support welding directly to the pipe surface 1

[adilmn]

Hi,
I think as per the standards/practice, It was not allowed to directly weld any structural part to the pipe surface.
but there was some U clamp found with the tack weld to pipe surface against the design document.
Can any one help me to identify the impact of such welding with the pipe grain structure? Is it the stress or any other thing?

 

[DVWE]

It is quite common to weld supports directly to pipe.

The devil is in the details; she also wears prada.

 

[RVAmeche]

One thing that may be worth considering is that the U-bolt base may not be strong enough if the pipe is growing or moving excessively. Also if it's a high temperature service you may want to check w/ the pipe designers to make sure this doesn't affect pipe stress (assuming the U-bolt welds don't break).

 

[racookpe1978]

You face two different issues.
Either one of them, both of them, or neither may actually be a serious problem.

1. There is an uncontrolled weld on the pipe wall, welded with unknown filler material by an unknown welder using an unknown procedure and unknown welding method and unknown (probably NONE!) preheat and postweld heat treatment).

2. There is an uncontrolled weld fastening a pipe support to the pipe at a specific location. This may, or may not, cause binding or resistance to movement that may, or may not, prevent thermal expansion in the expected directions with the expected free movement. Result? Extra stress on the other pipe supports, or extra stress on this particular pipe support that could cause a pipe support to break, or cause excess stress on the pipe or equipment nozzle.

Grind off the weld, grind the surface of the pipe smooth and (at a minimum NDE the pipe for flaws and stress cracks. Dye penetrant exam for surface, UT for subsurface cracking or delamination. You will probably find no cracks, because the heat is usually little for a true tack weld. But you don't know for sure.

Grinding off the weld for the NDE exam removes the pipe stress issue in the support network.

 

[LittleInch]

Welding a proper pipe support / shoe with approved welding procedures and testing is one thing, tack welding stuff on is different.

As racoope says much better than I can in reality it is probably OK, but "tack weld" is rather vague.

The risk of hard spots, cracking and corrosion is increased. There is potential for fatigue issues and concentration of stress.

Why anyone would want to tack weld a U clamp is beyond me. U clamps should not really be tight as they are not good anchor points, but are good at preventing movement in x and y.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[adilmn]

As racookpe1978 says, movement restriction is not affecting with the installed support since the clamp base plate is freely resting on the I beam and just locked with stopper to avoid the axial movement. If there will be any expansion or contraction ,it can move longitudinally.

If we make an additional tackweld on the pipe surface either with support, or with other structural part or with cable laying bars, what impact will result on that spot weld.
The stress will be pointed on that location will lead to corrosion or crack?

 

[LittleInch]

You need to post a picture or drawing as it doesn't make sense at the moment. where is this base plate?

You have just repeated the same question which has been answered.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[adilmn]

 

[MJCronin]

Well LittleInch, we got a drawing ..... but it still makes little sense.

Are the little brown things supposed to be attached or welded to something somehow ?

I don't see any welded attachments to a pipe ... Does the OP know what a pipe is ?

To me this looks like a sliding pipe support that doesn't slide anymore.

This is what happens when you hire a 3D CAD designer who has no idea what he is doing ...

Get rid of all of the old guys in the organization and chaos will reign .....

MJCronin
Sr. Process Engineer

 

[LittleInch]

adilmn,

You seem to have sent us two drawings of different pipe supports.

One has a typical half shell clamp type support which you tighten down and it provides a significant amount of axial strength between pipe and support, with what appears to be two guides which restrict the pipe sideways and vertically, buit not axially.

Then in the smaller picture we have what I guess you're talking about which a rather strange Ubolt type sliding support. U bolts are not great in this service as the tightening down doesn't work in axial force direction very well and there is a significant stress issue if you try to tighten it up, which is why I guess they have tack welded it.

So bottom line - this is a poor support for doing what you're doing and the support on the right should be used.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[mk3223]

Supposed the uses of U-bolt or bolted clamp are to avoid the weld to the pipe.
The U-bolt, typically loose to the pipe, is used to be bolted on the fixed support structure. The clamp can bee bolted tightly on the pipe and welded to the pipe shoe, which sit on the support structure.
The concern of any tack weld of the support on the pipe can be a case by case, and normally is prohibited since the really process condition is not "perfectly" clear.