SS piping - 304L vs 316L

In the paper mill you are probably using quite a bit of acid. Acid attacks the carbon found in steel corroding, pitting and structurally weakening it. Therefore the lower the C content (even after passivation) the better where acids especially H2S04 and HCl are concerned.

For a low corrosive environment you should be able to use either - at a cost savings if not already being done.

cr3

But lets see what the more learned than I have to offer.

If handling acids, what's wrong with using plastic piping?

Or is it still 1973 in paper processing?

It all depends on suitability of material for particular chemical.You may have to opt for higher series(Cr/Ni) for certain acids & elevated temperatures.Plastic is most economical for ambient temperatures & moderate pressure.

hi dr i am amr qc engineer in petrojet, i hope to find conact

met_3mr84@ yahoo.com

Hi Amr,

My e-mail is abujalala2005?@yahoo.com.

Thanks for responses so far. This particular case is vacuum piping from a suction press roll, which means 100% saturated air sucked through the sheet and press felt. The sheet pH is about 5, and there are trace amounts of chlorides from the bleaching process.

What I was hoping for was some some kind of guideline - "in excess of 100 ppm chlorine or 200 ppm sulphur, switch from 304L to 316L", something like that. I am still looking into detailed chemistry and will post whatever I find.

Scott

Grade 316/316L was originally designed for use in sulfite pulp mills to resist corrosion by sulfurous acid compounds. It is more resistant to pitting corrosion than other 18-8 alloys. (304 is an 18-8 alloy)

Source: Carpenter Specialty Alloys databook, pps.67/ 71.

I can't imagine that the actual cost to replace 304 sooner would be cheaper than the somewhat higher initial cost of using 316/316L, especially if the replacement is necessitated by the sudden failure due to corrosion. The downtime, the maintenance , labor, the clean up of spilled solutions. however, your accountants will say that that is future period potential expense, vs current period actuial expense.

So now look at your mission statement, If it says To be cheap bastards" use 304 and Always wear acid resistant clothing regardless of what they tell you. If your mission statement says anythin glike "intelligently manage risk" then the 316L is a no brainer.

If its contacting any type sulfurous acids, 316L it ought to be.

milo

At one time there was published corrosion data. Look for an old copy of Perry"s handbook.

agreed. you are on top of this.

milo

Thank you Milo.

Abdel Halim Galala

Abdel - thanks, now we're getting somewhere. Can you tell me what the form of the sulfur and its concentration (ppm, ppb) related to these corrosion numbers? I will, in the meantime, see if I can find a copy of the NACE andbook.

Thanks,

Scott

Hi thinman56

The NACE code I have is a hard copy, but I can scan and send you a few pages that will help you in that subject. Please send your e-mail.

Would you Please send Nace cod to me, Thanks,

augurozkan@hotmail.com

Scott, I don't know if you are still following this thread but I'm in exactly the same situation with the pulp machine vacuum lines and I was wondering what your decision was on the 304L vs 316L. We have carbon steel in some of the vacuum lines so I'm pretty temped to go with 304.

I'm also considering the use of Victaulic fittings for the vacuum lines. Any experience here?

S.

We stuck with 316, partly due to stubborn-ness and partly due to the myriad of possible contaminants in the wet end basement of a paper machine. I think the difference in cost has moderated some now. Interesting that some of our older vacuum lines are carbon steel as well and are holding up fine.

As for Victaulics, I'm not sure I would use them in vacuum. They introduce a leak point, and their usual benefit (easy dis-assembly for cleaning) is lost unless you have scaling contaminants you're worried about.

Good luck,

Scott

Thanks for the reply. Cost Delta for the pipe is still pretty big:

10"Ø 49% more in 316L
12"Ø 88% more in 316L
14"Ø 80% more in 316L

You are right -stubborness has locked us into a standard that is 50 years old. Getting people to look at sched 5s pipe instead of ID pipe has been extraordinary.