Bilge Pump Switch

[Dick Locke]

Heck yes..they are in a lot of "Quiet Switches" in homes for instance. Most
mechanical water level detectors in industry are large mercury switches in a
round float that resembles a boats bumper sort of. Even Honeywell thermostats
on the wall have mercury switches in them.

My father used to work for Honeywell and brought home balls of mercury
when I was a kid. I used to roll it around on the floor until it got
lost under the furniture.

That probably explains a lot. Either that or the X-ray shoe machines
that I put my head into and pressed the "on" button.

It's a wonder anyone survived childhood in the 50's....

 

[Karin Conover-Lewis]

Zactly. I can remember sitting in science classes in elementary and junior
high school, playing with mercury by passing it around hand to hand, dipping
pennies in it and watching them "turn into dimes," and any number of other
deadly activities. But now the authorities conduct house-to-house searches
of entire neighbourhoods in an effort to protect the sheeple from a bit of
mercury that's gone missing from a school. Thus my previous joke.

--
Karin Conover-Lewis
Fair and Balanced since 1959
klc dot lewis at gte dot net (old -- don't use)
klc dot lewis at centurytel dot net (new)

 

[Keith]

Maybe you need another insurance company. Mine are powered through breakers
and passed survey fine. The breakers allow me to turn them off if necessary.

 

[Keith]

....and I thought I was the only one who did that!
You're right, I think it explains a lot. But it sure was fun to play with.

 

[Derek.Moody]

I don't know about your boat, but ALL the boats I have anything to do
with have MERCURY SWITCHES, which are explosion proof!

They still spark at times even if it is contained. If your returns corrode
you may be running the whole at a sparking potential - and for longer as
you're short of current. Cables and connectors wear too and get kicked
and crimped during nearby maintenance which isn't done as well as you might
wish (or there wouldn't have been an oil leak in the first place). Things
do happen at sea, don't compound them.

Cheerio,

--

 

[Splitpair]

This may be solved by selecting the proper reed switch and magnet. With reed
switches the pull in distance is always closer to the switch than the drop
out distance. Raising the magnet could pull in the switch and holding to the
drop to distance could provide the answer.

SP

 

[Splitpair]

Oh yea. A few years back I was working in a medical office that was being
remodeled. One of the laborers found a bottle of mercury in a cabinet and
not knowing what it was or what to do with it decided being as its a liquid
just pour it down the toilet. He flushed and flushed dozens of times and
that blob of silver didn't move so he moved on. A few days later a city
building inspector noticed it and all H*** broke loose. The property owner
took the brunt of the cost with the owner and the prime contractor going
into bankruptcy.

SP

 

[Rosalie B.]

x-no-archive:yes

You all misunderstand what an explosion proof switch is.

A REAL explosion proof switch as used in industry is a very heavily
built item with all the joints being jagged (cant think of the word
now) - that is the space in the joint isn't in a straight line but
goes around a couple of corners.

The purpose of an explosion proof switch is NOT to reduce the spark
inside the switch, but (if the flammable or explosive mixture gets
into the switch) to contain the explosion that will result when the
switch is turned on and a spark is generated. Thus the explosion will
stay inside the switch and will not ignite the flammable vapor or gas
outside of the switch.

One definition is:

Explosion-Proof Switch – A UL listedswitch capable of withstanding an internal explosion of a specified gas without igniting surrounding gases.

Sometimes explosion proof switches are also water proof or have other
characteristics, but the term explosion proof does not mean that the
switch won't produce a spark.

In the same way a flammable cabinet is meant to contain flammable
liquids so that if there is a fire inside the cabinet it won't spread
to outside the cabinet and liquids spilled if the containers burst
from heat will not leak outside the cabinet.

I don't know if mercury switches reduce the chance of spark or not - I
suspect not.

They still spark at times even if it is contained. If your returns corrode
you may be running the whole at a sparking potential - and for longer as
you're short of current. Cables and connectors wear too and get kicked
and crimped during nearby maintenance which isn't done as well as you might
wish (or there wouldn't have been an oil leak in the first place). Things
do happen at sea, don't compound them.

