Ball Valve For Fuel?

[sailorman]

Marine ball valves for water are good also for fuel. Do not use PTFE because diesel melts it. I used sikaflex successfully. Sikaflex is not affected by diesel or solvents once cured.

Best read #9 then

 

[prv]

Marine ball valves for water are good also for fuel. Do not use PTFE because diesel melts it

But marine ball valves for water generally have teflon seats. Which is merely DuPont's brand name for PTFE. So if diesel did dissolve PTFE, those marine ball valves would be in trouble too.

Fortunately, I'm pretty sure it doesn't.

Pete

 

[Tim Good]

Do not use PTFE because diesel melts it.

This the thing I am up against. Some say PTFE is bad because strands can come off and clog injectors. Other say it is because it melts. If the latter than all ball valves using a PTFE seat would be a no go and rule out a lot of marine balls valves.

I think as Vyv says, PTFE is not itself eroded or melted by fuel, it is just a misunderstanding from the advice not to use PTFE tape on fuel valves.

 

[prv]

Other say it is because it melts. If the latter than all ball valves using a PTFE seat would be a no go and rule out a lot of marine balls valves.

If you want some further reassurance, this chart says that PTFE is "resistant" (the highest option) to diesel. Also to just about everything else except fluorine and monoethanolamine, whatever that is.

http://www.zeusinc.com/materials/ptfe/chemical-resistance-chart-ptfe

(Diesel is under O for Oil.)

Pete

 

[vyv_cox]

A fuel cock will usually be before the engine's fine filter, is there much realistic chance of strands of PTFE getting past that?

Yes, true of course, but people use PTFE tape on other parts of the fuel system, even on olives or flared connectors on the injectors and pump.

 

[vyv_cox]

If you want some further reassurance, this chart says that PTFE is "resistant" (the highest option) to diesel.

It is used throughout the oil industry for a whole variety of sealing purposes. A colleague worked on it for years as gaskets in LNG loading systems, at cryogenic temperatures. It was used as a seal material in offshore pipeline ball valves, anything up to 42 inch bores, 138 bar pressure, until it was understood that the glass-filled PTFE was wearing the stainless steel balls. It is the base polymer in the vast majority of natural gas compressor piston rings, temperatures up to 150C, pressures to 400 bar when I worked on them, probably more by now. All of these duties far more aggressive than diesel at ambient temperatures.

 

[Rock Dodger]

Hi Folks, I recently replaced my fuel tank and the brass cock that went with it. The tank leaked and the cock had a nasty drip (the doctor at the clinic was very discreet!). All the pipe connections were with brass olives which were OK. If you nipped up the nut on the cock it made it tight to turn and only made matters worse in the long term. I did away with the cock and replaced it with a stainless steel ball valve with PTFE sealing on the seats. This valve cost a few quid and is used, and recommended for use, on domestic heating fuel tanks, the contents of which are more or less diesel. It is tight, it does not drip. If there are tiny bits of PTFE from a (badly) taped seal then that should end up in the fuel filter (the clue is in the name). Check the tech. specs. for PTFE, they usually tell you it is safe to use with almost all liquid hydrocarbon fuels.

 

[Tim Good]

Ok so as a follow up I tried the BES valves Doug suggested. It so happens that they are actually the funky type with the locking latch afterall. they are the same as the expensive ones from Valves Online and better than the ASAP ones in my view:

£7 quid for stainless 1/4" and shipping is a flat £4.95

Oh and I managed to find a company to supply spare ball valve handles which you can see in the background (www.tom-parker.co.uk) which I'm going to fit to my large and very pricey bronze intake strainer which I had no intention of changing because of a rusted handle.

 

[bigman1]

PTFE is almost totally inert, and is not attacked by diesel fuel, or any other kind that I know of. It's the tape that's the problem, small fibres of it will inevitably break off when making joints up and some may well find their way downstream. I have some dramatic photos of a gas turbine that burnt and destroyed itself when a piece of PTFE tape became trapped across one of the combustor nozzles, diverting the flame path.

I helped a workmate a long time ago to do an emergency repair on a petrol carb.with ptfe tape and the petrol dissolved the tape quick time.

 

[vyv_cox]

I helped a workmate a long time ago to do an emergency repair on a petrol carb.with ptfe tape and the petrol dissolved the tape quick time.

'Teflon is inert to gasoline and all petroleum products. The problem with Teflon is it cold flows under pressure so that when tightened (when wrapped around your fitting) it will relax eventually and probably not seal properly. This is not something you want where gasoline can leak. '
http://www.answers.com/Q/Is_Teflon_tape_use_able_on_a_fitting_in_a_gasoline_tank

'PTFE gains its properties from the aggregate effect of carbon-fluorine bonds, as do all fluorocarbons. The only chemicals known to affect these carbon-fluorine bonds are certain alkali metals and fluorinating agents such as xenon difluoride and cobalt(III) fluoride.'
http://en.wikipedia.org/wiki/Polytetrafluoroethylene

'Teflon tape is a cheap and effective way to seal fittings in gasoline lines. It is a safe remedy because Teflon tape is inert to gasoline. However, it is essential you wrap the Teflon tape counterclockwise around the fitting, so that you do not unwrap the tape when you screw the fitting back into place.
http://www.ehow.com/how_7394077_stop-gasoline-leak-teflon-tape.html

'Gasoline 100 , and 130 OCT. A'
http://www.balseal.com/files/tech_library/tr60a_020707132405.pdf

 

[lw395]

I helped a workmate a long time ago to do an emergency repair on a petrol carb.with ptfe tape and the petrol dissolved the tape quick time.

Possibly not actual PTFE tape?
There are other sealing tapes around which do indeed dissolve in petrol.
Self-amalgamating tape for one.