Fuel polishing P/U and return tubes

[scherzoja]

I will be modifying my tank to install a dedicated pickup (P/U) tube and dedicated return tube. Tank capacity is about 50 gallons in one tank.

Should the P/U tube be as close to the deepest part of the tank as possible? Should it have any additional intake holes in the tube above the actual bottom end of the tube?

For the return tube, should it be bent so it shoots the returned fuel down towards the deepest part or shoot away from the deepest part to create a circulation or just straight to the bottom?

Is it better to return the fuel with as little disturbance as possible or as much aggitation as possible?

In other words, promote stratification or homogenize the strata?

This polish system will be independent of the engine P/U, Return, and filter system.

Thanks

 

[RichH]

Recirculation Pick-up should be at near the very bottom of the tank.

Best practice for the 'return' - should be against a side wall, etc. to minimize formation of oil-foam when the discharge is not under the liquid surface .... probable best is at 45° and 'aimed' at a 'corner' to help 'turn over' & mix the tank contents (even at ~2-3 gallons per minute recirculation flow).

Recirculation filtration is dependent on high turn-over (constant pumping at high volume flow) of the fuel ...
For spun bonded 'depth' cartridges select housing suitable for 'knife edge seal' of the spun-bonded filter in the 10-20µM (nominal) range ..... high turnover will produce tank residual particles at 'sub-micronic' levels - better than crystal clear.
Standard 'Industrial style' 2.5" or 2.75" OD X 10" long filter cartridge would be the most cost effective, and most readily available from industrial or ethical filter supply.
Choose Viton® housing seals - compatible with bio-fuels and 'mixes'.

FWIW - For personal usage Ive been using steel 10" housings and filter cartridges from www.shelco.com ... These are 'industry standard', not some proprietary configuration that 'locks' one into only one vendor. For 9.75" length filters and use 2 (1/4"thk) gaskets per 'end' in 10" housing. For spun bond cartridges, use housing with internal 'knife edge seal' - no gaskets, etc. need on the filter.

Pressure feed the filter housing; use pressure gage to monitor filter 'performance'. Make sure the tube, etc. connection are 'bomb-proof' when using 'pressure feed'.
Avoid 'compression' fittings whenever possible when using copper tube.

Avoid 90° short radiused elbows, keep 'connectors' to minimum whenever possible to lessen system 'pressure drop'.
Being 'neat' is nice but l-o-n-g sweeping transitions are better 'pressure-wise' and for higher flow output.
My pump preference is one of the Walbro 12vdc 'transfer pumps', rated for continuous duty.

Continue to use a biocide in your fuel.


hope this helps. ;-)

 

[Maine Sail]

+1 on what Rich said. Personally I use a Racor 900, because it was basically free and I like to be able to see the fuel clarity.. The filter cartridges are cheap, my cost (yours will be slightly higher without a good web search) for the Racor 900 is about $7.27 or less than the cost of two gallons of fuel.... The industrial filters work fine though. With a good system in place, starting with a clean tank, the filters will last a long, long time.

Our system runs whenever the engine does so the tank is turned many times each fill because it turns over approx 2X per hour... After 6 or 7 years the tank walls and internals are still 100% spotless. Ours picks up within 1/8" of the absolute lowest spot in the tank and returns on the opposite end with a little crook in the return tube causing circulation..

 

[RichH]

With a good system in place, starting with a clean tank, the filters will last a long, long time.

+2 on the clean tank.
The common and wrong premise is that recirculation polishing will 'clean' a tank.
The purpose of recirculation is to prevent tank fouling .... by constantly removing the 'seed particles' and microorganisms (fungus and bacteria) that cause the fouling.

Dont put a recirc. filter on the engine 'return line' .... total waste of time, as there is insufficient (turn-over) flow; thus, it will take infinite time to 'dilute' the developing particle load in the tank.
Rx: tank --> pump ---> filter ---> back to tank.

;-)

 

[scherzoja]

Thanks for the input.

Maine: return and P/U separated with generous distance? Return angled to promote circulation. Like in your pbase new tank diagram.

Rich: I'm pulling tank this week for cleaning, inspection, and modifications to add dedicated fittings for polishing system.

Generally, is it wise to keep returns as far away from their corresponding P/U tubes? I'll be adding additional tubes for generator & heater.

Thanks again for your help.

 

[RichH]

Generally, is it wise to keep returns as far away from their corresponding P/U tubes?
Thanks again for your help.

There usually isnt enough fuel flow in a return line to matter or make a difference.

Aim the discharge recirc. so that at least one tank corner is constantly 'swept' .... other than a Vee-bottom, corners in squarish tanks is where the bulk amount any particles that settle out will be located. Corners are relatively 'quiet' (dead flow zones) with respect to any 'mixing'.

 

[alexco38]

+2 on the clean tank.
The common and wrong premise is that recirculation polishing will 'clean' a tank.
The purpose of recirculation is to prevent tank fouling .... by constantly removing the 'seed particles' and microorganisms (fungus and bacteria) that cause the fouling.

Dont put a recirc. filter on the engine 'return line' .... total waste of time, as there is insufficient (turn-over) flow; thus, it will take infinite time to 'dilute' the developing particle load in the tank.
Rx: tank --> pump ---> filter ---> back to tank.

;-)

Per Racore instruction:
120A and 120B fuel filter/water separators are designed to be installed on the suction side of the fuel system with maximum flow capacities of 15 and 20 gallons per hour (GPH) respectively. The compact size and 4-port versatility make the 120 series a very popular
small filter for many applications.

Therefore I installed this way:
Rx: tank --> filter ---> pump ---> back to tank.

 

[Maine Sail]

Per Racore instruction:
120A and 120B fuel filter/water separators are designed to be installed on the suction side of the fuel system with maximum flow capacities of 15 and 20 gallons per hour (GPH) respectively. The compact size and 4-port versatility make the 120 series a very popular
small filter for many applications.

Therefore I installed this way:
Rx: tank --> filter ---> pump ---> back to tank.

I think Rich was referencing placing polishing filter in the engines return line..... Yes with Racor turbines they want the pumps go on suction side with other filters supply is often best but the downsides to supply, such as a leak, need to be weighed carefully...

 

[RichH]

Alexeco .... That is correct for the 120 series RACOR, they are not designed nor recommended for pressure feed service.

The discussion here is Recirculation filtration.

Fuel delivery line *Pressure feed* is for the realm of 'commercial' fuel system applications; not recreational applications. Such commercial situations/applications require a marine engineering etc. license, etc. to operate.

Vacuum feed is the course on recreational vessels as if the system leaks, it automatically shuts down. On a commercial vessel, its required to have someone onboard who licensed and is constantly 'watching' the operation.