Old
fighter jets from the 50-60ies have real robust pure mechanical one with a
high range and are unexpensive. vbr Carsten.
"James Frankland"
<jamesf@guernseysubmarine.com>
schrieb:
> Hi Jim,
>
> Yes, altimeter sounds good.
i understand what you mean with the test. Was
> going to
do exactly that myself. It was just the gauge I was being a
dope
> about. Its obvious now I've thought about
it.
>
> Had a quick look at altimeters. Loads of different
ones you can get.
> Cheapies, wrist watch ones, aviation, skydiving
etc. What make of
> altimeter are you using? I do have a
proper custom made caison gauge as
> well which came out of a diving
re-compression chamber. That might be ok
> but it will
need to be re-calibrated.
>
> Anyway, plenty of other
things to do first before I need to fit that.
>
>
Regards
> James
>
>
>
>
> On 27 March
2012 15:26, <
JimToddPsub@aol.com>
wrote:
>
> > **
> > James,
> >
> > To clarify:
The reading of 5,000 ft. is what I've chosen for pre-dive
> >
tests when the pilot is inside and the hatch has been latched.
When
> > testing the vessel for leaks in your shop
*with no one inside *you want
> > to take it as far as you can.
> >
>
> Even if you could pull a complete vacuum with a pump, the
maximum
> > difference you can achieve is 1ATM or about 14.7 psi.
which equates to a
> > depth of 33 feet or so in water. In
the shop test I'll go as far as the
> > pump and the altimeter can
handle (maybe 100,000 feet above sea level). If
> > it passes
all that, the next step is dunking it in water to the appropriate
>
> depth(s) or testing in a pressure chamber.
> >
>
> Jim
> >
> > In a message dated 3/27/2012 8:40:27 A.M.
Central Daylight Time,
> >
JimToddPsub@aol.com writes:
>
>
> > James,
> >
> > I'm planning
to install an aircraft altimeter for the same purpose. An
> >
altimeter is simply a barometer with a wide range, so you could use
that
> > instead. It has the sealed air chamber (aneroid)
which expands or
> > contracts in response to changes in external
pressure.
> >
> > With the hatch closed and latched you
can pump air out with an
> > external vacuum pump, turn the pump
off, close the valve, take a reading on
> > the altimeter, wait a
few minutes, then take another reading to see if any
> > air leaked
back into the sub. This can even be done with the sub
> >
unoccupied as long as the altimeter is positioned where you can read
it
> > through a viewport.
> >
> > In most cases
you can use the adjustment knob to set the altimeter to 0
> > for
the first reading. I plan to run the vacuum pump until the gauge
reads
> > 5,000 ft. altitude, shut the valve, and wait 5 minutes.
If the altimeter
> > reading drops to 3,000 feet for example,
I know a seal is leaking
> > inwardly. One caution: If
the sub is sitting in strong sunlight, you
> > could get some
increase in internal air pressure just from heat build-up.
>
>
> > This test is on my pre-dive checklist on every dive.
During a dive the
> > pressure reading should change very
little if your scrubber and O2 inlet
> > are in balance.
>
>
> > [image:
> > http://upload.wikimedia.org/wikipedia/commons/c/c3/Sens_alt_components.PNG]<http://upload.wikimedia.org/wikipedia/commons/c/c3/Sens_alt_components.PNG>
> >
> > Comments and criticisms are most
welcome.
> >
> > Jim
> >
> >
>
> In a message dated 3/27/2012 7:36:00 A.M. Central Daylight
Time,
> >
jamesf@guernseysubmarine.com
writes:
> >
> > Hi All,
> >
> > Mr
Numpty here.
> >
> > I kind of know the answer to this
already, but i thought someone may be
> > able to clarify my
mistake.
> >
> > I was very pleased when i spotted just
the sort of gauge i was after
> > mounted on the back of a sewage
tanker. A pressure gauge but one that
> > reads a negative
pressure as well as a positive. So it starts at 0 and
> >
can go to -1 or +1 bar. Idea was that it would go inside the cabin
to
> > monitor internal pressure. (I'd like it to be able to
measure a negative
> > pressure as well as i intend to drop the
internal pressure to test
> > for penetrator seal leaks).
>
>
> >
> > http://www.tankerspares.co.uk/product/100mm_dia._30-0-30_Bottom_Mounted_Vacuum_Pressure_Gauge_30-0-301-4
> >
> > I was just thinking about mounting it
up and ive suddenly realised that
> > its not going to work is it?
It must measure the port pressure relative to
> > the ambient
pressure, which if i just mount it on a bulkhead will always be
> >
the same no matter what the pressure actually is.
> >
> >
I suppose i'd have to make a pressure proof box sealed at surface
pressure
> > and pipe the port to the inside of the hull? So
its kind of like a
> > caisson gauge.
> >
> >
Just thinking aloud really.
> >
> > James
>
>
> >
>
>
>
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