Dear Friends

I work on a compressor that its allowable nozzle loads is too less and I can’t meet calculated load with them. Its worst component is moment around the Y axes and it is due to the secondary (displacement driven) load that generates due to pipe rout expansion along Z (in –Z direction). Please note that its operating pressure is 42 bars and its operating temperature is -120 C. Also note that I have tried a lot of work on this case but I couldn’t meet that. Finally I used a spring support horizontally in mentioned elbow in picture that can produce load in direction +Z and decrease moment around Y axes. But one of my colleges said me such as spring hanger isn’t real and we cannot use any spring support horizontally. I showed him type 20 from LISEGA catalogue as Angulated Spring Support but he didn’t convince.
Another thing that I want to know is that how can I model a horizontally spring support. I modeled it by using +ZROD with Fi= 61 KN as clod load and stiff= 533.3 N/mm as spring rate. Is it correct?
And last thing can I use Sway Brace or Rigid Strut instead of that?
I’m waiting for your answer and I was wondering if someone helps me.

You need some serious advice!!!You are all messing it up!!!Using sway brace or strut to serve the purpose of spring is a "never-heard-of " concept!!!

Add to it, the horizontal spring!!!that too modelled as Zrod !! I'm yet to encounter a horizontal spring!!!

Or explain your problem in more details if I misunderstood it!!!

Hello Dears,

I need your advice as soon as possible. Specially about type 20 lisega and its applications and how can we model it.
I hope if I can your guide.

Dear Mr. Mohamed,

I do not believe you can use the type 20 lisega spring for horizontal loading. I think you misunderstood the concept of the type 20 spring. The Type 20 spring is a replacement for the Type 29 spring when you want to support the pipe from below but you are worried about aggressive horizontal displacements (take a look at the catalog sketch for the Type 20 to see how it is used in practice).

I agree with AbdulRahman Sorour. You may have come up with a mathematical answer to your nozzle load problem, but it's neither real nor practical.


The Lisega type 20 spring is just spring hanger, end of story. A sway brace will not help either.

In my view, you have too many horizontal restraints. Just one Z dir restraint at the "most -ve Z" end of your geometry (where you have a rest support) would probably reduce Y moments on the compressor.

Oops, I should have written one X dir. restraint.

Can you attach your CII live file in this forum? Please show all possible support locations if possible and the compressor allowable. Please indicate on your support locations if steel is below or above your pipe. Also indicate if the pipe is subjected to pulsation analysis. I will try to qualify and will return to you the file whatever outcome is and let you know if your layout needs re-routing. I am using myself version 5.2.3 and in case your file was on version 5.3, I would think I may not be able to open. Somebody can correct me on this.

EddieB

Dear EddieB,

I've attached the CEASAR II and allowable nozzle load in this reply. Please note that we don't have any limitations for building structure. Any pulsation analysis is not required for this case but I want to know if it will be required, what should we do.
Also my CAESAR version is 5.00.7 and can't open latest version. So if it is possible indicate your results.

Thanks your attention.

Dear Mohammad

I would suggest to modify supporting arrangement. Change element length 60-70 to 3000mm, i.e. same as the length of element 30-50. Now provide restrain in Z direction at node no 70. Also remove the horizontal spring hanger provided at elbow.
Please verify with above change in the model. I hope the nozzle load specially My will be in limit with this change.

Kandarp

Thanks a lot Kandarp.
I have implemented your suggestion in my file and I think that it will be pass when do it for all suction, discharge, and side stream.
But you didn't my general query about LISEGA type 20.

Dear Mohammad,

Type 20 is an option when you have excessive horizontal/lateral displacements.
This alternative should be used over type 29 when adverse effect due to can/bottom spring needs to be avoided.(One may have to put PTFE on the sliding steel faces to reduce unwanted effect due to lateral displacement.)
Type 20 is suspended spring hanger. So the support system (spring) will not have much adverse effect as it is there with bottom spring.

But all this explanation does not mean that, it (type 20) acts as horizontal load bearing support. From the C II plot it is clear that it has been used to take axial (horizontal in this case) load which is not permitted.

Best Wishes

Montek

Hi there Mohammad,

I only rememebr this yesterday afternoon and realized some has already tried qualifying your nozzle. I can't open you model anyway becasue I am using version 5.2.3 and I am pretty sure you are using 5.3. If there is a way to save it in lower version please re-send it, else, I can remodel it quickly too.

Thanks.

Dear EddieB

My CEASAR version is 5.0. I word with this version for 3.5 years!
Probably your CAESAR has a problem.

No worry Mohammad, I already modeled it yesterday and soon I'll start playing with this. I love this kind of problem. I'll see how can I sent you back the file in case so you can open it. Mine is 5.2.3 and we're about few months to the latest 5.3.

Regards

Dear M.Mohammad,

Before jumping into any piping/supporting changes, please make sure your input is verified and all the conditions are correct. For example, your T1 case shows 85 and 90 deg.C of temperature for the vessel and directly downstream of the vessel the temperature becomes -35 deg.C. I am not sure if this is a realistic case. Is there a cooler directly connected to the outlet of the vessel? Also please check the pressures for cases 2 and 3, because they were not defined.

Please check and if the input is correct, we can start looking at the piping and supports.

Regards

Hi Mohammad,

I run the model but with the results, I am thinking I need to confirm the results of the following:
Piping:
Normal Ope. Temp= 36C (T1)
Minimum Ambient Temp=-46C (T2)
Design Temp=85C (T3)
Design Pressure=18 bars (P1)
Corrosion All.=1.27 mm (maybe 1.5?)
Same thing with Vessel (I normally put zero on Design Pressure of vessels),
so please indicate the same parameters. I don't know if you have the same practice as we also do but on setting for the temperature profile of vessels, we estimated design and normal operating temperature based on average results of incoming and outgoing flow - not on design temperature shown on the vessel equipment drawing which is normally high based on ASME Sec. VIII Div 1, 2 or 3.

Thanks!

T1 above is actually -36C and all data above are form your model. Please confirm.

Thanks.

Hi EddieB_2070 ,
Top= -36 C
Tde= -46 C
Tsun= 85 C
Pde= 18 bars
C.A= 1.27
For vessel all above data are valid.