304L versus 316L in pulp/paper environment

Chloride-containing solutions.
316 was originally developed for the pulp/paper industry -- the Mo alloying combats pitting corrosion.

Actually if you look at more recent usage you will see that duplex grades are the workhorses in P&P. The cooler applications are a good place to use the lean duplex grades. For the hotter more agressive locations you will often find 2205.
Since these alloys are at least twice as strong as 316L you can save a lot of metal and get good CSCC resistance at the same time.

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Rust never sleeps
Neither should your protection

It really depends on your application if 304L is better than 316L.

I agree that duplexes are a better choice in many applications if CSCC is a concern, which is not always the case. Also, there aplications where the duplex strength does not help. Vessel internals such as screen backing bars in a digester or loose lining in a pulp storage tank, are a good examples of this; they are not stressed, therefore no CSCC possibility and no advantage for strength.

I have heard several complaints, basically, from fabrication shops that wanted to use LDX2101 in lieu of 2205 but it was not available unless they ordered a large quantity. This has been a reported problem on relatively small shop fabricated vessels.

Depending on your application, 304L may be better than 316L (if you stay w/ the austenitic path). Cooking and white liquor plants seem to be this case. There are alot of papers discussing the techanical reasons for this claim. In many applications, it is really a marginal concern.

This is correct, EdStainless. Find any way to use lean duplex instead of 304/316/317. 2101 and 2003 are the replacements for 304 and 316/317, resepctively. These alloys are stronger, more corrosion resistant, and,most of the time, should be cheaper. It is a no-brainer.


Michael McGuire

dig makes a good point about more alloying not always helping. For example in caustic applications Mo will hurt you. Teh best alloys for caustic are 2304 (duplex, no Mo) and 26-1 (ferritic, 1%Mo). In this case Cr is what counts.

When looking into using duplex grades you have to throw away old asssumptions about how equipment is built and what thicknesses to use.

The min order quantity is a red hering. If I need to run a job in 304L or 316L the min order quantities are at least 40,000lb. The duplex grades are the same. If you want 317L or a special chemistry then be prepared to take 100T of material.

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Rust never sleeps
Neither should your protection

Thought I would jump back in and say thanks to all for the input. Corrosion protection from water is always a concern; from chemicals depends on where you are in the process.

Designs are often driven by stiffness requirements, not strength, so higher yield doesn't always result in less required material.

I will look into more of the duplex stainless steels, esp. cost comparison for new designs.

Thanks,
acurat