3 replies to this topic

[vvCephei]

Hello,

 

I'm doing a project which requires me to make a lab scale setup of a Reverse osmosis process where i would need to try and clean the fouling with chemicals. I would like to ask what time of material of piping would be suitable for my usage. I would be using Phosphoric Acid and Sodium hydroxide at around 0.1% v/v to 0.3%v/v with pressure around max 10 bar. I heard from my friend PVC is chemical resistance however i heard it doesn't deal well with pressure, but he said by increasing the schedule of the pipe would solve it.  I hope someone can give advice on this. 

 

Thank you.

[Art Montemayor]

See:

 

The best thing you can do when working in a laboratory or pilot platnt environment is to totally forget about using PVC (or any plastic) pipe for process fluids.  This is especially true when dealing with acids or strong caustics - like sodium hydroxide.  You simply cannot afford to have a leak, spill, or pipe rupture when dealing with these chemicals in a closed, lab environment.

 

Besides the fact that PVC has some other negative properties besides no handling high pessures, you will find that PVC has a notorious coefficient of expansion that forces you to allow for stresses built up by the pipe's expansion in length.  Additionally, you do not know how the different chemicals will react to the glue or binder used to make the different PVC pipe joints.  Remember: you are depending on glue to keep the joints structurally intact and secure, without leaks.

 

For your operation I would employ carbon steel pipe or tubing.  I would weld all joints and minimize the number of pipe flanges.  I would certainly never use pipe couplings for acids or caustics.  These always leak and are a constant hazard.

[emd.franz]

Hi!

 

I am not familiar with the whole process of reverse osmosis. Is this a hygienic practice? what is the temperature?

I agree with sir Art, I would not also use PVC when dealing with acids. In our plant, even the Stainless Steel 304 is not recommended in the Phosphoric acid line. For that piping we use S.S. 316. Please check on this material.. try to look search also on the compatibility materials for your chemicals and note your process parameter.

[samayaraj]

PTFE, PP, Polycarbonate, are having excellent resistance against phosphoric acid and sodium hydroxide. PVC is fairly good against phosphoric acid. So, you can use PTFE/PP/Polycarbonate coated carbon steel pipes.

Edited by samayaraj, 28 September 2013 - 04:22 AM.