About maintenance and functioning of kerosene pressure lamp
I wrote this while working at Kibosho Girls Secondary School in Moshi, Tanzania
1994-95. The relatively well-equipped school had mains electricity, but mains
electricity was both rationed out (because of draught in the hydroelectric area)
and generally undependable. So the school often used kerosene lamps for evening
studies. Kerosene is not a renewable resource, but until solar systems are more
affordable, they can be useful. One lamp can give a decent amount of light for
a classroom with maybe 50 pupils. The white light is easier on the eyes
than the usual yellowish light from wick lamps.
Kerosene PRESSURE LAMP (often called "karabai")
This is because it gives a strong
WHITE light like a CARBIDE lamp. A carbide lamp used a chemical called calcium
carbide. It looks like stones. If you drop it in water, the carbide reacts with
the water to produce the gas acetylene CaC2+2H20=2C2H2+Ca(OH)2
(sic p 207 Inorg Chem). This gas burns in air with a very white flame because
of its high carbon content.
The kerosene pressure lamp gets
its white flame in another way. It has a very efficient way of burning the kerosene.
The flame of the lamp heats the pipe which supplies the kerosene to the flame
and also the pipe which carries the mixture of gas and air. The kerosene becomes
so hot that it becomes a gas which burns easily with the hot air. The hot flame
burns in the "mantle" which is like a small sock made of asbestos.
Asbestos is a mineral (= from stone) fiber that can stand high temperatures.
But after being heated it is easily broken by touching or shaking. The mantle
is coated with an element called Thorium. This substance when heated enough
gives out lots of radiation in the form of visible light. An ordinary kerosene
lamp will send out much of its energy in the form of invisible infra-red (or
heat) waves. So a lot of the energy is lost as heat in an ordinary kerosene
The substance Thorium is quite
radioactive, so you should avoid breathing in the smoke which is given off the
first time you light the mantle. The ashes of a broken mantle should be disposed
of so no one will eat or breathe them.
light-A very interesting page about thermoluminescence
How do you use the pressure
lamp? The lamp is rather heavy so you may think there is kerosene inside though
it is almost empty. Remove the filling cap which also has a pressure guage on
it. Fill with kerosene, but leave some space for some air. Close the cap and
also the air screw that is in the cap. Turn the large red knob so its arrow
points up. Then a small wire will go up through the kerosene orfice (=small
hole). This cleans the hole and also closes it. Since there is no flame in the
mantle yet to heat the pipe, we must heat the pipe before we try to light the
kerosene. Put some alcohol (=spirits) in the heating cup (=the small yellowish
(brass) bowl around the base of the vertical pipe). This can be done with the
green plastic can that has a small pipe that can be stuck in through the largest
hole near that bowl. Light the alcohol with a match.
While the alcohol is heating
the pipe you can start putting in some "pressure" in the lamp by pumping
some air into the lamp with the pump. Sometimes the leather washer in the pump
has to be lubricated with vaseline or some other grease to pump well. Try to
form the leather so it presses against the sides of the pump cylinder. Don't
press it together more than necessary to get into pump cylinder. If the pressure
guage works, you can pump until it points at the red line. Hold the lamp base
firmly while pumping, because each pump stroke shakes the delicate (=easily
broken) mantle. Otherwise pump ( 100? ) times. If
there is only a little kerosene inside you have to pump many strokes, but it
keeps its pressure while burning. If there is a lot of kerosene, you get a high
pressure with a few strokes, but the pressure falls as the kerosene level sinks
and has to be pumped again.
When there is only about 1 mm
of alcohol left in the bowl, open the kerosene flow by turning the red knob
so the arrow points down. This lowers the wire out of the orfice. Hot kerosene
gases spray into the pipe and also suck air into the pipe which curves back
down to the mantle. There, the gases are ignited by the flame of the alcohol.
The hot kerosene flame makes the mantle produce a strong white light.
To increase the amount of light
around and below the lamp, put on the reflector: Hold the hanging wire (handle)
upwards and put the reflector over it, white side down.
You turn off the light by letting
out the pressure with the air screw on the filling cap. (You can quickly turn
off the lamp by turning the red wheel so it points up, BUT you should let out
the pressure too, otherwise some kerosene may leak out at the orfice and make
smoke. A quick turning off of the lamp can increase the risk of the chimney
cracking especially if there is a hole in the mantle.)
As with other lamps, if even
a drop of water hits the glass chimney when it is hot, the glass can break.
Protect it from rain and other water droplets.
What problems can you have?
If you open the kerosene flow before the pipe is hot enough, liquid kerosene
can spray into the pipe. This can make large flames come out of the lamp. If
the lamp is not near anything burnable, this is not dangerous, but turn off
the kerosene. The not-hot kerosene can make the mantle get covered with black
carbon. This prevents white light from the thorium even if the flame gets hot
enough. By turning off the kerosene for a second, air can reach the hot mantle
and burn off some carbon. If you quickly open the kerosene flow again before
it gets too cold you don't have to light it again. Let the mantle heat up again
some, then repeat (turning off the kerosene) until the mantle is white again.
Sometimes the light decreases
and is not helped much by pumping up more pressure. There can be some dirt in/on
the orfice. Turn the large red knob around one turn. This pushes the wire through
the hole and cleans it. Sometimes the dirt can be just above the orfice and
you can push it away with a small stick or wire from the side through the hole
near the orfice.
Sometimes you can't turn off
the kerosene completely and this means you can't burn off the carbon. It can
also make kerosene come out before the pipe is hot, causing big flames to come
out the top of the lamp. The problem is that the orfice hole and wire are not
making a tight fit. Either the wire is too thin or the hole is too big. You
will probably have to replace one or both (pin-200sh (=TAS Tanzania shilling
Sometimes you can succeed to
light the lamp properly, but the mantle gets slowly blacker and blacker. This
is also caused by a too big hole in the orfice. More kerosene comes than can
be fully burned, so carbon is formed like in the exhaust of an old diesel lorry.
Another problem can be a fast
loss of pressure. This can be caused by air leaks. If you pump up pressure,
you can find leak by listening, feeling, brushing on soapy water or putting
the lower part of the lamp under water and seeing where bubbles come out.
If the mantle with age or because
of rough handling, gets a crack or hole, some flame (fire) may go out that direction.
If the fire goes toward the glass chimney it can break it. Mantles (150sh) are
cheaper than chimneys (1400sh), so replace the mantle immediately. When replacing
the mantle, check that the parts that the mantle are tied to are screwed in
tight. The metal one can be turned as hard as you can by hand, but the white
ceramic head should be tightened carefully.
If kerosene starts coming out
around the pump handle after putting in pressure, the valve at the bottom of
the pump is not closing properly. The valve can be unscrewed with a screwdriver.
It may just have some dirt on the valve seat. If you hold the valve under a
liquid (kerosene, or water if you dry it properly after) and open the valve
repeatedly by pushing a small straight wire down through the hole in the top.
This can wash away the dirt. Try blowing from the bottom end (Cover 3 holes)
or sucking from the top to see if it closes). Put back if it seems tight, otherwise
clean again or replace. Tighten quite hard. pump up pressure and remove the
pump rod and see if kerosene is leaking up into pump.
Interesting questions (=possible school project?):
How much does a simple tincan wick lamp, "koroboi", consume (in kerosene and money)? How many people can use the light at once?
The same questions for a pressure lamp.
[and perhaps electricity from mains or from a diesel generator].
How much light is produced, how is that light different from different sources?
© Jeff Forssell karabai.html Created
1999; Last uppdate