Brine piping

[gibsi1]

We are currently upgrading our brine squeeze system, for cleaning our DI trains. The current piping is PVC, and has experience severe failures. The solution we are pumping is 10% NaCl, 1% NaOH, and the rest is currently DI water. We are switching the DI water out for recycled Cation water which is a little softer. The solution being pumped is @ 120* F. What kind of piping is recommended?

 

[moltenmetal]

What sort of failures are you seeing with PVC? Are joints popping apart, or is piping failing in the middle, or at supports? This sounds like a cyclic service- is there the possibility of big "water-hammer" pressure spikes during switch-over? Is your piping indoor, or is it exposed to the elements? PVC does degrade rapidly in sunlight.

120 F is warm, but below the upper recommended service temperature for PVC which is ~ 140 F (60 C). But that's for piping without significant pressure- plastics de-rate in pressure capability very rapidly with increasing temperature, so you have to be careful. In your system, the combination of pressure and temperature may be beyond the recommended limits for PVC. Have a look at the IPEX website, Georg Fisher etc.- you may find you're beyond the limits they recommend. If you aren't, and the failures are in the piping rather than in the solvent joints at the fittings, you may have discovered something new and I'm sure the piping manufacturer (and all of us here) would like to know about it!

If pure pressure/temperature handling is the issue, CPVC will give you higher pressure/temperature service, but probably not enough if PVC is failing. Polypropylene will give you higher pressure/temperature service still, but without the ease of installation (i.e. you'll need to thermally weld the joints, not solvent weld them). PP-lined steel piping will be one step up from that in terms of pressure/temperature handling and pressure shock resistance. But if you go that route, make sure your piping is painted with a high quality coating so spills or other exposure doesn't rot it out from the outside inward.

Others here would be better at recommending a best choice for a wetted metallic material for this service (based on experience rather than compatibility charts), if that's the way you want to go.

 

[gibsi1]

The pressure varies across the system. It seems as though 50-75psig is the norm. The PVC failures we were experiencing were mostly due to temperature shock. This is a cyclic system, seldom used. We were using DI water to mix with the brine, and the initial water slugs appear to be extremely hot. We are switching our water source, and will be heating the water for better control. The design crew is wanting to go with metallic piping, especially downstream of the steam heat exchanger that they plan on using. The George Fisher site was very helpful, but had little information on metallic piping. Any suggestions?

 

[gibsi1]

Anymore suggestions? I have a lot of info on plastic piping, but no metal...

 

[corrosionman]

```gbsi1 Rubber Lined mild steel piping is certainly your best choice. It is much more costly than any of the plastics but gives 100% reliability and installation costs are greatly reduced due to increased spacing of supports etc etc.
Very approximately it costs as much to rubber line the pipe as it does to fabricate it. Regarding pvc pipes, we once had lots of very puzzling failures which finally were identified as minute cracking caused by external contamination. I forget the name but it was an airbourne vapour in a surfactant plant.
Cheers, David Whitlock.

 

[PVRV]

We tried, GRE & GRP both have problems. I thought of, HDPE or mild CS internally lined with HDPE.

Cheers