Fuel Filter /separator on H34

[WasabiRush]

I traced a fuel leak to the fuel filter lines at the filter/separator, the large bolt on the top (see attached pic) and the spring valve on the bottom of the separator. So I don't have to prime twice, I plan to replace the lines and the entire filter /separator housing. When I research new units (Racor 120A) they don't have the bolt on the top. Also, I've seen posts that say the line size is 1/4 and some posts say 5/16. The OD of my current line is larger than the OD specs on 5/16 line. My questions are :

What is the purpose of the bolt on top? It looks like it has a crush washer on it.

Isn't it important that the fittings on the filter be the same size as the ID of the hose?

Do I need to put anything on the threads of the fittings when I install them?

Thanks much for any input you have.

John

 

[Ralph Johnstone]

Check the top of the white cast piece which holds the R12S spin on filter. If you can get a name and number, GOOGLE will show you a cross section of the casting and this will tell you who does what.

 

[jeepbluetj]

I'd wager a guess the top bolt was to allow filling the entire filter to ease priming. I'd also guess that Parker decided it wasn't worth putting it on anymore. (These are guesses, not facts)

Yes, you use an appropriate sealant on NPT pipe threads. Particularly in this day and age where all the fittings seem to be cut very badly.

The ID of the fittings will be, by definition, smaller than the ID of the hose. The hose has to go over the barbs.

As far as the hoses themselves, usually it's printed on it. Or cut one and measure the ID. (Or maybe another hunter owner will chime in)

 

[WasabiRush]

Thanks. Is Teflon tape okay on the threads with diesel?

My thought on the size being the same, meaning 1/4" barb with 1/4" ID hose. My experience has been if the hose is much bigger than the barb, it affects the seal.

 

[Ward H]

Check this link to the Racor series filters on Defender.com
Fuel Filter
Nearer the bottom of the page Defender list several port fittings for that filter unit. Port size 1/4-18 NPTF fittings with several hose barb sizes. Hose barbs are always identified by the hose ID they are sized for.
I used teflon tape on my fittings. Be sure not to have it overlap, or loose pieces over lap the holes of the fittings. Keep it on the threads.

 

[Ralph Johnstone]

Teflon tape, by itself, is not acceptable on pipe fittings carrying petroleum fuel. Very susceptible to leakage. The best combination is a first layer of teflon tape covered with an application of Permatex No. 2. The tape provides the meat to fill the sloppy fittings while the Permatex goes in to fill the microscopic gaps. It's now refinery level.

 

[flightlead404]

Thanks. Is Teflon tape okay on the threads with diesel?

My thought on the size being the same, meaning 1/4" barb with 1/4" ID hose. My experience has been if the hose is much bigger than the barb, it affects the seal.

First, make sure they are indeed NPT threaded fittings. NPT is tapered, but they could also be straight fittings which are not interchangeable.

NPT and straight fittings are both designed to seal mechanically without the requirement for sealer. If a sealant is required to make them leak free either they were assembled incorrectly, the fittings were manufactured out of spec, or they are damaged in some way.

I would avoid the use of teflon tape absolutely. It should not be necessary, and its often over/incorrectly used. Tiny fragments of teflon tape can be released into the fuel stream, potentially playing havoc with other components. Its just as bad on oil lines where it can clog internal galleys and squirters, and on coolant lines. Keep that stuff for your home plumbing.

You could sparingly use a little pipe thread lubricant, especially if your fittings have poorly cut threads. This can prevent galling during assembly, allow you to get a proper torque on the fitting making a better seal, and make the fitting easier to disassemble in the future.

From my limited data points liberal use of pipe dope on everything, even where its not supposed to be used, seems to be standard. As a general statement marine engine maintenance practices would turn any aircraft powerplant mechanic's hair white.

 

[Ward H]

First, make sure they are indeed NPT threaded fittings.

Racor port spec says NPTF fittings, which I understand stands for National Pipe Taper-Fuel.

If a sealant is required to make them leak free either they were assembled incorrectly, the fittings were manufactured out of spec, or they are damaged in some way.

So the NPTF fittings should not need pipe tape or pipe sealant? Guess that makes sense since our systems are operating at low enough pressures fuel lines are held onto hose barbs with hose clamps.

 

[WasabiRush]

Thanks for all of the replies. I just ordered the R120S filter assembly from Defender with two 5/16 barb fittings. I asked them to swap out the R12S filter for an R12P. Hopefully they'll do that.

