Push-to-Connect Tube Fittings for DI Water

[Bunt23]

I am re-designing a prototype machine in our facility that uses DI water to clean itself (it's kind of like a CIP tank cleaning application), and the prototype we currently have has stainless steel NPT push to connect tube fittings for all of the nozzles that spray clean the tank. I was wondering if anyone who has experience with DI water applications can tell me if it's OK to use nickel-plated brass rather than stainless steel. Below are the links to the 2 fittings I am deciding between. 1 has SS NPT threads, the other has nickel-plated brass NPT threads. SS is like $45 per fitting, and nickel-plated brass is like $3 per fitting.... I just don't know enough about the chemistry to know if nickel plated press will give us the corrosion resistance we need. Any help is appreciated! Thanks!

https://www.mcmaster.com/51065k23

https://www.mcmaster.com/7880t132

 

[SwinnyGG]

Two suggestions...

One, don't buy these fittings from McMaster-Carr. Buy them direct from the supplier.

SMC's 3/8" Tube to 3/8" male NPT fitting is less than $20. Just changing your source represents 50% cost savings.

Second, once you've determined the correct part number from SMC or Parker Hannifin or whomever, that manufacturer will be able to give you very detailed information about what that fitting is rated for.

 

[itsmoked]

If you're using plastic tubing you're wasting money bothering with metal fittings. Use plastic John Guest fittings and avoid all the chemistry entirely.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Bunt23]

Alrighty. Thanks guys!

 

[CGonsalves]

Here's something I found useful.

http://gregknowswater.com/di-water-compatibility-chart/

However, that is an outrageous price for fittings.

 

[EdStainless]

Don't use brass fittings (Ni plate or not) in DI if you actually care how clean the water is.
If temp and pressure allow go full non-metallic.
They build this equipment our of SS for a reason.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[Bunt23]

Just room temp and only 20 psi, so I'm thinking non-metallic will suffice. Again, thank you guys! I'm new to this forum but very thankful that I found it

 

[moltenmetal]

+1 for avoiding metallic fittings entirely. If you're using DI water because you need the water pure, any contact with metals is going to make it less pure. I'm not familiar with John Guest fittings but know that there are other brands, including a Parker brand, which are all plastic in the wetted materials with a non-wetted stainless steel gripper to retain the tube. There are also more conventional compression fittings which are all plastic- my personal favorite being Jaco.

 

[itsmoked]

I find that Home Despot has a good selection and I've not had any problems with their John Guest fittings. I have at least 40

under my kitchen sink @90PSI and not a one has caused me issues.


Keith Cress
kcress -

http://www.flaminsystems.com