Originally Posted by rustypirate
I was under the impression that the fuel filters should allways be on the intake/low-pressure side of pumps to prevent a high-pressure fuel system leak and to allow you to moniter draw on the filter to determine when to change elements.
You setup would be a bit different because of the day tank. I would love that and might install one in the future.
In my diagram:
- Replace the feed manifold with the day tank.
- Remove transfer pump (you only need one pump but also a backup for it).
- Move the clean fuel tap to the day tank (gravity feed).
- Remove filters between day tank and genset and engine because the fuel in the day tank is already clean.
- Remove pick-up tubes and plumbing between tanks and supply manifold (day tank). Just replace the fittings with a plug.
- Connect fuel return from engine and genset to day tank instead of return manifold.
- Create an "overflow" connection on the day tank that connects to the return manifold. Your return manifold has connections to each tank only.
- Insert a double Racor 500 filter between pump and day tank.
- Don't forget the vent for the day tank.
As you can see the setup becomes much simpler with the day tank. Filling it is the same as polishing; just make sure the valves on the return manifold are set to divert excess clean fuel from the day tank to the storage
tank you want.
The pump draws the dirtiest fuel from the tank sumps through the transfer manifold and the first filter. it then pressurizes the fuel to max. 7 psi and pushes it through the 2nd filter with 2 micron elements into the day tank.
The transfer manifold has a tap to drain water and solids (it doubles for pumping from a drum). If I didn't polish for some time, I first drain a bit to check for water/dirt, just to save the filter.
Please note that there might be regulations
that do not allow you to have a drain on the bottom of a sump in your tanks. In that case you need a pickup tube from above that goes as far down into the sump as possible (unlike most pick up tubes that stay clear of the sump). You can use a fuel hose instead that lays on the bottom of the tank. You really want to get the water and dirt first so that it can't collect there. It also means you can't use the drain valve on the transfer manifold and everything collects in the first filter.
You do need a spare pump installed and I would choose electric
over manual. Just plumb them in parallel and depending on the design you might need a valve in series with each one.
Now for the switches etc. Your pump does 2 things:
- fill day tank. I would make that automatic with two float switches.
- polish fuel. I use a mechanical timer switch for this.
Now, if the float switch for empty tank fails, you can use the (timer)switch for polishing fuel to fill the tank instead. If the float switch for full tank fills, it overflows back to a storage tank like if you are polishing fuel. For "tank full" there are accurate pressure switches available (connect to bottom of day tank). There are also ultrasonic sensors that fire from the top of the tank and measure the level that way. Just floats will be fine too especially because the fuel is always clean. Keep the day tank full when not using the engine/genset to prevent condensation
. You can use the "clean fuel" tap to check for water if you don't trust it.
I spent a lot of time engineering our fuel system and never found a better system apart from Algae-X stuff etc. that I don't believe in. I copied most from the Nordhavn setup ;-)
I use the enzyme based stabilizers (Star-tron it's called I think).