Vacuum service - wall thickness?
Vacuum service - wall thickness?
(OP)
Would appreciate to formula(s)/charts to measure minimum wall thickness for:
1) cylindrical shell (4 feet long), diameter 36"
2) flat plates/disks (to be used as ends) matching the cylinder OD (will be welded to shell ends).
Operating vacuum 0.05 psia
Material of construction SS304
flat plates welded to shell will be used as small brine reservoir at 0.05 psia and -40 to 50 degrees C
1) cylindrical shell (4 feet long), diameter 36"
2) flat plates/disks (to be used as ends) matching the cylinder OD (will be welded to shell ends).
Operating vacuum 0.05 psia
Material of construction SS304
flat plates welded to shell will be used as small brine reservoir at 0.05 psia and -40 to 50 degrees C





RE: Vacuum service - wall thickness?
Steve Braune
Tank Industry Consultants
www.tankindustry.com
RE: Vacuum service - wall thickness?
The PREN: how to measure the pitting resistance of stainless steel
FAQ338-285
RE: Vacuum service - wall thickness?
The vacuum is almost 14.65 psig, not 0.05 psig (it is 0.05 psia)
The brine solution is chromate inhibited. -40 to 50 C are the extreme ends, normally it is 0 to 35 C. The brine is lithium bromide 50 to 60 wt% with 0.3% chromate.
No experience with how to access ASME VIII, UG-28...is any internet access available or do I have to purchase reference/registration.
Due to the fact that our maintenance dept has already access to many SS304 shells and plates of various thicknesses, We just didn't want to overkill on the thickness..thus the question on the minimum...which we will likely add 1/8th to.
RE: Vacuum service - wall thickness?
Check out the pressure vessel design software websites and you may find a free demo or two to get you thru this one problem.
Steve Braune
Tank Industry Consultants
www.tankindustry.com
RE: Vacuum service - wall thickness?
By the way flat end plates will probably be thicker than your stock plates for a 36" vacuum vessel
Regards
Mogens
RE: Vacuum service - wall thickness?
There are formulas for calculating tank thickness required for external pressure in Eugene Megyesy's Pressure Vessel Handbook. Only problem is that it doesn't include the calculation for flat heads, only hemi, 2:1, and ASME F&D heads (which would be MUCH thinner than the required thickness of a flat plate). Listen to the advice others have given you.... look in the ASME code or pay someone to calculate it for you. The cost will be much cheaper than the liability risk of a poorly designed vessel.
jproj
RE: Vacuum service - wall thickness?
http://www.nationalboard.org/scripts/main_search.asp
RE: Vacuum service - wall thickness?
Mike
RE: Vacuum service - wall thickness?
I agree with the above comments about either getting an ASME VIII vessel designed for FV and/or at least using ASME VIII methodology....
kenvlach's comments and cautions abou the use of 304SS in brine of cours, are correct....and I agree
Freon, when all is said and done, you will find out that you need a wall thickness just in excess of schedule 10S for a cyinder of this size, material and operating temperature range.... I suggest you purchase schedule 40S pipe and ellipsoidal end caps for this service.....you will meet the ASME criteria ( You should still go through the calculations and/or certification)
My opinions only....
MJC
RE: Vacuum service - wall thickness?
I am used to apply the following finger rule in calculating vessel thickness under full vacuum: 6 mm every 1000 mm OD.
For flat discs calculation I suggest formulas of Roark book. That's all.
RE: Vacuum service - wall thickness?
As per the reference/data below what would be the difference between yielding and buckling for "flat end caps", or are they nearly one and the same due to the symmetry?
Thanks again,
Freon66
----------------
Roger Cortesi (SM Mechanical Engineering MIT)
21-Jun-02
Only Change Values in BLUE
References:
Woods Hole Oceanographic Institute Technical Memorandum 3-81
Failure Curves of Cylindrical/Spherical Pressure Vessels and Flat End Caps.
By Arnold G. Sharp, August 1981.
Roark's Formulas for Stress and Strain, 6th Edition
By Warren C. Young 1989 McGraw-Hill
Material Properties Used:
Youngs Modulus Yield Stress Poissons Ratio
[Pa] [Pa]
1.90E+11 2.05E+08 0.27
Depth Yielding Buckling Endcap Yielding [T/OD]
(m) T/OD T/OD T/OD
0 0.000 0.000 0.000
250 0.006 0.018 0.061
500 0.012 0.023 0.086
750 0.018 0.026 0.105
1000 0.025 0.029 0.121
.... .....
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RE: Vacuum service - wall thickness?
Refer to Roark's formula for flat circular plate of constant thickness with uniformly distributed load (vacuum) and fixed edges.
Another way is to weld two or more vertical ribs to each flat plate and apply the equivalent Roark's formula for rectangular plate. This solution allows to reduce the plate thickness.
Good work.