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Go Back   SailNet Community > On Board > Gear & Maintenance > Engines > Diesel
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Diesel This is a forum dedicated to diesel engines and their applicable accessories.


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  #21  
Old 01-25-2010
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Lehmans return quite a bit to the tank so you are polishing whenever you run the engine.

How about running a compressed air line down the fuel filler hose to agitate the tank?
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Old 01-27-2010
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Final selection for fuel pump and process

Well folks - just thought I would share what I have learned. Spoke to the head engineer at Walbro (fuel pump manufacturer). He recommended that I purchase the FRB22-2 to attach to the Racor 500fg. He thought that using before the filter would work and that the screen sediment filter on the pump would act as a prefilter, but also understand me wanting to filter first - either way this was acceptable to him. He said that this pump would have similar turn over pumping as the racor not to exceed 55 gph. He also said that while corrosion resistant he felt the advantage was that it has a smart spring assembly that results in less than 1.0 amp hour of power draw during use so that it was quite 12V battery friendly.
I have found out that the Whitby 42 fuel tanks (port and strbd) have only 1 large baffle in them so that aggitation with either a clean air line or manual method may get the stuff stirred up, and that the pick up line on the Whitbys are above the bottom so that I will need to aggitate the fuel to get all the bottom crud off. So that is what I will be setting up. Hope this helps others and thanks for all the input
Andy
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Where would this screen be? In the pick up of the pump? It will need cleaning so make sure it's easily accessable and removable.

Since walbro said it's OK to put the filter before the pump I'd go that way.

The tradeoffs are that the screen will keep some of the gunk out of the filter ($) but you will have to disassemble the system to clean the diesel & gunk soaked screen often. How often? Probably a lot at first until you get the gunk out of the tank. Then it shouldn't be needed much after that.

Good luck
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Old 01-27-2010
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Quote:
Originally Posted by cruisingmom View Post
Thanks folks for responding
I chose the Walbro because it was a marine rated diesel 12V pump with a separating screen filter on its intake for primary screening of junk (70 micron) prior to the RACOR.
Andy
Using a Racor in a fuel recirculation polishing system is a very expensive filter to use in a recirc. system. A Racor type filter is for removing a VERY small amount of debris from a relatively large system (0.005% or typically 30-50 GRAMS of crud is about all you get from the typical RAcor).

I'd recommend to
1. 'up' the throughput of the pump (typically 3 gallons per MINUTE per 100 gallon tank is 'reasonalbe'). The newer Walbro pumps are 'outstanding' vs. long service life.

2. Install a STANDARD INDUSTRIAL filter housing (industry standard is for use of filter cartridges of 10" length and 2.75" (or 2.5") outter diameter.
I'd suggest Shellco Filters Shelco Filters
Other: most industiral filter housing have 1/4" connection on the top/bottom of their housings
There are other manufactrers of industrial filtration products. Dont use HomeDepot stuff nor filters that are for home heating oil.

3. Use STANDARD industrial filter cartridges (available worldwide from zillions of manufacturers) Size the 'retention rating' @ 5X the retention of your FINAL filter in the RACOR Set (not including the OEM engine 'guard' filter. Choose a 'graded pore density' filter ('pores' get smaller as the fluid travels through the filter media). A graded pore density filter of polypropylene melt blown fiber should cost about $8 to 15.00 ea.
These are usually 'honestly rated' for their µM (nominal) retention; should be at least 90% retention at the indicated 'rating'. Avoid Home depot and other hardware store unbranded filters - as their ratings are very variable. ... you want 'quality' not cheap.

4. The recirculation system should be totally isolated from the standard fuel delivery system AND with an independent pickup tube AT the very bottom of the tank.

5. Run the pump BETWEEN the tank and the filter housing (pump PUSHES the oil). Therefore in PRESSURE MODE the pump will not 'stall' (no flow) until the pressure differential of 'crud' on the recirc filter is about 50 psig max. If you run the pump in 'suction mode' the pump will stall (at about minus 3-4 psi.
In pressure mode, if the pump inlet screen/strainer becomes 'choked' with (hard) debris you will begin to see negative pressure (or a drop of differential pressure) on the gage (see 5a.). Most debris in boat diesel fuel system is 'soft/deformable' (cellular debris of funguses, etc.) and the pump 'screen' at 70 µM will usually 'chop up' the deformables.
You will get longer filter life, more total gallon filtered with 'pressure feed' than with 'vacuum feed'.

5a. Apply a pressure gage between the pump and the filter housing. When operating compare the gage pressure to the filter manufactures "flow vs. deltP curve" to monitor the flow and to know WHEN to change the filter. You many want to use an electrical differential pressure switch wired to an alarm .... hi and LOW pressure switch so you know when to change AND for safety/enviro issues.

Dont get 'locked' into using one particular filter manufacturer because of 'geometry' - the worlds industrial 'standard' for filtration is 2.75" dia X 10-20-30-40 inch length filters. Cartridges with FLAT neoprene rubber endcap gaskets are suitable, so is 'knife edge' cartridge sealing for such fuel filtration.

Ive Been very deeply involved in filtration engineering for over 40 years. Racor makes the BEST filters for the PRIMARY fuel line filtration. NOt worth it for 'recirculation-polishing' filtration. Parker(Racor) has industrial filter divisions (and distributors) that can fill your needs if you somehow need to stay with the Racor brand.
Dont buy from an industrial supply source that requires a 'minimum charge'.

:-)

hope this helps.
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Old 01-27-2010
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Quote:
Originally Posted by xort View Post
Where would this screen be? In the pick up of the pump? It will need cleaning so make sure it's easily accessable and removable.

Since walbro said it's OK to put the filter before the pump I'd go that way.

The tradeoffs are that the screen will keep some of the gunk out of the filter ($) but you will have to disassemble the system to clean the diesel & gunk soaked screen often. How often? Probably a lot at first until you get the gunk out of the tank. Then it shouldn't be needed much after that.

Good luck
Screen - Its inside the covering/housing to the suction side of the pump.

Most debris in diesel fuel oil is 'soft and deformable' (cells and metabolic products/resins of or from funguses) and will get 'chopped up' by a 70µM 'screen' at increasing differential pressure.
If you have a supply source that 'particulates' a lot of hard particles (rust, etc.) then consider to apply a 'strainer' on the suction side of the pump.
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RichH,

I think the recommendations you made are very wise. In the end it should result in cheaper operation (Racor filters are expensive) and better operation due to the flow. I had forgotten to recommend a gauge in my post but they are very helpful.
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