SS and HCl
SS and HCl
(OP)
How would 316SS go within a water treatment plant wereby i am periodically dosing 400mg/L of HCL (0.04%) into a stainless steel line. At ambient temperature and a pressure of 1-3 bar.
I know that HCL has a severe effect on stainless at high concentrations but i am not sure at such a low concentration?
I know that HCL has a severe effect on stainless at high concentrations but i am not sure at such a low concentration?





RE: SS and HCl
Many other questions.
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RE: SS and HCl
The application is a chemically enhanced backwash on an ultrafiltration plant (using Norit Xiga membranes)
The flow rate during the CEB is 60m3/hr, dosing 30% HCL at 1330mg/L , this occurs for a short period before 10 minute soak. The chemicals are then rinsed out using ultrafiltered water.
RE: SS and HCl
The chloride concentration you mentioned is approximately equal to 400 ppm at ambient temperature. I also assume that the water contains the other bad ingredient, the oxygen. The stress corrosion cracking for this concentration would not be an issue until the temperature of water (during the exposure to HCL) remains ambient, say below 100-120 F. Also, the rinse after the chemical treatment reduces considerably the risc of corrosion with catastrofic consequences. You should start being concerned at around 1000 ppm (1000 mg/L)at temperatures at / above 140F. Also, the presence of highly stressed components (sharp bends with stagnant pool of high chloride concentration, etc)could cause concern. Your description of the equipment and process seems to guarantee many long happy years 'till retirement.
However, on the safe side, check the remaining water after rinse, for chloride concentration and make sure to wipe or mop-up the remaining water (don't dry with air or worst, with hot air).
Cheers,
gr2vessels
RE: SS and HCl
Thanks gr2vessels.
There will never be "drying" stage. The membranes will always remain wet. Basically, after the chemically enhanced backwash is complete, the system automatically goes into a filtration cycle wereby treated water will continously flow where the HCL solution was. There is also comprehensive deaeration steps designed into the membrane plant so there shouldnt be too much oxygen about.
The temperature will not get above 45C.
Do you have any references to the chloride concentrations that you mentioned?
RE: SS and HCl
RE: SS and HCl
Tom
Thomas J. Walz
Carbide Processors, Inc.
www.carbideprocessors.com
RE: SS and HCl
At these chloride levels and temperature I am not too concerned with CSCC.
You probably will see some general roughening of the surface over time with some metal loss in welds. At your temperatures this will be gradual and take a long time.
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RE: SS and HCl
You can probably find reference information here:
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I doubt that you will be backwashing and cleaning your UF membranes more than once every week or two. The short exposure will tend to minimize the possiblity of corrosion.
RE: SS and HCl
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Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm
RE: SS and HCl
With regular CEB's occuring there is no requirement for an extended CIP clean.
"Moltenmetal" raised an interesting point, that being the dosing point, where the concentration will be higher....the injection fitting itself will be plastic however this fitting will be screwed into the stainless pipe.....am i likely to get problems around this fitting?
RE: SS and HCl
Consider doing the injection in a piece of PTFE-lined pipe, preferably with a static mixer. Or risk localized attack in your "mixing spool". It will see higher local concentrations but may not be much of a problem due to the short duration of exposure followed by lots of flushing- but you will experience problems anywhere it will be here.
RE: SS and HCl
= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm