×
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

MDMT PV Elite
4

MDMT PV Elite

MDMT PV Elite

(OP)
Hi guys, please what can i do to reduce the MDMT of a pressure vessel. I have this warning at the end of the design "Warning: Computed overall MDMT was higher than the required value !".
Although ok with client spec but i there anything i can do to influence the value

RE: MDMT PV Elite

Why do you want to infuluence the value? Assumung that you gave given the proper input, if the above stated message appears, you need to provide impact testing.

If you need help furthur, you need to provide the furthur details so that others can understand the problem better.

RE: MDMT PV Elite

Apparently, your design is not adequate for the required MDMT. There are several things you can do.
I am assumining it is a carbon steel vessel and you don't give the materials you selected.
You can add normalization to the materials.
You can add PWHT.
If the problem is self reinforced nozzles you can go to SA-350-LF2
if all else fails you can add CLVN to the materials and do production impact testing.

Without your requirements or you materials selected, not much else cand be said.

RE: MDMT PV Elite

(OP)
ok, for clarity, i am designing an MP Separator, design condition is 33barg pressure, @100 deg C with vessel diameter 2.4m, T/T length is 7.3m.
The MDMT is showing a warning for the computed. the selected is -20 deg C, the computed is 35 deg C.
the warning is as highlighted above, that the computed is higher than required. So i don't know what to do.

RE: MDMT PV Elite

Here would be my initial guess.

At 33 bar (3401 kPag) and 8 ft diameter, with 1/16" C.A., I computed a vessel shell thickness of 1.5"; if you are getting a computed 35 C MDMT then you probably have specified a Curve A material (ASME Section VIII Division 1 Figure UCS-66 / Table UCS-66). You can almost get to the MDMT you want by specifying a Curve D material such as SA-516-70 N.

RE: MDMT PV Elite

vesselfab, I am pretty rusty in code. Where in the code stating PWHT related to MDMT ?

RE: MDMT PV Elite

shady2554,
The problem appears to be in the material selection window, make sure to select the correct heat treatment (normalized or not) and the correct impact test curve.
Cheers,
gr2vessels

RE: MDMT PV Elite

(OP)
Thanks guys you've all been of great help. I checked the curve and normalised it reduced the MDMT from 35 to 30deg F, and the warning is still there.

RE: MDMT PV Elite

shady2554,

What are the computed shell / head / nozzle neck thicknesses and materials? Some component or other is limiting.

Are you sure the material that the program is working with is Curve D? I somehow doubt it. Are things 4.5 inches thick?

If a piping component is limiting, see also ASME B31.3 323.

RE: MDMT PV Elite

jtseng123,

Refer to UCS-68(c) for PWHT and impact test exemption temperature reduction.

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