Simple weld length question

By Rob71zilla Date 09-12-2018 11:00

Hi Everyone. This is my first post, and I am not a welder. I have taken a Mig and Tig class in college but that's about it.

At work, I have a job that's requiring us to weld 1x2x1/16 tubes to 3/8" steel plates. These will be welded on walls and ceilings. The purpose of the tubes is to give something to mount 2" rubber tiles to, via screws. Each tile weighs about 40lbs and the tubes are 25ft long. Each rubber tile will mount to 2 tubes. My thought is that this is essentially zero force on the tubes.

Right now, we are using a 2" weld every 12" on top and bottom on the tubes. There is no math behind this, just went with enough weld to know we're safe.

My question is, how do I determine the amount of weld that I really do need? Any amount of weld that is over what's necessary is extra labor and money.

By Tyrone

Date 09-12-2018 12:14 Edited 09-12-2018 12:29

Hey Rob,
Welcome to the Original AWS Welding Forum.

Not a simple question. I'll give it a shot with assumptions. This is a basic calculation without factoring the loads, direction etc.

1) You want the weld to be as strong as the thinnest material = 1/16" (0.0625") tube. Think of it this way...a 1/16" weld the full length of the tube is equal to the tube strength. Assume carbon steel tube and filler weld has the same strength.

   Therefore you need 0.0625" x (25' x 12") = 18.75 in2 total weld

2) You gave your stitch pattern but didn't state the stitch weld throat size, I will work it backwards.

   2" stitches x 50 stitches = 100" total weld

3) Throat size of weld required

   18.75 in2 / 100 in = 0.1875" (3/16")

So...your 2" stitches every 12" will work if the stitches have 3/16" (throat). This has no safety factors.

Honestly, I would be more worried about the screws tearing out of the tube. 1/16" tubing is not much meat for thread engagement.

Tyrone

By 803056

Date 09-12-2018 18:44

I guess I'm stupid. First, I don't know what a stitch weld is. Second, I'm not sure I am envisioning exactly how these tubes are attached to the 3/8 plates, how the tubes are attached to the structure, or how the tiles are attached to the tubes.

A sketch would be so helpful.

Al