RT of Fillet Weld 1

[Meck91]

Folks,

Would appreciate your help,

Is this possible to do a RT of small bore fillet weld.
Previously I was of the impression that it is impossible to perform RT of fillet weld, however, after reading some literature I found that in most of the cases RT of fillet weld will not give you a proper indication of weld defects. Is this correct?

Secondly, If my closure weld is fillet weld, and to satisfy some jurisdiction requirements, I have to perform 100% RT in lieu of hydrotest. So how I should deal with this situation, should I go with UT for RT of fillet or any other advise would you like to give.

Thanks in advance.

Meck91

 

[metengr]

For fillet welds, I have seen RT used with limited success. I for one would avoid RT of fillet welds. If you need to have some evaluation of the volume of a fillet welds use surface NDT for the initial passes followed by surface NDT of a partially completed fillet weld followed by surface NDT of the completed fillet weld.

 

[stanweld]

RT of socket welds can be done; however, effective evaluation of the radiographic image is dubious at best. Assuming that the Design/Construction Code is B31.3, alternatives to the hydrostatic test are provided. The "golden weld" RT in lieu of hydrostatic testing is meant to be restricted to closure butt welds.

 

[deco0404]

If it is small bore, i'm assuming also that it is reasonably light wall, which pretty much precludes the use of UT. Can you give details of the joint & fit-up. As stated with previous two posts, RT on fillet welds is not the greatest way of determining joint integrity, but if it is the only option available to you, it can be done, but it is a tedious operation.

Declan

 

[Weldstar]

Agree with all comments, RT is possible on a fillet weld but will reveal very little infomation about the weld quality it self besides penertration and fusion characteristics of about 5-10mm on the film at once, hence why it takes so long to shoot a complete joint, if you are going to RT the thin wall joint X-ray would be preferable in place of Gamma to avoid over exposure as shooting a thin wall fillet means a large stand off and can be very difficult with Gamma.

If it is a socket style joint the one of the main purposes of RT on the joint is to check the gap dimension between the internal of the socket lip and the bottom of the branched pipe, most design and client specifcations require a 1.5mm minimum gap in order to allow for expansion and contraction during service.

Welding Engineer
MSc Weld Eng,IWE,CEng
Australia

 

[Kiwi2671]

Weldstar,
With all due respect I have to query your comment on socket weld gaps being designed for expansion / contraction during service.
B31.3 requires a 1.5 mm BEFORE welding to allow for expansion / contraction during the welding operation.
I have had numerous arguements with engineers who require RT of socket welds after welding and then reject if there is zero gap. It may have been a perfectly code compliant weld but contracted 1.5 mm during cooling after welding.(it is still basically a code compliant weld)
Surely if there was an engineering reason for a 1.5 mm gap AFTER welding the B31.3 committee would have revised the code to reflect this,
Regards,
Kiwi

 

[Duwe6]

Common problem when RTing 'for gap'. Only way to always look good on the RT film is to exaggerate the gap - 'pull back'. Even a gap of 3 mm may close up on stainless steel socket welds. I usually ask the pipefitter to hold a 4-5 mm gap on s/s, if I suspect that some idio . . . nervous engineer will want socket welds RT'd for gap.

 

[moltenmetal]

Any time we have such a client, Duwe6, we specify gap-a-let washers. Then you merely RT for presence/absence of the washer. Total waste of time, money and effort in my opinion, but the customer is always right if they are paying for it.