Caustic Service Material Selection

[NeedAHoliday]

I have a solutiona at less than 65C and at pressure of 230kPaa. It will contain <4% NaOH but could see upto 48% in case of process upset/failure. I normally use PVC or PP or HDPE for this type of service but I have recently begun to think about steel for some of my applications.

I don't want to go exotic but have read a bit on the subject and I think goold old faithful standard grade carbon steel pipe will be sufficient for the task.

Could you materials experts give comment??

 

[NickelMet]

Per the Caustic Soda Service Chart (NACE Handbook, 3rd Ed., pg 192), at the given temperature of 65°C:

- for the <4% NaOH, you are in the carbon steel use Area 'A' (no stress relief necessary normally, but does recommend the stress relieving of steam-traced lines)
- for the occasional upset to 48% NaOH, you will cross into Area 'B' which is also carbon steel use, but it should be stress relieved on the welds and bends (you cross over into this area around 25% NaOH)

Also, NACE has a booklet:
- RP0403-2003 "Avoiding Caustic Stress Corrosion Cracking of Carbon Steel Refinery Equipment and Piping".

Per the website info:

"This standard recommended practice is intended to provide guidance to those designing, fabricating, and/or maintaining carbon steel equipment and piping that is exposed to caustic environments. An informal review of current industry caustic handling practices was completed in 1999. This standard incorporates the findings of that survey as they apply to refinery applications."

~NiM

 

[NeedAHoliday]

Thank you for the response, most appreciated.

K.