Fastener material for indoor pools 1

[jaydigs]

I'm looking at installing a fixture overhead in an indoor swimming pool facility. I am aware of stress corrossion cracking and found some articles from various sources stating 254 SMO is the best material for this specific application. Does anyone know how 254 SMO would compare to say, AL6XN? I think they are pretty similiar but all the articles I've read mention 254 SMO as the best. I'd like to stay away from supplier claims or sales pitches so I've been sticking to articles from steel institutes and structural engineers. Thanks in advance for your help!

 

[CoryPad]

254SMO provides exceptional corrosion resistance. It compares favorably with AL6XN. 254SMO is available in rod form for screws, while AL6XN is only available in plate/sheet/tubing.

These superaustenitic alloys may be appropriate for your application, or they may be more performance and cost than you need.

Bulten is a very capable supplier of high-performance stainless fasteners.

http://www.bufab-stainless.se/eng/index.htm

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[strider6]

AL6XN and 254SMO are considered as equivalent for this service. Have a look at thje first article, as you can see an importat factor is the possibility to make maintenance / cleaning. AL6XN and 254SMO are the perfect choice if you want to install and forget about it since they will perform well even with minimal on no maintenace / cleaning.

http://87.230.33.128/_files/stainless_steel/Successful_Stainless_Swimming_Pool_Design.pdf

http://resource.npl.co.uk/docs/scie...guides/pdf/indoor_swimming_pool_buildings.pdf

hope this help u

S



Corrosion Prevention & Corrosion Control

 

[EdStainless]

For indoor pool hardware I would also suggest that you look at duplex stainless fasteners. An alloy such as 2205 will have fairly good corrosion resistance (much better than 316) and better chloride stress cracking resistance than the 6% Mo grades. The alloy is strong and less likely to gall compared to the 254/6XN options.

The second article is very good with great guidelines.

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Plymouth Tube

 

[Ron]

Not sure of the amount of load on your fasteners, but if relatively low or you can use numerous fasteners, consider filled nylon or various fiber reinforced plastics.

 

[jaydigs]

From what I've gathered about Stress Corrossion Cracking, it seems to only effect fasteners that are loaded in tension. Would this mean that fasteners that are only preloaded to keep things together (ie...no additional force applied) could be made out of a typical stainless? I know the Safety Critical fasteners would need the special alloy but because of the cost and availability if the non critical could be made of more common material I'd like to use them.

Thanks

 

[CoryPad]

Preloaded screw are notched parts that have a sustained tensile stress on them. They are susceptible to SCC. You don't need additional external forces to create a problem - they add to the existing one.

 

[EdStainless]

Cory is right, all bolts are SCC test fixtures, with severe crevice corrosion tossed in for extra measure.

I have seen fiberglass bolts used to keep a unit located as long as the full load is supported by structural members. In other words nothing could fall if they failed.

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Plymouth Tube

 

[rolledalloy]

Correction on the AL-6XN alloy it is stocked in round bar, pipe and fittings along with the product forms mentioned. Fasteners can be sourced in AL-6XN from a number of fastener manufacturers.

Superduplex stainless steels like Zeron 100, or S32750 have also been used successfully if added chloride resistance compared to 2205 is desired. Attachment shows some examples of superduplex use.

 

[CoryPad]

Thanks for the correction regarding availability of AL6XN in non-sheet forms.