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Old 03-29-2018, 07:45 AM   #1
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Fuel lines Plumbing

1) Got 2 @ 6BT5.9T's with 2 fuel tanks that are plumbed together ( with valves ea. ) to a common manifold.
2) From there, have separate feeds to 2 @ RACOR FG900's ( also 1 to another RACOR for the Gen. )
3) After the FG900's, to another common manifold and lines feed each engine Lift Pump ( have squeeze bulbs to prime each RACOR c/w valves etc )

Having had starting issues with Port engine, with repairs in the works before we launch, I want to do some plumbing revisions and also install 1 electric fuel pump somewhere in this plumbing circuit. Got Facet 4000E @ 4 - 5.5 psi @ 32 GPH. c/w 1/4" ports, also intend to build a by - pass. So a question:

a) Is one electric pump enough ? ( approx. burn rate @ WOT 9 - 12 Gal. )
b) ( one or two pumps ) Should it / they be on the supply side to the RACOR's or after the RACOR's ?
Can the Racors handle the 6 psi pressure ? or are they strictly vacuum ?
c) The fittings will be brass, what is the best diesel compatible thread sealant d) OR is this a total waste of time / money ?

Any thoughts on this would be appreciated........... Tx. fb
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Old 03-29-2018, 08:09 AM   #2
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Is the electric pump intended for priming the Racors or to run constantly to feed the engines? If it a primer, before the Racirs. If it’s to run constantly, why?

A common manifold is not good practise because you now have a single point of failure. Separating the fuel systems is much better. Also, a genset in the circuit can mess up the flow and cause problems for the fuel feed to the engines. It should have its own dedicated feed. You could also use a day tank that feeds all your services but dedicated feeds is better.

Ideally, the tanks would each feed an engine through two sets of Racors, one set for each engine. Install a crossover for balancing when needed. A tee at the tank shutoff for the genset and it’s own filter. Also, a hose shop can make up fuel lines to a specific length with threaded connections and they will be very neat, leak and fire resistant. Not the cheapest solution but the best.
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Old 03-29-2018, 08:17 AM   #3
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d) OR is this a total waste of time / money ?

Any thoughts on this would be appreciated........... Tx. fb
The more complicated you make the system, the greater the likely hood for fuel out or air in leaks. While I believe you can run the Racor under some pressure, the lid seal is designed for vacuum. While it's unlikely you will ever break or crack the bowl, I would rather be under vacuum and have the system shut down than have an electric fuel pump filling my bilge with diesel.

Clearly the system originally worked. Figure out your port engine problem and fix it.

Ted
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Old 03-29-2018, 08:51 AM   #4
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The more complicated you make the system, the greater the likely hood for fuel out or air in leaks. While I believe you can run the Racor under some pressure, the lid seal is designed for vacuum. While it's unlikely you will ever break or crack the bowl, I would rather be under vacuum and have the system shut down than have an electric fuel pump filling my bilge with diesel.

Clearly the system originally worked. Figure out your port engine problem and fix it.

Ted
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Old 03-29-2018, 09:17 AM   #5
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Originally Posted by O C Diver View Post
The more complicated you make the system, the greater the likely hood for fuel out or air in leaks. While I believe you can run the Racor under some pressure, the lid seal is designed for vacuum. While it's unlikely you will ever break or crack the bowl, I would rather be under vacuum and have the system shut down than have an electric fuel pump filling my bilge with diesel.

Clearly the system originally worked. Figure out your port engine problem and fix it.

Ted
All good points, Tx. incl. Xsbank ..... When the Port engine problem started it was likely by a faulty Lift Pump and that got my whole fuel supply process thinking started ( I got stranded with the Port Eng. btw ) so I thought I could get some fuel delivery if needed or if this happened again. On the other hand as Xsbank said, the priming function would be nice too ..... Maybe I will have another look at this whole thing ? ......... Tx again .....fb
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Old 03-30-2018, 01:45 AM   #6
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So what was the problem with the port engine?
Hard starting is likely to be from air intrusion or fuel starvation.
Make sure you’re not fixing a problem that doesn’t exist!
You already have the squeeze bulbs, I don’t see the necessity to add pumps, you’re just adding complexity to the likelihood of failure.
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Old 03-30-2018, 11:51 AM   #7
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I don't know the total fuel flow in 2-6BT5.9T's, but any pump has to equal that flow plus any generator and heater you might have. Having the pump before the Racors could cause leaks if the pump moves much more fuel than the engines draw. The electric would keep building to its maximum ability to make pressure. The pump would be better after the filters if it's going to run all the time.
I have a 200 gallon day tank, twin Racors, common manifold, then individual lines to each engine and boiler. Each engine has a secondary filter. My Detroit mains alone draw 70 gallons an hour and return about 62. I have 35 gallon/hr. 12v electric pumps in the engine lines that are normally off and used for filling filters and bleeding the generator sets. (Detroits don't need bleeding) The engine lift pumps draw thru the electric pumps. The electrics also serve as emergency fuel pumps. The Racors are before any pump.
I have common manifolds and they are the normal setup in ships, tugs and other commercial vessels. Yachts have trouble with tank fuel because they don't use up as much fuel as commercial and don't use conditioners often enough or at all. Conditioners that comes in new fuel only lasts a few months.
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Old 03-30-2018, 01:47 PM   #8
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Cummins 6B’s don’t circulate near the amount of fuel as DDs, don’t have exact numbers, but demand iqs much lower.
The Cummins lift pumps are capable of doing their job, unless the tanks are extremely far away or far below the engines.
The generator has its own lift pump.
For safety’s sake, it’s not a great idea to push the fuel to the filters.
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