Use of SS316/316Ti

Is this one of UOP's platformer regeneration towers? I am a refinery inspector and I have one of their Continuous Catalyst Reformer (CCR) units assigned to me. If you plan to deviate from their specs, you may want to talk to them first. Is there significant price difference? When I get into work tomorrow, I will check out the 316Ti with our group.

Also, if this is the same, you may want to ask them about problems customers have had with the standpipe orifice in the disengaging hopper. We solved the problem without their suggested design change and have exceeded their expectations on minimizing fines.

Yes sir,ur right,this is for project: UOP's CCR platforming unit.But i dont have any backup or some reference that cud prove that whether use of SS316Ti is justified.

Regarding Price difference it is there, which I have to check from my purchase dept.The reason vendors are giving for this deviation is tht they can easily find this material(SS316)for plates but the same is vry difficult to get for pipes/fittings(nozzles) etc. to be fixed to Regeneration tower.

But taking a deviation and following up with UOP may take some time,and to approach them i want to be clear from my side first.Anyhow it seems tht deviation has to be taken but,lets see if v can cm to sm conclusion regarding benefits/disadvantages of using Titanium@design temp.

Thank u :-)

I am metallurgist, not corrosion or deign engineer.

That temperature range includes the range where in grade 316, chromium carbides will form (precipitate out) in the grain boundaries. this results in sensitization and leads to corrosion. (rapid corrosion, as the grain boundaries for m a wonderful network....)

In 316 Ti the titanium Ti is a stabilizer that prevents the precipitation of chromium carbides in the grain boundaries during sustained high temperatures. this prevents chromium from forming carbides and so reduces sensitization and thus corrosion. read this tech sheet :

http://www.alleghenytechnologies.com/ludlum/Documents/316ti.pdf

Straight 316 is susceptible to the chromium carbide precipitation at the service temperatures that you listed and will fail much much faster than parts made from 316Ti.

You would do your company and customer a great service by making them aware of these facts.

milo

Milo -you are such a good Metallurgist and honest teacher!

BR

mm

Thank you MUKULMAHANT.

'In the first place do no harm' comes to mind.

As engineering professionals, we have an obligation to serve society, as well as our employers objectives. This forum gives us a chance to assist and mentor all around the world.

We're all on this planet together.

Thank you for your positive feedback.

milo "no rocket powered turtles were hurt in the posting of this email"

Sensitization of 316 due to high temperature is an issue if you have also a Corrosive Fluid , that will corrode the sensitized steel giving intergranular corrosion due to the lower content of Cr precipitate as carbide along the grain border.

Stabilized SS grades are also the 321(Ti stabilized) and 347 (Nb stabilized) .

I don't know what is exactly the fluid inside your tower but if there is the possibility even if remote of the presence of water condensation or other corrosive fluid i think that a stabilized grades is the right choice.

I've found some document regarding 316ti and SS sensitization:

http://www.msm.cam.ac.uk/phase-trans/2005/Stainless_steels/Sensitisation/single_page/

http://www.bssa.org.uk/publications.php?id=10

http://www.bssa.org.uk/topics.php?article=71

hope this help

S.

www.corrosionist.com