Cheerio,

grandma Rosalie

 

[Paul E. Bennett]

NO WAY have they got the required current rating, also I would be
concerned about water penetration of the magnet and reed units if you use
off the shelf alarm parts.
The idea does have merit however and if 'bare' reed switches and magnets
were encapsulated in epoxy, that sorts out the water intrusion problem.

OK so far.

To solve the low current rating problem you would need to use a relay
rated for the pump stall current mounted high and dry, far from the bilge,
controlled by the reed switch and add a diode accross the relay coil
(cathode positive, 1N4148 would be fine) to prevent arcing in the reed
switch.

I would go for a heavier diode than the 1N4148. Something more like a
1N4001 would be more suitable. In addition to the diode across the coil
also add a 100R resistor and 0.1uF capacitor (in series) in parallel
to the coil and diode. This will also reduce the switching interference
that can be caused.

A suitable diode rated for the motor current connected across it,
cathode positive would also increase reliability by reducing arcing at the
relay contacts.

Better than a Diode here would be a VDR of a suitable rating for the
motor.

--
********************************************************************
Paul E. Bennett ....................<email://[email protected]>
Forth based HIDECS Consultancy .....<http://www.amleth.demon.co.uk/>
Mob: +44 (0)7811-639972 .........NOW AVAILABLE:- HIDECS COURSE......
Tel: +44 (0)1235-811095 .... see http://www.feabhas.com for details.
Going Forth Safely ..... EBA. www.electric-boat-association.org.uk..
********************************************************************

 

[Brian D]

Given that the gov'mint works so DAMN hard to prove their lack of ability,
it just plain makes it hard to believe they've got an ounce of sense once in
awhile, even when they do ...

Brian

 

[Ian Malcolm]

x-no-archive:yes


You all misunderstand what an explosion proof switch is.

A REAL explosion proof switch as used in industry is a very heavily
built item with all the joints being jagged (cant think of the word
now) - that is the space in the joint isn't in a straight line but
goes around a couple of corners.

The purpose of an explosion proof switch is NOT to reduce the spark
inside the switch, but (if the flammable or explosive mixture gets
into the switch) to contain the explosion that will result when the
switch is turned on and a spark is generated. Thus the explosion will
stay inside the switch and will not ignite the flammable vapor or gas
outside of the switch.

One definition is:

Sometimes explosion proof switches are also water proof or have other
characteristics, but the term explosion proof does not mean that the
switch won't produce a spark.

In the same way a flammable cabinet is meant to contain flammable
liquids so that if there is a fire inside the cabinet it won't spread
to outside the cabinet and liquids spilled if the containers burst
from heat will not leak outside the cabinet.

I don't know if mercury switches reduce the chance of spark or not - I
suspect not.

grandma Rosalie

Since mercury switches are hermetically sealed to prevent the mercury
escaping as vapour, it should be impossible for any flamable vapour to get
into the switch, which usually consists of a glass capsule coated with a
tough plastic (sometimes steel with a ceramic seal). Reed switches also
totally enclose the contacts in a glass capsule. Unless the switch is
broken, it cant ignite vapours outside its capsule. The only risk is, if
there is a short circuit, and the switch closes on it, it may be blown to
bits, at which point I want to be ashore and not too near the edge of the
dock, if there is any gas in your bilge! An UL listed enclosure round the
switch capsule with labrynth seals as you describe would be a really good
idea. I wouldn't trust a bare capsule unless I had potted it in epoxy
with milled fibre filler.

The main disadvantage of a mercuary switch is it has to tilt to work which
means its in the float and the cable to it bends each time the float moves
so must eventually break. Also, if you have an aluminium hull, its a hole
waiting to happen.
--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk [at]=@, [dash]=- &
[dot]=.
*Warning* SPAM TRAP set in header, Use email address in sig. if you must.
'Stingo' Albacore #1554 - 15' Uffa Fox designed, All varnished hot moulded
wooden racing dinghy circa. 1961

 

[Jere Lull]

I don't know if mercury switches reduce the chance of spark or not - I
suspect not.

A mercury switch in a sealed tube, all contained in a watertight (or so)
float seems pretty good to me. Frankly, I think corroded wires are more
likely to be a spark source.

When I was a kid, the tube was glass (but I suppose it could be plastic
these days). My dad (an EE) thought mercury switches were safer and put
in all he could. None of them have failed in 55 years, some of the
mechanical ones have.

