What metal OK for RO water?

[banditpowdercoat]

OK, some may know I'm attempting to build a completely automated RO/DI water top off and membrane flush unit. BUT, I am wondering what metals are OK to come in contact with the RO? Most SOlenoids are Brass, but I have found some that are 304 Stainless Steel. I am needing a bunch of valve so cost is an issue. I have found, I think, a good source of 2 way valves, but I also need 3 way valves and have found some in 304SS. Is that gona hurt my water???

[mark]

I would think all metals that are good for potable water (concern is the SW side).

[fkshiu]

If it's DI water then NO metal is good as a storage container. The "ion hungry" DI water will react with the metal on contact.

[banditpowdercoat]

I wasn't thinking for storage, but for the control valves. I am building a automatic RO/DI Storage FILL, as well as a AUto Purge and Membrane flush setup.

DI will mess with the metal though?? Bummer. Was hoping to get away with it....


Heres some gogle info I'm finding.

DI water penetrates (316L & 304) SS with a rate of up to 20 mil/yr. For best results use 316L that is electropolished and passivated. However, this would not prevent ions leaching from S.S. Heat makes things worse.

There are DI water heaters made of Stainless steel from Cole-Palmer and others. Also Watlow has DI water heater made of S.S. & made of Quartz.
However, I would like to know or obtain a references about the rate and type of ions leaching from 316L S.S. specially at elevated temperature.

[fkshiu]

Originally Posted by banditpowdercoat

I wasn't thinking for storage, but for the control valves. I am building a automatic RO/DI Storage FILL, as well as a AUto Purge and Membrane flush setup.

DI will mess with the metal though?? Bummer. Was hoping to get away with it....


Heres some gogle info I'm finding.

Well, it'll probably be OK if there's no DI sitting on the metal constantly, but I'm the paranoid type and wouldn't do it with my own system. I'd just get a big ass brute trash can for your ATO resevoir and refill manually as needed. Saves on a catastrophic RO/DI failure when a float valve sticks (or something like that) which seems uncomfortably common among reefers.

[banditpowdercoat]

There's not going to be a catastrophic failure. See, the Automation of things is my Job. Failure is NOT an option. But, some of the solenoids will have RO/DI in them at all times so that leaves the metal out...

[midgetwaiter]

You are making this harder than it needs to be.

Your membrane flush is on the waste water side so you never come in contact with RO and it goes down the drain anyway, so it doesn't matter.

In order to switch the RO on and off to fill your holding tank I'd seriously suggest switching the input water. If you switch on the output side you will need to use an RO safe valve and you have increased leak potential because the unit will be pressurized. There's at least twelve points on a pressurized RO/DI unit that could fail but it you shut off the feed you only have one fitting that has any pressure.

[banditpowdercoat]

Originally Posted by midgetwaiter

You are making this harder than it needs to be.

Your membrane flush is on the waste water side so you never come in contact with RO and it goes down the drain anyway, so it doesn't matter.

In order to switch the RO on and off to fill your holding tank I'd seriously suggest switching the input water. If you switch on the output side you will need to use an RO safe valve and you have increased leak potential because the unit will be pressurized. There's at least twelve points on a pressurized RO/DI unit that could fail but it you shut off the feed you only have one fitting that has any pressure.

OK, Heres the deal.
This is for an automation of a 4 tank setup. The setup is going to be PLC(Programmable Logic Controller) controlled. The RO unit WILL have a main Solenoid controlling inlet. But also solenoids to run the RO unit for 20 min before filling the Main reservoir. Also, there will be a Run timer that after X hrs of water making, the RO unit will go into a Membrane Flush mode. When the reservoir gets to a pre determined level, the PLC will control the RO unit for a Purge, and fill of the Res. The PLC will also control independent level of 4 tanks. With this PLC, there will be safety timers for maximum RO run time as well as level control is managed bu Ultrasonic non contact level sensors. Nothing to stick, no salt creep to worry about etc.

Once this is complete, I'll be making a lighting program with another PLC.

I LOVE designing and building things

[golf nut]

Originally Posted by banditpowdercoat

OK, Heres the deal.
This is for an automation of a 4 tank setup. The setup is going to be PLC(Programmable Logic Controller) controlled. The RO unit WILL have a main Solenoid controlling inlet. But also solenoids to run the RO unit for 20 min before filling the Main reservoir. Also, there will be a Run timer that after X hrs of water making, the RO unit will go into a Membrane Flush mode. When the reservoir gets to a pre determined level, the PLC will control the RO unit for a Purge, and fill of the Res. The PLC will also control independent level of 4 tanks. With this PLC, there will be safety timers for maximum RO run time as well as level control is managed bu Ultrasonic non contact level sensors. Nothing to stick, no salt creep to worry about etc.

Once this is complete, I'll be making a lighting program with another PLC.

I LOVE designing and building things

why not build the whole thing out of polymers and drive it with buried magnets

[banditpowdercoat]

Originally Posted by Mr OM

why not build the whole thing out of polymers and drive it with buried magnets

I could, but wheres the challenge in THAT????