring (in variable spring hanger with large displacement or high load variety) or incorrect selection of expansion joint...

if there is high differnce between OPE and SUS thermal expansion is the origin of this and you must add flexibility or reduce friction load or location of support for example use of support that guide the displacement throw the nozzle...

if the load in seismic is very high you must use snubber or .. to reduce the seismic load....


if you can not reduction the moment in this case send the case for me to check it

BEST REGARDS
A.SADEGHABADI
sadeghabadi@yahoo.com

For the pump suction you should have a rigid vertical support on the horizontal line connected to the suction. This support can sometimes reduce your loads, both deadweight and thermal.
Code this support without friction and check your results.
If you still have a thermal problem you will need to do a reroute for more flexibility.

how do you normaly identify the cause of the load..

do you process with ambient temperatures first and then change to design?

"How do you normally identify the cause of the load?"

Pipe is not very intelligent. It really has a one-track mind - push/pull on me and I will strain. Therefore, logic would dictate that, in order to alter the loads on a pump nozzle, it becomes necessary to alter the deflections for the load case in question in a way that makes them more favorable to the load limits on the nozzle.

And then, there is always the option of adding flexibility to the piping system via expansion loops, flexible elements, and all the other tricks of the trade.

"Do you process with ambient temperatures first and then change to design?"

If you are unfamiliar with the concept of solving simultaneous linear equations perhaps you are in the wrong line of work. If you revise your restraint system for, say, the sustained load case without regard for the other load cases, then begin working on another load case, and apply the same sort of thinking, then proceed to a third, etc., you are likely to make your current project a career. I doubt this will be acceptable to your superiors.