Is there anything in any of the codes that disallows the welding of dogs and pullers onto pipe? If so please reference. My understanding that this is acceptable if done right at the bevel. However, why couldn't a welder weld dogs or pullers on 2 or 3 inches back from the bevel as long as the pipe was preheated and the welder was qualified and the proper rods were used and the dogs were removed when complete without damaging the pipe?
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welding dogs or pullers onto pipe 6
- Thread starter Downhand
- Start date
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- #2
I'm not aware of any code disallowing this practice. It is a common technique for pipe and plate fabrications. Most of the guidelines are found in the customer specific requirements, if you have any at all. You already touched on proper preheat, qualified welder/tack welder, proper rods, but also important is to ensure that the dogs are of the same material, and at a minimum, MT is performed after the they are removed.
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DVWE is correct, there is no code disallowing this practice.
At our facility, when using dogs or "hickey" bars to allign plates in stainless steel Condenser Flash Tanks, we have a policy in place that after the attachment weld is made and then ground back to base metal we PT the area to insure no cracks have appeared.
At our facility, when using dogs or "hickey" bars to allign plates in stainless steel Condenser Flash Tanks, we have a policy in place that after the attachment weld is made and then ground back to base metal we PT the area to insure no cracks have appeared.
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Guest102023
Materials
It will depend on the alloy. Carbon steel is forgiving; low alloy grades, not so much. But preheat as per WPS, complete removal by grinding, followed by MT is a minimum.
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Kiwi2671
Structural
- Oct 15, 2010
- 281
Downhand,
It is considered poor practice to weld dogs etc on pipes, be they carbon, low alloy or s/s.
A properly equipped pipe shop will have all the necessary equipment to fabricate piping spools without having to weld temporary attachments anywhere.
Regards,
Kiwi
It is considered poor practice to weld dogs etc on pipes, be they carbon, low alloy or s/s.
A properly equipped pipe shop will have all the necessary equipment to fabricate piping spools without having to weld temporary attachments anywhere.
Regards,
Kiwi
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- #6
Kiwi2671
Structural
- Oct 15, 2010
- 281
rmw,
It does not really matter whether it is performed in the "field" or in the shop.
Dogs or temporary attachments are usually welded on to assist in either pulling the pipes together or removing misalignment.
One sling choked around each pipe with a chain block / turfer / come-a-long in between to pull them together works fine.
As for misalignment, pipe clamps come in numerous sizes and the "Deerman" clamps come in some pretty large diameters.
I will state again, there is no reason at all for temporary attachments on piping if the company supplies the correct fabrication equipment.
Regards,
Kiwi
It does not really matter whether it is performed in the "field" or in the shop.
Dogs or temporary attachments are usually welded on to assist in either pulling the pipes together or removing misalignment.
One sling choked around each pipe with a chain block / turfer / come-a-long in between to pull them together works fine.
As for misalignment, pipe clamps come in numerous sizes and the "Deerman" clamps come in some pretty large diameters.
I will state again, there is no reason at all for temporary attachments on piping if the company supplies the correct fabrication equipment.
Regards,
Kiwi
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- #8
Funny,
We can weld a small piece of metal onto a piece of pipe to pull it in place and it is called a dog. We can weld a similar looking piece of metal onto a pipe for a slightly different purpose and it is called a hanger clip.
Kiwi, we are not disagreeing. In a perfect world a perfect company will have a perfect set of perfect tools and equipment and plenty of them on the job, be it shop or field. Unfortunately in the world I mostly work in, that world has never existed. We have had to improvise and watching a craftsman work with some fairly crude dogs and wedges on pipe and/or vessel shells is quite amazing frankly. To watch him clean it up afterwards so that it can't be determined where they were is priceless.
rmw
We can weld a small piece of metal onto a piece of pipe to pull it in place and it is called a dog. We can weld a similar looking piece of metal onto a pipe for a slightly different purpose and it is called a hanger clip.
Kiwi, we are not disagreeing. In a perfect world a perfect company will have a perfect set of perfect tools and equipment and plenty of them on the job, be it shop or field. Unfortunately in the world I mostly work in, that world has never existed. We have had to improvise and watching a craftsman work with some fairly crude dogs and wedges on pipe and/or vessel shells is quite amazing frankly. To watch him clean it up afterwards so that it can't be determined where they were is priceless.
rmw
Kiwi2671
Structural
- Oct 15, 2010
- 281
rmw,
I am not standing on a soapbox and preaching - I have welded pipe in the jungles of Papua New Guinea and the deserts of Australia so I know exactly what you are saying about making do with what you have.
The welding on of the dog / temporary attachment is not the problem, the removal of them is.
Undercut, porosity, tear marks and then dirty great grind marks after they have been cleaned are just some of the problems.
C/S pipe can be painted, but who wants to buy S/S piping systems covered in grind marks.
Regards,
Kiwi
I am not standing on a soapbox and preaching - I have welded pipe in the jungles of Papua New Guinea and the deserts of Australia so I know exactly what you are saying about making do with what you have.
The welding on of the dog / temporary attachment is not the problem, the removal of them is.
Undercut, porosity, tear marks and then dirty great grind marks after they have been cleaned are just some of the problems.
C/S pipe can be painted, but who wants to buy S/S piping systems covered in grind marks.
Regards,
Kiwi
Kiwi,
We are singing from the same hymn book here. That is why I carefully used the word "craftsman". What you described doesn't seem to fit that description to me. I been able to work with some pretty skilled guys.
Where I had this "make do" experience, I was the person responsible for making sure that what you described didn't happen and would have been the one held accountable had it.
Flash3780, compared to scalding dogs, welding them is a heck of a trip. PETA wouldn't like either one, however, as you note.
rmw
We are singing from the same hymn book here. That is why I carefully used the word "craftsman". What you described doesn't seem to fit that description to me. I been able to work with some pretty skilled guys.
Where I had this "make do" experience, I was the person responsible for making sure that what you described didn't happen and would have been the one held accountable had it.
Flash3780, compared to scalding dogs, welding them is a heck of a trip. PETA wouldn't like either one, however, as you note.
rmw
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