Small Vertical Pressure Vessel Leg Support Design
Small Vertical Pressure Vessel Leg Support Design
(OP)
Hello all, I hope someone here can help me, forgive me if this is the wrong forum to post such a question. For background, I am a chemical engineer but I've been tasked with mechanically designing a reactor (pressure vessel) so I'm not too used to mechanical designs so I'm here for some assistance.
Information about my vessel:
Diameter = 1.5m
Ellipsoidal heads
Height = 2m
Design pressure ~ 25 bars
So as the title suggests, I'm trying to design some supports for this vessel. I'm using Pressure Vessel Handbook 10th Ed by Megyesy as reference. This is the image that they provide:

My questions are:
R = radius of head, is the centre of this circle the centre of the vessel?
Is S the tensile strength of the material?
H = leverarm of load, what does this mean?
A and B aren't clear, are they the dimensions of the base plates on the bottom of the leg support?
The end of the calculations don't seem to yield anything of importance.. just that the sum of the stresses do not exceed the stress value of the girth seam, does that mean the stress calculations are just used to check if leg support is viable?
Finally, this table:

mentions an angle size, what angle is this, it doesn't even mention what angle...
If anyone can help I'll be very grateful.
Thanks
Information about my vessel:
Diameter = 1.5m
Ellipsoidal heads
Height = 2m
Design pressure ~ 25 bars
So as the title suggests, I'm trying to design some supports for this vessel. I'm using Pressure Vessel Handbook 10th Ed by Megyesy as reference. This is the image that they provide:

My questions are:
R = radius of head, is the centre of this circle the centre of the vessel?
Is S the tensile strength of the material?
H = leverarm of load, what does this mean?
A and B aren't clear, are they the dimensions of the base plates on the bottom of the leg support?
The end of the calculations don't seem to yield anything of importance.. just that the sum of the stresses do not exceed the stress value of the girth seam, does that mean the stress calculations are just used to check if leg support is viable?
Finally, this table:

mentions an angle size, what angle is this, it doesn't even mention what angle...
If anyone can help I'll be very grateful.
Thanks





RE: Small Vertical Pressure Vessel Leg Support Design
What angle are they using in the first image though? and what R? My dish isn't spherical, it's ellipsoidal.
RE: Small Vertical Pressure Vessel Leg Support Design
Second, there are many alternatives for vertical PV support. Acceptable designs include: angle legs, hollow tube supports, WF supports and complete support skirts. Search the internet and this forum !
Third, IMHO, the most important consideration for PV leg designs is to properly set the elevation for the bottom head from grade. You probably want to have some distance between the bottom head and grade to get access to such things as drain valves and level devices. 36 inches is typical .... could be more.
Fourth, study pictures of similar vessels. Some require reinforcing/ [poison) pads where there is a change in materials ( stainless steel to carbon)
Fifth: talk with your fabricator about his experience
Lastly, congratulate your MBA boss for assigning important and complex work to engineers with no experience in that field.
Remember, just before all MBAs receive their graduate degree they receive a tattoo that states " Anybody can do any job in any amount of time, you just have to count the manhours..."
MJCronin
Sr. Process Engineer
RE: Small Vertical Pressure Vessel Leg Support Design
Is something like this acceptable?
RE: Small Vertical Pressure Vessel Leg Support Design
Have you designed the rest of the vessel ? is everything else besides the legs ok?
Did you take into account loads acting on the process nozzles ? did you do a fatique calculation?
Please understand that design on pressure vessels is not about choosing different components from a book or catalog and magically making it working .
RE: Small Vertical Pressure Vessel Leg Support Design
Try to change job and search a responsible company.
Regards
r6155
RE: Small Vertical Pressure Vessel Leg Support Design
My vessel will be situated indoors and it is small, there are no seismic activities, there are no bending forces. As far as the actual vessel, yes I've taken all of that into account, I've designed the thickness of the vessel with my material to be able to withstand all loadings it is subjected to. These are somewhat preliminary calculations so I've used the equal area method to account for the nozzles/flanges. As far as the legs go, I've used the standards given in that book (angle size, L, W etc) and then I've done the required stress calculations. It turns out that because there's no wind or seismic activity, the standard length works fine. I will go ahead with this, and have it checked.
RE: Small Vertical Pressure Vessel Leg Support Design
RE: Small Vertical Pressure Vessel Leg Support Design
RE: Small Vertical Pressure Vessel Leg Support Design
Oh,and by " loads acting on the process nozzles " you should read WRC 537 and WRC 297 . It has nothing to do with " equal area method to account for the nozzles/flanges ".
RE: Small Vertical Pressure Vessel Leg Support Design
RE: Small Vertical Pressure Vessel Leg Support Design
Some more questions :
- what design code are you using ( in EU there is 13445-3 and it is harmonized with PED 2014/68/EU )
- what is your design temperature ?
- what materials are you using ?
- what software are you using ?
- what kind of fluid is in your vessel ? do you have gas ?
RE: Small Vertical Pressure Vessel Leg Support Design
RE: Small Vertical Pressure Vessel Leg Support Design
Something like this :
There will come a time when you will need acess to those coils.
RE: Small Vertical Pressure Vessel Leg Support Design
GoguGili, if you think this is true you are in a wrong way. Please read more about manhole (inspection opening).
Regards
r6155
RE: Small Vertical Pressure Vessel Leg Support Design
RE: Small Vertical Pressure Vessel Leg Support Design
Lega213: check asme section VIII, div. 1 , mandatory appendix 2
RE: Small Vertical Pressure Vessel Leg Support Design
RE: Small Vertical Pressure Vessel Leg Support Design
And i didn't ask you if your vessel has gas for nothing : if your vessel goes into category 4 acc PED you will need the review of a Notify body ( mainly TUV or Loyd's ).
RE: Small Vertical Pressure Vessel Leg Support Design
RE: Small Vertical Pressure Vessel Leg Support Design
Some use of manhole:
1)Welding final closure seam
2)Radiographic examination or other NDE during fabrication and in-service.
3)Cleaning
4)Surface protection: painting, lining, …..
5)Surface finish: grinding, polishing,….
6)Install / dismantle internals
7) More than one manhole may be required due confined space regulations.
8) Quick- actuating closure
9) Inspection of high stressed and high risk areas.
....and more
Pressure vessel design is not only calculations, good experience in fabrication and inspection is required too.
Regards
r6155
RE: Small Vertical Pressure Vessel Leg Support Design
- ASME PTB 10
- ASME STP PT 02
- CEN/TR 14549
- appendix N in ASME B31.3.
RE: Small Vertical Pressure Vessel Leg Support Design
http://www.hse.gov.uk/pressure-systems/law.htm
What design pressure / operating pressure is the reactor to be designed for?
RE: Small Vertical Pressure Vessel Leg Support Design
RE: Small Vertical Pressure Vessel Leg Support Design