Teflon tape on diesel firtings

[cmedsailor]

I have just replaced a cav filter with a racor one and used teflon tape on the threads of the filter fittings. I made sure that it was not a large quantity and not “falling” beyond the end of the threads. Could that cause an issue? Even if something manages to go through the diesel hose wouldn’t the fine filter of the engine stop it from entering the engine?
Thanks
EDIT: I should add (if it makes any difference) that I have used a PTFE (USO GAS, DIN EN 753/1) tape. Those used for gas installations which I believe are resistant to hydrocarbons in general.

 

[Boater Sam]

I have just replaced a cav filter with a racor one and used teflon tape on the threads of the filter fittings. I made sure that it was not a large quantity and not “falling” beyond the end of the threads. Could that cause an issue? Even if something manages to go through the diesel hose wouldn’t the fine filter of the engine stop it from entering the engine?
Thanks

Teflon or PTFE? Not a good idea if it gets as far as the injection pump.

 

[john_morris_uk]

Isn’t there some specialist gunge you’re supposed to use? I was about to research this very topic as I’m about to install a new fuel tank and new engine and new fuel lines etc.

 

[scottie]

I don’t think that anything is advisable on fuel lines if you can avoid it

 

[john_morris_uk]

I don’t think that anything is advisable on fuel lines if you can avoid it

So compression fittings or some other sort of metal to metal fittings only then?

 

[jdc]

Racor filters use American NPT threads rather than BSP. The difference - apart form the threads per inch - is that the NPT thread profiles are designed to seal without needing any gunge or tape. So the short answers are:

1. Use the correct fittings - probably 1/8th and certainly NPT
2. don't use any gunge or tape

 

[Pete735]

Loctite 577 is what you need, expensive but an excellent product for sealing diesel threaded joints if you are in any doubt. I have used it many times over the years and never had a failure. It has the added advantage that you can break the joint if you ever need to (ie for a mod) without needing herculean strength. Also good for petrol and water although I have never felt the need for the latter joints.

I am sure if you do a search on YBW you will find it has come up many times before.

 

[penberth3]

Teflon or PTFE? Not a good idea if it gets as far as the injection pump.

Teflon is a "brand" of PTFE.

 

[Daverw]

+1 for 577

 

[ean_p]

Racor filters use American NPT threads rather than BSP. The difference - apart form the threads per inch - is that the NPT thread profiles are designed to seal without needing any gunge or tape. So the short answers are:

1. Use the correct fittings - probably 1/8th and certainly NPT
2. don't use any gunge or tape

I don't think that this is correct. NPT threads need a sealent at all times. NPTF aka Dryseal fittings are a one use sealent free fitting. If reused ( which isn't recommended) then sealent should be used. As it should if an NPT fitting is used with an NPTF fitting. The F by the way stands for Fuel but Dryseal fittings,as they are often known, are used in many liquid and gas systems. Don't confuse NPTF with NPT(F) as the latter simply indicates a female thread form. BSPT threads ( the more international standard which aren't compatible with NPT threads) function in the same way.
A liquid sealent like liquid PTFE etc is the common recommendation for most situations nowadays.
Take care not to over tighten the fittings as the ' wedge' effect generates enormous forces .
NPP & BSP fittings are of course a different story.......

 

[cmedsailor]

I have also edited my initial post. Probably I should add (if it makes any difference) that I have used a PTFE (USO GAS, DIN EN 753/1) tape. Those used for gas installations which I believe are resistant to hydrocarbons in general.

 

[dansaskip]

Like Pete735 and ean_p says use a liquid thread sealer like Loctite or other brand - making sure that it is suitable for diesel use.

 

[Daverw]

A lot of the confusion I think stems from the inter mixing of taper and parallel, this helps alignment, parallel to parallel always need sealing washers , copper, dowtey,,Ali or fibre etc and mostly locking nuts to align. also BSP is used without the T bit to indicate taper.

 

[jdc]

I don't think that this is correct. NPT threads need a sealent at all times. NPTF aka Dryseal fittings are a one use sealent free fitting...

You're right, I should have added the F. It still means that adding tape or gunge isn't required in Racor filters.

 

[ean_p]

You're right, I should have added the F. It still means that adding tape or gunge isn't required in Racor filters.

?

 

[superheat6k]

I am a huge fan of Loctite 577 (and not ever any other maker's compound), and we use this solely in my business for sealing refrigeration fittings, where PTFE is attacked by the fluorinated gases we use.

Others will not like it, but I find a wrap of the thicker grade of PTFE plus a wipe of 577 works for me on diesel compression joints. I believe the PTFE wrap gives the joint a degree of flex. Anyway I extensively replaced copper fuel piping on both my last boats using this method and did not ever suffer weeping joints. Indeed a bigger problem on older boats is where you can end up with a mix of both 3/8" and 10mm copper. 3/8" is smaller than 10mm, but will slide into a 10mm compression fitting, but will not seal properly, even with the correct olive, no matter how much PTFE or 577 you try.

I would therefore suggest a careful measurement with vernier of any copper piping you plan to modify to establish if it is 3/8" or 10mm OD, then stick with what size your boat started with, although generally I find the available range of imperial pipe fittings is better with 3/8". Be also wary that NPT and BSP sizes refer to the pipe's ID, whereas for fuel lines most references, olives, etc will refer to the pipe OD.

As an aside 577 is very useful for refreshing tired O rings where a spare is not available, such as the bowl on a Racor filter. Always avoid getting 577 inside the pipes or fittings being sealed. The amount needed is minimal, just fill the threads, having excess right over the threaded surface just ends up as waste as the joint is assembled. I do find the smell left on my fingers after using 577 is not pleasant.

 

[john_morris_uk]

Loctite 577 is what you need, expensive but an excellent product for sealing diesel threaded joints if you are in any doubt. I have used it many times over the years and never had a failure. It has the added advantage that you can break the joint if you ever need to (ie for a mod) without needing herculean strength. .

My tube of Loctite 577 arrived yesterday! Thanks for the tip.