Skip;
I think the key to getting reliability in a solenoid valve is the selection
of the seals it uses internally. Any seal material "wetted" by Halon should
be compatible (obviously) but finding out what seal material a manufacturer
uses isn't always easy. Parker publishes a good seal compatibility chart and
it's on the Internet at:
http://www.chomerics.com/products/documents/Fluid_compatibility_guide.pdf
<http://www.chomerics.com/products/documents/Fluid_compatibility_guide.pdf>
.
It looks as if the best seal material might be Viton but there are LOTS of
different Freon compounds, and some of them have other material
recommendations. Surprisingly, Teflon is not suitable for Freon compounds. I
suspect a valve made for chemical service would have its wetted components
specified. The valve also needs to have an appropriate pressure rating, of
course.
Regards, Neil Tucson, AZ
-----Original Message-----
From: Higginbotham Land Speed Racing [mailto:saltrat@pro-blend.com]
Sent: Tuesday, October 30, 2001 10:21 AM
To: Albaugh, Neil; land-speed@autox.team.net
Subject: Fire Light
Good ideas Neil. I think I understand the circuit but it would need to keep
the warning system "on" when the bottles are actuated....I think. Maybe a
SPST switch would work if the warning system turned on the rear bottle and
all you wanted to do was turn it (the bottle) off and on?
Another question:
Do you know of any solenoid valves that will not get contaminated with Halon
and then start leaking?
I have used solenoid (servo) valves for three years now and have found that
the valves get contaminated with agent and fail too often. Once a valve
turned itself on when the car was just sitting there!!! I have tried simple
Nitrous valves and sophisticated air valves. They all seem to get
contaminated and fail (read LEAK!). I am about to go to manually controlled
valves with handles in the cockpit. Ball valves maybe with an over-center
linkage of some sort to keep it "on" in accordance with the rulebook. Not
much room in the drivers area however and I need 3 valves (bottles). One for
front engine, one for cockpit and one for rear engine(s).
Skip(
At 10:37 AM 10/30/01 -0600, you wrote:
Skip;
You have good points. I agree with your assesment of the resistance wire
problems. There is also the problem of delay time-- similar to the problems
with fire sensing by thermostats, etc. I did see a couple of UV fire sensors
sell on eBay recently for only about $30, so there are some bargains to be
had if one is lucky enough to find them.
I also agree with your wanting to be able to shut off the fire bottles
manually. I'd suggest wiring a SPDT (ON- OFF- ON) switch in series with the
solenoid valve so that in the center position, the system is "OFF". Flip
the switch to the "up" position to arm the automatic flame detector and in
the "down" position the fire bottles are manually activated. I can give you
more detail on how that would be wired if you're interested.
Regards, Neil Tucson, AZ
-----Original Message-----
From: Skip Higginbotham [ mailto:saltrat@pro-blend.com
<mailto:saltrat@pro-blend.com> ]
Sent: Tuesday, October 30, 2001 9:09 AM
To: Albaugh, Neil; land-speed@autox.team.net
Subject: RE: Solid suspension and visibility comments
Neil,
The problem with resistance wire systems is false alarms.......not a good
idea at 300 MPH +. Too hard on the heart! And IR systems are a little
pricey for me.
Auto fire extinguishing is OK if you don't want to control the extinguisher
manually. I do. I feel like I can turn on the fire bottles until the fire
is out and if I'm not stopped yet, I can turn off the fire bottles and save
the agent for later in the shut-down if the fire relights or was not out to
begin with. Also manual control might let me breathe in the small
cockpit!!! Too subtile?
Hard to reason with a fire that is behind you though!!! Auto system might
be the best in the long run. I worry about false actuation.......
Skip
At 09:50 AM 10/30/01 -0600, you wrote:
>Skip;
>
>That's a good idea. You could probably wire that into a solenoid- operated
>valve to actuate the fire bottles automatically, too.
>
>I've seen some aircraft fire detection systems that are based on a wire
that
>changes resistance. Some of the newer flame detectors sense ultraviolet
>radiation so they aren't confused by IR heat radiation from the collectors
>or other hot spots.
>
>Regards, Neil Tucson, AZ
>
>
>-----Original Message-----
>From: Skip Higginbotham [ mailto:saltrat@pro-blend.com
<mailto:saltrat@pro-blend.com> ]
>Sent: Monday, October 29, 2001 5:54 PM
>To: Albaugh, Neil; land-speed@autox.team.net
>Subject: RE: Solid suspension and visibility comments
>
>
>Neil,
>I have a fire detection system in the liner/lakester. Turns a bright red
>light on in the cockpit. No false alarms yet.
>Skip
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