Fuel Filter Minimum Flow Rate ?

[OBXSkipper]

I'm very grateful for this forum, it's great to go to a place where there is such a large body of knowledge, experience and opinion. I have searched so many threads and posts my head is about spinning. I have a Lehman 120 in my boat and from everything I have read there is a very small amount of fuel flow and very little return. When looking at a large filter say a Racor 900 that has a turbine to help separate contaminants, does that little turbine actually get enough flow to be effective ? More to the point can I use a bigger filter unit and still get good water separation? For example the Racor Turbine Series has a small unit (FG500) and much a bigger one (FG1000). The FG 1000 filter element is only marginally more expensive, but has a lot more surface area, so should last longer. However when filtering diesel for an engine that only burns
2-3 gallons an hour will the increased diameter of the turbine part make for slow spinning fuel and negatively affect the water separation? Thanks

 

[Pete Meisinger]

I have a pair of 900's for my F.L.120 and they do a great job. I think the word "turbine' is misleading. One would think there is a blast of a cyclone inside the casing but that is not the case.

I don't really know how they work, but they do.

pete

 

[Marco Flamingo]

Just my kitchen sink physics:

Water and contaminants slowly settle out of diesel, hence the goop at the bottom of a fuel tank that has had bad diesel over the years. That goop can be stirred up under some conditions and enter the fuel lines, where it may travel fast enough to stay in suspension. Upon entering a second "tank," like the bowl on a Racor filter, the fuel slows and water/particulates may settle out again. The higher the flow through the filter bowl, the less likely the crud will settle out. The "turbine" in the Racor filter can help settle the particles in high flow situations. The turbine would be less effective in low flow situtions (1-3 gph), but then it isn't as important in low flow as particulates could settle naturally. The filter element itself would remain effective in either low or high flow.

I have Racor 500s on my 80 hp Lehman (rated at 60 gph). WOT fuel flow for me is just over 1 gph. That isn't enough to get any centifugal "spin" in the Racor, but I still get settling of particulates in the filter bowl. If I burned 20 gph, the "turbine" might be of some utility. For me, the "turbine" is like fins on a Cadillac.

 

[O C Diver]

My Racor 1000 does extremely well at separating out water on my JD 4045. At cruise, it pulls 15 GPH through the Racor which is rated for 180 GPH.

Watching the turbine swirling action on my fuel polisher is impressive. It uses a Racor 1000 but the pump is pulling 150 GPH. It also traps the water in the bowl very nicely.

As already mentioned by others, the water separation works whether you have flow or not.

You could also add a plunger style fuel pump in parallel to the engine to increase the flow rate. I helped a buddy do this on his Lehman and now has 30+ GPH going through his Racor. The very simplistic reliable plunger style pumps are available up to 50 GPH.

Yes, I would definitely go with the Racor 1000!

Ted

 

[C lectric]

I don't have your engine but the larger the filter capacity the less likely you will suffer an unintended engine shutdown. Of course as long as you do checks on a reasonable timetable so it does not become overloaded at which time it very well could pass some of the stuff on, especially water. And yes, overloaded filters will pass water through if the water level gets high enough.

I don't have a see through but when I refuel within about a half hour I drain a sample from the filter. Almost always I refuel and then go dock.

 

[Comodave]

Our last boat had SP225 Lehmans in it. We had Racor 900s in it. If you are worried about water in the fuel then put WIF sensors in the Racor. I did that on our last boat and hooked the sensors to Borel Manufacturing alarms. The alarms have an exhaust temperature alarm and you can also have them put in WIF and high water alarms in the panel too. The Borel alarm system is simple to install and relatively cheap but works great. I put them in our current boat too.

 

[Choices]

Boat Nut that is an excellent idea.
I have a 500 on my 135. I have changed it once in five years cause it was dirty. Lots of media and very little flow.

 

[OBXSkipper]

OC and Others thanks for the input,
Ted are you saying that your friend has an additional circuit plumbed in with the associated valves and splitters that allow him to pass the 30 gph of fuel through the Racor and returned to the tank as a separate "polishing" circuit ? Thanks Steve

 

[O C Diver]

OC and Others thanks for the input,
Ted are you saying that your friend has an additional circuit plumbed in with the associated valves and splitters that allow him to pass the 30 gph of fuel through the Racor and returned to the tank as a separate "polishing" circuit ? Thanks Steve

There is a tee after the Racor and before the engine. Off the tee is the fuel pump. After the pump, the fuel line tees back into the return line from the engine. My recollection is that there are valves on both tees to isolate the pump circuit. The pump is wired on its own breaker so that it can be used as a fuel polisher when the engine isn't running.

Ted