Fuel Line Material Question

I was poking around elsewhere online, & ran across a post, where a boat's owner was having to install a new fuel line for her diesel, as the old one had cracked.
Please show me a little mercy when fielding my question, as I'm well below both my sleep & caffeine quotas, Groan ;-)

My question is, is would it be possible to use another type of material for fuel lines, like say something along the lines of braided stainless steel brake lines? Or even just braided stainless steel jacketed lines, or braided Kevlar brake lines themselves. And if not, why not?
I know that on my car (a non-diesel) parts of the fuel line are simply rubber tubing, built to a certain spec. Thus my query re. Marine Diesel fuel lines.

The metal & or Kevlar jacket in such lines would/should (theoretically), give you good wear abrasion & resistance, but would still have the line remaining flexible. Avoiding the cracking problems inherent to metal tubing.
And obviously pressure shouldn't be a problem, as I've worked & sailed on many a racing yachts where the pressure on the hydraulic sail & rig controls on some of the vessels ran from 3k - 5k psi. Such as the; backstay, vang, mast jack, shrouds, etc. And some of that tubing/plumbing was/is simply Kevlar reinforced rubber.
Below are some links to Lewmar/Navtec Hydraulic; Rigging, Plumbing, Lines, & Equipment for reference. TIA.
http://www.navtec.net/product-listin...earch&type=143
http://www.navtec.net/product-listin...&vall=1&page=1
http://www.navtec.net/products.asp?i...=152&channel=2
http://www.navtec.net/products.asp?i...=155&channel=2
http://www.navtec.net/product-listin...earch&type=143

 

The link goes to some instalink site where you need to open an account to see it. Are you asking about feed lines or high pressure ones to the injectors?

 

DO NOT use lines intented for other fluids like brake fluid, motor oil, gasoline, etc. these have different compounds to resist the chemicals they are designed to contain, mixing them up will likely result in the fuel line breaking down and leaking.

the only exception would be a solid metal fuel line intended for the pressures the system operates on.

If you need diesel fuel line, use ONLY line intended for use with diesel fuel. same is true for gasoline, brake fluid, automatic transmission fluid, etc.

So you need to know both the operating and max pressure of the system, and the type of fluid that the replacement tubing is designed to carry. I do not think there is any such thing as a universal fluid line that can use all fluids from coolant to brake fluid.

 

Petros has covered the basics.

I would add that hoses for marine applications are covered by various additional standards - 'any' diesel hose will not do. Has to be fire resistant. Cannot be attached using a barbed fitting and worm drive clips - swaged fittings are required (may be exemption on this below a certain vessel size) but will be labelled with approvals Fire Acol, USCG, NMMA SAE etc.

Your local hose supplier can make up hoses with threaded fittings swaged onto the correct grade and size of hose - can even use the stainless or kevlar braided protection (but he must put a tag stating the rating in the fitting if you go this route as the braided cover will obscure it).

Do not use (internally) Galvanised pipes or fittings for diesel - acids in the fuel can disolve out microscopic particles of Zinc (galvanising) which can cause serious damage to injectors.

Also PTFE Plumbers tape is a no no. Many people have been lucky with it - the role is to LUBRICATE a tapered thread such that you can get a metal to metal seal - if you achieve a metal to metal seal the PTFE becomes irrelevant (as long as it's upstream of the filters in case bits get into the fuel)
A couple of turns may be OK but the guys who put on a dozen turns for good measure tend to fail - it does not work well as a gasket and will soften significantly over time.
Silicone instant gasket (fuel grade) is much better, and Loctite threadlock ditto (provided disassembly never required).

 

Gents, thanks for the answers/steering me in something resembling the proper direction. I was/am curious by nature, & my original query was keying off of the idea that perhaps there is a better type of hose for some applications, such as getting diesel fuel from the pump to the injectors (on the high pressure side, so to speak).
I know that low pressure lines, are pretty much a no brainer, as well as that fuel lines DEFINITELY need to be rated, both for what they're carrying, plus, at pressure X, etc. And being resistant to both various petro based products, in addition to; fire, vibration, heat, & other wearing type conditions found in an engine compartment & similar spaces.

Ditto on being clearly tagged as being rated for such, & that on a lot of hoses in these various types of applications do have both specialty types of materials built into them, & into how the end fittings are attached. And that in the grand scheme of things, having a hydraulic or diesel hose made to a certain size really isn't all that complicated. Just a PITA if you're way off of the beaten track for extended periods.

I was simply wondering if say, someone had run across something newer, & better than hard metal tubing, with flared & crimped on ends, for carrying diesel. Kind of like WAY back when, when propane for most applications on vessels was carried by hard metal lines, almost exclusively. Until the advent of flexible hoses, with KISS, flared on, threaded end fittings. Which both simplified AND made things safer for all of us, when it comes to stove & heater installations, & such.

So yeah, I'll do some knocking on the doors of diesel mechanics, without overly trying to reinvent the wheel. Albeit, it'd surely be nice to have a simple DIY setup so that advanced amateurs could easily, & safely, custom make their own diesel fuel lines.

I was/am curious by nature, & my original query was keying off of the idea that perhaps there is a better type of hose for some applications, such as getting diesel fuel from the pump to the injectors (on the high pressure side, so to speak).
I know that low pressure lines, are pretty much a no brainer, as well as that fuel lines DEFINITELY need to be rated, both for what they're carrying, plus, at pressure X. And be resistant to both various petro based products, in addition to; fire, vibration, heat, & other wearing type conditions found in an engine compartment & similar spaces.