I ordered 5/16 hose and solid band clamps from Amazon. Now, as long as I don't have issues with 5/16 hose at the tank or feeder pump I should be set. Oh, I also ordered two Racor shutoff valves from Discount Racor. I'll put those on the filter housing to make changing filters easier.

 

[flightlead404]

Racor port spec says NPTF fittings, which I understand stands for National Pipe Taper-Fuel.



So the NPTF fittings should not need pipe tape or pipe sealant? Guess that makes sense since our systems are operating at low enough pressures fuel lines are held onto hose barbs with hose clamps.

The tapered threads are designed to seal at the mating surfaces of the thread (they have a formal name I don't remember). Straight threads are designed to seal with the face of the male fitting against the inside face of the female fitting (again, there's proper terminology I can't remember).

So yes, it strictly does not *need* anything additional to seal. In fact, based on my experience, such things often reduce the quality of the seal.

Again, remember, this is for clean (clean!! Hospital clean! Brain surgery clean! Personally I buy non-lint clean room wipes and go through 100's when doing a motor, prob over the top for this though) fittings in serviceable condition, assembled correctly. If your threads are damaged, poorly cut, there's foreign material in there, and so on it will leak. Adding some goop might save you a couple bucks on a new fitting but honestly is not the way to go and has a good likelihood of leaking in the future. Not as serious on a diesel as a gasoline engine and maybe, maybe I'm just picky, but after 30+ years of personal aircraft maintenance and air cooled engine hot rodding, I've never had a fuel/oil leak and especially not a resulting engine fire!

If you're re-using fittings that have pipe dope of some kind on them, particularly if its the kind that sets up hard, my first reaction would be to simply throw them away and get new. If that's not possible then I would clean and inspect them carefully. A brass bristled brush s/b fine, but I'd start with plastic tools, red scotch brite etc, and avoid steel brushes. Steel wire brushes can live tiny microscopic particles of mild steel embedded in the surface of less hard metals that will corrode later. That was a rather expensive lesson I learned back in the mid-90's . A set of 930 heads ain't cheap

IDK what the nominal pressure upstream of the fuel system is upstream of the injector pump, but pretty low since its moved with a diaphragm pump. Higher pressure lines will be hard lines, or swaged fittings, and will use a flare fitting of some kind.

 

[WasabiRush]

Thanks. Copy No thread additives.

The upstream pressure is 2540 psi.

 

[flightlead404]

Upstream? From tank to separator/1st stage filter?
That sounds more like the pressure after the injector pump.

 

[WasabiRush]

You're correct. I meant from the injector pump up to the injectors. I used the wrong terminology.

 

[Ralph Johnstone]

Where does it all come from ? ? ? ? ?

There are NO NPT threads that go together without sealant. NPT threads grinding together dry create minute crevices for leakage. The sealant acts as a lubricant and assists in the threads going together tighter then they could without the sealant.

When assembling an NPT joint, avoid getting the sealant (tape or liquid) on the first two threads. This ensures no sealant gets back into the flow stream. Use sealant sparingly.

Try putting your filter fittings together without sealant and see what happens over a few days. And these are the specs right out of petroleum refineries.

 

[Ward H]

There are NO NPT threads that go together without sealant.

I agree with that but aren't NPTF threads different than NPT?

 

[Ralph Johnstone]

I agree with that but aren't NPTF threads different than NPT?

They differ in the height of the crown and depth of the root "supposedly" reducing the possibility of spiral leakage and other such crap. They are still subject to leakage and hence it is recommended that you still use a sealant on these threads "just to be sure". I still maintain it's the sealant which acts as a lubricant that prevents the threads from galling rather than being screwed together dry.

Never dealt with NPTF in refineries, we needed something that was rough and ready and highly unlikely to leak. That was teflon tape with a wipe of Permatex.

Good enough for a refinery, good enough for my boat's fuel system.

 

[flightlead404]

You're correct. I meant from the injector pump up to the injectors. I used the wrong terminology.

Leak can be very dangerous at those pressures. Could certainly pen

Where does it all come from ? ? ? ? ?

There are NO NPT threads that go together without sealant. NPT threads grinding together dry create minute crevices for leakage. The sealant acts as a lubricant and assists in the threads going together tighter then they could without the sealant.