 

[Ian Pogson]

I'm sure I have seen a RULE PUMP float control that has a latching or
hysteresis built in. Try their website.m

If you want to go the home-spun route look at Farnell, RS or CPC
catalogues - there are things like multiposition sliding float reed magnet
operated float switches but they are usually pretty light - current wise.
Also a few people also do stock level control relays (query voltage) which
will accept input from basic metal probes - earth - high level start - low
level stop. These probes need to be insulated from each other but they can
be any size and any conductive material.

My company makes off-the-shelf control circuit (for bigger mains operated
pumps) which can be 12VDC operated, will control your bilge pump (of any
size) and will provide LED and switched outputs for remote indication /
alarm purposes. I'm not trying to sell to the group. In fact we can't handle
one-offs as a rule but could make an exception if desperate.

 

[Horace Brownbag]

On Mon, 27 Oct 2003 02:19:00 GMT, [email protected] (Larry W4CSC) wrote:

Anyone else have Mercury fillings that drive them crazy from time to
time?

Yeah, but it has nothing to do with amalgam or with fillings.....

 

[Dazed and Confuzed]

1N4148 1 time surge 1 amp forward peak reverse volts 75V
1N4001 1 time surge 15+ amps peak reverse volts 50V

The one is slender on forward current, the other on reverse volts -
but a 1N4004 up would do the reverse volts spike nicely with
respectable one time forward surge current.

Brian W

or parallel 2 of them.


--


Life lesson #48:

You can continue to puke long after you think you should be done......

 

[Rick]

Yeah, but it has nothing to do with amalgam or with fillings.....

That goes along with everything the National Institutes of Health says.
It seems that the amalgam thing is right up there with multiple chemical
sensitivity and a few of the other neuroses of that peculiar group of
people who cling to holistic cures and the dangers of distilled water
and fear of powerlines and green squirrels.

The theraputic value of the comic relief supplied by these whackos is
surely what prevents these ills in "normal" people.

Rick

 

[Brian D]

Don't forget aluminum pans and ...ummmm, oh yeah, Alzheimer's.

Brian

 

[Ian Malcolm]

1N4148 1 time surge 1 amp forward peak reverse volts 75V
1N4001 1 time surge 15+ amps peak reverse volts 50V

The one is slender on forward current, the other on reverse volts -
but a 1N4004 up would do the reverse volts spike nicely with
respectable one time forward surge current.

Brian W

I just looked some numbers up in my old Maplin catalogue:

12V coil 16A rated relay: coil is 106 ohms
minature reed switch: max current 0.5 amp

I make that about 140mA coil current if the battery is boiling and there
is 15V on your nominal 12V supply. Looks like I am pushing things a bit
as the 1N4148 is only rated for 75ma continuous, but I think X 2 is
acceptable for a repetitive surge with such a slow repetition rate and
fairly low energy content. If you want it bulletproof 1N4002 (100V PIV 1A
If) or higher in the same series would be great.

You will note I never specced a diode for accross the pump other than to
say it should be rated for the motor current. Ideally it should be rated
for the STALL current, but I think that you'd get away with some
parallelled 1N5401 3 amp diodes for most pumps in common use. (Of course,
if you are running a fireboat pump, you'll be useing a contactor not a
relay, and I wouldnt expect any of the diodes I specced or the reed switch
to last longer than a marshmallow in a blast furnace.)

P.S. There IS NO reverse spike with the diode there as it shunts it. It
only has the battery voltage applied to it. I think my choice was pretty
conservative. I've got 100 V down as the PIV for 1N4148 and 1N5401 in the
old catalog I keep handy for speccing this sort of stuff, If you are
getting 100V spikes on your 12V bus, you've got other problems than
premature failure of bilge pump switches. -)

P.P.S. Thanks for the peer review. Appriciated!






--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk [at]=@, [dash]=- &
[dot]=.
*Warning* SPAM TRAP set in header, Use email address in sig. if you must.
'Stingo' Albacore #1554 - 15' Uffa Fox designed, All varnished hot moulded
wooden racing dinghy circa. 1961

 

[David Flew]

I'm sure I have seen a RULE PUMP float control that has a latching or
hysteresis built in. Try their website.m

If you want to go the home-spun route look at Farnell, RS or CPC
catalogues - there are things like multiposition sliding float reed magnet
operated float switches but they are usually pretty light - current wise.
Also a few people also do stock level control relays (query voltage) which
will accept input from basic metal probes - earth - high level start - low
level stop. These probes need to be insulated from each other but they can
be any size and any conductive material.