Ditto on being clearly tagged as being rated for such, & that on a lot of hoses in these various types of applications do have both specialty types of materials built into them, & into how the end fittings are attached.

Just kind of wondering if say, someone had run across something newer, & better than hard metal tubing, with flared & crimped on ends, for carrying diesel. Kind of like WAY back when, when propane for most applications on vessels was carried by hard metal lines, almost exclusively. Until the advent of flexible hoses, with KISS, flared on, threaded end fittings. Which both simplified & made things safer for all of us, when it comes to stove & heater installations, & such.

So yeah, I'll do some knocking on the doors of diesel mechanics, without overly trying to reinvent the wheel. Albeit, it'd surely be nice to have a simple DIY setup so that advanced amateurs could easily, & safely, custom make their own diesel fuel lines.

And, yes, FYI, I'm an ex-Navy & regular firefighter, so I'm all too familiar with how much "fun" it is to put out a high pressure fuel oil spray fire (with water, yes, that's correct, with water...) while standing on a metal grating for a "floor", where the fire can reflash & envelope you at any moment while you're trying to put it out by cooling the fuel & ignition sources down below temps which can ignite such fuel sources.
AKA I get that there's likely no such thing as a free lunch here, but'll keep looking And any added tips, would surely still be welcomed, of course.

 

Whats the issue with steel injector lines, they last a very long time?
If its flexible it can expand so that wont work on a conventional injection system as it will delay the timing.
With common rail the pressure is so high, forget flex tubing.
How about temp and fire, steel looks good there and certainly looks good on the production line.
If it was flex people might think they can fix them themselves and we know how that would end up..

 

Nope, you are all pretty much on course but off track... My comments come from years of experience in Racing (Cars and Motorcycles). I'll sum up as quickly as possible.
- The braided sheath, be it SS or other material, adds the strength to the line and has nothing to do with the core material or what fluid it is intended to carry. Your choice in application of braided sheath has more to do with abrasion than anything else. SS lines that vibrate and touch another component or neighbor line can 'saw' through each other.
- Generally speaking all of the AN lines can withstand the higher pressures required for braking, fuel injection, cooling etc. All of the lines are made to the highest spec so that companies aren't making dozens of varations, there is enough to choose from already with line size (-AN for fluid volume, and core/sheath material). This does not mean some manufacturers are not better than others.
- The general difference in core material is rubber vs. PTFE (teflon). There is a growing number of 'knock off' and cheaply manufactured chinese hose out there. The quality of rubber they use in these lines may not be rated for fuel, and the addatives and ethanol content of modern fuel breaks down rubber. If an -AN line is PTFE it can handle brake fluid which is the most corrosive of all unless you are using silicone (DOT 5). Trust me, if a line is designed to handle brake fluids it will have have no problem with fuel (gas or diesel), but that does not mean you should use it, and here is why;
- The big difference between braided lines sold for fuel use vs brake fluid/oil/coolant is that they are conductive lines. The fuel traveling through the tubing creates a static charge and searches for a ground which can result in explosion. A conductive core allows the charge to find its way to the fitting/engine block/to common ground. Is there a difference between braided fuel line for gasoline/diesel/race fuel/alcohol? No, not that I have ever seen, because as I mentioned before the manufaturers want to avoid multiple products so they make the conductive core fuel line to the highest standard to carry all fuel types.
One of my tech reps from a parts manufacturer told me implictly that I "can and should feel safe using PTFE lines for any application other than fuel, the hose diameter must be correct for the application of course, under just about any pressure I can throw at it. So the only thing to remember for fuel is that you use conductive line for fuel and then you can proceed smartly. There has been at various times a push in the industry to make all lines conductive which would simplify the manufacturing and distribution process, but that idea never caught wind." (paraphrase)
Braided AN lines are great, withstand high working pressure, and they look good. Utilizing AN fittings as well can simplifly and expidite maintenace. Problem is, for us mere mortals, price! The braided line is more expensive yes, but its the fittings that will kill you, between roughly $25 to $50 USD each and you can end up with dozens of fittings to cover a fuel system alone. By rough memory I had about 30 AN-6 fittings on a race motorcycle, but that was fuel, oil, and coolant. Yes, you can use braided AN lines with regular barbed hose fittings but that is just silly and your system is only as strong as the weakest link. If you are using Stainless Braided AN lines you'll want to not only use the appropriate AN Fittings but they need to be installed correctly to include using proper tools to cut (unraveled stainless wire is not only ugly, dangerous to a mechaincs hands, but also a clear indicator or poor installation). An oil line blowing on the track can not only loose you the race but it can get you in a wreck anlong with other cars. Almost every failure I have sen had to do with poor installation vice wrong choice of material, hose diameter, core material, etc.

Genrally speaking, unless its a power-racing boat, I wouldn't see the need to justify using SS Braided AN line for a diesel fuel supply on a boat. Some conditions could possibly justify it but those would be pretty rare to justify the cost. If you do, just make sure its conductive fuel line.

 

And dont use braided stainless line on a boat as we used to say once salt water got on them
You can hear the fittings corroding off the ends.....
Race boat that you dismantle every race maybe
I dont think there are any standards either so no ratings, no insurance, plenty of liability