Lap-welded Patch Plates on Repair of Fixed Roofs

[Guibar]

Hi everyone.

Is there any guide or recommendation about weld patch plates as repair of fixed roofs?

I could not find any indication in API 653.

Regards

 

[Dhurjati Sen]

Think of the safety angle of Operation and Maintenance personnel before going for a patch. API 653 thinks the same. You need to replace the corroded portion of the roof from weld to weld.

DHURJATI SEN

 

[HTURKAK]

API STANDARD 653 section 9.11 (REPAIR OF FIXED ROOFS ) applicable for your case..
Regarding the size of replacement parts,

API RECOMMENDED PRACTICE 575 section 10.2.5 states ( Roof Repairs
Roof plates can usually be replaced in the same manner in which they were installed when originally constructed.....)

the expression (weld patch plates ) implies hot work is permitted..is this true ? what is the service ?

 

[r13]

API 653 only provides requirements of plate thickness, and source for stress check, not the method. Per the language from API 575 indicated in response above, IMO, the answer to your application is no, unless the original roof plate was installed as thus.

 

[Guibar]

Hi everyone. thanks for all very clarifing answers. HTURKAK, we can perform hot work on it. The tank has been cleaned.

 

[MechEngTrojan]

There are some non-metallic alternatives that you could use until the next T&I, but then you will probably need to replace the plate as a permanent repair.

 

[IFRs]

API 653 is mostly silent on this, only mentioning roof plates in 4.2, 9.12 and 10.3.4. As mentioned above, API 575 only says that the manner in which you install the repair plates must be the same as the original, typically seal lap welding. Normal cone roof plates are not on the pressure boundary, their condition does not affect the ability of the tank to safely hold liquid. In my opinion, as long as you cut out the corroded area back to good steel you should be good to go.