×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Length/Diameter (L/D) Ratio

Length/Diameter (L/D) Ratio

Length/Diameter (L/D) Ratio

(OP)
Hi guys,

Anyone knows is there any requirement in ASME Section VIII mentioned about the length/diameter ratio?

If no, any guideline/rule of thumb to follow?

P/S: It is an 2:1 elliptical horizontal pressure vessel

RE: Length/Diameter (L/D) Ratio

Internal pressure: no. External pressure or other situations where there might exist longitudinal compressive stresses: the L/D ratio comes into the calculations, but there is no limit per se.

RE: Length/Diameter (L/D) Ratio

Quote (hubert88)

It is an 2:1 elliptical horizontal pressure vessel

????

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

RE: Length/Diameter (L/D) Ratio

The L/D ratio is used for cylinders, see UG-28(c)(1) in ASME VIII-1.

For elliptical heads you don't need the L/D ratio, see UG-33 in ASME VIII-1.

Regards.

RE: Length/Diameter (L/D) Ratio

Sorry, I forgot that for dished head with a skirt, then the skirt (or flange) of head shall be calculated as a cylinder per UG-28. For the dished portion of head you use UG-33.

Regards.

RE: Length/Diameter (L/D) Ratio

(OP)
Sorry that I didn't write it clear about my question.

Basically, we are proposing a pressure vessel with ID: 2000mm and TL/TL: 5500mm.

But the client commented the length/diameter ratio (5500/2000 = 2.75) is too small.
Usually, it needs at least 3.

So, my question is, does the ASME Section VIII mentioned about this requirement?

RE: Length/Diameter (L/D) Ratio

Firstly hubert, ASME Section VIII itself is not concerned with L/D ratio except when considering vacuum design. Check the formulae for thickness calculations. Secondly, the L/D ratio will, or should, result from process considerations and not just from a general guideline.

You’ve also not stated the function of the vessel. A slug catcher will likely have a different L/D ratio than a separator, or a compressor suction drum, for example. The process requirement will generally dictate whether a vessel needs to be long and skinny, short and fat, or vertical/horizontal.

RE: Length/Diameter (L/D) Ratio

What's the L/D of a sphere? Are we to design all spheres to a 3:1 ratio? And how, precisely would one do such a thing?

What's the L/D of a common household propane container - as with the 20 pound tanks usually used for grills in the US?

The ASME is a mechanical organization. Whether or not the container functions as the process engineer intended it to is not a concern for Section VIII. Sounds to me as though your client got some rule of thumb from a process engineering perspective and is now trying to ask "intelligent sounding" probing questions since he has little experience to base a conversation on.

RE: Length/Diameter (L/D) Ratio

Please see Pressure Vessel Design Manual by Dennis Moss 4th Edit. Procedure 2-16: Optimum Vessel Proportions and you can find L/D ratio 3, 4 and 5. The maximum volume for the least surface area, and weight..............and more.

Regards
r6155

RE: Length/Diameter (L/D) Ratio

Shipping clearances, lifting capacity, overhead crane clearances, available plate lengths and rolling capacities, available head sizes enter into it.
If there is no other criteria, specify volume only and let fabricators pick the most economical dimensions- which may vary from fabricator to fabricator, from place to place.

RE: Length/Diameter (L/D) Ratio

Industry practice for optimum dimensions for horizontal and vertical vessels, at least from a cost perspective, is for L/D to range from a minimum of 3 to a max of 6 - this is usually applied to vapor liquid separators and gas scrubbers. Higher L/D (approaching 6) leads to a lower plate thickness and easier fabrication in most cases.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources