Sea cock id (for servicing)

[vyv_cox]

This reply has prompted me to wonder why stainless steel fittings are not used for all hull openings on a yacht. Their use would make a lot more sense (to me) than the corrosion-prone technology that we have inherited.

The susceptibility of stainless steel to crevice corrosion is perhaps the main reason. Offshore oil platform submersible pumps were bronze but for cost saving reasons stainless steel was substituted. Despite considerable design effort it proved impossible to eliminate stagnant areas and crevice corrosion resulted. A couple of superalloys were tried but these are also susceptible. Ultimately the pumps were made in bronze again.

I met with a manufacturer of stainless steel valves and fittings a few years ago. He told me that none of their production equipment could be made resistant, despite much research. Apparently the only s/s alloys that are not susceptible are high nickel 900 series, as used by Rolex for their casings (for dermatological reasons, not for corrosion resistance)

 

[wingcommander]

fortunately not always the case you just need to spec the right model......
RS PRO Stainless Steel Full Bore, 2 Way, Ball Valve, BSPP 25.4mm | RS

Yes I usually carry a couple of these in the van for isolation on domestic with poor preasure to showers etc . They are available in dzr also though I am not sure of the ball material. Much better choice than a gate valve . I hadn't realised they were as popular in the marine .environment . Every days a school day.

 

[[70521]]

This reply has prompted me to wonder why stainless steel fittings are not used for all hull openings on a yacht. Their use would make a lot more sense (to me) than the corrosion-prone technology that we have inherited.

I always wonder why metal fittings are used in a GRP boat when it would make more sense to use plastic ones.

 

[vyv_cox]

I always wonder why metal fittings are used in a GRP boat when it would make more sense to use plastic ones.

Until very recently we had no plastic fittings with sufficient strength. Glass reinforced nylon has made the difference.

 

[PeterV]

I had identical 3/4 inch gate valves on my Westerly. They unscrewed off the skin fitting Ok so I thought I’d strip them to refurbish them. The gland nuts fell into several pieces when I tried to undo them. I replaced with 3/4 inch DZR ball valves.