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Up Topic Welding Industry / Inspection & Qualification / NDT in Hot tapping activity
- - By tfdavid (*) Date 08-25-2010 14:51
As an inspector of hot tapping activity, where a split tee (fitting) consisting of two half sleeves that are jointed around the pipe by longitudinal and circunferencial welding,  API 1104 doesn´t mention what are the NDT´s required to control the longitudinal and circunferencial welds. It only mentions the acceptance criteria of defects for each NDT. Radiography is very difficult to apply because it is a pipe and no access to inside it. For another hand, US are not applied to the circunferencial welds because of the configuration of the weld that doesn´t allow the US instrument to get the right angles to send out the waves and receive them back in order to read appropriate signals of the defects. So the circunferencial welds are only submited to Magnetic particles. What do you think? Is this enough to assure the structural safety of the weld? Is there any code that demands specific NDT for this particular case of welding a fitting to the pipeline under pressure?
Parent - By L51174 (**) Date 08-25-2010 17:09
MT would be my first option (if no method was specified) for the circumferencial welds as they are fillet welds, PT being my next choice. You didnt mention the pipe size so if it was a multi pass fillet I'd want to get a look at the first pass, as well as the finished weld. MT may also permit you to examine the first pass without coming below interpass temperature. The longitudinal welds are groove weld with the pipe as backing? Could possibly be RT'd, again depending on the pipe size, but MT of the root and final may be adequate. These fittings are cast I believe so without a calibration standard or mockup of similar shape, material and heat treatment I wouldnt try UT.

Thats my best guess, anyway. Does the drawing not specify any NDT method?
Parent - - By raptor34 (**) Date 08-26-2010 03:05 Edited 08-26-2010 03:09
I have done many hot taps in my day and here is what is typically done,  In the case of seamed pipe and if the seam will be in the bore it will be x-rayed to check the integrity of the seam.  Next UT is done on the line to determine base thinkness.  Some companies will then do a wet mag of the parent pipe to check for hydrogen cracking.  After the hot tap is welded out it will again be wet magged.  As far as code requirements for an NDT method, API 1104 20th B.5 says that it should be a method able to detect hydrogen cracking and suggests MT and UTSW.
Parent - - By jon20013 (*****) Date 08-26-2010 05:31
Try to lay your hands on an API RP 2201 Safe Hot Tapping Practices in the Petroleum & Petrochemical Industries.  Regarding NDE I would tend to agree an MT should be enough.  I wouldn't try PT because your base metal temperature will obviously be relatively high.
Parent - - By 3.2 Inspector (***) Date 08-26-2010 13:39
Let's pray that it's not a SS pipeline ^^

3.2
Parent - - By Shane Feder (****) Date 08-26-2010 14:28
3.2,
API 1104 is not applicable to SS piping systems so you can stop praying.
Regards,
Shane
Parent - - By 3.2 Inspector (***) Date 08-26-2010 14:41
Geeeee, my lucky day.
jon mentioned API RP 2201 Safe Hot Tapping Practices in the Petroleum & Petrochemical Industries.

Should I keep praying?

3.2
Parent - - By Shane Feder (****) Date 08-26-2010 15:23 Edited 08-27-2010 01:10
Seriously 3.2, I/we realise that English isn't your first language but a lot of your responses come across as very sarcastic.
Hopefully it is the differences in languages and not intentional,
Regards,
Shane
Parent - By 3.2 Inspector (***) Date 08-26-2010 16:41
How was the bar tonight?

3.2
Parent - - By raptor34 (**) Date 08-28-2010 02:17 Edited 08-28-2010 02:27
I disagree with that.  I have seen miles and miles of SS pipe laid to 1104.  Granted the NDT method would change to PT, but I have seen it done.
Parent - - By Shane Feder (****) Date 08-28-2010 03:17
Raptor34,
My comment was API 1104 is not applicable to SS piping systems.

From API 1104 2005
1.1 SCOPE
This standard covers the gas and arc welding of butt, fillet,
and socket welds in carbon and low-alloy steel piping used in
the compression, pumping, and transmission of crude petroleum,
petroleum products, fuel gases, carbon dioxide, nitrogen
and, where applicable, covers welding on distribution
systems.

Which steel group does SS fall into - carbon or low alloy ?
Neither so it is not applicable,
Regards,
Shane
Parent - By jon20013 (*****) Date 08-28-2010 03:21
Not completely unlike so many folks using D1.1 for stainless steel ~ I include people who SHOULD know better in this comment.
Parent - By raptor34 (**) Date 08-28-2010 22:17
I stand corrected.
- By Tim Rich (*) Date 03-28-2011 09:22
I can tell you how we do it in our oil refinery.
1. UT for base thickness ( the pipe for beeing hot tapped)
2. PMI all materials to be welded including the welding rods
3. Hot weld meetings which includes ops., safety, coordinators, welders, and management.
4. verify flow is in correct range and monitored throughout all welding (and hot tap, stopple)
5. use 7018 3/32 only for root pass, fill and cap on carbon
6. vt and wet mag root pass and cap (on hot piping) pt (on cool piping)
7. hydrotest split or barrel type tee at completion of weld
8. Hydrotest hot tap machine and stopple machine (after heads are changed)
9. Hot tap meeting (same people as hot weld meeting)
10. Go for it!
Up Topic Welding Industry / Inspection & Qualification / NDT in Hot tapping activity

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