Guys, i need your help again...

I have questions about piping on oil storage tanks:

1. do we consider nozzle displacement (-Y) due to tank settlement?
2. do we also consider nozzle displacement (+Y) due to thermal expansion?
3. should the first support of the piping located sufficiently far away from the tank (about 8 meters for 10" pipe) to allow for tank settlement?
4. OR should the first support be spring support?

Chris,

I hope the following will help:

1. If the settlement acts in vertical only, YES.
2. If the settlement acts in vertical only, YES. The tanks are mostly at low temperature against the piping and the vertical thermal expansion may be ignored at tank nozzles, and this may provide slight conservative analysis for piping under expansion and settlement and for the flange loading.
3. Does not have to be. This is the pipe stress engineers' job to determine by considering the loading on the flange and the settlement. Sometimes, adding an horizontal loop and spring hanger support close to the nozzle help.
4. If the settlement is excessive (?) spring hanger absolutely helps. I would leave all the jobs to the pipe stress engineer by providing the available pipe route options ( or access for pipe routing and support structures around ).

Ibrahim Demir

The question is not as good as the answer the answer is top notch.

Of course you should consider settlement! It may be enough with a fixed support to cause leakage leading to de-inventorying the tank!

And do not neglect nozzle rotation due to tank wall bulging. That could be another quick way to testing your bund walls.

question is not as good as the answer? ooops! sorry.Ü

by the way, is it possible to have a perfect soil. like no settlement at all? or are there any ways of preventing the soil to settle?

If you have the pipe support foundation included in the tank or any other foundation when the foundation settles everything moves together.

However under large tanks the ground will always settle.....

If you support the tank on piles driven to bedrock you will likely have no settlement to consider. Virtually any other tank support option will result in consideration of settlement.

A vertical product storage tank is parctically a perfect machine for soil compaction. It will apply, over time, loads that vary by 2000 psf or more, over a broad area. That's how a vibratory soil compactor works, except that the compactor applies many pulses per minute to a small pad. The tank applies one pulse every few weeks as it fills and is emptied.

Experienced professionals say, Installation of piping after the tank is hydro tested will mitigate the settlement effects to a large extent! I’m not sure if this is the universal practice (piping installation after hydro test).

Since we are discussing settlement…

What allowable stress do experts suggest (use) for this non-repeated anchor movement? Some people take guidance from ASME sec III and use the 3.Sc limit.

May be this topic is discussed several times but till date I did not get a concrete reply!!

1. do we consider nozzle displacement (-Y) due to tank settlement?
2. do we also consider nozzle displacement (+Y) due to thermal expansion?

----> You can model Tank shell & Nozzle as pipe which contains Temp. & pressure and then allocate displacement(settlement) on Node(Bottom of Tank)
This method covers Nozzle movement and Tank settlement.

3. should the first support of the piping located sufficiently far away from the tank (about 8 meters for 10" pipe) to allow for tank settlement?

---->This depends on settlement (i.e 50mm or 1000mm) and valve maintenance & accessibility

4. OR should the first support be spring support?
---->You have to consider as below
1.Is there sufficient space? If yes, you can route pipelne using many loop without spring.
2.Can you avode interference of Underground line
3.Can you make pipe line as a group

Normally, I use spring on local sturucture.
O small size---> One spring
O Large size---> continuous Two spring

Consider lucrative design!
Using spring or not is your own business.

you have to consider both displacements

1) tank settlement (-y)
2) nozzle thermal expansion(+y)

in the analysis.

and supporting near the nozzle , has to be decided by u based Availability of structure, so that it will not effect piping forces and moments on nozzle.

How will we consider settlement in CAESAR?

You can give each node a forced displacement. If you want to know reaction forces at that point too, use a cnode here.
You have to give a displacement for all 6 degrees of freedom. If one is not entered CII will give it free movement in that one direction.

We normally assume (or specify as need be) that piping to a tank is installed after the hydrotest. The tank will settle some amount due to hydrotest and a (typically) smaller amount further over time due to operational loads. Civil Dept. supplies both the initial hydrotest settlement and the long-term additional settlement.

I ever involved in case settlement. Here are some pictures. But not relate to tank but pipe rack, dummy supports, and near to some pumps. The soil settlement was not uniform and faster than calculated in engineering stage.

Try to read Piping handbook 7th edition by Mohinder Nayar "Process piping Systems-Storage Tanks" This will guide you for the supports you will use. Of course it depends on the configuration of your piping and analysis result.

You should consider all possible displacements. Also ask the tank builder for the displacement of the nozzle (movement in outward direction and rotation) when the tank is filled. I've seen some strange things happening with rather flexible tanks.

can anybody tell how bulging effect is taken care in analysing the tank nozzle ?

Code your nozzle as API 650 & check the report. The radial deflection due to fluid & temp is the bulge (do remember to subtract the thermal expansion part from this to get pure bulge due to fluid). Impose this as displacement at tank nozzle in your analysis.

I would also suggest you also consider nozzle diplacements due to bulge rotations in vertical & other horizontal planes (apart from bulge)in your analysis.

Supremo,

You will get lot of guideline and reference books on tank piping.But i like to share one of my experience on piping on oil storage tank in North Canada which we never thought during design...

settlement(-Y) around 100mm and Frost heaving (+Y) 50 mm ..we consider first/few support near the nozzle as Spring Can. But latter as per client comment we need to make a special support arrangement ( Goal Post) to convert it to Spring hanger to avoid damage of Spring can due to oil spillage.

If the line size is very large,load on support may also cause settlement of support itself which may give some advantage on pipe stress. Co-ordinate with civil team regarding support settlement.

OK you have a line connected to your tank with spring supports. The springs are presumably there to allow for movement and to limit nozzle loads.

What happens if it's a large diameter line and the pipe may be empty ? In larger lines the liquid weight may be 5x the pipe metal weight, so when empty you end up with a huge upthrust force and consequent bending moments due to out-of-balance of the spring loads.

And then the nozzle load is ??

If the pipe will be supported by spring(s), the effect on nozzle due to WNC load should be considered as MoverZ had emphasized. If the tank is designed to API 650 and at seismic zone location, check the mandatory requirements of API 650 Table E-8 for possible seismic movements (+/-Y) of tank foundation if the seismic zone is applicable.