Soldered joints in copper fuel lines?

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KenMcCulloch

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Is there any really good reason not to use soldered joints in a copper fuel line inside the engine compartment? It seems that such joints are safe up to something like 180deg C, which is well above the 100C specified for ISO7840 flexible hose. My thinking is that if there were to be a fire in the engine space the eventual failure of a soldered joint would perhaps be the least of my worries.
 
KenMcCulloch said:
Is there any really good reason not to use soldered joints in a copper fuel line inside the engine compartment? It seems that such joints are safe up to something like 180deg C, which is well above the 100C specified for ISO7840 flexible hose. My thinking is that if there were to be a fire in the engine space the eventual failure of a soldered joint would perhaps be the least of my worries.
Click to expand...

Your logic is correct, although misunderstood by some. But aren't compression joints easier to make?
 
KenMcCulloch said:
Is there any really good reason not to use soldered joints in a copper fuel line inside the engine compartment? It seems that such joints are safe up to something like 180deg C, which is well above the 100C specified for ISO7840 flexible hose. My thinking is that if there were to be a fire in the engine space the eventual failure of a soldered joint would perhaps be the least of my worries.
Click to expand...

Just out of interest, why do you want to use soldered joints? What's wrong with compression fittings with copper olives?
They are easier to make or replace than soldered joints, and obviously more fireproof. Leaks result from not supporting the pipes with enough clips. That's my view anyway..
 
Vibration can be a problem with soldered joints as can fire, it is notable they are prohibited under BSS and RCD. Not even allowed to use them on heating systems let alone engine supply.
 
For the price of a length of tube, avoid having any joins if poss.
It's an arbitrary rule perhaps, but c'est la vie..

I don't think a properly soldered fitting will fail any sooner due to vibration than a compression join, both will fatigue the tube at the step change in thickness.
Silver soldering will probably harden the copper unless you anneal it carefully afterwards?

Why bother, comp fittings are cheap easy and work, then everyone is happy.
 
The previous owner had used soldered joints on the boat's copper pipe water system, vibration caused them to leak. I fitted compression joints and they have been fine ever since. I also changed the copper pipe fuel system because that was leaking caused by vibration and the engine was cutting out. I replaced it with hose, again no problems.
 
How did the joints become leaky?
Did the soldering fail, or the pipes fracture at the joints?

How do you know vibration was the cause?

It could be the real cause was 'not soldered properly' or 'fatigue due to inadequate support'.
But for fuel or gas on a boat, there is no real merit in soldering, just use compression and keep the surveyors and clipboard wielders happy.
 
>How did the joints become leaky? Did the soldering fail, or the pipes fracture at the joints?

The water pipes' soldering failed because of vibration. What surprised me is I had the same problem with the copper pipes in the fuel system leaking through the compression joints each side of the two filters. Over tightening or under tightening causes leaks but that becomes immediately obvious when you start the engine and check the connections. It is possible/likely that both were caused by long distance sailing where engine use is extensive and it won't happen with weekend and holiday boats.
 
KellysEye said:
>How did the joints become leaky? Did the soldering fail, or the pipes fracture at the joints?

The water pipes' soldering failed because of vibration. What surprised me is I had the same problem with the copper pipes in the fuel system leaking through the compression joints each side of the two filters. Over tightening or under tightening causes leaks but that becomes immediately obvious when you start the engine and check the connections. It is possible/likely that both were caused by long distance sailing where engine use is extensive and it won't happen with weekend and holiday boats.
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Often fuel leaks are not immediately obvious, they leak air in instead of fuel out.
I'm surprised the actual soldering failed, I suspect the root cause might be bad soldering of greasy fuel pipes?
The solder in an end feed or yorkshire fitting should not see much vibration stress.
Any metal pipe is prone to fatigue from vibraion if not properly supported.
 
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