LP Flare Header repair waiver PWHT

[MrR1]

We have corrosion localized to the bottom of the line mainly due to deposits along the bottom of line. We want to repair corroded Carbon Steel LP Flare Header by welding external lap-patches/plates to the bottom part of the header (only for significantly corroded straight run parts (5mm - existing WT) from 4-8 o'clock on 30"/32"/36" line). Header's Operating Pressure =0.1 Barg, Operating T= 45-50deg C, insulated with electric heat tracing. The header originally was PWHT-ed and Hydro tested.

[highlight #FCE94F]Is it possible to weld plates without PWHT right after the line will be cleaned?[/highlight] What kind of hidden/open obstacles we might face with this option (corrosion cracking, chloride cracking, thermal stress, weld across the bottom of the thin line at the end of each section of lap patch and possibility to burn through) and how to avoid/minimize it?

Please help with this non-standard situation.

 

[georgeverghese]

Normal operating press= 0.1barg; process design pressure = ??

 

[MrR1]

georgeverghese,
Process Design Prssure: 5 Barg. Max operating Pressure which was during operation: 4Bar in September-2012.

 

[SJones]

For what reason was PWHT required in the first instance?

Consult ASME PCC-2.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.