Fuel pipe - copper or Flexible?

[Anthony]

Hi,

Will be removing stainless steel fuel tanks for repair, and fitting new filter etc, so looking at replacing all fuel tubing.

Currently its mainly 15mm copper, with mixture of compression and soldered (not clear if silver soldered or normal), going to flexible at engine feed. Also have a 22mm copper pipe cross flow between the two tanks, and a number of (now grotty looking) gate valves to control feed from tank 1/2/both.

Anyway point is, what is best thing to replace all the piping (inc return and breather) with, copper as currently, or ISO7840 fuel hose?

I am currently leaning towards 'proper' ISO 7840 fuel hose, on the basis that its designed for the job, and able to flex with vibration. Thats said the copper pipe has been there for god knows how many years, and no major leaks that know about.

If copper whats best way to connect, compression fittings or solder? Compressions could shake loose, vs soldered that could melt in fire (dont really want to get into silver soldering / brazing).

The two tanks are a few feet from other other, and not much longer to the engine, so we are not talking about huge runs, although they will need a few bends / curves in them

I look forward to you collective wisdom as always /forums/images/graemlins/laugh.gif

Thanks

Anthony

 

[john_morris_uk]

No real comment about the pipe material - I expect others better qualified can comment. However why the negative thoughts on silver soldering? The other day the fuel return pipe sheared on my Volvo. A few minutes with a blow torch and the correct flux and some silver solder and its good as new. Not hard so long as you have the correct flux and clean metal, and if you pay the postage I'll give you some! Can't spare any silver solder as the bit I have I scrounged and its lasted me years so far....

 

[Strathglass]

Use copper pipe for main run. If it is threaded inside plastic tubing this will protect the pipe.

At the engine end use a 'made up' ISO 7840 fuel hose with tails at each end. Use compression fittings to join the tails to the copper pipe and the engine.
Also use compression fittings to join the copper pipe to the water trap (if physically separated from the engine) and the fuel tank.

Made up ISO 7840 fuel hoses are available from ASAP in various lengths and termination pipe diameters.

Iain

 

[ongolo]

What none of you is aware, diesel disolves copper!!!!!!!!!
No car manufacturer ever uses copper on diesel. Test for your self, once in a whuile one does see copper pipes put on a diesel engine, they are aways absolutely shiny,because........... diesel disloves copper.

Admittedly the process is slow, but if you expect the pipes to last, DO NOT USE COPPER.

regards ongolo

 

[Stemar]

Re: diesel disloves copper.

That's interesting. Please don't tell Jissel, her fuel pipes are copper, and AFAIK coming up to 35 years old!

Personally, I'd use copper pipes with compression fittings (fireproof!) at any joins between the fuel tank and the primary filter, then a flexible to the pump.

From the British Waterways guide:

"All fixed fuel feeds and pipes permanently charged with fuel, including balance pipes, must be made of fire resistant and impact resistant material: softened copper, stainless steel, aluminium alloy or (for diesel installations only) mild steel of suitable size ... To reduce the risk of fuel connections leaking, any connection which permanently carries fuel must be made with efficient screwed, compression, cone brazed or flanged joints. Soft soldered and push-on joints will quickly fail if exposed to excess heat, potentially adding more fuel to a fire. They must not be used."

It doesn't apply to sea going boats as legislation, but IMHO, it's a good guide. I suspect that silver soldered joins would be OK, as they would have to get pretty hot before they leak.

By the way, it's a good idea to have the fuel cut-off outside the engine compartment so you can still turn it off in the event of an engine fire

 

[Superflid]

Re: diesel disloves copper.

After watching a combine harvester, on a farm I was living, burn to a crisp I'm less keen than most to suggest that "blowtorch" and "fuel line" are a good combination.

I'd go to the pub while you got the job done........

 

[Guest]

Re: diesel disloves copper.

Diesel, or at least the sulphur in it , forms Zinc Sulphate, which is like a gel in diesel fuel.

For this reason galvanised tanks must not be used.

