5 replies to this topic

[tummalap.chowdary]

hai,

this is T.P.Chowdary,

i want to know How to calculate column material thickness required according to pressure working,

waiting for valuable replay

[paulhorth]

Mr. Chowdary,
Judging from your recent three posts, you do not seem to have benefitted from an engineering education. This forum cannot be a substitute for that.

To make a calculation of vessel wall thickness is usually the task of a Mechanical engineer. To do such a calculation you will need the following information:

• The vessel design code (which may be legally imposed for the country you are working in)
• the Design pressure (not the working pressure)
• the Design temperature
• the material of construction with its specified grade
• the corrosion allowance
• other factors such as wind forces and bending resistance, vacuum design, etc.

If you can define all these items, come back to us with the information.

Paul

[tummalap.chowdary]

thanks for reply,

May be it is mechanical engineer job, but we have to judge it is it correct or not, e have some idea regarding that,

i gone through coulson & Richardson vol 6 in my course duration,

here one thing is i want to know ASME vessel code, for my country (INDIA) there is no specific code and fallows ASME,

for distillation column Which code is applicable,

Remaining things
Temp-150 C,
pressure-2atm, Vaccum of 300mm WC
MOC- SS304,
C.A - 0.2 mm,
wind speed - 100 km/hr(max)

waiting for your reply,

T.P.Chowdary.

[Art Montemayor]

Tummalap:

I empathize with your concern for learning more about the mechanical design of a pressure vessel. As a chemical engineer working in developing countries I had to quickly develop a skill for developing preliminary mechanical designs of pressure vessels – and supervise their fabrication. I had an advantage over other chemical engineers in that I worked during the summers of my university years in a shipyard where my father was a boilermaker. I learned a lot of hands-on skills working with pressure vessels and steel fabrication. I became a welder during that time and this has helped me amplify my engineering expertise in process plant projects and their evaluation.

I always try to encourage young chemical engineers to become more knowledgeable with regards to pressure vessel design and fabrication during their early years. If you are interested in learning preliminary design of pressure vessels, I recommend you to go to the following website where you will find a large amount of useful and practical engineering expertise and guidance on how pressure vessels are designed – complete with instructions and examples:

http://www.pveng.com/

You should also go to:

http://www.pveng.com...DesignTools.php

where you can download all the essential basic tools and information that allows you to do a preliminary mechanical design of a pressure vessel. This type of design only involves vessels under internal pressure – not external pressure (i.e., vacuum). For pressure vessels under vacuum, you require a lot more complex and involved calculations and I would leave that type of exercise to an experienced mechanical engineer.

Good luck in learning more engineering.

[kkala]

Another way is to concentrate on Chapter 13 (Mechanical Design of Process Equipment) of "Chemical Engineering" Vol 6 of Coulson and Richrdson. The Chapter seems to be written clearly and in sufficient detail for a preliminary estimate of thickness for purposes of cost estimate or rough check of vendor's design. You have already used the book, so you have got some familiarity with it. Among others, points of interest are:
1. Stresses developed on the lateral surface of thin cylinder (para 13.3.4)
2. Allowable stress for steel (including SS304) at several design temperatures (Table 13.2).
3. Welded joint efficiency (para13.4.5).
Pressure vessels of process plant are specified for 100% radiography on the welds.
4. Minimum practical wall thickness (para 13.4.8).
5. Design of thin-walled vessels under internal pressure (para 13.5).
6. Design of vessels subject to external pressure (para 13.7).
7. Weight loads (para 13.8.1), wind loads (para 13.8.2), earthquake loads (para 13.8.3).
8. Vessel heads (para 13.7.3), vessel supports (para 13.9), etc.
We checked vendors' data of a 10 barg flare stack (1984) using this book (external pressure, ie vacuum was not checked). Material was carbon steel, but calculations could be in similar way for SS304.
Note: Quick check of vortex shedding induced vibrations were taken from Hydrocarbon Processing, not found above.
It is noted that info in parenthesis concerns the first edition of "Chemical Engineering" Vol 6 (Pergamon, 1983).

Edited by kkala, 23 May 2012 - 03:59 PM.

[paulhorth]

Tummalap,
You should follow the advice provided by Art and Kkala in their posts.
I would also query some of the data that you have presented.

• pressure 2 atm: you do not say whether this is absolute or gauge pressure, whether this is working or design pressure. Furthermore the unit "atm" is not a standard engineering unit, you should be using bar or kg/cm2. in any case, 2 atm whether gauge or absolute is too low to be a sensible design pressure for a practical vessel.
• vacuum 300 mm WC: Considering that a full vacuum is 10m water column, this figure makes no sense at all.
• Corrosion allowance 0.2 mm: If you have selected 304 stainless steel, the corrosion allowance should be zero. If you expect to get any corrosiion then 0.2 mm is too small an allowance since any slight crevice or pit will be deeper than this.

I do not understand what you have said about the design code. Is this vessel to ASME VIII or not?
I suggest that you should first make an effort to define more carefully what you are trying to design, then you should turn to the references provided by Art and Kkala.
Paul