chas
New member
Can I use PTFE tape on joints in a diesel supply pipe? In the dim and distant past, I had some advice on this but I cannot remember if the answer was yes or no! Would appreciate any advice.
Thanks
Thanks
PTFE tape & Diesel
- Thread starter chas
- Start date
vyv_cox
Well-known member
Not sure if it was my advice you received previously, I know I have posted on this subject. The answer is "never!!!" Particles of tape are always cut off by the threaded connections and they will pass downstream mixed with the fuel. With luck they will be trapped by a filter but it does depend where you use it - anywhere in the supply pipes to the injectors is downstream of the secondary filter anyway. PTFE tape will easily block injector clearances or jam under the needle and prevent seating.
One of our gas turbines suffered this problem after an overhaul. The flame became offset and distorted by PTFE tape in a fuel nozzle, burnt through a combustor liner and combustor housing. All happened in about 2 minutes and cost nearly US$0.5 to repair.
Best to use no sealants at all. Washers like Dowty types and soft copper ones should ideally be replaced every time. Compression fittings will normally survive re-use many times. Calor-tite is useful if you really have to use something to prevent leaks and it doesn't seem to have any knock-on effects.
One of our gas turbines suffered this problem after an overhaul. The flame became offset and distorted by PTFE tape in a fuel nozzle, burnt through a combustor liner and combustor housing. All happened in about 2 minutes and cost nearly US$0.5 to repair.
Best to use no sealants at all. Washers like Dowty types and soft copper ones should ideally be replaced every time. Compression fittings will normally survive re-use many times. Calor-tite is useful if you really have to use something to prevent leaks and it doesn't seem to have any knock-on effects.
steve_cronin
N/A
PTFE is used throughout the chemicals industry. I seem to remember reading somewhere that it was only suceptible to "..molten alkaline metals.."
Hunter boats sealed every diesel line joint* on our last boat with PTFE tape and when I complained that the fuel tank filler seal was leaking they were surprised that the standard black neoprene ring supplied by their tank manufacturer ( originally made for petrol) hadn't been swapped for a PTFE (Fluolion) one in their factory. They mailed me a replacement which has lasted (I may stand corrected Andy?) to this day.
Steve Cronin
Hoarder of all sorts of odd information
* not after the first filter though. These will have copper seals that shouldn't be augmented with mechanical substances which could clog injectors etc. Even Red Hermetite could do this and just gets in the way if you ever need to open a joint for air bleeding, say.
Hunter boats sealed every diesel line joint* on our last boat with PTFE tape and when I complained that the fuel tank filler seal was leaking they were surprised that the standard black neoprene ring supplied by their tank manufacturer ( originally made for petrol) hadn't been swapped for a PTFE (Fluolion) one in their factory. They mailed me a replacement which has lasted (I may stand corrected Andy?) to this day.
Steve Cronin
Hoarder of all sorts of odd information
* not after the first filter though. These will have copper seals that shouldn't be augmented with mechanical substances which could clog injectors etc. Even Red Hermetite could do this and just gets in the way if you ever need to open a joint for air bleeding, say.
brianrunyard
New member
Did you really mean "cost nearly US$0.5 to repair"?
50 cents seems far too cheap.
Brian
http://homepage.ntlworld.com/brunyard
50 cents seems far too cheap.
Brian
http://homepage.ntlworld.com/brunyard
KeithH
Member
I agree with Vyv. I have seen PTFE tape used on threads on cone type compression fittings, which only does harm. The sealing face is the cone/socket metal-metal seal, and the thread only supplies compression force. Adding tape on the thread actually reduces the pressure on the cone/socket.
PTFE tape is wonderful when used on taper threads, as used in water pipe service. This is where the slight interference between the tapered threads form the seal. It is so much better than the older materials. However, PTFE is often used where it does no good.
KeithH
PTFE tape is wonderful when used on taper threads, as used in water pipe service. This is where the slight interference between the tapered threads form the seal. It is so much better than the older materials. However, PTFE is often used where it does no good.
KeithH
G
Guest
Guest
I was always told .... if it don't leak without tape --- NEVER use it ! It will after you do !!
And it seems to be true ... as when you put the bloody fitting back after maintenance - it always leaks if the tape isn't just right, but if fitting never had tape and was corrected tightened etc. and then cleaned before refit ---- no problem !!
And it seems to be true ... as when you put the bloody fitting back after maintenance - it always leaks if the tape isn't just right, but if fitting never had tape and was corrected tightened etc. and then cleaned before refit ---- no problem !!
vyv_cox
Well-known member
Yes, I seem to have left the "million" out. The half cent wouldn't have paid for the tape!
steve_cronin
N/A
Yes I'll agree with that. Using tape on Conex & Compression fittings in general could have no effect other than a deleterious one but on the Hunter fuel system there are two taper fit joints on the feed and the plastic return has a back to back nipple joint in the cockpit locker where two sections of brass terminated plastic join.
Steve Cronin
Steve Cronin
steve_cronin
N/A
Yes I'll agree with that. Using tape on Conex & Compression fittings in general could have no effect other than a deleterious one but on the Hunter fuel system there are two taper fit joints on the feed and the plastic return has a back to back nipple joint in the cockpit locker where two sections of brass terminated plastic join.
Steve Cronin
Steve Cronin
chas
New member
Thanks to all. I shall have to find another way of sealing the leaks.