My company makes off-the-shelf control circuit (for bigger mains operated
pumps) which can be 12VDC operated, will control your bilge pump (of any
size) and will provide LED and switched outputs for remote indication /
alarm purposes. I'm not trying to sell to the group. In fact we can't handle
one-offs as a rule but could make an exception if desperate.

Cross posting isn't my normal behaviour, but I'll do it this time in the
hope that Rule may pick it up. It seems to me that we have better things to
do than re-design reliable ways of controlling bilge pumps. We are
discussing this because of common experience with failure of one brand of
bilge float switch. And the common point of failure seems to be the wiring.
Now the wiring is subject to pretty nasty environment ( i.e. bilges) but
it's at normal pressure and temperatures. Surely it's not that hard to fix
the root cause of the problem, which is the wiring. I'd rather pay 10% more
for the switch, or have to order it in specially and wait a week than have
to spend time and effort in developing a one off alternative.

David

( who has amalgam fillings, has coated pennies with mercury, and can't
remember what this altz..... thing is all about.)
DF

 

[Rosalie B.]

A mercury switch in a sealed tube, all contained in a watertight (or so)
float seems pretty good to me. Frankly, I think corroded wires are more
likely to be a spark source.

That's true - not only for mercury switches. My point was - mercury
switches may reduce the chance of spark but they are not
explosion-proof as that has a specific definition. Explosion proof
switches go together with wiring in conduit or otherwise shielded.

The reason for explosion proof switches is that normal switches are
not safe for class 1 locations. There are lots of spark sources OT
switches to be checked for in class 1 locations - telephone bells (the
old fashioned kind) and iron or steel tools are two of them. (This is
a place like a paint factory where they are compounding oil paint or
the inside of a spray booth anywhere.)

I don't really know what a mercury switch looks like. I do know that
they use mercury in neon signs, because I've sampled for it in sign
shops. I've also checked dental offices.

I've also heard that business about amalgam, and have a lot of it in
my teeth. I suspect that those people who say that they have a
reaction to it have something else going on (because the symptoms they
report don't 'fit' with mercury exposure), or else that they have
become sensitized to levels below detection levels.

There used to be many more industries where mercury was used - the Mad
Hatter in "Alice in Wonderland" was 'mad' because of exposure to
mercury salts.

"At low levels of exposure, symptoms are mainly related to nerve and
brain function and include memory loss, mood instability, tremor and
other stress-like symptoms: poor coordination, headache, visual and
hearing problems. Recently, reproductive health has been shown to be
affected, with abnormalities in menstrual cycle, poor outcome of
pregnancy and subfertility in both men and women. The immune system is
also damaged by mercury exposure."

Seventy-six male ex-mercury miners who had been exposed to relatively high concentrations of mercury vapor (over 1.0 mg/m3) and with a past history of mercury intoxication were compared to age (+/-3 years)-, sex-, and years of education-matched controls. Although the extent of the workers' symptoms caused by mercury poisoning, termed erethismus merculialis, markedly decreased after the cessation of exposure, the prevalence of neurological symptoms (such as hand tremors, headaches, and slurred speech) and symptoms of senility (such as low-back pain, loss of sexual desire) in the ex-miners was significantly higher than those in the controls. Matched-pair analysis showed that performances of motor coordination, Simple reaction time, and Short-term memory in the ex-miners were significantly deteriorated compared to those of controls. There are slight but persistent effects on neurobehavioral function, especially on motor coordination function, among mercury miners more than 10 years

after the cessation of exposure."Another possible source of mercury exposure (other than chemistry lab,
or a broken thermometer) is eating fish - some years ago swordfish
were found to be heavily contaminated with mercury. There have been
industrial releases in Japan, and Sweden.

When I was a kid, the tube was glass (but I suppose it could be plastic
these days). My dad (an EE) thought mercury switches were safer and put
in all he could. None of them have failed in 55 years, some of the
mechanical ones have.

grandma Rosalie