fuel manifold installation

[paulga]

I have a Racor 500FG (Racor "Gen" in the photo below). I'm planning to install a fuel manifold with 3 outlets to use the racor's filtered diesel to also feed the diesel heaters as well as the generator. 3 ports is preferred due to space limitation.

I think 500FG's fuel outlet port 3/4" -16UNF according to its manual. The rubber hose sending to the generator has "5/16 SAE" letter on the hose. I'm browsing manifolds on mcmaster



1. should the manifold be mounted at the same level of or below the racor's outlet port? if so the space is a challenge, see the pic below
2. should the manifold inlet port be at least 3/4" to avoid restricting the flow?
3. any preference on manifold material? Anodized aluminum, steel or stainless steel?

 

[twistedtree]

Just a word of caution before you get too far with this... When sharing a fuel supply like you propose, you need to be certain that when one device is running, it won't pull air back through the non-operational devices. This means there must be some sort of check valve in the fuel supply line for each device, and it needs to work. This is one of the reasons why manufacturers say not to share fuel supplies with other devices.


What you are planning might work just fine. Or it might have intermittent problems and be very difficult to diagnose. At a minimum you should consider installing a shutoff valve at the manifold where each fuel line comes off. That might be useful for maintenance, and would certainly be useful for diagnosing any issues that might arise.

 

[mvweebles]

Its been a couple years since I looked at the McMaster manifold stuff, but I seem to recall that by the time the dust settled on all the parts, the Reverso Manifold (HERE) wasn't much more expensive and purpose-built for diesel (NOTE - they make one for oil that is $200 less than this $422 unit. I have no idea what the difference is but would guess it's not a good idea to use the OIL one for DIESEL). You may want to ping Defender to see if they can special order for a bit of a discount of Reverso's MSRP.

https://reversopumps.com/ma-3/

Air intrusion issue TT notes is real, but at your flow-rates, unlikely to be an issue. I have air intrusion issues when I run my 400 gph transfer pump, but mostly because I tee-d into my sight gauge plumbing. While the air intrusion issue was a surprise, I fully understood the system could not be run underway due to contention issues (fuel transfer/polishing systems really should be fully isolated with dedicated fuel ports on tanks).

I would suggest mounting the manifold as low as practical not because of the Racor, but because of fuel level in the tank(s). In theory, should not make a difference but in practice, it may.

Good luck -

Peter

 

[Bmarler]

The reverse manifold is a good product, but pretty expensive for what it does. The oil manifold is plastic, the diesel one is anodized aluminum.
Here’s a 5 outlet manifold in anodized aluminum for less than $50. I use this company’s products regularly and and am happy with them. Put in your own valves and your good. This one is 3/4 inlet, 3/8 outlet. Plenty of other sizes and configurations available. I think that the bigger inlet size allows more fuel flow and less chance of starvation.
I agree with Peters advice to mount it low. Easier to get the air out and puts positive pressure in the manifold.

 

[Bmarler]

Oops, I forgot to link the manifold. https://www.automationdirect.com/adc/shopping/catalog/pneumatic_components/manifolds/mra-5fd

 

[O C Diver]

I would determine the total fuel flow before determining size. A guess would be that your total flow (factoring in return fuel from the generator) will be under 30 GPH, probably less. 1/2" fuel line will easily handle that and likely 3/8" line will as well. No point going above the smallest fittings or fuel line feeding the Racor unless less you plan to replumb it.

I wouldn't consider doing this without output line valves on the manifold. Aluminum is fine for the manifold.

Ted

 

[paulga]

Thanks for the warning.
I never considered this scenario that the gen lift pump is so powerful that it could lift all fluid and then air from the heaters by way of the manifold.

Just a word of caution before you get too far with this... When sharing a fuel supply like you propose, you need to be certain that when one device is running, it won't pull air back through the non-operational devices. This means there must be some sort of check valve in the fuel supply line for each device, and it needs to work. This is one of the reasons why manufacturers say not to share fuel supplies with other devices.


What you are planning might work just fine. Or it might have intermittent problems and be very difficult to diagnose. At a minimum you should consider installing a shutoff valve at the manifold where each fuel line comes off. That might be useful for maintenance, and would certainly be useful for diagnosing any issues that might arise.

 

[TJM]

Be sure to select "Diesel" as the wetted fluid. Ball valves have o rings and they NEED to be compatible with the fluid. Otherwise they will breakdown, swell or crack and that is not good. Corrosivity is not the issue. I get mine from KTI systems.
I texted you pictures of mine. I have 3 diesel manifolds and 1 engine oil manifold on the boat.

 

[fgarriso]

I would go with 3/4 inlet and 1/2 outlets. You can always install a 1/2 to 3/8 bushing if needed. You don't need fuel flow issues at the manifold.

 

[paulga]

The reverse manifold is a good product, but pretty expensive for what it does. The oil manifold is plastic, the diesel one is anodized aluminum.
Here’s a 5 outlet manifold in anodized aluminum for less than $50. I use this company’s products regularly and and am happy with them. Put in your own valves and your good. This one is 3/4 inlet, 3/8 outlet. Plenty of other sizes and configurations available. I think that the bigger inlet size allows more fuel flow and less chance of starvation.
I agree with Peters advice to mount it low. Easier to get the air out and puts positive pressure in the manifold.

Racorstore only has 4 sizes of barb fittings 5/16, 3/8, 1/2, 5/8 (all inches)
these fittings have 3/4" - 16 UNF on the thread side

what fittings can adapt 3/4" -16 to 3/4" barb?

 

[Bmarler]

Racorstore only has 4 sizes of barb fittings 5/16, 3/8, 1/2, 5/8 (all inches)
these fittings have 3/4" - 16 UNF on the thread side

what fittings can adapt 3/4" -16 to 3/4" barb?

if you're talking about the manifold i linked, it's listed as 3/4 npt inlet. regular barb adapter will fit.

 

[paulga]

if you're talking about the manifold i linked, it's listed as 3/4 npt inlet. regular barb adapter will fit.

I'm considering to use a 3/4" hose to connect the racor outlet (3/4" -16 UNF) to the manifold inlet (3/4" NPT). The racor side needs some fitting from 3/4"-16 to a 3/4" barb. Racorstore does not have this elbow (they only carry four sizes elbows, see my post above), so what I need could be an elbow coupled with a barb

 

[twistedtree]

I'm considering to use a 3/4" hose to connect the racor outlet (3/4" -16 UNF) to the manifold inlet (3/4" NPT). The racor side needs some fitting from 3/4"-16 to a 3/4" barb. Racorstore does not have this elbow (they only carry four sizes elbows, see my post above), so what I need could be an elbow coupled with a barb

You could use 3/4" hose, but it would be overkill. Even a big main engine can typically be serviced by 1/2" fuel hose.

 

[KnotYet]

I'm considering to use a 3/4" hose to connect the racor outlet (3/4" -16 UNF) to the manifold inlet (3/4" NPT). The racor side needs some fitting from 3/4"-16 to a 3/4" barb. Racorstore does not have this elbow (they only carry four sizes elbows, see my post above), so what I need could be an elbow coupled with a barb

Maybe these: (obviously go with the metal versions, not the plastic ones)
https://www.mcmaster.com/products/hose-barbs/shape~90-elbow/pipe-size~3-4/hose-id~3-4/

 

[Bmarler]

You could use 3/4" hose, but it would be overkill. Even a big main engine can typically be serviced by 1/2" fuel hose.

he's supplying a multi outlet manifold. probably overkill, but maybe not in this instance.

 

[twistedtree]

he's supplying a multi outlet manifold. probably overkill, but maybe not in this instance.

Understood, but through a Racor 500? Regardless, 3/4" can do no harm if that's what he wants.

 

[Bmarler]

Understood, but through a Racor 500? Regardless, 3/4" can do no harm if that's what he wants.

i think it's more about volume reserve than flow.

 

[Bmarler]

is a #12 orb hydraulic the same parallel 3/4-16 thread as unf?

 

[twistedtree]

is a #12 orb hydraulic the same parallel 3/4-16 thread as unf?

#8, I think. It appears to use 3/4"-16 threads. I think that's what the Racor fittings are.

 

[paulga]

Maybe these: (obviously go with the metal versions, not the plastic ones)
https://www.mcmaster.com/products/hose-barbs/shape~90-elbow/pipe-size~3-4/hose-id~3-4/

the 3/4 x 3/4 elbow only has npt thread. Racor requires unf thread.

 

[paulga]

Is this bushing for unf to npt adaption?