 

[boatmike]

Er... Copper is an approved material for fuel lines by all certification authorities as far as I am aware. I have worked on ships that are over 40 years old where copper fuel lines are as good as new. All Eberspacher diesel heaters are now supplied with copper fuel lines rather than plastic as plastic is not approved by Lloyds etc. You state that diesel dissolves copper. Where does this opinion come from? What evidence do you have to back up this claim please?

 

[john_morris_uk]

Re: diesel disloves copper.

I was rather assuming that one takes the fuel line off the boat into the workshop and ensures that there is no fuel left in it before applying the blow torch....

 

[Superflid]

Re: diesel disloves copper.

[ QUOTE ]
I was rather assuming that one takes the fuel line off the boat into the workshop and ensures that there is no fuel left in it before applying the blow torch....

[/ QUOTE ]

There are others not so wise John. /forums/images/graemlins/grin.gif
Like the aforementioned combine harvester mechanic.....

 

[cliff]

[ QUOTE ]
What none of you is aware, diesel disolves copper!!!!!!!!!
No car manufacturer ever uses copper on diesel. Test for your self, once in a whuile one does see copper pipes put on a diesel engine, they are aways absolutely shiny,because........... diesel disloves copper.

Admittedly the process is slow, but if you expect the pipes to last, DO NOT USE COPPER.

regards ongolo

[/ QUOTE ]The main objection to using copper is the vibration problem. If the pipework is not securely fixed or is badly fitted, any vibration can lead to work hardening of the copper and ultimately failure. Note the "Authorities" specify soft copper ie annealed copper. My preference would to go for cunifer piping for "marine" boats and copper for inland waterways although the difference in cost is neglible
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[boatmike]

I don't have any problem Cliff with using cunifer. I also take your point re annealed copper. Any type of pipework should be secured to avoid vibration. The standards for road vehicles are entirely different as in this case exposed pipework is exposed on the underside of a vehicle and needs to resist stone chips etc. On a boat you dont have this problem. I know this was not your point in the first place but I still see no evidence for copper "dissolving" in diesel and unless someone tells me why, I think the evidence of longevity on warships I have worked on leads me to believe this is rubbish. Every joint on a diesel (even a vehicle mounted one) is sealed with an annealed copper washer. Why don't these dissolve?

 

[pappaecho]

I am a bit surpised that you have 15mm copper tube as the feed pipes. I would have thought 10mm soft copper tube would be enough unless the engine is 6 cylinder and then I would go to 12 mmm soft copper tube. The advantages are that you unroll it from a coil and hence do not have to join it unless you need to join it. It also has much thicker walls than 15 mm copper tube, because if it was as thin as the 15mm it would collapse. My boat is 26 years old and has 10mm soft copper to and from the fuel tank , via separator and then via armoured flexibles to the main fuel filter etc.
If diesel eat copper, then again it has got a lot more to eat than 15mm thin wall tube

 

[cliff]

[ QUOTE ]
I don't have any problem Cliff with using cunifer. I also take your point re annealed copper. Any type of pipework should be secured to avoid vibration. The standards for road vehicles are entirely different as in this case exposed pipework is exposed on the underside of a vehicle and needs to resist stone chips etc. On a boat you dont have this problem. I know this was not your point in the first place but I still see no evidence for copper "dissolving" in diesel and unless someone tells me why, I think the evidence of longevity on warships I have worked on leads me to believe this is rubbish. Every joint on a diesel (even a vehicle mounted one) is sealed with an annealed copper washer. Why don't these dissolve?

[/ QUOTE ]When using clean, refined, polished Diesel they dont disolve. Perhaps Ongolo is making reference to the crappy diesel they get in Namibia. Where we have acidic fuel and sulphur present we could have a minor problem. My boat is piped in 1/4 and 5/16 Cu with rubber flexies to the engine and NO problems with the Cu. If and when I change it I will look at CuNi (Cunifer) but that could be years down the line.
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[snowleopard]

solder

FWIW, i had an oil boiler fitted recently. the installer told me that solder is illegal for domestic use in oil lines, compression joints must be used.

 

[poter]

Re: solder fittings

Yes thats true our oil fired boiler has a copper feed line with compression fittings, but is not subject to vibration. For A boat installation I would go along the soft copper route, with cone olive fittings the olives IMHO should be copper.

poter