Welding material of different thickness
Welding material of different thickness
(OP)
We've been having some discussions about welding materials of different thicknesses and can't come to a conclusion, so maybe someone here can help.
The instance we've been talking about is welding a sleeve onto a carrier pipe. The carrier pipe is .250" X-70. The Sleeve is .750 X-52.
The argument is whether the top edge of the sleeve needs to be tied in or if the leg of the weld should only be as long as the carrier pipe is thick.
_______________________
/| Sleeve
/ |
/ |
/ |
____/________|________________________
Carrier Pipe
______________________________________
_________________________
| Sleeve
|
|
/|
_____________/__|_________________________
Carrier Pipe
__________________________________________
The argument for the first diagram is that the top edge of the sleeve should be tied in to get the full strength from the sleeve.
The argument for the second diagram is that the shorter leg of the weld causes less stress on the carrier pipe than the longer leg will.
Let me know what you think.
Pat
The instance we've been talking about is welding a sleeve onto a carrier pipe. The carrier pipe is .250" X-70. The Sleeve is .750 X-52.
The argument is whether the top edge of the sleeve needs to be tied in or if the leg of the weld should only be as long as the carrier pipe is thick.
_______________________
/| Sleeve
/ |
/ |
/ |
____/________|________________________
Carrier Pipe
______________________________________
_________________________
| Sleeve
|
|
/|
_____________/__|_________________________
Carrier Pipe
__________________________________________
The argument for the first diagram is that the top edge of the sleeve should be tied in to get the full strength from the sleeve.
The argument for the second diagram is that the shorter leg of the weld causes less stress on the carrier pipe than the longer leg will.
Let me know what you think.
Pat





RE: Welding material of different thickness
For your particular application, sizing the fillet weld leg length to match only the thickness of the carrier pipe wall will result in added stress concentration to the weld joint because of a notch effect.
To avoid having a notch, I would extend the fillet length to match the thickness of the sleeve to provide for a tapered transition. You can offset the fillet leg length on the carrier pipe side to reduce the amount of weld metal needed to form the fillet.
RE: Welding material of different thickness
For static loading or non-rotating components (no fatigue loading) you could use a fillet leg size that matches the thickness of the carrier pipe.
RE: Welding material of different thickness
RE: Welding material of different thickness
Sorry, but I have to disagree with your post. Fillet welds have typically higher strength reduction factors because of non-uniform stresses versus full penetration butt welds.
The source of fatigue crack initiation and propagation may or may not occur at the weld root versus weld toes. This is the reason why the NBIC does NOT allow the use of patch plates externally fillet welded to pressure retaining items as a repair.
RE: Welding material of different thickness
I would never disagree that a butt weld has much better fatigue and strength factors than a fillet weld.
RE: Welding material of different thickness
1. Why is the sleeve of X52 while the carrier is of X70 material(Basically, this would be the main contributor to the big diff in the thicknesses)? Is the sleeve a load bearing member or for say anode fixing?
2. What is the application and what is the code for fabrication (is it pipelines?)
3. Is it possible to taper the ends of the X52 sleeve with a 1:4 transition to meet the minimum leg length/throat requirements of the fillet weld as per the strength calculations?
4. What is the minimum throat of fillet weld required as per the design calculations and what is the consumable proposed for welding the materials of diff strengths?
Thanks and regards
Sayee Prasad R
Ph: 0097143968906
Mob: 00971507682668
email: sayee_prasad@yahoo.com
If it moves, train it...if it doesn't move, calibrate it...if it isn't written down, it never happened!
RE: Welding material of different thickness
2. The sleeve is for a hot tap. It has a 8" 600 ANSI flange that an 8" 600 ANSI ball valve bolts up to. The Design code is DOT 192, ASME B31.8
3. When I ordered the fitting I didn't realize that it wouldn't be beveled at all, but it may be possible to order them with a bevel in the future.
4. Don't know off hand.
RE: Welding material of different thickness
The point is that you will surely have had to do an engineering calculation for the sleeve to have obtained the minimum thickness of the sleeve. Exterpolating the same calculatons, you should be able to arrive at the minimum throat calculations for the fillet and work out the best possible leg lengths in this case. The consumable you will be using for the fillet weld will surely be LH with a strength in between the 52 and 70 grades. So you also should be able to use the actual strength of the weld metal/consumable to your benefit to arrive at a lower leg length if the client/code does not restrict the same.
Thanks and regards
Sayee Prasad R
Ph: 0097143968906
Mob: 00971507682668
email: sayee_prasad@yahoo.com
If it moves, train it...if it doesn't move, calibrate it...if it isn't written down, it never happened!
RE: Welding material of different thickness
RE: Welding material of different thickness
The pipeline is flowing natural gas at about 55 deg F and a velocity of about 7-8 ft/s.
Thus far, I haven't seen anything in the code that would prohibit a weld that didn't tie into the top of the sleeve.
It appears that there are different points of view on this page just as here in the office.
If the throat of the weld meets the minimum requirements, is there any benefit to tying in the top edge of the sleeve?
Can the full strength of the sleeve be achieved without tying in the top edge?
Pat
RE: Welding material of different thickness
RE: Welding material of different thickness
If the throat of the weld meets the minimum requirements, is there any benefit to tying in the top edge of the sleeve?
Can the full strength of the sleeve be achieved without tying in the top edge? "
Not tieing into the top of the sleeve would mean you have a sudden transition and this could be detrimental from stress distribution point of view. Hence, as a minimum, even if you wanted to avoid this, I would as a good practice ensure a taper on the sleeve end (1:4) to ensure a smooth transisiton, provided the design calculations allow me that change in the thickness of the sleeve.
Thanks and regards
Sayee Prasad R
Ph: 0097143968906
Mob: 00971507682668
email: sayee_prasad@yahoo.com
If it moves, train it...if it doesn't move, calibrate it...if it isn't written down, it never happened!