Fuel line replacement

[FairweatherDave]

Been studying old threads on the subject and it looks like I need to do a fresh installation of my copper pipework, with fuel grade rubber pipework where it connects to the engine (short length). I can do compression fittings and appreciate pipe bending must avoid kinking the pipe (via either a pipe bender or spring). Do I need to flare the copper pipe to avoid olives slipping off? I have read about swaged copper fittings, but not sure where they come in to things. I need to go back to the boat to see what is there. To get out of trouble I was using flexible fuel pipe slipped over straight copper, with jubilee clips. The compression fittings also had a smear of blue gunge, a sealant like gasket goo or loctite? I'm at Thornham Marina for the next month if anyone is about with too much copper pipe on their hands (ASAP sell rather long lengths . Advice greatfully received, and recommendation of local professionals (PM me). Cheers
Dave

 

[superheat6k]

Be careful of the minor but critical differences between metric and imperial copper sizes. When an olive is slid on it should be almost tight on the pipe, and certainly snug. When it is done up the olive compresses into the pipe forming a seal and locking into the pipe so there is no need to flare the end. The line fittings must match the copper size. This is a particular issue with 3/8" and 10mm pipe sizes. As pipe fitting sizes are still generally referred to by their imperial size then there is a sound argument for keeping everything on the piped system imperial.

Now for some controversy I will get shot for ...

When I re-ran my fuel system pipes on both my last Turbo 36 and current Corvette 32 I routinely put a couple of wraps of PTFE tape plus a smear of Loctite 577 over the olive. Purists will say this is wrong, but my pipe joints don't leak. We use Loctite 577 for sealing refrigeration gas fittings up to 40 Bar, and we do not get leaks with this stuff on any threaded joint, and it works well also as a gasket and O ring refresher.

I definitely do not like jubilee clips onto plain copper tube. If you need to connect to a rubber section then first fit a proper hose barb with a compression fitting onto the copper.

 

[lpdsn]

Are you worried about copper and bio diesel?

I've just kept the copper pipework. Although there's a minor issue with bio diesel I think a lot of the scare stories are overdone. What I have fitted though is a vacuum guage before the lift pump, which I can't recommend too highly. Apart from anything else it allows me to see if a filter is starting to block up.

I also keep a cheap (£7.99) mini compressor on board that can be used to blow through the pipes if I have any doubts (can blow up fenders and dingies too). I wedge a coke bottle on the other end of the pipework to catch any gunk. I've used it twice but I don't think either problem was caused by bio diesel and copper.

 

[FairweatherDave]

Many thanks superheat6k, I am not qualified to shoot you! Appreciate your knowledge.
Thanks lpdsn....I'm not worried about copper and bio-diesel, although I have read about it. Copper still seems the standard installation with flexible hose where it meets the engine. I fancy the ease of flexible hose installation the whole length but it seems the majority still favour copper. Interested in more detail on a vacuum guage if anyone has any links. I've got a mini-compressor at home but used the dinghy pump and gaffer tape to blast the pipe back up to the tank when I thought it might be blocked.

 

[lpdsn]

Interested in more detail on a vacuum guage if anyone has any links.

I've posted the info before, but basically I bought a cheap boy-racer style 2" vacuum guage from a Chinese website. I also bought a T-piece - 8mm, with a 4mm branch and some 4mm hose (as the guage I'd bought fitted a 4mm hose). I reckon all told, including wiring for a light and a few other bits and pieces it cost <€30.

It's a long run from tank to engine on my boat so I've found 3"/Hg to be a good reading and 5"/Hg OK. I look to change the filter at 8"/Hg max. Lower if I'm planning a longer trip. Having had a filter block quickly with gunk one time I know 10"/Hg is the level where the engine revs are affected and 12"/Hg is enough to stop the engine. Of course the values might be slightly different with other boats/engines.

 

[FairweatherDave]

Many thanks lpdsn. That got me started into the many threads on improving fuel delivery etc. What a subject . I won't be doing too much to change the system at the moment as I am on a 30 days in and out deal at the marina, and need to focus on scub and antifoul etc, but plenty of food for thought.