Help for Pressure Vessel Beginners 1

[rsaeed]

Good Day,
I was going through the ASME Section VIII Div 1 and was also studying one of the vessel calculation results from PVELITE. I am grasping most of the calculations but some are still on top of my head. I will be grateful if somebody can resolve them with there strong background in this field.
1- The vessel (Inlet Separator) is ID=3500mm lenght tan to tan is 15meters. This size is given in the data sheet and am not getting where did it come from? Whats the criteria of selecting this size as we could have same capacity with different combinations of dia and lenght.
2- In PV Elite result file which is of roughly 300 pages I am not getting the load cases explanation as they have used the symbols like NP, EW, WI, FW BW, BS, EE, FS, HW, HI etc. can anybody tell where can I get the case details.
3- What is effective diameter multiplier?
4- The material specification is only "SA-516 70". There is no other letter like "N" or something so is that normalized or not.
5- I have reached the formulas area for HEAD but What is the basis of selection of head TYPE like ellipsoidal or Hemispherical etc????
There are few more queries so far but if somebody can resolve these, that will really be appreciated.
Regards
Rsaeed

 

[rsaeed]

Hi
I got few things since last night which I am pasting as I get that, rest of them are still question in my head.

The load cases are present in the user guide of PV ELITE which is easily downloadable from the following link

http://www.cadfamily.com/Download.asp?ID=292931

and load cases from that are as follows:

=====================================================
Load Case Abbreviations
NP No Pressure
IP Internal Pressure
EP External Pressure
HP Hydrotest Pressure
EW Empty Weight
OW Operating Weight
HW Hydrotest Weight
WI Wind Load
EQ Earthquake Load
HE Hydrotest Earthquake
HI Hydrotest Wind
WE Wind Bending Empty New and Cold
WF Wind Bending Filled New and Cold
CW Axial Weight Stress New and Cold
FS Axial Stress due to Applied Axial Forces (Seismic Case)
FW Axial Stress due to Applied Axial Forces (Wind Case)
BW Bending Stress due to Lat. Forces for the Wind Case, Corroded
BS Bending Stress due to Lat. Forces for the Seismic Case, Corroded
BN Bending Stress due to Lat. Forces for the Wind Case, UnCorroded
BU Bending Stress due to Lat. Forces for the Seismic Case, UnCorroded
If you checked the box to perform vortex shedding calculations, the following load case descriptors may be used:
Load Case Descriptors
VO Bending Stress due to Vortex Shedding Loads (Ope)
VE Bending Stress due to Vortex Shedding Loads (Emp)
VF Bending Stress due to Vortex Shedding Loads (Test No CA.)
=========================================================


Thanks and still waiting for valuable replies.
Rsaeed

 

[gr2vessels]

raeseed,
1. We are mechanical engineers famous for our ability to design a vessel precisely to the process engineers requirements (aka process datasheet) without questioning their ability to specify what they need. You have reached to the stage when you now are ready to aquire a new degree in chemical engineering, so you may specify a new shapes for this dreaded separator. However, until then I suugest you talk to the process engineers who put a lot of work into that separator size, shape, internals sizing to perform a specific process. Believe me, if you try to put a destillation column to work horizontaly, it won't.
For start, read a few books on the process sizing of separators. It will help.
2. If you go on the loads page, click on F1 button and you'll get a detailed, printable explanation of those symbols (seems you already got them).
3. Click on the Wind Diameter Multiplier line and click once more the F1 button, read carefuly the explanation.
4. There is a long, long list of ASME materials in the PV Elite database, but they can only fit so much on your screen. Double click on the material or click the materials button next to the selected material and the material list will reveal the variety of materials and the details of the one you selected. By clicking on another line you can change the selected material. Also, you are missing badly a short or a loooong training course with Coade for PV Elite (the book is mainly for reference, but with practice one day you might...).
5. The selection criteria is a mixture of engineering and commercial issues, like strength, cost, ease of manufacture, etc. There are many studies for each type of the heads discussing the pros and cons for each type, try for start the internet, then a mechanical engineering course.

 

[rsaeed]

gr2vessels thanks very much and sorry if I offend you in any way through my silly questions (if any). I laughed at first answer actually I am not actually questioning their ability, not at all. I didnt know about that and was curious how to do that and also i was not sure weather mechanical engineers do this or chemical anyways if its the input for us then its all good I have already too many things to learn so leave it to chemeees..
Secondly mate I dont have any software with me.. what i have is only a result of that vessel which is in construction phase at the moment and I also have ASME code sec VIII div 1 so thanks for your advices and if I got the software then will be able to use that.
Also for the wind multiplier I got the explanation from the user guide downloaded from internet.
Thanks once again for all this support.

 

[gr2vessels]

rsaeed,
I am sure that you are on the right track to be a good pressure vessel engineer;- not now, but when you are grasping the rules of pressure vessels, then you got the right to question every one, including the book and your teachers, because that's the only way to progress. I'll be proud you to prove me wrong. Just don't give up on learning!
Cheers,
gr2vessels

 

[rsaeed]

Thanks mate, you really motivated me. After a lots of disappointments atlast I started this. I was always an all rounder doing bits of everything because of the need of the projects but now trying to focus on getting some detailed know how of one area like pressure vessel. I am asking this sort of questions as I have limited resourses. The software is very expensive, and obviously its good to learn the concepts then will see what options I will get.

I am again thankful for your extra support. You are really a nice person. Sorry for again and again intrupting you
Tommorow will post new problems

Meanwhile I am attaching the result file of PVelite whose post mortem is in process on my desk . So that other people who look into this thread can understand the discussion. Also firstly will be easier for me to ask.

Last question for today, On page 21 of the attached result and in the last table with the heading : Stresses on Elements due to Hydrostatic Test Pressure:
I got the stresses came from formula S= (P*(R+0.6*t))/(E*t)

P 5884.31
R 1750
t 65
E 1
from formula S=161954.3168
But where did the Allowable stress came from whereas the material is SA-516Gr70N.?
Cheers
from Perth australia

 

[gr2vessels]

Under the main tabs you have the Design Constraints, which allows you to manipulate to some extent the allowable stresses for hydrotest. Look up what have you clicked on, perhaps check what's applicable to your project, review the print-out for the input data.
It appears that you have clicked on the 'Hydrotest Allowable stress at 90% of yield' button. It is not uncommon, but you should use it in special cases when your hydrotest is closely controlled.
Cheers,
gr2vessels