48909

Residues from Mechanical Polishing Hastelloy [UK] 

May 30, 2008

As part of a recent chemical plant, a vessel was designed and produced from Hastelloy C-22 with a mechanical polish. During plant commissioning, there were no issues when commissioning with boiling water, but once boiling solvent (MEK, MIBK) was introduced grey residues started to appear on the filters downstream of the vessel. This has been analysed as containing hastelloy.

My question is whether this is simply inclusions of residue from the mechanical polish that was not cleaned properly or it is some other phenomena that someone has experienced. The parts of the plant that were electropolished do not experience this phenomena hence I suspect it may be polishing residue.

I'd really appreciate any comments or expeerience on this. Also if it is included polishing residue, how should it be cleaned?

Best regards

Huw Thomas

Huw Thomas
Product Designer - Reading, Berkshire, UK

Hi, Huw. I suspect that your suspicion is correct. Polishing compounds consist of abrasives suspended in binders, and the binders are soluble in solvents, which leaves the grit behind.

Although I have no experience in commissioning piping systems, we see a similar problem with buffed components when cleaning is attempted in a vapor degreaser (the binder runs off but some of the grit stays on the parts). In the metal finishing field we recommend cleaning with something that imparts mechanical energy first (ultrasonic cleaner, spray washer, the scrubbing bubbles of an electrocleaner, etc).

Regards,

Ted Mooney, P.E.  finishing.com Brick, New Jersey

Ted

Thanks for the reply.

Are you aware of any chemical treatment that would help remove the included material. Ideally without affecting the polish but I'm expecting that is highly unlikely.

Would in-situ electropolishing be of use in removing the surface and opening up any traps where the materuial is being held?

Thanks

Huw

Huw Thomas
- Reading, Berkshire, UK

Hi, again. You have me at a disadvantage because, as I say, I've never commissioned a piping system like this. But my experience is that chemical treatment leaves the abrasive particles behind. Electropolishing is not a cleaning process, but requires a precleaned surface. But if you are able to electropolish in the circumstance, I think you can electroclean with detergent and alkali.

Regards,

Ted Mooney, P.E. 
finishing.com
Brick, New Jersey

Hello,

Probably the solvent are cleaning up the "smooth" leaft by the grit media.
Other way:
Total Removal of imbeded grit particles is difficult. We have tried all methods.
Here are some suggestion for next time:
Use less Grit pressure.
Use smallest grit media.
Use short dwelling time.
\
Jose Castellanos

Jose Castellanos
- Minneapolis, MN, USA