 

[Bmarler]

View attachment 145274

Is this bushing for unf to npt adaption?

most likely it is.
i found this fitting that would be cleaner. https://www.discounthydraulichose.c...wGbCZNKyvOFbtmc36M5BvAHv881LcaqoaAgTcEALw_wcB

from parker: Parker SAE standard fittings with UN/UNF threads and screw-in connectors with O-ring are designed for connection with UNF screw-in threads. They are also known as O-Ring Boss (O.R.B.) connections. Correctly assembled, they offer as good performance as the best leak-free connections with screw-in threads.

 

[paulga]

Thanks for clarifying.

the connection has an o-ring, so no other sealant is necessary, correct? is hand tighten good enough for the o-ring?

I didn't see a target torque for the fuel ports on the racor housing

most likely it is.
i found this fitting that would be cleaner. https://www.discounthydraulichose.c...wGbCZNKyvOFbtmc36M5BvAHv881LcaqoaAgTcEALw_wcB

from parker: Parker SAE standard fittings with UN/UNF threads and screw-in connectors with O-ring are designed for connection with UNF screw-in threads. They are also known as O-Ring Boss (O.R.B.) connections. Correctly assembled, they offer as good performance as the best leak-free connections with screw-in threads.

 

[Bmarler]

Thanks for clarifying.

the connection has an o-ring, so no other sealant is necessary, correct? is hand tighten good enough for the o-ring?

I didn't see a target torque for the fuel ports on the racor housing

correct, no sealant needed. make sure the mating surfaces are squeaky clean, then tighten the fitting up till you cant get another turn (hand tight) point the barb the direction you want, then hold the barb and tighten the nut/o-ring pretty snug. the barb should be locked into position.

 

[paulga]

correct, no sealant needed. make sure the mating surfaces are squeaky clean, then tighten the fitting up till you cant get another turn (hand tight) point the barb the direction you want, then hold the barb and tighten the nut/o-ring pretty snug. the barb should be locked into position.

Thanks for confirming.
this elbow is an interesting niche item.
From my perspective, the nut/oring is a slider along the threads. once the threads is tightened, the pointing direction of the barb is fixed. will see.

 

[Bmarler]

Thanks for confirming.
this elbow is an interesting niche item.
From my perspective, the nut/oring is a slider along the threads. once the threads is tightened, the pointing direction of the barb is fixed. will see.

Those type fittings work very well. I use the orb to jic fittings all the time on industrial hydraulic systems. They hold a few thousand psi with ease.

 

[paulga]

correct, no sealant needed. make sure the mating surfaces are squeaky clean, then tighten the fitting up till you cant get another turn (hand tight) point the barb the direction you want, then hold the barb and tighten the nut/o-ring pretty snug. the barb should be locked into position.

if install a 1/2" npt to 5/16" barb to one of the manifold outlets, does the tightening process take into account that both brass and aluminum are soft?

 

[twistedtree]

So-called ORB (o-ring boss) fittings are I "think" what Racor uses. They are UNC threads with an o-ring to seal it. It looks like a #8 ORB fitting is 3/4"-16 UNC, with an o-ring. That will be on one and, and you can get a hose barb for the other end, I expect.

 

[Bmarler]

if install a 1/2" npt to 5/16" barb to one of the manifold outlets, does the tightening process take into account that both brass and aluminum are soft?

Absolutely. You need to develop a sense of how the fitting is seating in the threads. It should get progressively harder to turn, and you develop a sense of how much pressure to exert on the wrench. When you feel it turn without a gain in pressure, you’re slipping the threads and compromising the connection. Just like tightening a bolt till the head pops off.
There’s more latitude putting brass into steel than when doing brass to aluminum. Aluminum is very soft and requires a softer touch. Use the tape, then sealant approach and you’ll be fine. Be absolutely certain you leave the end threads bare so you don’t get debris in the fuel system.
Also, use care with the fittings you linked. Those type are free to swivel after installation and depend on an o ring to seal. Those are more prone to failure. I wouldn’t choose those for my fuel system.

 

[Bmarler]

So-called ORB (o-ring boss) fittings are I "think" what Racor uses. They are UNC threads with an o-ring to seal it. It looks like a #8 ORB fitting is 3/4"-16 UNC, with an o-ring. That will be on one and, and you can get a hose barb for the other end, I expect.

Yes #8. I don’t know why I keep thinking #12. I will edit my posts for future searchers.

Ok, my previous post linking the fitting was too old to edit. Here’s the #8 to 3/4 hose barb adapter.
https://www.discounthydraulichose.c...w-8MOqVkTufNAwXHMdgq8u4dS6ISbp2IaAh_fEALw_wcB