Right cleaning method for butt welds

[Javier Sanchez]

Hi to all! I am manufacturing an equipment for water handling in pipes in SS304 and I have some doubts about the right cleaning method for the butt welds for pipes, accesories, etc. The pipes have to be painted by project specfication (regardless being of steinless steel) and I am wondering if the shot blasting process prior painting would be sufficient to remove impurities from the weld. Is this a valid mechanical process for weld cleaning or a chemical process (e.g. pasivation) is always compusory? Is there any specific reference in ASME B31.3 or ASME IX code? I could only find suggestions for cleaning, but not proper instructions. Thanks in advance!

 

[nabeel3]

Check weather the painting is for Piping identification purposes, which is pipe colour coding. In that case u need only brush the pipe with the paint, no blasting is required. Usually wire SS wire brush is used for cleaning. i am not sure if blowing some compressed gas is used for cleaning.

 

[EdStainless]

Blasting works as long as the air is oil free (not just mostly free but completely) and the blasting grit is new and contains no Fe.
Typically if SS is to be painted the entire surface is prepared.
Most paints don't like sticking to SS, especially when it is smooth.
And I hope that this is in a dry environment.
Paint on SS can be bad news.

 

[mfgenggear]

OP
Being a while. But here is was I remember.
Blasting has a tendency to smear. However
It is great a fast way to remove oxide, and impurities.
It should be followed with hand cleaning with
Scotch bright and acetone cleaning solution if still allowed .
Welding should follow immediately after cleaning
By pipe fitter and welder.
I can't recommend enough to hire a weld engineer to obtain the procedure and weld schedule,
And run penetration and weld testing.

 

[Javier Sanchez]

Thanks to all for your answers. Painting is required for the whole pipe as protection agains corrosive environment (despite being SS), not just for pipe identification. The painting procedure is designed to be suitable for this kind of material, and as shot blasting is required to prepare the surface, the idea was to skip cleaning of welds after farbication because they will be already cleaned during the preparation of surface for painting.

From your answers I get this is a valid process and there is no incompatibility with ASME codes. Let me know otherwise. Thanks!

 

[mfgenggear]

Op
What does ASME say, that what needs adhered to

 

[Javier Sanchez]

Op
What does ASME say, that what needs adhered to

It says that either mechanical or chemical cleaning is necessary. But not necessarily the two of them

 

[mfgenggear]

OP
As general procedure I write in to do both.
Mechanical to remove oxide, surface corrosion,
To obtain clean parent material.then wipe off with a chemical cleaner like acetone.