Dear Mr.Herman Pieper ,
Thanks for your detailed reply. Initially we also thought of repairing it upto 15 mm thk. But our previous experience in the company on DSS shows internal creater cracks inside castings though they appear to be pinholes from outside. Cobalt RT source is not available in our place for RT of the defect location.One of my colleague suggested me to carryout Phased Array Technique.
Can you please write me your experience with phased array technique on such castings.
Regards
Srinivasa Murthy Hari
On Sun, Mar 7, 2010 at 9:22 PM, hpi001 <pieper-qsi@kpnmail.nl> wrote:
Dear Sir,
Unfortunately it's not easy to perform Non Destructive Examination on
castings especially when you want to find some small pinholes in 100
mm thick Duplex Stainless Steels. I'm working for a foundry where we
cast such pump casings as well and I must say the only reliable way of
NDE is radiographic examinations, but than only for larger type of
failures. We always perform 100% Dye Penetrant examination on the both
internal and external surfaces of pressure containing parts as casings
in order to find any pinholes. If we find any pinhole we remove the
failure as far as possible by way of gouging and perform repair
welding. I have to say that this involves always materials in the as
casted condition so we easily can execute such repairs because this
will be followed by final solution heat treatment in order to solve
any unwanted microstructural . We often try to find indications with
Ultrasonic Examination, we even tried Phased Array but than as we
assume the casting is without any identification because of the UT
examination often not acceptable indication will be found during
machining.
In my opinion there are no examination methods to identify the path of
such pinhole through the wall thickness.
If, and I assume this will be the case, the casing is in the final
condition I only can propose to remove the indication carefully up to
a depth which can be welded without getting any problems with final
dimensions due to shrinkage. I don't think it will be technical
possible to remove the full indication but when you can repair the
location afdoende for about 15 mm depth from both surfaces you won't
have a problem with the pressure inside the casing.
If you allow repair welding be sure that the company who's performing
such has a PQR for repair welding without any heat treatment
afterwards. Because when you need to perform such heat treatment you
can get problems when assembling the pump afterwards because of
possible distortion.
Best Regards,
Herman Pieper
--
On 7 mrt, 10:16, Hari Srinivasa Murthy <harimur...@gmail.com> wrote:
> Dear Friends,
>
> Recently in one of our water injection plants, we experience leak from a
> pump casing.The leak was due to a suspected minor pinhole. Pump casing is of
> Duplex Stainless Steel (ASTM A 891). Casing thickness is about 100 mm. Pump
> working pressure is 5000 PSI.
>
> We have opened the pump performed DP on the casing internally and
> externally to identify the path of the leak and causes of leak. We have
> identified 4 suspected spots from inside the casing, which could lead to
> the leak. We have taken Radiography (using Ir192- 14.2 ci) of the casting
> with high exposure times but could not get any clear result. We have also
> used available low frequency VSY UT probe to detect the cause of the leak.
> This probe could provide us details of casting defect up to 15-16 mm only.
> We could not decide the leak path withis information.
>
> With the above background, I would like to request our forum specialists to
> suggest me NDT methods to identify the leak path throughout the casting
> thickness and to share related experiences if any in your facilities.
>
> Regards
>
> Srinivasa Murthy Hari
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