Started making fuel line with Evil Energy PTFE hose and fittings. As I get to the last threads of tightening the fitting the hose begins to turn with the fitting nut. What am I doing wrong? I seated the ferrule and could see the liner fully in the ferrule. Hose slid right on the fitting and no part of the outer SS or nylon was caught in the ferrule. Should it be lubed on the hose before assembly? I lube the threads with a drop of light oil.
I did finish one short line from the cell to the filter and pressure tested it with air submerging the fitting in a bucket of water and there's no leaks.

When it's fully tightened and assembled correctly, there will be a small gap between the nut and the fitting. That's normal. I do use a bit of lube on the fitting threads, but when it's tight it's tight. The nut won't always go all the way to the fitting.

Look closely at the fittings and you'll see what I mean. I run the same stuff.

https://imgur.com/a/e7iq5Tr

I was under the impression the nut had to tight all of the way against the fitting.

I also never get them tightened all the way together. Never had an issue at all.

I've always used an air gap of .015, never flush against the nut, never had a problem.

Bob

Interesting, I called Evil Energy and they insist fitting has to be tightened all of the way. The short hose that I did complete I did get the fitting tightened all of the way but as I said the hose wanted to turn. It air checked good at 50PSI.
I did see a site that said to lube the hose with the proper lube, but never said what the proper lube was.

I don't know what each manufacturer would recommend, but I have a bottle of Earl's hose assembly lube.

Is the Earl's lube for PTFE assembly?

quote:

Originally posted by Eman:
Is the Earl's lube for PTFE assembly?

I guess if I'm building a hose, I grab the hose assembly lube without worrying about all the particulars. I quick Google didn't reveal anything.

The nut does not need to be fully seated to the fitting. I use a bit of assembly lube on my stuff, just enough to keep it from galling....

For what it's worth:

I was told to allow a .015 air gap because tightening it any tighter causes the internal wall of the hose to twist and ripple. That creates a flow problem.

It all might be BS, (the flow issue) but I've never had a leak allowing the air gap.

Bob