When assembling an NPT joint, avoid getting the sealant (tape or liquid) on the first two threads. This ensures no sealant gets back into the flow stream. Use sealant sparingly.

Try putting your filter fittings together without sealant and see what happens over a few days. And these are the specs right out of petroleum refineries.

lubricant. not the thick goopy crap that sets up like cement.

 

[Ralph Johnstone]

lubricant. not the thick goopy crap that sets up like cement.

You're confusing Victaulic fittings with NPT fittings. A Victaulic fitting requires lubricant on its internal rubber gasket. NPT fittings require a sealant on the jam fit pipe threads.

I'm sorry but I've got to ask. Where do you get this stuff ? Is it off the internet or do you just make it up in your spare time ?

There is no lubricant used with NPT pipefittings from what I have ever seen in any specifications for maintenance or construction of piping containing NPT fittings. One of the most basic requirements of a liquid sealant is that it remain flexible under all conditions and not solidify to a hard mass. Once a sealant becomes hard, it will eventually crack and permit leakage of the fluid being transported.

@WasabiRush posted asking for information on connecting NPT fittings on his fuel lines. I feel for him. I'm sure he's now sitting with his head spinning, wondering which way to go after you've taken every industrial practice regarding threaded pipe and turned it on its head.

 

[flightlead404]

You're confusing Victaulic fittings with NPT fittings. A Victaulic fitting requires lubricant on its internal rubber gasket. NPT fittings require a sealant on the jam fit pipe threads.

I'm sorry but I've got to ask. Where do you get this stuff ? Is it off the internet or do you just make it up in your spare time ?

There is no lubricant used with NPT pipefittings from what I have ever seen in any specifications for maintenance or construction of piping containing NPT fittings. One of the most basic requirements of a liquid sealant is that it remain flexible under all conditions and not solidify to a hard mass. Once a sealant becomes hard, it will eventually crack and permit leakage of the fluid being transported.

@WasabiRush posted asking for information on connecting NPT fittings on his fuel lines. I feel for him. I'm sure he's now sitting with his head spinning, wondering which way to go after you've taken every industrial practice regarding threaded pipe and turned it on its head.

I think you're misreading what I wrote, or misattributing.

I clearly stated earlier that both NPT and straight threaded (and indeed AN style flare fittings) are all designed to seal mechanically. The need for a sealant indicates damage, incorrect assembly, or out of spec manufacturing.

YOU then stated "There are NO NPT threads that go together without sealant. NPT threads grinding together dry create minute crevices for leakage."

Then YOU stated "One of the most basic requirements of a liquid sealant is that it remain flexible under all conditions and not solidify to a hard mass. Once a sealant becomes hard, it will eventually crack and permit leakage of the fluid being transported." Which is EXACTLY my argument against them.

The YOU also stated "NPT fittings require a sealant on the jam fit pipe threads." which is a direct contradiction to YOUR OWN STATEMENT.

However the reasoning you stated was NOT to seal, but to prevent thread damage during assembly. In fact you went on to call it a "lubricant" not a "sealant".

Somewhere in a different post on this thread I mentioned that a LUBRICANT can assist in assembly and prevent thread galling. I even provided a link to a lubricant.

A lubricant is not a sealant. A lubricant, as stated, can assist in assembly to ensure the proper torque (and therefore thread to thread seal) is achieved without galling. But the lubricant is not providing the seal, the fitting itself is doing that.

Honestly I think you and I are in violent agreement, but using slightly different terminology.

My main message is to stay away from teflon tape and use of "pipe dope" or other actual sealants. If the fitting is leaking at operational pressures its probably damaged.

 

[flightlead404]

From Wikipedia:

NPTF

National pipe taper–fuel

Dryseal USA (American) Standard Taper Pipe Thread

For dryseal connections in nearly every type of service, especially fuel connections

Note: "dryseal". More...
National Pipe Taper Fuel (NPTF), also called Dryseal American National Standard Taper Pipe Thread, defined by ASME B1.20.3, is designed to provide a more leak-free seal without the use of PTFE tape (often referred to by the popular brand name "Teflon") or another sealant compound. NPTF threads have the same basic shape but with crest and root heights adjusted for an interference fit, eliminating the spiral leakage path.

Contrast with:

NPS

National pipe straight

American National Standard Straight Pipe Thread

For rigidity; sealable only with sealant; sometimes male straight enclosed by female tapered for low-pressure sealing

Which is NOT what we're discussing here.