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RE: Pressure Vessel Repair

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Daryl,

Stay away from the crane support.  It is not that stable in a wind and the
deflections are excessive for my taste.

Try using external vertical stiffeners spanning the cut out.  Design the
stiffeners to take the dead and wind loads.  They can be offset from the
shell to provide access to the weld seams.  Remove the stiffeners after
repair and grind and NDT the attachment welds.

Stability during PWHT is another matter.  I have a project now that requires
PWHT in the erected position and the dead loads are trivial under ambient
temp. but a major problem at 1300 degrees F.




Ronald A. Hill, P.E.
HILL Consulting Engineering
PO BOX 26525
Birmingham, Alabama 35260 USA
Phone: 205-823-4784
FAX: 205-823-4145
email: ronhill(--nospam--at)hillce.com
Messenger: ronhill(--nospam--at)hillce.com
http://www.hillce.com

-----Original Message-----
From: Daryl Richardson [mailto:h.d.richardson(--nospam--at)shaw.ca] 
Sent: Thursday, April 07, 2005 12:03 AM
To: seaint(--nospam--at)seaint.org
Subject: Pressure Vessel Repair


Fellow Engineers,

        I have been asked to participate in discussions regarding the best
way to go about repairing a pressure vessel which seems to have problems
with hydrogen embrittlement.  This problem has resulted in  a major petro
chemical processing plant (commercial value in the order of $50,000,000.00)
being shut down.

        The vessel under consideration is 8'- 6" ID and approximately 70'
tall; the material is A212 gr B with a stated tensile of 70,000 p.s.i.; the
wall thickness is 3.75 inches (obviously high pressure and/or high
temperature).  The vessel in inside a building about 23 feet high (hence, it
protrudes through the roof by about 50').  The dry erection weight is about
300,000 pounds.  The vessel is about 44 years old.  The affected area is
about five feet in length and located between 18' and 23' from the base.
The once in 30 year design wind speed is about the equivalent of 120 miles
per hour.

        Some radical ideas are being considered for carrying out the repairs
as you will see from the client's letter, below.  Any thoughts or comments
you may wish to share would be welcome.

        Regards,

H. Daryl Richardson

Following is the text of the client's letter (I don't know anything more
than is contained in this letter).


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