Bronze through hulls with stainless ball valves.

[alla_breve]

My engine intake and sink outlet have got the combination in the title. I check and exercise then regularly. Electrolytically is this a real no no? (They’re deliberately not bonded). Heads cocks are Blake’s so no problem there. Would bronze ball valves be any better, depending what the balls are made of I suppose? I do not want “plastic”, sorry to disappoint fans of them! Thanks.

 

[geem]

As long as the valves are 316 there is no problem of electrolysis. I have had this set up for the last 8 years on some of my through hulls.

 

[vyv_cox]

Are you sure they are stainless? Chromium plated brass is more common.

 

[alla_breve]

Are you sure they are stainless? Chromium plated brass is more common.

Thanks for reply Vyv, i'm pretty sure the bodies are stainless, they're standard "industrial" ones , I think I got them from RS. Balls look stainless with a white "plastic" seal. Stainless handles.

 

[PabloPicasso]

My sea toilet outlet was dzr with stainless ball and the inserts that hold the ball in place failed.

I replaced it with a tru design composite type like this.
No metal parts to corrode

 

[Dockhead]

Are you sure they are stainless? Chromium plated brass is more common.

Indeed. I've seen a lot of ball valves, and never seen stainless balls except in stainless valves. In bronze valves, they are normally chrome-plated brass, better ones chrome plated bronze, or in the cases of the newer, more expensive Maestrini ones, bare plastic.

The run in PTFE seals, so no metal to metal contact with the valve body.

 

[[70521]]

Thanks for reply Vyv, i'm pretty sure the bodies are stainless, they're standard "industrial" ones , I think I got them from RS. Balls look stainless with a white "plastic" seal. Stainless handles.

I've highlighted the words that strike terror into my heart concern me. Unless you are 100% confident that these products are the genuine article then use something that is.

 

[alla_breve]

They are these:
RS PRO Stainless Steel High Pressure Ball Valve 3/4 in BSPP 2 Way | RS Components

Materials :

• Body, Retainer and Ball - ASTM A351-CF8M and ASTM A351-CF8
• Seat A & B - PTFE/RTFE
• Stem - AISI 316
• Thrust Washer & Packing - PTFE
• Gland Ring, Spring Washer, Stem Nut - AISI 304
• Handle – Stainless Steel
• Handle Sleeve - PVC
• Locking Device – Stainless Steel

 

[geem]

They are these:
RS PRO Stainless Steel High Pressure Ball Valve 3/4 in BSPP 2 Way | RS Components

Materials :

• Body, Retainer and Ball - ASTM A351-CF8M and ASTM A351-CF8
• Seat A & B - PTFE/RTFE
• Stem - AISI 316
• Thrust Washer & Packing - PTFE
• Gland Ring, Spring Washer, Stem Nut - AISI 304
• Handle – Stainless Steel
• Handle Sleeve - PVC
• Locking Device – Stainless Steel

They look exactly like mine?

 

[[2574]]

• Body, Retainer and Ball - ASTM A351-CF8M and ASTM A351-CF8
• Seat A & B - PTFE/RTFE

so is that a definitive “yes” that the ball itself is stainless?

At ASAP supplies the price difference between DZR and bronze is not significant so bronze throughout seems right.

 

[PabloPicasso]

Is there a reason to use metal (corrosion resistant) ball valves instead of composite ones?

The composite ones don't have corrosion issues to worry about. Or am I missing something?

 

[[2574]]

Is there a reason to use metal (corrosion resistant) ball valves instead of composite ones?

The composite ones don't have corrosion issues to worry about. Or am I missing something?

Physical size. I am renewing throughout but regrettably the composite TruDesign type are physically too big to fit in some of the tight spots - and I don’t want a blend of valve types in the boat.

 

[vyv_cox]

Is there a reason to use metal (corrosion resistant) ball valves instead of composite ones?

The composite ones don't have corrosion issues to worry about. Or am I missing something?

Main reason might be their size. In the small heads of my boat even the three Blakes seacocks occupy considerable space. Plastic ones would be impossible.

 

[vyv_cox]

• Body, Retainer and Ball - ASTM A351-CF8M and ASTM A351-CF8
• Seat A & B - PTFE/RTFE

so is that a definitive “yes” that the ball itself is stainless?

At ASAP supplies the price difference between DZR and bronze is not significant so bronze throughout seems right.

In the stainless body referred to above the ball is stainless. In the bronze valves sold by ASAP the ball is plated brass (or were last time I checked). There seems to be a technical reason why bronze balls are not made, at least in Europe, not sure about USA. There is also the option of a plastic ball in a bronze body, also ASAP, but although well engineered this is a very expensive option.

 

[[2574]]

In the stainless body referred to above the ball is stainless. In the bronze valves sold by ASAP the ball is plated brass (or were last time I checked). There seems to be a technical reason why bronze balls are not made, at least in Europe, not sure about USA. There is also the option of a plastic ball in a bronze body, also ASAP, but although well engineered this is a very expensive option.

Vyv,

Thanks, that explains the price difference between these two:

 

[Pye_End]

If the stanless ball valve is in contact with a bronze skin fitting, would the skin fitting de-zinc? Isn't this the same issue as putting a bronze propeller on the end of a stainless shaft?

 

[vyv_cox]

If the stanless ball valve is in contact with a bronze skin fitting, would the skin fitting de-zinc? Isn't this the same issue as putting a bronze propeller on the end of a stainless shaft?

Bronze cannot dezincify, there is no zinc in it apart from 5% as an antioxidant. Galvanic corrosion occurs between a bronze/brass prop and stainless steel shaft, hence the anode. Potentially the same with skin fitting and valve.

 

[alla_breve]

Bronze cannot dezincify, there is no zinc in it apart from 5% as an antioxidant. Galvanic corrosion occurs between a bronze/brass prop and stainless steel shaft, hence the anode. Potentially the same with skin fitting and valve.

So am I ok with stainless and bronze then Vyv, or is the galvanic corrosion too bad? Does it gradually weakens the stainless (higher up the table)? Brass seems pretty close to Bronze, so perhaps the brass balls in the bronze valves make them no improvement? I dont like to mention the cost factor, but the RS ones are £25!

 

[[2574]]

So am I ok with stainless and bronze then Vyv, or is the galvanic corrosion too bad? Does it gradually weakens the stainless (higher up the table)? Brass seems pretty close to Bronze, so perhaps the brass balls in the bronze valves make them no improvement? I dont like to mention the cost factor, but the RS ones are £25!

In this thread here (see #5): Another Seacock Question - replacing through hulls and ball valves with Blakes? Vyv mentions that ASAP DZR valves have a DZR ball fitted. It seems to me that the best balance of Longevity/Risk/Cost is Maestrini DZR throughout

 

[vyv_cox]

So am I ok with stainless and bronze then Vyv, or is the galvanic corrosion too bad? Does it gradually weakens the stainless (higher up the table)? Brass seems pretty close to Bronze, so perhaps the brass balls in the bronze valves make them no improvement? I dont like to mention the cost factor, but the RS ones are £25!

Almost at the bottom of the metallurgy/brass and bronze page on the website you will find a typical failure. The chromium plating pits and flakes, increasing the friction enormously. The brass stem dezincifies and breaks, rendering the valve useless. Voltage between stainless and bronze/brass in the series is not huge but stainless will inevitably suffer crevice corrosion. DZR is about the best all metal valve/skin fitting combination today.