sorry if my questions is not a challenging one but i have doubt regarding moments...what is the best solution to overcome problem with moments especially at the pump nozzle, if i dont have the pleasure to remodel my pipe routing?this questions trigger me since my analysis is giving about 1.5times more from the allowables...ooo actually this is a model where 5pumps connected to one header...

thank you in advanced...

Dear,

1)To take full advantage of API-610 piping of 2 times allowable loads, you may qualify suction & discharge piping together in CAESAR II.

2)You may conform to max op temp instead of design temp, if both differ in your problem.

3)You can take average temperature approach for portion of spare pump piping from isolation valve to header common meeting points.

4)You can justify high installation temperature, if you install the piping in hot summer days. How much this idea will be justified will be dependent on your selling power.

5)If process group permits use of warm-up lines to keep spare pumps (if any ) of 5 pumps you referred, you may have the problem simplified.

regards,

sam

Hello, siti,

This has been a very popular topic throughout the history of this discussion board. Use the search feature near the top of this page and search on the keyword "pump" (see the line: my profile | directory login | register | search | faq | forum home). You will find a wealth of suggestions regarding pump piping from many piping engineers.

Also,look into getting a copy of a recently issued Welding Research Council document:

Title: Guidelines for the Design and Installation of Pump Piping Systems.
V. A. Carucci and J. A. Payne
Welding Research Council Bulletin 449

Regards, John.

im aware that according to API 610, the loads are still acceptable if it is less than 2X the allowable loads...but in my case, the pumps are according to the manufacturer standard that somehow are refering to ISO5199....but i doubt that because the allowable given by manufacturer is only 450Nm....

Not all pumps are per API. Lighter duty pumps are often per ANSI and vendors set their own allowables which are most often much less than API allowables for a given size nozzle.

That said, particularly if you have a moment that is 1.5x a given allowable, be aware that most often the allowable (if given explicity as Fx, y, z and Mx, y, z vs. some kind of resultant) is a +/- number.

I have often had to adjust the spring settings from Caesar predictions to tune the pump loads. In a case like yours, I would end up with the moment being -3/4 of allowable with the pump idle and +3/4 of allowable in operation so you stay within the range of the allowable. This is especially true for me with multiple pumps tied together.

Another point to look at is the pipe size. Often times, I've seen that the piping straight off the nozzle goes up to the size of whatever manifold all the pumps connect to. You can probably convince your process engineer (if he isn't a cub) that the pressure drop will be fine if you stick to the size of the pump nozzle for the piping run gong from the pump to the manifold. The smaller pipe naturally has a lower stiffness and puts less load on the pumps.

I think i can help here.
Iso 5199 is aimed at process pumps and is not realy intended for the large loads witnessed for utilities.

I have done ISO 5199 calcs, and they can be very tedious. it is absolutly important that you read fully iso 5199 (ensure the year is correct), as there are lots of twists and turns within the results (look out for pump baseplate size, moments at flange face, signage.)

I found it best to do a spreadsheet and fiddle with it until i had an acceptable figure.
if you forces etc are to high, Try only to analyise the operating case, as this code (like many) is about limiting the forces and deflections on the motors and bearings during runing, and thus ensuring long pump life.

Particulally do a operating run with the temperatures at the NORMAL operating temperature

In my case (Cooling towers) max/min temps were -2/+30, however, the NORMAL pump running temp was usually 6 deg. hence the forces reduced considerably as this was the case for 95% of the running time, this was deemed acceptable.

Otherwise, if you results are still way out of wack, have the process department stipulate API pumps or other which are usually stronger.

I would stray away from using gizmos such as springs or bellows, unless absolutly nessecary(ie pumps already bought)

one last thing, assuming you are controling suction and discharge movements with supports, be very clear on the gap if any guides are to be included, these can have a severe effect on the forces etc.

good luck

It is often the case when the piping is at very high temperature we try to add number of elbows to provide the flexibility. I have noticed that in some cases, by adding loops forces reduce substantially, but moments sometimes can increase as we add more twists and turns in the system. So, I would suggest you should evaluate if your moments are sensitive to excessive flexibility, and if it helps to sacrifice some of the bends. If you have not already done it, play with location and type of supports to see how it affects moments.