Stainless Steel Material for Sea Water Application 1

[manian]

there is a requirement for a range of swing check valves of different sizes with working pressure of approximately 8 kg/sq.cm for sea water application. body and internal materials are of 18-8 SMO stainless steel. is it acceptable to use this material for sea water service ? if not, any other alternatives ?

 

I believe SS 416 and 316 are resistant to salt water. Check out

http://www.engineersedge.com

, they have some material choice pages available.

Good luck!

 

[arunmrao]

As a cast grade you will have to go in for CF8M grade stainless steel. This is cast equivalent for 316 grade. HOwever, if you need better corrosion properties with superior weld properties you may use CF3M or 316Lgrade. In case you need any cast components you may contact me.
Dr Arun Rao

 

Although type 316 has superior resistance to corrosion in sea water compared to other "18-8" "Stainless" (Corrosion Resistant) Steels, it is still subject to pitting (especially when or where the water is stagnant). If the application is critical or longevity is a concern, an inherently corrosion resistant material such as copper-nickel should be considered. Stainless Steel (CRES) relies on the integrity of a passive surface layer. Incidentally (Phil), type 416 is not even a distant cousin of 316 and will corrode very rapidly in sea water.

 

[Moray]

We keep this type of valve in stock, and we have an "on-line valve solutions" feature for peole out there in the ether to ask questions of our engineers.

The URL is

http://www.score-group.com

 

I have heard of using "passivated stainless" on Navy ships. You might try asking about this.

 

[Robg]

I have supplied isolation valves for brackish sea water applications in a variety of different materials with a mixture of success. The best material, disregarding cost, has been Titanium. These were metal seated butterfly valves for bi-directional Class VI shutoff. I think the best material for the dollar is A351-CN3MN, which is a 6% Moly cast steel. This has been very succesful in eliminating corrosion/pitting and is a fraction of the cost of Titanium.

 

[MJCronin]

Manian,

I believe RobG above, has the best advice. Additionally, I suggest that you check out the following site for materials discussions on valves, piping, pumps, etc. for seawater service.

http://marine.copper.org

and for general seawater corrosion info, try:

http://corrosion.ksc.nasa.gov

Good Luck !!...................................MJC

 

Although neither 304 nor 316 stainless is the material of choice for sea water applications, will one of these materials stand up to the application with any better results or longevity, than the other? I've actually seen several corrosion resistance guides that say that 304 is better for sea water.

 

[Nitron]

I think titanium and its alloys offer the best solution. When considering the cost of material remember that you need equal size (volume) not weight of the material. So although titanium costs much more per kg than steel alloys the same size part will only weigh half as much and thus the material cost will that much lower. You will find that the total cost of the part is not that sensitive to the cost of material.
We can increase the surface hardness, wear resistance and corrosion resistance of titanium even further by ion nitriding.
Contact me if you need more ifo etc.
Pramod Kotwal
Nitron, Inc.

 

[msmedesign]

also dublex and monel trim is widely used for seaa water applications
engin

 

[marklobo]

I posted this response to another thread: We have had an increasing number of requests for custom valves fabricated of duplex 2205 (UNS S31803) material. It is widely available (try Great Plains Stainless) and also meets the requirements to DIN 1.4462.

B16.34 limits temperature to 750F, and the BPV is even more conservative, however.

 

[mgp]

In the North Sea offshore industry it is quite common to use 6MO stainless steels for Seawater service (wet firewater systems and water injection). I guess maybe Manian's reference to SMO could mean e.g.

Sandvik 254 SMO (= UNS 31254)
(a trademark of Avesta Sheffield AB)

Also Sandvik SAF 2205 (= duplex 2205 = UNS31803) or Titanium is used, but SS316 or 304 being is normally never accepted.

Try the site

http://www.steel.sandvik.com/

or

http://www.avestasheffield.com/steel_grades.asp

They have specs for SMO254 and SAF2205

Regards
Mogens

 

[AGBurd]

I know very little about valve material sellection, but I have years of experience working on salt water disposal pumps (positive displacement plunger pumps). Almost all of them had cast aluminum bronze fluid ends. I never saw a corrosion related failure on any of these pumps.

 

[stanier]

Have you considered using a thermoplastic material? You will not get corrosion at all then. the cost will be significantly less than the ss you have suggested. Also Red Valve doa duckbill type valve in natural rubber.

As source of info for ss is

http://www.nidi.org