RO vs DI and Humidification

[MitchWitt]

Reference: thread338-310277

I am somewhat surprised in reading some of the posts and comments on RO and DI Water.
Both have been in wide use for over 20 years in Semiconductor and Pharmaceutical manufacturing.

DI is produced after the Reverse Osmosis process. Key word is "after".
For humidification of non semiconductor related processes/clean rooms, I don't see the cost benefit of de-ionizing
RO water. A properly operated RO system should be more than adequate for clean steam humidification.
The optimum material for piping RO water is anyone of a variety of plastic piping systems including (from best to least desirable) IR Fused
PVDF, IR Fused Polypropylene, CPVC and Low Extractable PVC. Note: CPVC/PVC joined with socket type fittings is undesirable as sockets are
not high purity rated. Make no mistake, RO Water is high purity, by definition.

For clean steam one must install clean piping. Because of the temperature the favored material is stainless steel, electro polished 316L to be exact.
The primary document world wide that covers every aspect of installing high purity stainless steel for this service is ASME BPE 2019. This material
is joined using automatic orbital GTA welding. It cannot be manually welded.
The systems are all butt welded by automatic process. The piping, valves, regulators, etc., are all quite
specialized as is the welding process. This welding needs to be performed by experts. You are inviting problems if you employ any company to
perform this work that does not regularly install work in semiconductor or pharmaceutical plants. I've been involved in this specific discipline
since the mid 1980's and have seem my share of disaster's. Contact me with any questions.

 

[EdStainless]

The purity of RO depends on the membranes used and the operational details.
For drinking water applications getting the TDS to a couple of hundred ppm is usually what is desired. No one would drink water with 2ppm TDS because it tastes awful.
One thing that often overlooked with either RO or DI is the dissolved gas content. A high purity water with some CO2 in it can be very aggressive.

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P.E. Metallurgy, Plymouth Tube

 

[quark]

I am not sure about electronic industry but there are definite rules for Pharma. The condensate quality of steam utilized for humidification must conform to the final quality of water we use for production. For ex. if the production is of oral solid dosages then humidification steam condensate should conform to purified water starndards (conductivity of 1.3 microsiemen/cm and other parameters). One stage RO is not sufficient.