Making diesel-proof unions in a pipeline.

[sequena1]

I think I remember (that's age for you!!!) reading that one shouldn't use PTFE tape when making up fuel line unions because diesel dissolves it. Is that right; and if it is, is there anything else that should be used instead? As ever, will be grateful for your thoughts.

 

[spynappels]

Try going to your local plumbers merchants and asking for Stag Red, its used in Kero lines in oil central heating. It is perfect for fuel lines.

 

[gandy]

I'm pretty sure Diesel won't dissolve PTFE, but it would be difficult to use without risking bits of the tape getting into the fuel system. Clean good condition unions shouldn't need any sealant. In the real world you can use Blue Hylomar, readily available from car places (I got mine from a filling station).

 

[savageseadog]

Unions should be metal to metal and not need any sealer. Try annealing the bits to help things along.

 

[Clyde_Wanderer]

[ QUOTE ]
Unions should be metal to metal and not need any sealer. Try annealing the bits to help things along.

[/ QUOTE ]
You mean try annealing the copper sealing washers to soften them and make them more pliable so they seal better.
I have used the metal washers with a rubber inner seal moulded to them with no problems, the type used in hydraulic hose fittings.

 

[Bodach na mara]

I am interested in this thread because I have several persistant leaks in my fuel system. Some are at valves (the lever stop-cock type), some at fittings (all T-joints) and the worst are at a CAV water separator where the pipes enter. In all cases, the diesel fuel seems more "searching" than any other fluid except perhaps antifreeze.

 

[duncanmack]

Petrol is worse.

Usually leaking because the unions have been overtightened and have damaged the sealing abilities of the copper olives. Lever type stop cocks usually leak because the taper plug is no longer a good fit in the housing. Can be addressed by lapping it in or replacing the cock.

BTW LPG is the worst. I suspect that CORGI training/ registration is about NOT overtightening fittings and how to test if you have. /forums/images/graemlins/grin.gif

 

[rutten]

My diesel tank is integrated in the (steel) hull. There is a bolt in the keel to empty its contents (from the outside). Loctite have a product that prevents diesel leaking past the bolt's thread. And yes, diesel dissolves pvc.

 

[alan006]

There is a product called Red Hawk which is ideal for diesel and petrol. Diesel will get past PTFE.

 

[TobyJug]

Loctite 577, found to be completely effective on all metal pipe thread sealing applications.
Being anearobic it cures almost immediately after assembly of the parts. Gives some mechanical strength yet can be undone. Excellent on large threaded connections.
Its fairly expensive but keeps for years and no, I have no commercial interest in loctite products.

 

[RivalRedwing]

ASAP sell Hylomar 5059 which I found to be an excellent sealant when I replaced my diesel line - 1 year in and not a single leak (touch wood) - would agree with earlier posts about overtightening being the biggest problem - always remember that if you only gently tighten a fitting you can always tighten it little further, if you over tighten it then all you can do is replace.

 

[DaveS]

I re-made all the joints on my suction line last year using Blue Hylomar and so far everything's been fine. I would agree with comments about tightening gently.

 

[DinghyMan]

When I did my LPG training many years ago we were taught to mark the fitting and only ever tighten 1 1/2 turns. As stated elsewhere you can always tighten it up but have to replace bits if its too tight. We carried a vary large box of fittings around with us and the first fix for leaky joints was always replace olives and fittings.
We had a couple of hand pumps, a bit like a bicycle pump with a gauge and length of rubber hose which we used for testing everything, still got one somewhere in the workshop.

Never bothered with Corgi as we were working outside UK.

 

[david_bagshaw]

cav water seperators frequenty leak due the the wrong type of fitting beig used & cracking the light alloy lid !

Loctite do some excessiely expensive jointing cpd for fuel lines, but it works!