thePetroStreet

We have a cladded vessel at our plant containing low pressure corrosive service. While in operation the external shell of carbon steel got corroded due to leakage from sight glass; total damaged area is like 2 feet by 3 feet. Now the situation is that the cladded material SS 316 is exposed. The thickness of cladded plate is barely equal to the pressure design thickness. We want to seek advise on the repair of the same. Should we go for the repair and if yes what should be the procedure?

We have gone thru a similar kind of situation recently. There is no complexity in repairing such damaged CS part of the cladded vessel. A very simple repair procedure can be employeed for this as below:
1)- Flush the uneven corroded portion of CS part from exposed cladding very carefully w/o damaging / penetrating in exposed cladded sheet. The purpose is to make the surface even.
2)- Place a 2'x3' CS or SS sheet on corroded area & weld at lower amps so that welding heat does not damage the fusion of cladded sheet with the vessel.
Electrodes shall be used as per the materials welded.
Hope this would help.
Nabeel

Nabeel,

1-What kind of NDT required for above procedure.Is vessel needs to be hydrotested??
2-Is there any referance available for above kind of repair in international codes??

RGR

Dear Forum Member,

Please follow API 510 CODE or ASME/ANSI NB-23 CODE as reference.

Thanks
NNREDDY

Look in PCC-2 also for this specific repair.
As per Article 2.1 "Butt weld insert plates in pressure components, the repair procedure adopted by Nabeel appears to be OK if he has considered all the requirements listed.

Hi,
Usually thickness of cladding is not considered to contribute either partially or fully to design thickness unless this thickness is included during min. thickness(design thickness) calculation for that vessel. Damaged/corroded shell plate may be repaired by removing a section and replacing it with an insert patch (flush patch). Please refer to NBIC-23, API 510 or ASME PCC 2 more details

Regards,

Inconel

Thanks everybody for the valuable inputs.