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!

*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

CJP - Complete Joint Penetration Welds

CJP - Complete Joint Penetration Welds

CJP - Complete Joint Penetration Welds

In AISC it appears as though the only way to accomplish a CJP / Full-Pen weld is either to weld from both sides or apply a backing (backer?) bar.

In a case where I might specify a Partial-Joint Penetration weld for up to 1/4" material, butt (or square) to 5/16" or thicker, will my "partial" actually produce a "full-pen"?

I have a case where the general contractor frequently repairs PEMB columns after tow-motors (or other) collide with the columns to the extent that necessitates removal of the lower 8' of 0.188" wall intermediate column, and (the G.C. is) replacing it with 0.322" Schedule 40. Therefore, since I'm welding 0.188" Round HSS to Schedule 40 Pipe, I can neither weld from both sides nor install backing.

Again... will my "partial" actually produce a "full-pen"?

I frequently specify a "full-pen" weld, all around weld for HSS Rectangulars when designing stair stringers composed of adjoining, diagonal and horizontal members. Is this wrong?

I realize I need more education in welding.

Thank you!

RE: CJP - Complete Joint Penetration Welds

Yeah, unless you test and qualify the procedure (and get lucky) this isn't going to work. Even if you groove both sides of the weld with a large angle, you'll lose 1/8" of capacity using prequalified welds. Using a more conventional single side groove, you'll lose 1/4"

The first question is, do you actually need capacity there, and if you do can you get it in another way?

Repair is likely near the bottom, max moment is near the top unless it's built as fixed base. Buckling resistance is likely not going to be affected by the discontinuity near the bottom. Axial stress is not going to be an appreciable fraction of the section strength. I'm assuming there aren't seismic detailing requirements.

Alternatively, you could try to groove the larger pipe in such a way that the extra material is backing for the weld. It's not prequalified, but the procedure might test out.

RE: CJP - Complete Joint Penetration Welds

Would a full pen weld even give you full strength? Is the base metal on the pipe strong enough?

RE: CJP - Complete Joint Penetration Welds

When splicing a pipe column I've seen (actually I haven't seen this but I have heard of it) weld shops cut off a short piece of the pipe (maybe 4" long) and they cut a slit in it (in the 4" direction). Then they fold the piece together until it will fit inside the end of the pipe column. They'll put 2" into the pipe and leave 2" sticking out so that the top piece can fit over it and they have their backing bar.

RE: CJP - Complete Joint Penetration Welds

Typically you can get a pipe smaller size that will fit inside the larger pipe. 3Ø Std. pipe fits into a 3.5Ø pipe, and it will be used a a backer. Modifying a pipe can work provide no gap exists in the material, seems like a lot of work.

RE: CJP - Complete Joint Penetration Welds

To get a proper complete penetration weld on a pipe section (or actually any section), there are several things you'll need to do.

First, specify that the welder be qualified in pipe welding (per AWS D1.1 requirements). He/She should be qualified without backing.

Next, design the joint as a pre-qualified joint per AWS.

Next, specify the welding process that is compatible with what you want to achieve. Since these are field welds, I would stay away from either GMAW (Gas Metal Arc Welding....(MIG)) or GTAW (Gas Tungsten Arc Welding....(TIG)) as these are more difficult to control in the field as compared to the shop. Use SMAW (Shielded Metal Arc Welding....common "stick" welding) or FCAW (Flux Core Arc Welding...similar to MIG but does not require shielding gas). Specify that the welding be done with a separate root pass and then filled to complete the penetration.

Next, specify nondestructive testing to determine if the contractor achieved a complete penetration weld. Since these are likely "Tee" joints, radiography will be limited, so ultrasonic flaw detection would be more appropriate.

No...your partial penetration weld will not consistently achieve full penetration requirements.

RE: CJP - Complete Joint Penetration Welds

"I would stay away from either GMAW (Gas Metal Arc Welding....(MIG)) or GTAW (Gas Tungsten Arc Welding....(TIG)) as these are more difficult to control in the field as compared to the shop." ... and even trickier with a light breeze...

There's a really good article on NDT in the Engineering Writer's Guild forum on this site.


RE: CJP - Complete Joint Penetration Welds

Quote (Ron)

FCAW (Flux Core Arc Welding...similar to MIG but does not require shielding gas)

Two types of FCAW: "FCAW-S" (flux only) does NOT use a shielding gas, but "FCAW-G" (dual-shield) does.

RE: CJP - Complete Joint Penetration Welds

These are really light column sections. Why not just replace the whole thing? No matter the welding type or inspection type, I tend to distrust welds on structural pipe without backing bars.

RE: CJP - Complete Joint Penetration Welds

Why not overdesign the pipe a tad (30%+/-) so you can use a partial penetration weld? That's what I usually do.


RE: CJP - Complete Joint Penetration Welds

hokie... That is what we were advising from the beginning. We feel this is also a lot less labor.

Thank you all for your replies!

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! Already a Member? Login


White Paper - Reshoring Prototyping and Production
In this whitepaper, we'll provide insight into why and when it makes sense for U.S. manufacturers to reshore prototyping and production, and how companies can leverage the benefits of working with local design, prototype, and manufacturing partners during the pandemic and beyond. Download Now
Engineering Report - Top 10 Defect Types in Production
This 22-page report from Instrumental identifies the most common production defect types discovered in 2020, showcases trends from 2019 to 2020, and provides insights on how to prevent potential downtime in 2021. Unlike other methods, Instrumental drives correlations between a variety of data sources to help engineers find and fix root causes. Download Now
White Paper - Addressing Tooling and Casting Requirements at the Design Stage
Several of the tooling and casting requirements of a part can be addressed at the design stage. If these requirements are not addressed at the design stage, lot of time is spent in design iteration when the design reaches the die caster. These design issues lead to increase in time and cost of production leading to delay in time to market and reduced profits for the organization. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close