-------------- Original message from "Ed Anderson" <eanderson@carolina.rr.com>: --------------

Hi John,

 

There has been some debate about where the filter should go.  Some folks feel its purpose is to protect the pump and place it before the pump, others feel it is to prevent clogging of the fuel injector screens and place it after.

 

I personally believe placing a high pressure filter after the pump is the preferred solution.  I use a coarse filter

(wire mesh) before the pump to keep any large foreign matter out of the pumps.  If your injectors clog it doesn't matter what kind of filter you have before the pump or how well the pump is protected.  Others will argue that a fine filter before the pump protects both - unless of course the pump starts to shed material.

 

One thing to consider is that a filter of any kind will cause a pressure drop, the finer it is (and therefore the more restrictive) the more of a pressure drop.  Pressure drops before the intake of a pump can lead to cavitation and formation of bubbles in the fuel line leading to "vapor lock".

 

In the auto, the screen inlet in the tank acts like a coarse filter ( before the pump) and the filter outside the tank is a finer filter.

 

There you have my 0.02 on the topic

 

Ed

----- Original Message -----

From: John Downing

To: Rotary motors in aircraft

Sent: Wednesday, March 07, 2007 9:50 AM

Subject: [FlyRotary] fuel filter

Looking at the pictures of fuel filter, pump installations, the filter is after the pump.  In auto installations the pump in tank has a screened inlet and then filter someplace between the pump and the injection system.  The plane has a gascolator and do I place the pump next like auto installations, then into the filter like the auto installations, or why not.  JohnD