[JustGus]

G'day from New South Wales. First post!

I'm a relatively new welder and was hoping to get some advice. I need to build a support for 90mm PVC pipe that will run to a rainwater tank. I've considered a few options to do this.
The distance from the eaves to the water tank is 7.1 metres and cannot have a support in the centre, as cattle run through that area. I have access to 50mm Duragal SHS that's 2.5mm thick. The Duragal is in 4 metre lengths.
I thought I'd use stick instead of MIG to do the job and would love some advice on what approach to use for a span of just over 7 metres. Here's options I'd considered:
Option A - Simply lay out 2 sections of SHS lengthwise with around 1 metre overlap and weld the length of the metre on both sides. Pros - Easy to do. Cons - A bit ugly. Lacks symmetry, as there's the (heavy) 1m length of double tubing in the middle. Not sure this'll work unsupported across 7m.
Option B - Simply butt two, 4 metre sections end-to-end and weld a length of flat bar on the top and bottom to join them. This would be pretty easy to do, but again, not sure if this would be sound.
Option C - Order a single 8m length and just cut and weld that to supports. Pros: Easiest option. No worries about weld strength. Cons: Costly as delivery will be expensive and means I don't use existing steel.

In all these options I'm assuming that while the steel will bow a bit in the centre, it'll still be sound to support a maximum of 47kgs (the weight of the PVC, full of water, when filled to capacity).

There's likely other, better options out there. If so, would love to hear them! Thanks in advance for any advice!

[US.Fabricator]

Well hello, im still a newbe here on the forum but been fabricating for a while/20yrs ago. back in my time when i was blue collar they didnt have forums or internet based job boards, there was an employment office and it was word of mouth to find work. and if you had to learn something there was an old timer that would teach or show you..

Not sure why someone would say they are not pros at welding when hardly anyone has done it all in my opinion.
I would consider a pro more of that of a journey man with at least 5 yrs in one specific area, tanks boiler ship etc ..

Sir ,
when you dealing with meters for me it first needs to be converted to feet since metal suppliers here sell material by the
foot/weight so you dealing with 22.9659 (23^ feet)

90mm pvc pipe is roughly 3-1/2" that will run to a rainwater tank

50mm Duragal SHS that's 2.5mm thick. The Duragal is in 4 metre lengths.
If you put two sticks end to end to make 8M that gives you plenty to span but not enough to hold weight.
I would consider camber two 8m lengths together and stich weld the two while at a camber , it will hold the camber for you
Bonus if you can stagger the seams between the two stacked lengths and then stich weld every 4-5 inches

MHO


Stick will do the job a lot less than mig with gas consumption but if you have NR211 wire its self shielding

[SusKatCas]

JustGus,

Since you have a meter of extra SHS, cut off a 10cm chunk and trim two corners and reweld to make a nice square backing tube that is 50 - 2*2.5 = 45mm square. Maybe make that backer tube 44mm square so it fits in easy. You can slide that into the end of each joint and make a nice full pen butt weld.

That tube appears to be pretty stout stuff. You might not need an camber if its load is really only 47 Kg. I estimated the tube mass at 33.5 Kg. You could easily mock that up on the floor though to see if pre-cambering was a good idea.

I think stick or MIG would both be fine. Since you still have 90 cm left you can even run a few test pieces.

Cheers, Alan

[US.Fabricator]

@SusKatCas,
that was a cool weld symbol! I like it !

how did you draw that into the message block ? im new to to the forum and still learning how to use the site ..lol

Yes the backing strip will work perfect but time consuming, to make a backing strip and to weld all the way around the square tube might be excessive if you were stacking two 8m lengths.
if you use two lengths end to end (only) (not stacked) then i would option in for the backing strip.

If you do stack and camber you can stich weld at that splice location on both sides constructing a truss type span..

in short:
1- 8m length (span) splice with backing strip as explained

2- 8m length stacked with camber stich weld along the length on both sides no backing strip needed (stich at splices)

[US.Fabricator]

@SusKatCas,
that was a cool weld symbol! I like it !

how did you draw that into the message block ? im new to to the forum and still learning how to use the site ..lol

Yes the backing strip will work perfect but time consuming, to make a backing strip and to weld all the way around the square tube might be excessive if you were stacking two 8m lengths.
if you use two lengths end to end (only) (not stacked) then i would option in for the backing strip.

If you do stack and camber you can stich weld at that splice location on both sides constructing a truss type span..

in short:
1- 8m length (span) splice with backing strip as explained

2- 8m length stacked with camber stich weld along the length on both sides no backing strip needed (stich at splices)

[SusKatCas]

MHO,

I just drew a simple sketch in MS paint, saved as .jpg. Then, below the box where you type your reply there is a box headed "Options" the next tab to the right is "Upload Attachment." Once there you choose a file, then use next button to right to upload.

I did a quick look at deflection and bending stress they were both pretty low. I agree the backing strip might be overkill, but he said he was a new welder. So, worst case he gets a little extra practice and I think that is the best way to get a full pen weld.

Cheers, Alan

[Poland308]

Support the pipe from the top side and drop Clevis hangers. 8ft space max on the hangers to keep out the sag on the pvc.

https://pipingtech.com/products/pipe-su ... s-hangers/

[JustGus]

Thanks so much for the messages. I wound up having to do the job before the first message came in. I resorted to Option C (single span) and cutting a bit out the vertical supports, to mirror the rounded edge of the profile of the horizontal sections, then dab welded each section. It's working great.