Flanges ok for Sulphuric acid?
Flanges ok for Sulphuric acid?
(OP)
I'm overseeing a project where we're running 1 1/2" SS316 pipe that will transport 20% sulphuric acid from a tote via a chemical pump to the top of a makeup chest (tank). There will be, I believe, 4 or 5 90 deg turns.
Is it ok, in your opinion. for us to use flanges, or should it be welded only to prevent leaks. It would be difficult due to space constraints to do all welds.
Thanks
Is it ok, in your opinion. for us to use flanges, or should it be welded only to prevent leaks. It would be difficult due to space constraints to do all welds.
Thanks





RE: Flanges ok for Sulphuric acid?
You need to change material of construction.
RE: Flanges ok for Sulphuric acid?
Please give me some type of reference to support your comment. We've already purchased and begun welding the piping.
Thanks.
RE: Flanges ok for Sulphuric acid?
Check Perry's or something that does not come from the guy you are purchasing from.
Also you say it has an A rating up to 30%. SS316 is good when above 85%. For that matter carbon steel is fine at 90% and above. Lower concentration acid has higher corrosion rates than higher concentrations.
RE: Flanges ok for Sulphuric acid?
RE: Flanges ok for Sulphuric acid?
RE: Flanges ok for Sulphuric acid?
RE: Flanges ok for Sulphuric acid?
RE: Flanges ok for Sulphuric acid?
What do you mean by lined pipe?
We're going to try weld this line so we don't have flanges (or minimal number) if possible.
RE: Flanges ok for Sulphuric acid?
Temperature and liquid velocity are also factors in the material selection process
Consider and evaluate flanged PTFE lined piping, install flange guards.... they are cheap
Some info here:
http://www.resistoflex.com/sulfuric.htm
The Resistoflex piping will not be cheap, but easier to install than welding alloy in the field.
Let me guess, this is your first experience specifying piping systems and you boss, a newly degreed MBA, wants results ...NOW!
More stuff:
http:/
http://www
htt
Star..???
MJC
RE: Flanges ok for Sulphuric acid?
In the last link of the last post, it states on pg. 5 that:
Q.
When should I use stainless steel vs. carbon steel?
A.
Stainless steel should be used in place of carbon steel if iron contamination
is a problem in your process. Also, stainless steel is acceptable for 100%
sulfuric acid - carbon steel is not. Stainless steel is also preferred at low
(<20%) acid concentrations. Stainless steel has a greater resistance to
"hydrogen grooving".
I'm confused by the comment that "Stainless steel is also preferred at low
(<20%) acid concentrations."
I thought less than 20% was more corrosive than 20% and that stainless (304 or 316) would be eaten up at those levels.
Would please help me understand this?
Thanks
RE: Flanges ok for Sulphuric acid?
RE: Flanges ok for Sulphuric acid?
RE: Flanges ok for Sulphuric acid?
A20 will work but it needs to be at correct velocities and temperatures. Call your acid supplier or tech resources within company and get these recommendations.
The lined pipe is lined with Teflon (ptfe) and comes in 20' spools or specific length as specified. All spools would be flanged and should have flange covers. Also make sure your crews understand how to put it together.
Just curious, why do you even have 20% acid. It is far better to leave at high concentrations.
RE: Flanges ok for Sulphuric acid?
I've got an engineer from one of the supply companies researching the correct velocity and temp for Alloy 20 for this application. Thanks for the tip.
It sounds like it would be less complicated from an installation standpoint to install Alloy 20 than to go with teflon lined pipe.
Thanks.
RE: Flanges ok for Sulphuric acid?
we have used some for moving acid to a cooling tower, etc.
but you have to watch out for UV ratings if outside as well.
RE: Flanges ok for Sulphuric acid?
RE: Flanges ok for Sulphuric acid?
RE: Flanges ok for Sulphuric acid?
RE: Flanges ok for Sulphuric acid?
Forget about high alloys- using unlined metallic piping for this service is equivalent to using a sledgehammer to jam a very square peg into a very round hole.
If it truly is pilot scale and this is tubing rather than piping, there are plenty of non-metallic options worth pursuing as long as you keep both pressure and temperature limits in mind.
The stuff will come to you in an HDPE drum.
The problem with PEX isn't the PEX itself- it's the connections. PEX is usually used in potable and hydronic water applications with brass hose barb type fittings using an external crimp or shrink ring. Brass = NFG for your application obviously. Some polysulphone fittings are available from some vendors, but they're limited. External compression fittings are also available (see Jaco as one example).
RE: Flanges ok for Sulphuric acid?
Are you saying don't use Alloy 20 because it's too expensive? I don't understand your comment.
Can you recommend a good vendor resource that can give me a non-metalic recommendation, which you seem to be suggesting would be preferable to Alloy 20. I need guidance on how to adequately handle the fittings.
It is pilot plant scale (less than 100 ft of linear pipe) but we also want to make sure we don't have a problem with a forklift running into it or it otherwise being compromised. Our main concern is safety, price second.
Thanks in advance.
Dave
RE: Flanges ok for Sulphuric acid?
RE: Flanges ok for Sulphuric acid?
Laboratory protocol is to add acid to water. This is difficult in larger scale since you aren't mixing in a glass beaker.
The more dilute the more corrosive so you need to look at materials of the mix vessel, the interface point between acid and water and how to remove dHmix.
RE: Flanges ok for Sulphuric acid?
RE: Flanges ok for Sulphuric acid?
PP- or teflon-lined CS pipe will give you both corrosion immunity and mechanical robustness at less cost than A20. Look at www.resistoflex.com for some info on the system. You can get TFE-lined hoses as well as pipe and flanged fittings, with the liner wrapping over the flanged ends so that they're entirely TFE-lined on all wetted surfaces.
Dilute sulphuric is very hard on metals and alloys- any of them aside from perhaps tantalum. And you can't afford tantalum, as much as you want to promote safety over cost.
You can protect against the forklift with routing, bollards etc. A "motivated" forklift can destroy the best-designed piping system, whatever you make it out of!
Have a look at www.chemline.com , who have an excellent chemical resistance guide for plastic materials.
Diluting sulphuric is going to be another matter entirely. You need to not only worry about the corrosion due to the varying concentration, but you also have to worry about removing the enormous HEAT OF DILUTION.
RE: Flanges ok for Sulphuric acid?
It is substantial
If you have a senior engineer at your company you should really ask for some help on this one.
You shouldn't be relying on vendors and a forum of people you don't know for such detailed engineering solutions.
Sulfuric is nasty stuff and things can go badly quickly
RE: Flanges ok for Sulphuric acid?
Big spike at 83%.
RE: Flanges ok for Sulphuric acid?
RE: Flanges ok for Sulphuric acid?
RE: Flanges ok for Sulphuric acid?
I think you're crossing the line with that kind of question, if indeed your label of "chemical" is accurate.
RE: Flanges ok for Sulphuric acid?
RE: Flanges ok for Sulphuric acid?
You're right. Sorry for my laziness. I'm back in engineering after an 8 year stint running a business. I appreciate very much everyone's help on this issue.
RE: Flanges ok for Sulphuric acid?
On the mixing ratios - you mention 50 gal of 98 acid to 200 gal of water to get 20% acid - I suggest you consider the specific gravity of that acid.