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Bolt Hole Repair Coupon

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MrGezus

Petroleum
Apr 29, 2014
73
Hello all. Thank you in advance for any information that you can share.

Every so often our facility needs to repair a bolt hole that was drilled in the wrong place. In the past we have qualified welding procedures to take corrective action. However the welder qualification is very difficult. We have gone through 30-40 coupons on several welders trying to pass these qualifications.

I am unsure if our hole design is best practice. What would a proper bolt hole repair coupon look like?

Capture_vgwnkp.jpg


This picture is how we machine our coupons. I have read that it is easier to do it with a different shape, but I cannot think of where I saw that. Our biggest issue is only having one or two welders qualified to perform such a weld.

Any help will be greatly appreciated.

ASME Section IX
API 6A
 
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What you need is to have a plug weld procedure. Get rid of the pointed bottom, introduce a larger radius at the bottom to side wall transition. I would guess the problem is lack of fusion defects or inadequate fill based on current geometry.

Have the welder qualify on a flat plate using the modified weld prep. Qualification can be done by sectioning through the coupon and ensuring complete fusion and penetration. This is all that is needed.
 
Also, use the search feature above because other similar questions probably have been asked;

thread330-232318
 
Are you trying to complete fill the hole with weld (filler) metal? Or are you "plugging" the hole with a shape that goes in the hole?

That tiny opening and small 60 degree opening angle isn't giving the welders enough room to get to the bottom of the hole with any accuracy and thoroughness.
 
Yes, we are trying to fill completely with filler metal. I don't know the reason for it. It is mostly used to repair bolt holes drilled incorrectly in an API block. If we were to use a plug and weld on top, and have to re-drill only a few degrees away from that, there would be loose plug metal.
 
That much filler metal into a deep hole is very, very difficult to lay in perfectly and without "any" defects from bottom to top. Use a threaded plug, welded around the top with a pair of 37 degree bevels in the base metal and plug. 3/8 deep or less, no more than 7/16 weld.

Better yet. STOP putting the holes in the wrong place in the first place!
 
I wish they would stop putting holes in the wrong place. It doesn't happen often but it does happen. We cannot use a threaded plug as the hole will be drilled in to a portion of the misaligned hole. This is why we have to weld it. Does the weld qualification coupon have to follow any guidelines to be correct? In API 6A (Excavation for repair) shows a second design that I think can be used.
 
"We cannot use a threaded plug as the hole will be drilled in to a portion of the misaligned hole. "

How far out-of-position are the worst holes?
The largest catalog "solid" keensert is 1-3/8" requiring drilling a 'tap drill" sized hole of 1-5/16".
page 6 here -
 
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