looking for the best material 2

[dilon]

We are looking for the the best material to use to remodle a foam line. The foam consists of sodium hypchloride (bleach) they are telling me that is a 10% mix.

 

[metengr]

Could you provide some additional information regarding the handling of this product?
What is the service temperature during handling the foam?
Does the 10% concentration you mention pertain to the strength of the sodium hypochlorite solution (bleach) used or to the ratio of bleach to foam solution?

Does the foam contain other chemicals?

 

[dilon]

I am new to this so is will give you every thing that I can.
the chemical that they are using is: chlor-10 (10% sodium hydochlorite) they are mixing it with city water. 200ppm
the other chemical they are using is called foam chlor:
ph@1% 12.45; phosphorous content 1.% available chlorine 1%: 265ppm; 50ppm. they are mixing this with city water 4oz per gallon.
they are currently using PVC pipe they want to switch to Stainless steel.

I know you probley need more information, but this is what I know.

thank you.

 

[metengr]

I would recommend you stay with the PVC piping. For your application, any of the conventional stainless steel piping grades like 316L stainless steel (which is an upgrade over 304L SS) will be marginal in performance at room temperature with this level of chloride ions in solution. Any increase in temperature will increase corrosion. To assure adequate protection from crevice/pitting corrosion at butt welds in the line, you would need to upgrade to a higher nickel and/or moly-containing stainless. This would significantly increase your cost for piping material.

Why are you considering changing the PVC piping material? Is it appearance or plumbing code?

 

[dilon]

thank you, I tried to tell them this. but the do not want to hear that as a answer. they are haveing trouble with their joints.

have you heard of duplex 2205? would this work?

 

[Carburize]

I would not use 2205

 

[EdStainless]

2205 would be worth looking at for this. The real problem isn't when the system running, but when it sits stagnent. 304 and 316 would not work. The main runs of tubing might be fine but joints and welds would be a disaster. Your total level of chorides is fairly low, <100ppm and the pH is high, these would normally not cause any pitting in 316SS. However once flow stops and surfaces start to dry off the local concentrations will be very high and I wouldn't rely on pH to save me.
2205 has good pitting resistance, it is often used in heat exchangers at Cl levels up to 5,000 ppm. It is also a high strength material so you could look at using thinner walls in order to save some costs.
WARNINGS:
You need to buy material that has been properly processed. In addition to ASTM A789 or A790 (tube and pipe), you need to require A923. This will assure that the material was annealed correctly.
The welding procedures need to be qualified for both mechanical properties and corrosion resistance. I would use only automated orbital welds with over-alloyed filler metal. No autogenous or manual welds.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[dilon]

thanks to all. This and any other information that we can get will help. The company that put the line in for them is not standing behind there work, so the want to replace the line with ss. We do not normal do this type of work. We manufacture all the conveyor systems for them, so they asked us to take a look at what we can do.We a scrambling to get enough information back to the customer.

 

[metengr]

dilon;
I would suggest you get to the bottom of why the PVC pipe joints are leaking. I would guess that the pipe schedule that was originally selected for this application is not adequate, and the joints may be suffering from vibration/bending forces in service, causing them to crack from fatigue. Check the hanger locations to assure adequate support. Changing from PVC to stainless piping will be very expensive in material and especially installation costs!

You should explore the cause of the PVC joint leakage, and solve this problem. This is a much cheaper alternative.

 

[dilon]

metengr,
I just spoke with the end user. They are telling me the pipe is sch 80 pvc. they have replaced all the origanle valves with new ones the are telling me they are using the propre methods for attaching and making joints per the previous company spec. The system has been ther for 10 years. I asked them to make sure they are using the correct "pipe dope" they can back and siad we think we are. I told they to make sure the "pipe dope" is not the problem.

 

[EdStainless]

If the PVC system is suffering because it is old you might want to consider CPVC or some other more oxidation resistant plastic.
Switching to a metalic system will cost more than you want to spend.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[dilon]

they are telling me the pipe is fine. The only reason they are replacing the vavles is when they break one.