Just curious, how are you finding the extents of the cracks/cracking? NDT?
BTW, Welcome to the forum...I just noticed this was your first post.
Thanks for the welcome.
Yes correct we are performing PT of the surfaces to locate the areas and also performing PT of the repairs to ensure the welds are sound. We are going into this with a lot of unknown such as the severity of the pipe failures. Our client has stressed this needs to be done in a quick fashion, which is concerning. The pipe could be severely damaged and needs to be replaced in which we would weld in new fittings and possibly have to weld with a solar flux on the interior. If the damage is minimal (cracking) we plan on either using 304 SS patchwork plates and or running a surface bead over the cracks to seal them. Either way I want to approach this with a good plan and hoping for some other ideas or concerns I have yet to consider.
One other thing. I do nto see how asphyxiation can be an issue. If you are in a confined space you have to vent for smoke and fume anyway. So, vent for argon.
To start, not enough info.
But my sense is you are fixing to get into a big ol chocolate mess. The cracks are most likely stress corrosion cracks. They may very well be extensive. And John asks the million dollar question. Have you NDE'd the extent of the cracks. What method?
You are going to have a tough time fixing or patching cracks with no purge.
If its just a temp fix with no threat to injury in service you might consider a full encirclement collar. With this you can use fillet welds and not need a purge.
This can buy you time until a proper shut down and fixing it the non cheapo route.
I work in a paper mill. There are a few areas in which we have repaired cracks resulting from hammering/deadheading pumps.
Of the ones I have repaired most are close to laterals or areas in which piping is very rigid.
We have repaired many if these by gouging/grinding the cracks out, welding , then welding patch plates over the area. Often times this is done with water and pulp/recycled paper still in the line.
All this said, each case is different. If a root with no oxidation is necessary for the piping to function you are just out of luck. On maintenance and repair situations it often becomes necessary to do things that aren't normal practice. No matter what, it's just not a perfect world when it comes to repairs. However you can do things to maximize how long a repair lasts. Here are some things to keep in mind.
1) The piping was caused to crack. If you don't eliminate the cause it will probably happen again in less time than it took the 1st time unless you change something. A 100 percent efficient weld joint in the wall of a pipe is no stronger than the original pipe wall. If vibration or impact is the cause its much weaker probably.
2) welding over the top of cracks or putting plates over the top of cracks without first arresting the crack will reduce the time the item will be in service before the crack comes out again. Drill the crack ends or blow a hole in them and round up with a burr bit. Vee the crack out enough to get cjp.
3) If a sudden failure of the entire line while in service cou lo cause injury/death you probably need to look harder at what is causing the issue and replacing damaged sections of piping.
These are all based on my limited experience. I strongly suggest getting the owner to buy into whatever repair options are decided upon with them fully understanding the risks associated. Don't discount the value of a real engineer over the words of some welder. I'm the latter.
Gerald
A couple of things to take into consideration is the age of the facility. If a new installation, was everything done to ensure success with start up. If its an older plant, stress and bad maintenance could have an effect. Solar Flux has to be applied on the inside of pipe. With no purge and the chance pulling impurities back into the puddle most repairs will fail under stressful conditions. If the cracks were caused vibration, the surrounding base metal could be compromised also. Good luck, sounds like a exciting job.
Due respect to all of the professional responses. Is there an approved Repair Procedure in place?
