SS316L pipes internal Oxidation or Corrosion , Cleaning

[URKumar]

Hi,
we have an issue on site with the SS316L pipe internal joints areas "Oxidation / Corrosion" marks, need and expertise advice how this can be handled to clear the marks any other solution w/o proceeding with circulation cleaning, reason being asked for all the pipes are installed on-board of vessel. please advice.
REgards,
RK

 

[quark]

Passivate the piping with 5% Nitric Acid. Circulate for half an hour to an hour.

 

[Dhurjati Sen]

Dear URKumar,

What is the pipe size? How did you find out the oxidation / corrosion marks in the internal portion of the welded joints?

Regards.

DHURJATI SEN
Kolkata, India

 

[EdStainless]

First you have to decide what it is you are doing and what you want for a result.
IF this is superficial then 5% nitric is perfect.
However if you have heat tint or other serious issues then you would have to actually pickle with Nitric/HF to remove it.
More background is needed.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy

 

[URKumar]

Dear Dhurjati sen,

my apology for late response, as im on year end holiday,
regarding your query for the pipe size it is 8" line and ship owner notified the black strains inside of the welded joint. this could happen deep inside of other joints as well, so to understand more, how this can be cleaned without circulating method.. ( need an advice if any other possibilities to rectify this issue ),

Regards,
Ravi

 

[Dhurjati Sen]

Dear URKumar,

1. Ask the ship owner exactly how did he find out the black stains?

2. Carry out a boroscopic survey of a few weld joints at random from your side.

3. Find out what are the cleaning / circulation activities Operations would carry out before commissioning this piping.

Now you could reach a decision.

Regards.



DHURJATI SEN
Kolkata, India