What metal for diesel fittings or doesn’t it matter?

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john_morris_uk

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I’m about to fit a new diesel fuel tank to Serendipity and so all the fittings are getting renewed. I’m so used to using bronze or stainless on a boat but in this context it’s got me thinking and wondering. The tank is in stainless with 1/2” bsp female connections. I’ll need elbows and tails (or the connectors for hoses I’ll have made up with professional crimped ends) plus valves for the three feeds: heater, main engine and generator. (I wasn’t planning on putting valves in the excess fuel returns…!) I guess most diesels use brass and I’m guessing this is still ok here as there shouldn’t be any water, and certainly no seawater anywhere near these connections. I’ve got the option of bronze or stainless though.

Any thoughts?
 
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I used copper tubing when I re-engined with a new plastic tank 15 yrs ago. Short run from tank to primary filter then flexible tubing. This is what was recommended at the time. No problems to date.
 
My stainless steel tank with brass fittings is coming up to 40 years old and is mostly still in excellent condition. The only problem was on the fine-threaded drain plug right at the bottom of the tank, which corroded due to water inside the tank. Eventually it leaked and on removal fell out after a quarter of a turn as the threads had all gone. I replaced it with BSP brass whose threads are far more robust.
 
john_morris_uk said:
I’m about to fit a new diesel fuel tank to Serendipity and so all the fittings are getting renewed. I’m so used to using bronze or stainless on a boat but in this context it’s got me thinking and wondering. The tank is in stainless with 1/2” bsp female connections. I’ll need elbows and tails (or the connectors for hoses I’ll have made up with professional crimped ends) plus valves for the three feeds: heater, main engine and generator. (I wasn’t planning on putting valves in the excess fuel returns…!) I guess most diesels use brass and I’m guessing this is still ok here as there shouldn’t be any water, and certainly no seawater anywhere near these connections. I’ve got the option of bronze or stainless though.

Any thoughts?
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Your thinking is correct - no issue with brass on a diesel tank. No need for the extra cost on bronze or SS fittings.
 
Brass, stainless or copper are all ok, from personal experience; galvanised is always warned against.
Fire-resistant rubber hoses of an MCA-approved standard are easy to use and arguably better than metal, as they don't get work-hardened. You can also bounce a hammer off them with no ill-effects, unlike eg copper.

One point which may or not be helpful: My Beta 43 fuel returns actually do have cocks on them.
I have port and starboard tanks, and with supply and return cocks, I can draw from, and return to, any combination of either or both.
I chose, for the minimal extra cost, to fit cocks on everything when we refreshed all the pipework, just in case it might ever come in handy.
For example:
You might want to empty one tank and fill the other for some reason over the course of a day's motoring.
Returning fuel has always just been forced through two filters.

Yes, it would be interesting to see what happened if both were shut, and you tried to run the engine..
 
Here's why you shouldn't use copper with diesel: Are Copper, Zinc, and Brass Mucking Up Our Fuel? - Practical Sailor

Copper lines should not be used because fuel polymerizes (thickens) in copper tubing during long periods of disuse and can clog fuel injectors.

Having said that, I used short lengths of copper pipe when I installed twin filters on Jissel and never had a problem in the 15 years I kept the boat.

On Jazzcat, the fuel lines are reinforced plastic. "Fire Hazard" I hear you say. Perhaps, but the fuel tank is plastic, so the hoses will be the least of my worries if I get a fire in an engine bay
 
Stemar said:
Here's why you shouldn't use copper with diesel: Are Copper, Zinc, and Brass Mucking Up Our Fuel? - Practical Sailor

Copper lines should not be used because fuel polymerizes (thickens) in copper tubing during long periods of disuse and can clog fuel injectors.

Having said that, I used short lengths of copper pipe when I installed twin filters on Jissel and never had a problem in the 15 years I kept the boat.

On Jazzcat, the fuel lines are reinforced plastic. "Fire Hazard" I hear you say. Perhaps, but the fuel tank is plastic, so the hoses will be the least of my worries if I get a fire in an engine bay
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Your tank is less likely to be in engine compartment!

reinforced plastic was used for many years with the advantages of flexibility and allowing sight of air bubbles but discolouration and hardning were considered more of a problem along with not being fireproof
 
I have stainless tanks with brass couplings but all rubber (fuel rated) hoses. Most importantly I have a drain cock at the bottom of the tank to drain off water each month, typically 5-30 ml.
 
Curious to know where your genset is installed?

If the new tank has pick up pipes fitted in the top dangling down into the fuel then I would not bother with valves what purpose would they serve?

Certainly little point on the returns.
 
burgundyben said:
Curious to know where your genset is installed?

If the new tank has pick up pipes fitted in the top dangling down into the fuel then I would not bother with valves what purpose would they serve?

Certainly little point on the returns.
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Always good to have an emergency shut off on the supply. You'll want to isolate the flow if you have an engine fire!
 
pyrojames said:
Always good to have an emergency shut off on the supply. You'll want to isolate the flow if you have an engine fire!
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Really? I wouldnt. I'd be getting off.

If the pipes go into the top of the tank the flow will stop as soon as the engine stops or the supply line is compromised by the fire.
 
R.Ems said:
A slight digression..


Wouldn't you first try and fight the fire? With a bit of practice, prompt action, and suitable extinguishers, many yacht fires could be put out.
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Assuming there's an auto extinguisher and its gone off but there are signs the fire is still live in the engine box, no, I wouldnt open the box, maybe if there was a fire port I'd release an extinguisher into the engine room.

I would not be faffing about shutting off a fuel cock.

If the fire had escaped the engine box, I'd be off the boat.
 
GRP tank, copper fuel pipes, brass fittings. All 42 years old and in perfect condition. The fuel pick up pipes are all connected through the top of the tank. Four pick up and two returns. Never a problem. Might I suggest with your new tank that you have a large access lid for the time you need to get in for a thorough clean and a small brass 1" screw opening for inspection or for use of a dip stick if the fuel sender fails. This small opening can also be used to 'vacuum' the tank bottom with a filter and electric pump if you suspect dirt or water in the bottom. It's far easier to use this small opening regularly than start to messing about with seals, screws and large lids
 
Solid fuel lines are rapidly becomeing extinct now except on commerical vessels, and that is for a different reason. An A-rated flexible hose is better in almost every way than the solid equivalent. Semi-rigid or hard plastic lines have no place on any vessel, IMO
 
Moodysailor said:
Solid fuel lines are rapidly becomeing extinct now except on commerical vessels, and that is for a different reason. An A-rated flexible hose is better in almost every way than the solid equivalent. Semi-rigid or hard plastic lines have no place on any vessel, IMO
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Even if it passes close to exhaust elbow?
 
IanCC said:
Even if it passes close to exhaust elbow?
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Assuming you mean the water cooled exhaust elbow then yes, it's fine. Regs state that the surface temperature needs to be below a certain limit in marine engines (hence why exhausts and manifolds are water cooled or have insulating lagging).

But as also mentioned, the felxible hose is really easy to route away if there is any cocern.
 
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