as i have looked to tankage piping stress analysis; all of them use expansion joint to bear tank settlement and bottom nozzle rotation, but i soon realized that with other consideration, the exp. joint will be eliminated(use lap joing flange;spring hanger, flexible loop,...);

now i am worried about the difference between this solution;
and where is the best location of tank valves(near the nozzle or far from the nozzle)
could you please guide me about the critical points of view in tankage piping stress analysis.

There are many reasons for using a double tied bellows on a low tank nozzle. It takes care of settlement, bulge rotation and allows a direct pipe route to the bund.

Other solutions are available but should be used with care, and would depend upon good knowledge of expected settlement and rotations.

A lap joint flange is no help at all. I don't understand this reference.

You should be aware that if the line is large, say 36 -48" and may at times be be empty, its filled weight could be five times its empty weight. This is likely to cause enormous nozzle moments and forces if springs are designed based on the filled weight, as would be the norm, and would defeat the object of specifying springs in the first place.

Normal operating usually requires the tank valve to be at the nozzle, assuming it's an isolating valve for the tank.

I am not an expert, but here are some of the points to consider If your client doesn't want to have expansion joint on your bottom nozzle:

1. Know what standard was used in the design of the tank nozzles.
2. Most likely your tank will be desiged using API 650. Verify with the tank manufacturer if Appendix P of API 650 is applicable to your nozzle.
3. If applicable, follow Appendix P and compute for the nozzle stiffnesses, nozzle movements & nozzle allowables.
4. If not applicable, try to get the above information from the vendor.
5. Talk to your Structural group, get the maximum expected tank foundation settlement.
6. Model your piping as designed and considering the above data,
check the code stresses, nozzle loads, support loads, etc.
7. Try placing your first support far enough from the nozzle to minimize your nozzle loads.

Our mentors here will surely correct my mistakes.

Hope this helps.

thanks MoverZ , julius2

the reference that i have mentioned for using lap joint flange is "rip weaver" Ref. ch. tankage design.

could tied bellows expansion joint bear bending due to tank bottom deformation?

what is your idea about locating isolating valve and control valve on tank foundation to dose not have any relatine vertical displacement due to tank settlement.

about spring most refrence emphesize that the first support far from the tank must be spring support or adjustable one.

at last i have seen in "lummus" guide line that do not recommend expansion joint for hydrocarbone services.

then what is your idea about above?

Lap joint flanges will allow free axial rotation during assembly but once tightened, they offer no more flexibility than any other flange. In addition they have a poor track record in cyclic / bending service.

Supporting the isolating valve (located at the nozzle) from the tank foundation is good practice. Your reference to the first support goes back to an undestanding of settlement, wall bulge and rotation. As Julius2 has mentioned, there is flexibility in the tank wall that may help you (ref API 650 App P)... it depends on the pipe size and tank proportions.

Whoever wrote your lummus guide has not looked around many tank farms.

Cheers.

Inquire amongst the Civils as to what the likely settlement of the tank is based on soil borings. Once you have a clear number the problem will be readily apparent, also its solution(s).


Weavers book is speaking as a generallity, in this work as in life one must separate generalties from specifics.