Gidday,
I have to say that I am getting tired of dealing with the capabilities of
various seals for both my fuel and brake systems. Whoever comes up with an
inert, stable seal material for all applications will make millions very
happy, few quite unhappy, and themselves very rich. I specifically am
challenged with Viton for fuel systems vs Buna or other materials. I have a
recently purchased a SUCO fuel pressure switch, which is actually an oil
pressure switch. It was sold to me with the assistant highlighting it has
an internal Viton seal. Well, I took a gamble and bought it, but subsequent
to that I have stumbled on something I have read once before on the web
---From a Long Eze pilot back in 1988 who had an engine failure directly
attributed to the collapse of a viton component within a Facet pump. For
interest I have pasted the accident summation below.So, I now have
potentially a $85.00 component.
Even in the example below, when the author admits he is using 100LL, which
to my knowledge is not avgas, then quotes the seals in his pumps, Viton, as
being not stable in Avgas, nor Buna N seals. So, unless I got it wrong he
states he is using one type of fuel and then states another will cause the
problem. I can only presume I have this wrong, as why else would an author
write such as speel. If however he did get it wrong, or in fact I did, it
highlights the confusing nature of these issues. They all change again when
you start talking brake fluids, and they vary amongst them too depending on
whether you are talking silicone or synthetic, or petroleum based. So, if
anyone can reassure me that my switch won't rot away to nothing and will
actually do its job in mogas, but not avgas, well it is this type of
definitive statement I want. Or, of course, if there is another path to
clear up this mist, well I'd appreciate it.
LONG-EZ. DEFIANT, ELECTRIC BOOST FUEL PUMP ALERT
From CP57, Page 11 (October, 1988)
Returning to his home base airport after a flight, a Southern
California Long-EZ pilot was approaching the 45 degree entry to downwind
when, abruptly, his engine quit. He was unsuccessful in getting it
restarted but, to his credit, he flew the airplane, announced his situation
and made an uneventful, successful landing. Feeling a little weak around
the knees, he pushed his airplane into his hangar and went home.
The next day, he conducted a careful examination of the aircraft and
discovered that the Facet solid-state fuel pump was completely blocked and
would not allow any fuel to pass through to the engine driven mechanical
pump! One of the two valves in the pump had deteriorated in the 100LL fuel
and had worked its way out of the metal cage that normally prevents this,
and had been sucked into a position that prevented the flow of fuel. The
part number on the mounting flange of this pump was 480615. The plunger
valve was made of VITON- this pump is no longer being manufactured.
Before next flight, check the part number of your pump. If you have
one of the following part numbers 40023, 480615, 480616, remove the pump
and replace it.
The most desirable Facet solid-state pumps that we recommend are part
#40108 for 12 volts and part # 40154 or 480610 for 24 volts. Both pump fuel
at a regulated maximum 6 psi, and the valves in these pumps are pure nyIon
which, other than swelling very slightly in avgas, are not affected nor do
they deteriorate. The design of these valves (the foot valve and the
plunger valve) are such that they cannot physically get into a position
where they can prevent fuel from flowing through the boost pump. Both of
the above pumps have AN-style, 370 flare fittings which fit 3/8" tube, AN
818-6. Nuts.
Facet manufactures over one hundred variations of the small square
solid-state fuel pumps. The above two pumps have AN-type flare fittings
machined right on the pump bodies and we prefer this type because they are
easy to install (no elbows or nipples required), but also because these two
models have only nylon valves, no rubber, Buna, or Viton. Many of FACET's
other models have Viton plunger valves or Buna N check valves and these
will deteriorate in avgas. These are specifically for use in some other
liquid known not to affect these materials.
To check your pump, remove it and look into the inlet and the outlet
using a small flashlight and verify that the inlet valve (foot valve) is a
round, white dome or ball (nylon), not a flat, black rubber disc. Verify
that in the outlet there is a white nylon valve under a steel pin which
crosses the port and retains this valve. If this valve is dark gray or
black (Viton), remove the pump before next flight and discard it. If you
have to a pump with female pipe threads (to accept elbows or nipples) due
to your firewall layout, choose one with 3/8 NPT female threads rather than
the 1/8NPT female threads, but examine it closely to be sure it has while
nylon valves in the inlet and the outlet ports. Discard it if there is any
black or gray Viton, Buna N or rubber valves.
If you have had your Facet fuel pump more than a year or so, you
probably have one that could go bad. AT a cost of approximately $30.00, it
is not worth the risk. Remove it, discard it and install a new one as
called out. We believe that the serious consequences that could result from
a fuel supply stoppage, more than justifies the immediate replacement of
any suspect pump.
We have replaced the boost pumps on Burt's Defiant and on Mike and
Sally's Long-EZ and we recommend in the strongest possible terms that you
do the same.
Reg
Tony Renshaw
Sydney Australia
Classic 236 B.B. Taildragger
Tail, Wings, Ailerons, Flaps Complete and Connected
Lower Fuse in Jig, Tail Torque Tube installed
Mass Balance assembly installed and deflections sorted
Roof Panel between doors completed.
Photos at:
http://forum.okhuijsen.org/modules.php?set_albumName=TonyR&op=modload&name=gallery&file=index&include=view_album.php&PHPSESSID=902b69917a45f8b18ac84fe3f85a704b
Intended Engine: 912S CS prop (model undecided)
Instrumentation: Undecided
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