Material Spec for Fasteners (Offshore Application) 1

[bmoorthy]

Hello All

I am looking for the ASTM specification for Fasteners for Pressure piping in Offshore applications (Taking Corrosion effect into consideration- Warm, Moist, Marine applications). We are aware of A 193/A 194, A 453 and A 320 etc)

The question is which grade is suitable for the above application? Is there any NACE recommendation (As regards selection of material) for the above conditions?

 

[metengr]

What are your expected service temperatures for the fasteners?

 

[bmoorthy]

40-180 deg c

 

[boo1]

The most popular material stocked is 316L stainless steel. Other materials which are used are: other grades of stainless steel, Hastelloy™, AL6XN™, Inconel™, monel, titanium, and Duplex 2205™.

 

[SJones]

Why not galvanise the fasteners like most others? You will require sour service bolting only if a) the operator believes it to be necessary and specifies it; or b) the bolting will be enclosed and cut off from ambient air circulation. Recommendations are given in ISO 15156.

Steve Jones
Materials & Corrosion Engineer

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

 

[1969grad]

If you would otherwise use A193 and A194 for the service then have them epoxy coated for offshore. You might check the tempature limits of the epoxy coating if you really have a 180 C operating temperature.

 

[TVP]

Steve,

Is it really preferred practice to use galvanized alloy steel bolts rather than a more corrosion resistant base metal like duplex stainless? I work in the auto industry, so my experience with offshore/deep sea applications is nil. It seems to me that issues with coating damage, crevice corrosion, etc. would be too great with coated fasteners, and that robust practice would be to use ferrous or non-ferrous materials with inherent corrosion resistance. I would appreciate any insight you care to provide.

 

[boo1]

Galvanize does not hold up in the marine enviroment.

 

[SJones]

Electroplating is probably a little more popular but to class it as the "preferred option" is probably overstating the application.

http://www.nace.org/nacestore/dept....ded+Fasteners:+Methods+of+Protection+to+Reduc

Steve Jones
Materials & Corrosion Engineer

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

 

[TVP]

Steve,

Thanks for the additional info, including the NACE link. I think it is great that they are making old conference papers freely available!

 

[mshimko]

I'd recommend you consider stainless steel, either 316L or 17-4 ph. This is what we use on Navy ships.

 

[unclesyd]

Just talked with my stud and nut buddy about what is being used by some of his supply house customers.
These alloys are being called for. There is no particular order.
660B
Alloy 718
Alloy K500
Alloy 400
Inconel 600 and 625
Incoloy 825
Super Duplex 2550
Super Duplex 2760
Aluminum and Silicon Bronze
A good percentage of these fasteners are Teflon coated, Green, not too many Black or Red going off shore. These coatings are being used on the 660B, 718, and the Super Duplex.
There is also calls for Dupont SP11C . One being called for more and more on all materials is the 1014 coating.


There is still a lot of coated alloy steel fasteners being used that are zinc plated, both electrolytic and mechanical, the Teflon Coated.