×
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

PRESSURE VESSEL REPAIR

PRESSURE VESSEL REPAIR

PRESSURE VESSEL REPAIR

(OP)
What is the correct procedure to carry out a repair of a semi spherical head on a LPG bullet that was damaged by transport. The head was deformed and buckled towards the inside. Can it be straightened out and can it be repaired using a patch of the same material on top of the damaged area?

RE: PRESSURE VESSEL REPAIR

beercia-

"Cut to fit, paint to match!"

Cut out the damaged section and butt weld in a formed patch. Make sure you are using SA grade material of the same type as the head and that the weld procedure is ASME qualified. Don't forget the PWHT if necessary to maintain ductility for an autorefrigeration contingency. Depending on where you're at, you may be required to have an Authorized Inspector involved. At the very least, make sure you are using a crew which is pressure vessel certified/qualified/experienced.

Hammering out the damaged section and covering it up with a fillet welded lap patch are not good solutions. Depending on where you are, that may be considered not only poor engineering but illegal.

jt

RE: PRESSURE VESSEL REPAIR

jte is correct installation of flush type patch is correct repair method.  

Inorder to maintatin the joint effeicney of this head as per degsing calculations (assuming original je=1.0) a full radiographic exmaination of the repair weld must be performed.

wbh

RE: PRESSURE VESSEL REPAIR

Assure that the vessel design temperature is not below -20 degree F.  Low temperature design temperature changes the rules.

RE: PRESSURE VESSEL REPAIR

jte has outlined the correct path. See current NBIC.

RE: PRESSURE VESSEL REPAIR

beercia,

I suggest that you strongly consider filling for monentary damages from the shipper and getting a new "bullet"

LPG/propane horizontal tanks are commonly called "bullet" tanks and are typically equpped with "hemispherical" heads. The contour of the construction makes this type of head  difficult to repair. Furthermore the high strength materials typically used (I seem to remember ASTM A622???) cause repair problems

The MAWP for propane is 250 psig....nothing to fool around with.

This type of tank is so common and produced by so many vendors,it may be worthwhile to just replace it. At least compare the cost of a competent "R" stamped repair with replacement.

Or...... perhaps, do you work for some tyranical butthole MBA that is forcing you to repair of this dog.....

My opinion only

MJC

RE: PRESSURE VESSEL REPAIR

This is if you do not want a patch work and want the job to look like a modification instead of rectification and If you want to avoid Radiography. Instead of a patch provide a dummy Nozzle. That is cut out the deformed portion, Weld a Nozzle pipe (Size it accordingly) and provide blind flange. Perform Hydro test.

Second option:Check with your local authorities regarding the possible use of FEM to check whether the job is safe as it is (Leave it as it is)

Third Option: Provide Heating coil from out side (In the deformed location) and jack it from Inside to the required shape and subsequently perform SR. Here simulation test or PTC is not required, subesquently perform (Optional) UT and MPI and perform Hydro test.

Option 4: In one of the past case (De oxy tower) we had our shell deformed due to transportation, after extensive discussions with client and their consultants we provided pad covering the deformed area. ( This was not a U stamp job, Code was used as only as a design standard the job is not in US). Here we used FEM to check whether the deformed locations could be left as it is and found it safe. It is now 7 years every thing is fine till date. Yearly inspections results are satisfactory.


 (Assuminig the job is Carbon steel).

RE: PRESSURE VESSEL REPAIR

bmoorthy-Option 4-WOW! We refer to this as a "scab" or "bandaid" patch. There are many very good reasons not to do this and that is why it is not permitted in most areas of the US and Europe. It fixes nothing.

Not to rude,but I am glad I am nowhere around this one!

The rest of your ideas may be "doable".

RE: PRESSURE VESSEL REPAIR

I'm with MJC on this one...quit fooling around with half hearted repairs...this is LPG, someone could get hurt.  Recommend a replacement head as a minimum, but more likely a replacement vessel (cost factors).

Lane Baker
Baker Quality Services
LaneBQS@att.net

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