Author Topic: Weld Symbols  (Read 8027 times)

tiggerfaebigger

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Weld Symbols
« on: February 18, 2011, 06:01:44 AM »

Hi Lads,
I hope all is well.
I have a quick question if you do not mind.
I came across a weld symbol today which confused me a wee bit.
The symbol showed a double v-butt with bevel preparation depth of 16mm each side on 36mm thick plate which results in a root landing of 4mm.
Now i am sure  that if the penetration of the weld is to be greater than the depth of the groove bevel  then the depth of penetration should be given in parentheses (xx) after the depth of bevel. If the depth of penetration is obmitted then i take it then all is required is penetration of 16mm each side of the plate.
Thanks in advance for your replys.
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control-arc

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Re: Weld Symbols
« Reply #1 on: February 18, 2011, 09:15:40 PM »

im not a design engineer but it seems strange to just leave 4mm of incomplete penetration, its not really goin to save time or money

i had a look in as 1101.3 "graphic symbols for general engineering - welding & nde"

i found clause 4.2.4 "depth of preparation specified, design throat thickness (DTT) not specified, or specified eleswhere"
this just shows the symbol and says nothing about size of weld.
the "specified elsewhere" might be worth checking, the DTT may be written somewhere else on the drawing eg: "all welds to be complete penetration unless noted otherwise" but when  they do this they usually leave preparation size and shape to the  choice of the fabricator.

the usual way to draw a weld symbol for an incomplete penetration butt weld with penetration depth equal to the preparation depth is to just specify the DTT (xx) and desired preparation shape eg: double vee, single vee, etc

for depth of prep different to DTT the symbol requires both size of prep and DTT to be displayed

it could also just be an error on the drawing, it may be worth checking with the client just to be sure.
i have recently seen a drawing with symbols for a fillet weld in a corner joint with the symbol on the wrong side of the reference line,it was obvious what they wanted but wrong none the less, hope this helps
« Last Edit: February 19, 2011, 02:11:40 AM by control-arc »
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Flash

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Re: Weld Symbols
« Reply #2 on: February 18, 2011, 10:49:22 PM »

Hey TFB
firstly make sure you know what standard you are working to 1101.3 or ISO2553 as there are differences
but from your description it sounds like 1101.3
maybe post an image of the weld symbol and confirm what standard you are working to
R
Flash
« Last Edit: February 18, 2011, 10:58:38 PM by Flash »
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Graham Fry
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Ballbearing

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Re: Weld Symbols
« Reply #3 on: February 20, 2011, 11:05:27 PM »

The other possibility is that it is intentionally a PJP to get away from having to UT/RT or even having to backgouge.
Hypothetically, a SAW weld from both sides should be able to achieve 18 mm depth of penetration (on a 16 mm prep) without backgouging so you will end up with a CJP but because it is classified as a PJP it does not require volumetric testing.
Hope I have made sense,
Cheers,
BB

PS. Flash, have sent a couple of e-mails to [email protected] but have had no response - did you receive them ?
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Flash

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Re: Weld Symbols
« Reply #4 on: February 21, 2011, 01:20:21 AM »

Sorry about the emails BB, technical error, I should stick to welding, I have a new machine and forgot to setup the welding flash admin account on it
thanks for pointing it out
R
Flash
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Graham Fry
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tiggerfaebigger

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Re: Weld Symbols
« Reply #5 on: February 21, 2011, 02:44:08 AM »

Hi Lads,
The weld symbols should be to AS1101.3. The rest of the drawing is complete penetration welds which leads to the confusion.
There is no throat thickness evident just a bevel depth. The welding process is inershield and the client specifies that all critical butts are 100% UT/MT and all other butts 30% UT/MT even partial pen butts are UT.  My thinking is that the welders should achieve 2mm penetration either side of the butt weld and therefore achieve a full pen weld anyway, however if they do not, then do you go with the depth of bevel for the required penetration? The other way is to back grind to clean metal in order to achieve full pen.
 I think i have just answered my own question!
Thanks
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Flash

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Re: Weld Symbols
« Reply #6 on: February 21, 2011, 03:03:42 AM »

Hi TFB
its optimistic to thing that innershield (DC-) will penetrate to pick up the root
Generally the depth of pen is verified by UT if it is Partial Pen to make sure you have the required throat

You could go to full pen to make sure, but it depends how many meters you have to do using this configuration, if it was 1m no worries, if it is 100m I would not be so keen
R
Flash
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Graham Fry
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tiggerfaebigger

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Re: Weld Symbols
« Reply #7 on: February 21, 2011, 05:15:14 AM »

Hi Flash,
Yeah your right to think its optimistic and UT is required to verify the throat thickness and the NDT report will state the size. As the drawing is not showing the throat and only the depth of bevel my only action would be a back grind to ensure full pen to prevent repairs at a later date.
Thanks
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cassgazz

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Re: Weld Symbols
« Reply #8 on: February 22, 2011, 05:17:45 AM »

Could always shoot the client an email as to what they require, at least this way there is a permanent record. Even print the email off and compile it into the MDR if they say partial pen.

My thoughts though - having a 4mm root face +/"-" 1mm, full pen would be the better option.
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