52312

Valves rust because of water remaining after hydro test  

June 5, 2009

Dear all ,

We are manufacturing ball valves used in petrochemical industries. all the valves manufactured are tested for Hydro test with the water at different pressure ratings. After testing there is a possibility of remain some part of water inside the valve. Due to presence of the water there is a possibility of rust generation in valve which creates a problem at the time of erection which will be done approx. 3 to 4 months from the date of testing. We are doing manganese phosphating applying rust protective oil
Pls suggest
what will be the best thing to protect from rust?
What will be the recommended water quality?
What will be the other process which can improve rust protection other than manganese phosphate with applying rust protective oil?
Is it the D M water is good for the same.

Thanks

Anil Jadhav
manufacturing manager in valve industry. - Pune, Maharashtra, India

Hi, Anil. I'm sure you know the right answer and are avoiding it because it may be difficult to implement, but the valves have to be dried. To try to redesign the whole component and process to try to accommodate handling, shipping, and storing wet parts is the wrong approach.

If they are hard to dry with heat alone, you can try a vapor dryer (same as a vapor degreaser); but test it to make sure it doesn't hurt the manganese phosphate.

Regards,

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

Hai Anil,

Better go for Rilsan coating, it is like a powder coating but the thickness it will go little bit higher, based the the thickness your modify the part dimension before and after coating, or still you have a problem do high phosphorus electroless nickel plating

Kannan Boopathi
- Salem, Tamilnadu, India

Explore the possibility of pressure testing with a synthetic oil as a medium instead of water.After testing,store the valves in a suitable position to drain off and then dry wipe.Since you mention petrochemical industry,any small remains of oil in the valves might still be allowed, I guess.

Ravi Rao
- Belgaum, Karnataka, India

I do not know if you can find an equivalent in India, but we supply an Epoxy/Phenolic themosetting powder specifically formulated for the valve industry (approved by Water Board Germany). Should also resist most petro-chemicals. However, Ravi may have suggested a better route to explore.

Terry Hickling Martex Paints Ltd    Birmingham, UK