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Reinforcing Pad Vent Hole Location

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wsmith22

wsmith22

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Nov 9, 2005
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Is there a standard location to orientate the vent hole on a reinforcing pad for ASME Section VIII, Div.1? ASME B31.3 says to put it on the horizontal centerline (not at the crotch). API-650 same thing. The Dennis Moss Handbook says at least 45 degrees from horizontal centerline. My shop says on the vertical centerline of the shell. Does it really matter?

Moss also indicates that an air test should be done on the reinforcing pad. My understanding is that this has never been the intent of ASME Section VIII, Div.1 and is not required.

Thank you,

Wes
 
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wsmith22, I don't believe there is any Sec VIII, Div. 1 standard location. I generally try to put 'em on a longitudinal CL.

I also don't believe air test is required by Code either, but it is pretty much universally done. To me, it's money not worth saving...

Regards,

Mike



The problem with sloppy work is that the supply FAR EXCEEDS the demand
 
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Wsmith22:
I don’t know the ASME codes as well as you guys should, so take this with a grain of salt. If there are no significant repad stress implications, I would put the vent hole as low as practical on the repad. I would like it to drain rather than take on and store water, if this can happen.
 
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See Process Industry Practices PIP VESV1002 Vessel Fabrication Specification
"Reinforcing pad attachment welds and accessible surfaces of inside nozzle to vessel wall welds shall be tested for the absence of leaks with a gauge pressure of 15 psig (100 kPa) dry air or nitrogen and bubble forming solution.
This test shall be prior to the final hydrostatic or pneumatic test as applicable"

Also this test is made when pad is over vessel weld seams.
Inspection is made from inside of vessel (if possible)

Also see ASME V for bubble solution test.

Regards
r6155
 
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What would be the problem if a repad leaks? Isnt it's sole intention to provide additional strength and distribute stresses of supports/brackets/nozzles more evenly?
 
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r6155, thanks for the detailed sketch. Although I understand that situation, a lot of (other) repads dont necessarily 'run' over weld seams.
As an exmaple, see the attached repad for a lifting lug.

Im not criticizing the application of vent hole, I strongly suggest them myself too, but whats the rationale on air testing that repad?

sketch_kvsizd.png
 
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Air test in pads (continuous fillet welds) is one more inspection examination to detect possible defects (cracks) not found with others examinations. Air test (bubble test) is rapid and easy to do, especially for lifting lugs on big weight components.
Regards
r6155
 
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Although a simple test and often required in client specifications. Air test is not required for Sec VIII Div. 1 - See UG-37(g). These holes may be left open or plugged (often with grease). One odd situation of the code for segmented reinforcing pads - UG37(h)(2) - "Each segment of the reinforcing element shall have a clear path to a telltale hole and shall be tsted as required by (g).....yet the below interpretation.

Interpretation: VIII-1-13-10
Subject: UG-37(g), Split Reinforcement Pads (2010 Edition, 2011 Addenda)
Date Issued: April 25, 2013
File: 13-115
Question: Is the compressed-air and soapsuds test mandatory for split reinforcement pads?
Reply: No.
 
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Air test in pads (continuous fillet welds) is one more inspection examination to detect possible defects (cracks) not found with others examinations. Air test (bubble test) is rapid and easy to do, especially for lifting lugs on big weight components.
Click to expand...
I agree it's easy, but I dont see the big plus for doing it on standard repads which dont comprise to a pressure bearing part (e.g. nozzle), or which are welded over a weld seam.

What if there's 1 small crack in the (continuous) fillet weld? i dont see why the repad would fail then.
 
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@ XL83NL
Try to understand that defects are not allowable and shall be repaired, like cracks.
Please see in my sketch “WELD TO BE TESTED”: fillet weld around pad in nozzle is not the objective for examination. Air test is the objective to detect leaks in the weld between nozzle neck and shell.
Same concept to pad over a weld seam. Think about in service inspection too.

Regards
r6155
 
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I do understand, but I think a crack in a fillet weld on a repad (when it's not a repadded nozzle or a repad over a weld seam) is a lot less important than a fillet weld in a set-on nozzle to shell weld seam.. The only issue I can think of is that that crack would start to propagate due to cyclic behaviour, and eventually rip off the complete repad.
 
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XL83NL, the vessel's in service condition is a consideration as well. Suppose a re-pad, any re-pad, any location, is pressure tested and found acceptable, no leakage under pad, no leakage from fillet weld.

Now then, as the vessel ages in service this pad may be monitored, by visual means (grease or sealer squeezing from the vent hole) or by actual pressure test for condition of vessel components beneath the pad.

If leakage at the pad were permitted at fabrication this would not be possible.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand
 
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