Tank annular bottom plate welding visual inspection

[Sam]

dear experts,

During weld visual inspection of storage tank annular bottom plate butt joints welding with backing strip, i found some length (50 mm) with excess penetration and Burn through (root concavity) on backside (soil side). it means it is on backing strip side.

annular plate thickness = 10 mm

backing plate thickness = 3 mm

1) may be burn through defect is only in backing strip or it may extend up to annular plate ?

2) i have removed excess penetration from backing strip side. we can see some fusion problem at backstrip. but is there chance it will extend upto annular plate ?

How will we evaluate this defects ?accept or reject. because we may got full penetration for annular plate and defects are in only backing strip. it is very difficult to remove full joint and reweld with new backing strip.

regards,

sam.

[Jorge Mejía Lema]

Ok!! Mr. Sam, I will recommend to do UT Phase Array, to discover if the annular plate has a good welding thickness. The backing is only to get a welding penetration.

Regards,

jml

2013/10/24 Sam <onlypri...@gmail.com>

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[Perumal Govindan]

Take radiography of an annular plate and interpret as per API 650 or as per code / as per client requirement.

Further refer below for more info which is mentioned in API 650,

8.1.2.9  When bottom annular plates are required by5.5.1, or by M.4.1, the radial joints shall be radiographed as follows:

 (a) For double-welded butt joints, one spot radiograph shall be taken on 10% of the radial joints; 

(b) For single-welded butt joints with permanent or removable back-up bar, one spot radiograph shall be taken on 50% of the radial joints. Extra care must be exercised in the interpretation of radiographs of single-welded joints that have a permanent back-up bar. In some cases, additional exposures taken at an angle may determine whether questionable indications are acceptable. The minimum radiographic length of each radial joint shall be 150 mm (6 in.). Locations of radiographs shall preferably be at the outer edge of the joint where the shell plate and annular plate join.

P Govindan  

[Samun Bhatia]

Dear sir, can we check by RT of that area and compare density of defect to annular plate? B,se UT phase array is not in the contract. As 3mm backing strip we may got complete penetration at annular plate.
Sent from Mobile

Jorge Mejía Lema <jmeji...@gmail.com> wrote:

Ok!! Mr. Sam, I will recommend to do UT Phase Array, to discover if the annular plate has a good welding thickness. The backing is only to get a welding penetration.

Regards,

jml

2013/10/24 Sam <onlypri...@gmail.com>

dear experts,

[Bala Murugan]

Dear All,
Yes i agree with Mr. Perumal, as we also done 10 % RT In annular
bottom plate and it is possible.

Thanks,
Bala