Angles less than 30 deg.???

Date 07-23-2003 15:04

Thanx in advance for any guidence or experience that anyone has to offer.
We are preparing to start a job that involves Pipe trusses contructed primarily of .375" wall 16" dia. pipe (a500 gr.B I think).The detail for the webbing between the chords is the same dia. but comes into a 1" plate with a fillet weld. The plate is welded to the chord first such that part of the connection is a pipe to pipe fillet and a portion is plate to pipe.
Based on the detail that I have seen, the angle at the plate to pipe fillet will be on the order of 22-25 degrees. Having reviewed table 4.10, I made note of note #7 directing me to 4.26.1 (for dihedral angles less than 30 degrees) where it appears to require not only a 6GR test for the welder but also a "mock-up" with additional testing to be performed.
First please clarify for me the dihedral angle measurement, is this from the centerline of the plate to the centerline of the pipe, or based on the outside dimensions for same, I dont think this will make much difference in this case. And secondly, is it a correct interpretation of D1.1 2002 to require a 6GR test for a fillet weld with an angle less than 30 degrees.
Again, thanx for any input or comment.

By jwright650 (*****)

Date 07-23-2003 18:21

QC,
I'm trying to picture the connection you described. Is the 1" plate an end plate on the bottom chord, that is in a vertical position, with one of the stringers intersecting the bottom chord and the plate at the same time? If so, the angle (stringer to plate) you are inquiring about is less than 30 degrees from the vertical 1" plate. You described a fillet weld from the stringer to the plate, how about where the stringer meets the bottom chord? Fillet also? or CJP?
John Wright

By jwright650 (*****)

Date 07-23-2003 18:37

Did you notice the note #5 (Table 4.10) that mentions Table 4.8 for appropriate groove details? Table 4.8 is a chart for something else. Error in the note?
John Wright

By jwright650 (*****)

Date 07-23-2003 18:44

Never mind, I re-read your post and you did say fillet welds and not CJP at the pipe to pipe connection.
John Wright

By BankerQC (*)

Date 07-23-2003 19:21

Thanx for the quick respone !
Please allow me to try and clarify. The 1" plate will be fillet welded to the top or bottom chord at a 90 deg. angle. The diagonal member (pipe)
will come in and be fillet welded to the plate and fillet welded to the pipe (chord) as well. it appears from the design drawings that the plate to pipe angle will be less than 30 degs. (acute angle ?)
Thanx again.

By jwright650 (*****)

Date 07-23-2003 19:50

Yes, That's the way I see it too.
John Wright

By jwright650 (*****)

Date 07-23-2003 20:24

Then your pipe to plate centerlines will be less than 30 degrees and your pipe to pipe centerlines will be greater than 60 degrees.
Yes, I think you will need to test and mock up as you described in your original post. I guess they want you to prove the welder's ability and the WPS in those tests.

If you look at Figure 3.2 it mentions that <30 degrees is not prequailified and special welder qualifications (Table 4.8) apply. There is that Table 4.8 again that has nothing to do with this at all.

By - Date 07-24-2003 04:51

Mr. Campbell,
D1.1 Annex B has a definition of dihedral angle. It is based on a plane perpendicular to the local weld axis at the OD at the point of measurement. It can be applied to plate as well as tubulars.

I believe that you are misinterpreting paragraph 4.26.1. If you look closely at Table 4.10, the Note 7 that gets you to para 4.26.1 is referred to at all of the possible qualifation types where a dihedral angle of less than 30 degrees is possible (plate fillets, plated CJPs, tubular CJPs, etc). Paragraph 4.26.1 is therefore written in a sort of generic manner. In your situation the applicable part of 4.26.1 is the reference to 4.12.4.2 (also written somewhat generically). This gets you to the heart of the matter, i.e. the acute angle heel test shown in Figure 4.26. To sum up, you do not need a 6GR test for fillet welds joining plate to tubulars, but you do need an acute angle heel test for local dihedral angles of less than 30 degrees.
Mankenberg

By jwright650 (*****)

Date 07-25-2003 11:06

After reading Mankenberg's reply, I'm in agreement with him on this one. Does anyone else see this interpetation any other way? Just looking for assurance for BankerQC, so he will feel better about how to proceed with testing.
Thanks
John Wright

By BankerQC (*)

Date 07-25-2003 11:41

Thanx, for that response Kipmark , after re-reading the relevent sections I can see the logic of your interpretation. I do think however that the manner in which it is presented in the text/tables of the code is rater unclear and I hope our client will agree with us on this issue.
Thanx again gentlemen for your imput and any furthur thoughts that anyone may wish to present.

BobC

By - Date 07-28-2003 01:49

Mr. Campbell,
I'm sure that in your travels through D1.1 you've found many places where things could be presented more clearly (Table 4.5 and its notes come immediately to mind). I work for a "client" at a very large shipyard, and there is alot of back and forth with the shipyard on D1.1 interpretational issues. You will likely have others relating to welder and welding procedure qualification.
Best regards,
Kip Mankenberg