316 SS in high chloride water 5

[murr52]

Ok, my problem is a particular pump needs to be designed for water with chloride levels upwards of 3600 ppm and a PH of around 7.5. The pump manufacture wants to use 316 SS for the wetted parts and claims verbally that this will not corrode(atleast not too much for the design life). I am looking for any links or research someone might know of that can guarantee 316 SS for use in this concentration of chlorides. Max temp for this water is around 100 F but typically around 70 F

My concern is that everything I can find on 316 SS seems to be borderline for this chloride concentration with this PH.

Thanks,
M.

 

[EdStainless]

I wouldn't do it. This chloride level is where you see alloys like 2205, 317LMN, and 904L being used. A 6% Mo grade would be overkill, but it would work.

Are you pumping from a well? is there any oxygen? Will it run 24x7 or be shut down regularly?

You could get away with using 316 for the impellers if the bowls were made from a less corrosion resistant alloy (such as Ni-Resist) to provide galvanic protection. I would also make sure that there was carbon steel piping at hte outlet to provide a bit more protection.

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Rust never sleeps
Neither should your protection

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[murr52]

The system is cooling water and will unless the plant is shut down or one pump is taken down for maintance operate 24/7. Most of the water is from well water that comes out with 1200 ppm chloride but the pump is expected to see 3600 ppm chlorides. The water analysis I have available does not show anything about oxygen content but the water will be exposed to the atmosphere with however much oxygen that would entail.
It has been suggested to Coal tar epoxy all the wetted parts but the impeller. You think if only the impeller was 316 SS and it was operated for all intensive purpose forever it will last 20-30 years?

Thanks,
M.

 

[kenvlach]

No. Stay away from this manufacturer who "claims verbally..."

316 SS is unsuitable for this much chloride at these temperatures:

 

[EdStainless]

No, a coating will not hold up.
And you would need the exposed bowls to provide galvanic protection to the impellers. This means that they will be corroding. This limits their useful life.
Your system will be open and oxygenated.
20-30 years at those levels will take better metallurgy. Think of equipment suitable for seawater service.
If they are saying 3x concentration I would presume that you will see 5,000ppm before it is over.

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Rust never sleeps
Neither should your protection

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[murr52]

http://www.alleghenyludlum.com/ludlum/documents/316_317.pdf

I just ran into this which mentions on page 3 that 316/317 is capable of handling up 5000 ppm chloride which, good guess Edstainless is the maximum expected but not operating. The customer is really leaning towards the 316 because of the price to upgrade these large pumps to a higher alloy, but if they fail...

The chart you have supplied Ken shows that 316 should handle what is 0.3% concentration chlorides at around 100 F(37.7 C for the chart). I am still searching and have a little time on this but all published info I can find seems to show that it is close but not beyond the capability of 316 SS for this service.

Although opinions on this page seem different, and although I felt weary about this system at first published information makes me feel like 316 will handle the chlorides.

Do you know of incidents where failure has occured for this type of service?
or any suggestion on a different material that wouldn't cost a arm and a leg to upgrade from 316 SS but could withstand the chlorides?

Thanks,
M.

 

[murr52]

Ohh just realized, that the link says 317 can handle 5000 ppm, hmmmm well, 317 SS for this service? opinions

Thanks,
M.

 

[kenvlach]

The chart above shows that 0.36% chloride at 100^oF (38^oC) is right on the curve for 316 [note the bottom axis is a log scale].
But, "chloride levels upwards of 3600 ppm" are clearly above, as will also be chloride levels if any drying during shutdowns.
Ken

 

[SJones]

Assuming a centrifugal pump:

1. Super duplex throughout with a PREN >40

or

2. NiAl Bronze, C95800 with Monel k500 gizzards

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/

 

[moltenmetal]

This is cooling water with a little chloride- not a severe service by any stretch of the imagination. The temperature and pressure are low enough that polymeric materials will withstand these conditions indefinitely. Unless this is a giant flow, get yourself a lined pump rather than screwing around with higher alloys! Why settle for corrosion resistance when you can have corrosion immunity instead?

 

[EdStainless]

Is cleaner water available to flush a pump when it is shut down? That would help a lot.
Don't fall for 316 or 317. At todays metal prices 2205 should be a better deal.
NAB C95800 would be a very good choice also.
If this is a single stage then a lined (not coated) housing is a good option.
Shaft and seals need to be high alloy since at shutdown they will see concentrated brine as they dry. These should be superduples, K-500, or other Ni based alloy (625).

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[murr52]

2205, Should last for these pumps entire lifetime and most likely more, but the cost of upgrading is still being considered. We don't know yet how much upgrading to 2205 would be but definately asking for a option to have the pump made of material superior to 316SS, depends what pump manufacturer wants to use for specific material.

Thanks for advice all keep it coming,

Any more published information you can provide would be extremely helpful.

Thanks,
M.

 

[JohnNabors]

Have you looked into Kolsterising the 316? That would dramatically improve the wear resistance (to about 1100-1200 Vickers) and significantly improve the corrosion resistance. If you aren't familiar, here's a link:

http://www.kolsterising.bodycote.com/

That page makes the statement that 'corrosion resistance is unchanged' but it is actually improved in 316 because of the Mo content.

 

[murr52]

What about possible getting a titanium nitride coating on the metal?

Will titanium nitride hold up to these chloride levels?

Thanks,
M.

 

[EdStainless]

Surface coatings by their nature only provide superficial help in wear and corrosion resistance. Most reactioncoating actually degrade corrosion resistance, and try to make up for it with greatly increased wear resistance.
Unless you are looking at a metallurgical overlay so that the surface is a significantly different chemistry then you will not achive long term reliability that way.
Your real problem will not be the bold, exposed surfaces. It will be in crevices, at joints, seals and such and on the back side of parts.
I have seen high Cl water pumped with 316 pumps. The seals were continually flushed with clean water and the pumps were fully backflushed with clean water when ever they were shut off. The problem with that is one bad shutdown will destroy the pump. Not high on my list for reliability.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm