Brass or Stainless steel valves?

[jphil3310]

Hi,

I have a piece to write for uni with regards to the use of stainless steel in corrosive environments - I've decided to focus on subsea applications - looking at fittings and valves etc. I've found this piece on compression fittings and valves - can anyone point me in the direction of any other useful resources?

Thanks,

 

[wornandwound]

Hi,

When you said "subsea applications", I am assuming subsea applications for oil and gas industry as that is the application that the majority of these equipment will be used at. Even though subsea applications are increasingly common, there are not a lot of materials available online.

If you have access to ISO 13628 and ISO 10423 or the equivalent (API 6A & API 17D), that will be a good place to start. Most of the industry players are referring to these standards.

 

[TugboatEng]

Two subjects to look in to are crevice corrosion and dezincification. Those are both serious problems for the two materials.

 

[gerhardl]

To get a more precise answer you will have to give a more detailed description of the applications you want to discuss.

There is a large difference between smaller valves for hydraulic oil, gas as air or oxygen for equipment for free diving or submerging equipment down to a limited deep of, say, a couple of hundred feets (60m), and valves for deeps down to more than 600m (and far deeper,) and sizes up to 500mm and far above.

The chemical composition and temperature of the sea water and fluid details will also weigh heavily.

All above, plus material price and fabrication cost will decide final considerations.

If you could narrow down to a simplified, concrete case, it would be more simple to comment.

 

[gerhardl]

One more thing: brass is the 'olden times' salt water valve material, used for marine purposes traditionally. Cost of brass has gone sharply increased since 1950s'. The material has limited strength. Number of producers, available valves and valve sizes in brass has diminished.

For stainless steel compositions the price has (relatively) decreased in comparison. The knowledge of stainless steel metallurgy has increased vastly.