fuel fill

higgs · Oct 23, 2012

Marelon is resistant to diesel so why not? It certainly will not cause any galvonic corrosion.

capta · Oct 24, 2012

I would highly recommend that you go with the bronze one. I do not know for sure, but the plastic one may not hold up if you ever want to remove the hose after some years. Getting hoses off hose barbs can be difficult and require quite a bit of force at times.

higgs · Oct 24, 2012

If you have to get the off in the future, you can always easily replace the barb if it gets damaged.

higgs · Oct 24, 2012

Chances are you will never have to remove the fill hose. I think it really doesn't matter what the fitting is made of as long as it is not damaged by diesel fuel. Even then, since it is at the top of the filler, it will not be subject to a lot of diesel. The pump nozzel will most likely go deeper than the fitting so it will only be subjected to the fuel when heeled until you use enough fuel to keep it clear. Don't overthink this.

Ron20324 · Oct 24, 2012

I think that mixing metal and non-metal fitting is asking for trouble. They have a different reaction to heat and cold expansion/contraction. Stick with like materials.

Allan12210 · Oct 24, 2012

Ron20324 said:
I think that mixing metal and non-metal fitting is asking for trouble. They have a different reaction to heat and cold expansion/contraction. Stick with like materials.

Agree with Ron. I used to design clean water systems for the hitech industry. When we would join metal to plastic pipe we always used a flange on each with a gasket or o-ring between them. There is a 10x difference in coefficient of expansion between plastic and metal. On a hot day a tight fit between the two could crack eventually.

Allan12210 · Oct 25, 2012

Blitz said:
Thanks all. Yes, that's what we do - everythink things...

I was thinking a bronze fitting but was a little worried about any reaction between the chrome plated deck plate and the bronze. thoughts?

Separately would sealing the threads with Teflon tape be ok?

Neal,

No reaction in our lifetime between those two. Besides they need to be immersed in seawater for that to happen. Teflon tape is good. Then you can take them apart again easily.

Allan

higgs · Oct 25, 2012

I think there is a tendency to overthing things on this site. Bronze or Marelon isn't going to make much difference.

Chris Patterson · Oct 26, 2012

Am I wrong in thinking that the fill should be grounded? I know diesel doesn't spark, blah, blah, but a recent survey had noted on the report that it should be grounded.
I do NOT know, but that thought just came upon me..

Richard Bryer · Oct 26, 2012

My survey this year called for the fill to be grounded- which it wasn't at manufacture

shannon28 · Jan 1, 2013

I know that this is a little late, but here goes.

1, Even though the Forespar catalog says that the ball valves, seacocks and fittings are NPS not NPT according to an email I received from Forespar this year what is printed in their catalog is incorrect. With the Forespar NPS fitting you may be able to get a few threads of the barbed fitting on the fuel fill but at significant structural cost.

For those of you looking at Marelon ball valves and seacocks, the only barbed fittings that will work correctly are Forespars.

2. TheForespar tail piece is simply Dupont Zytel, 70G13l BK nylon (AKA Marelon). It's resin base is Duponts nylon 6/6, a nylon resin that absorbs a significant amount of moisture and, when it does, looses a significant amount of strength and swells. I think you'll find it hard to get off later on.

3. The critical issue is the difference in thread pattern. A male NPS thread pattern starts and ends with the same thread size throughout. It's designed just like a regular bolt. It's a pretty sloppy thread and depends on compression if bottomed out and a lot of pipe sealer. The NPT female thread starts with the same size thread as the NPT but tapers down so that after the first two turns the NPS thread is simply too big to accommodate the NPT thread. Not a very substantial connection.

4. Nylon is quite resistant to fuels, which is a good point. However, it does have a serious moisture problem.

5. The bronze fitting is overkill, but it is the ideal option.

6, Because there is most likely little chance of impact, my second choice would be a glass filled nylon fitting. I know of one manufacturer who molds NPT threaded fittings made out of the same material as Marelon. I believe that you can get them from McMaster-Carr (http://www.mcmaster.com/#standard-nylon-barbed-hose-fittings/=kupn1y).