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Working on the diesel tank - a triumph for the theory


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I saw it being advised against for fuel filter joints.

 

IIRC the reason wasn't that the tape was chemically incompatible.

 

It was that small pieces of the tape, dislodged by the act of tightening the fittings, might end up in the injector pump or injectors, doing them a mischief

That's unlikely to happen if the tapes wound onto the thread in the correct direction for a R/H thread or for a L/H thread, with the correct tension and an 1/8'' or so back from the end of the fitting.

Edited by bizzard
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PTFE tape goes almost transparent with diesel, perhaps people think it is dissolving!

Gold cyanide attacks PTFE but I can't remember what it's used for! biggrin.png (glamorous suicides?)

I know exterminators use it for fumigating ships ect to eradicate rats.

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It was that small pieces of the tape, dislodged by the act of tightening the fittings, might end up in the injector pump or injectors, doing them a mischief

 

Yes it *might*, but it doesn't. It's one of those theoretical possibilities that are a non-problem out therer in the real world.

 

As Biz says, it might be a problem when used incorrectly, but that applies to a lot of things!

PTFE tape goes almost transparent with diesel, perhaps people think it is dissolving!

 

 

Yes, this. I've been told by people this is the tape dissolving, possibly on here actually. It can easily be disproved by keeping a bit of PTFE tape in a jar of diesel for a few years and periodically getting it out for inspection...

Getting back to the PTFE debris 'problem', bits of PTFE get left behind in the thread when dismantling a screwed joint previously sealed with PTFE. So if the joint needs to be re-made, the threads need carefully cleaning first.

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My diesel tank drain tap is male threaded and capped so even if it's accidentally kicked open it won't spill diesel everywhere. Surely this is mandatory?

 

If I want to drain the tank I just put a couple of feet of hose on the end of the uncapped tap and drain it all into jerry cans. No need for all those fancy pressure calculations.

Edited by blackrose
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There is a ptfe tape sold specifically for gas and fuel use, slightly thicker and less tendency to break up.

 

Yeah, and it seems to be a better solution than the thin stuff for most applications. Is there any reason not to use it in other systems like, say, potable water?

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My diesel tank drain tap is male threaded and capped so even if it's accidentally kicked open it won't spill diesel everywhere. Surely this is mandatory?

If I want to drain the tank I just put a couple of feet of hose on the end of the uncapped tap and drain it all into jerry cans. No need for all those fancy pressure calculations.

Yes a cap or bung is mandatory. My worry was not that it would get kicked open but that the whole tap would get kicked off as it stuck straight out by several inches right next to the path taken by my foot as I step down into the engine bay.
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I saw it being advised against for fuel filter joints.

 

IIRC the reason wasn't that the tape was chemically incompatible.

 

It was that small pieces of the tape, dislodged by the act of tightening the fittings, might end up in the injector pump or injectors, doing them a mischief

But my link proves that PTFE is compatible with fuel! The yellow PTFE is designed for gas but will also work well for fuel as it is thicker and stronger than the white.

Edited by mross
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I have one here, yellow reel, the thick stuff, it says. Gas quality PTFE, Conforms to BS.EN.751-3 1997. For all common gases and liquids. One wrap. 50% overlap, like paint spraying.

Edited by bizzard
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Please, can you provide a link for any PTFE tape sold for fuel? I'm curious because I've never heard of it. PTFE is impervious to fuel.

If you search for "one wrap ptfe tape" you'll find a thicker tape than the usual flimsy white stuff. Many 'pro' sites state that the use of tape (of any thickness) is deprecated for fuel line use due to the possibility of 'bits' floating around, and that a liquid thread seal is a superior method.

 

As far as I'm aware there is no specific 'fuel use' tape although several sites (Screwfix for example) state that their ptfe tape is "suitable for water use only" which I presume (always a dangerous thing to do) is because it is so thin. Screwfix list a thicker tape which they state is "suitable for anywhere that has a heavier thread such as gas pipes" which would appear to support my presumption.

 

I have one here, yellow reel, the thick stuff, it says. Gas quality PTFE, Conforms to BS.EN.751-3 1997. For all common gases and liquids. One wrap. 50% overlap, like paint spraying.

Yup, that's the stuff.

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But my link proves that PTFE is compatible with fuel! The yellow PTFE is designed for gas but will also work well for fuel as it is thicker and stronger than the white.

Really only suitable for tapered threads though, where there's enough slack on the threads at the beginning to get it started properly, otherwise more stretching when winding is needed.

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My mate, a time-served plumber. who is now in education, swore by boss white and hemp, but this was for heating systems, not potable. He used to assemble those lovely cast-iron radiators which were supplied as separate castings which had to be screwed together - not a job you would want to re-do if leaking!

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Boss white (or boss blue) and hemp is still the best solution for big threads like immersion heaters( not the ones with fibre washer or an O -ring). PTFE tape struggles to properly fill the gaps on anything more than about 1in BSP.

 

Heldite is wonderful stuff for diesel.

 

N

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I'm afraid that wasn't me.

Quite right! It was BWM in post #31. I do apologise FtS.

There is a ptfe tape sold specifically for gas and fuel use, slightly thicker and less tendency to break up.

Please, can you tell me of any PTFE tape sold specifically for fuel?. I know yellow is for gas and green is for oxygen, but I'm not aware of any for fuel.

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