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Saturday, November 13, 2010

Fuel System Design

The other side of "filling" the fuel system is "distribution". As we have five fuel tanks (three mains, two day tanks), a little thought needs to be given to layouts as there will be two hoses running to each tank (supply and return). Consideration should also be given to plumbing (valves and pipe fittings) to support the following features.
  • select any tank as the "current" fuel source
  • transfer fuel from any one tank to another
  • polish fuel between tanks as well as within one tank
  • easy to understand and operate 
  • selectable backup filter
  • easy access for filter changes and system bleeding
One device that will enable most of these features is the FilterBOSS  from KTI systems. I posted about their original FilterBOSS some time ago. Since then, they have released  a new device called the FilterBOSS Commander  that is nicely integrated with various dual filter manifold systems (made by Parker/Racor) and sell as a complete package. The device features an electric circulation pump, vacuum pressure gauge and a valve to switch between filters, should one get clogged.
The FilterBOSS simplifies most everything here. What is left is designing a means of selecting source and destination fuel tanks. Things get tricky the more tanks you have. With each tank comes another set of valves and pipe fitings. Multiply that by five tanks and things start to get a little complicated. But, no worries. Another little black box (also sold by KTI) will help things.

These are compact machined anodized aluminum manifolds (the black boxes in the picture). They feature a number of 3/8" NPT ports and holes for bulkhead mounting. Just thread in your valves and fittings, block any unused ports with a plug, and you have saved yourself having to deal with numerous elbow and tee fittings. Also, the reduction in the number of pipe joints means less chance of fuel leakage. So, with these devices in mind, the design of the layout on the bulkhead can be done.

Click on the drawing for a larger version
Red are supply hoses, Blue are return hoses

The trick here is to layout things neatly and logically, eliminating fuel line crossings as much as possible. This drawing is somewhat to scale. The manifolds and valves are scaled to real relative sizes. The drawing looks sort of complicated, but operation of the system will be pretty easy. Simply select your source and destination tanks via the valves on the manifolds, and the FilterBOSS will do the rest!

This is still in-work and, of course, subject to change till everything is installed.


Philippe said...

Hi, I have started reading your blog recently (great blog!) as I am going soon to work on a refit of a sailboat I just bought. The fuel lines drawing, was it done and optimaized by hand or with a software? Thanks.

robert said...

Hello Philippe. For the diagram, I just used my CAD software. Nothing special. Though I am looking out for such "optimized" software for the electrical layout.