The yield strength of both B7 and B16 is 105,000psi at ambient temp. Changing the bolts will probably not solve the problem. You will need to look at the joint as a whole and check the following -
1. Flatness of gasket faces
2. Gasket type – jacketed/spiral wound/camprofile/flat metal versus joint type. An example of a poor combination would be a male/female joint with a jacketed gasket.
3. Tightening method – manual slogging/manual torque wrench/hydraulic torque/tension.
4. Torque or tension value
5. Sequence of tightening
6. Flange rotation
7. Surface finish of gasket face must suit the gasket type
8. Alignment of flanges
9. How the gasket is held in place – using tape or sealant
10. Lubricant used and corresponding torque value calculation
Of particular interest in my experience were joints in a steam reboiler where steam is on the tube side with fluctuating levels of condensate in the outlet section of the bonnet. Here, in spite of addressing all of the above, we still had leaks. Finally had to use live loading washers to stop the leaks.
Ashok
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of M S R K S Prasad
Sent: Friday, August 12, 2011 5:40 PM
To: materials-welding@googlegroups.com
Subject: [MW:12205] ASTM A 193 Gr B7 to B16
Dear members,
I am thinking of changing MOC of one of the exchanger channel cover bolts from B7 to B16 as the exchanger channel cover is leaking very frequently. Whenever it leaks we tighten it manually the leak minimizes after few days it resurfaces.In each tightening the nuts are moving by about 10 to 15 deg.
I request members to suggest whether the choice of B16 is OK are any other bolting material is better than B16 is available.
with regards
--
To post to this group, send email to materials-welding@googlegroups.com
To unsubscribe from this group, send email to materials-welding+unsubscribe@googlegroups.com
For more options, visit this group's bolg at http://materials-welding.blogspot.com/
The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.
DISCLAIMER : This e-mail and any files transmitted with it ("Message") is intended only for the use of the recipient(s) named above and may contain confidential information. You are hereby notified that the taking of any action in reliance upon, or any review, retransmission, dissemination, distribution, printing or copying of this Message or any part thereof by anyone other than the intended recipient(s) is strictly prohibited. If you have received this Message in error, you should delete this Message immediately and advise the sender by return e-mail. Opinions, conclusions and other information in this Message that do not relate to the official business of PETRONAS or its Group of Companies shall be understood as neither given nor endorsed by PETRONAS or any of the companies within the Group.
Comments