Fasteners for Marine/Offshore and Sub sea application

[bmoorthy]

Our client is concerned about the rusting of Fasteners (Including SS B8M grades) hence has asked for coated fasteners (For all fastenersa) cut accross the applications.

I am concerned about the coated fasteners(Run in thousands of various sizes) because its inherent tolerancing problem. Especially in high pressure aplications since when the fasteners are produced/Manufactured (enmass).

It is very difficult to verify whether the manufacturer of fasteners are meeting the requirements (Of coating thickness and maintaining tolerances). We are at sole mercy of the fastener manufacturers.

Now corrosion is a real problem, is coating the only solution. Our client is insisting on coating even 453 Gr 660 fasteners 9Which is duplex grade) my understanding is that Duplex grades are highly suitable for marine application.

Are there better grades(Other than coated B7m, Coated 453 Gr 660 and B8 grades) of fasteners which are better suited for Offshore applications?

Are ther NACE publications which gives guidelines for Fasteners selection?

 

[Heckler]

Do a google search on "Sacrificial Anodes". This is an interesting article.

http://www.screamandfly.com/home/engine_tech/galvanic_corrosion/galvanic_corrosion.htm

 

[Goahead]

Hi,

non coated corrosion resistant fasteners should be preferred, in my opinion.

See:

http://www.specialmetals.com/docume...ant Alloy Solves Marine Fastener Problems.pdf

also:

http://doc.tms.org/ezMerchant/prodt...OM-9906-21/$FILE/JOM-9906-21F.pdf?OpenElement

Best regards,

http://www.welding-advisers.com/

 

[EdStainless]

Fasteners are available in both duplex grades (the 25% Cr grades are not really seawater resistant, but might work) and in NiCu alloys (Monel to use a tradename). I have used a lot K-500 bolts over the years.
The other common sewater alloys: CuNi, 6%Mo stainless, and Ti, are far less common in fasteners.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

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

 

[TVP]

Ed,

I posted something in the Corrosion forum as well, and would appreciate your feedback. My inclination is similar to that of Goahead or the options that you provided, rather than using galvanized steel fasteners.

 

[SJones]

Moorthy's post appears to be referring to topside pressure equipment rather than immersed fasteners which allows several views to be taken dependent upon the operating and maintenance practices to be adopted. If they are in a submerged application, why bother about them when the facility should be equipped with a properly designed CP system?

Steve Jones
Materials & Corrosion Engineer

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