ORIGINAL: speedbrake
Kelly,
I'm installing a 600R in a R54. This is my first turbine. The manual isn't clear about the fuel system. The instructions say to connect the main tank to the header tank, then the header tank to the shutoff valve, then to the fuel pump, then to a fuel filter, and finally to the turbine. However, the diagram provided shows a different arrangement. What is the correct way to set up the fuel system?
The fuel pump I have doesn't have the mark mentioned in the manual describing the "in" nipple. It has instead an arrow going across the two nipples. I assume the arrow indicates the direction of fuel through the pump; thus the point of the arrow is the exit nipple - fuel to the turbine (?).
Please advise,
Thanks,
Keith Lindsay
Hi Keith,
The pump supplier has since changed. You're correct that the arrow designates the direction of flow, so the one closest to the pointy end of the arrow goes to the turbine.
The shut off valve can go before, after, or one on both sides of the pump if you wish to have multiple emergency shut offs. Having it after the pump may cause a little more heat generation in the pump motor brushes due to the fact that the motor is effectively stalling when you close the valve while running. The advantage to using the valve after the pump is the net positive pressure on the o-ring seals. They are designed to operate with internal pressure, not a net vacuum. (same with all Festo or similar branded connectors) However, placing the valve on the inlet of the pump, so long as it has a reliable seal, does have one minor advantage. Upon closing the valve while the valve is running, the resistance to the inlet will instantly cause the pump to cavitate and run closer to a free wheeling condition. The current draw will be minimal and the valve won't see any undue wear since its still lubricated. Personally though, avoiding the extra leak point in return for a small amount of brush wear (if you ever need to shut it off with the valve) is a good trade-off. I always install the valve after the pump.
So, what I'd do in your case is:
Main Tank ---- UAT ------ Fuel pump ---- Filter ---- Ball Valve ------- Motor
The ball valve can be placed before the filter with no side effects, just go with whichever method is easier to install.
Other notes:
The filter position is critical for 2 reasons. 1st, you need to be aware that a fuel pump itself will create debris in the fuel system, a little more so when its new or near end of life. The filter should be placed between the pump and engine for this reason alone. Secondly, if the filter were placed before the pump, upon collecting debris and increasing its restriction it can cause cavitation in the fuel pump. That can cause all sorts of problems from the irregular fuel flow into the engine, again more reason to place it after the pump. If you’re using a UAT, the filter will be redundant before the pump anyway, since the UAT has an integrated filter. The UAT’s filter won’t cause a lot of restriction though, since its surface area is very large.
Keep in mind that the all fuel lines before the pump should be the largest reasonable size that you can use, and as short as possible. The pump's inlet should be as close to atmospheric pressure as possible for a healthy fuel system.
Good luck with the engine!
Kelly