VITA TECHNICAL BULLETIN
WASTE OIL-FIRED OVEN
This simple, low-cost bakery oven is fueled by waste,
automotive
crankcase oil. The
design has undergone extensive testing.
It is designed to be built from locally available materials.
This oven is capable of maintaining a 160 degrees C to 190
degrees
C baking temperature on .946 to 1.4 liters of waste oil
per hour depending upon chimney draft.
This oven is a result of
a student design project by University of Maryland students
under the direction of VITA Volunteer Clifford L.
Sayre. The
other members of the project are:
Leon Chuck, Richard Freeman,
Morris Hoover, Maureen Houle, Barry Kornett, and Thomas
Sieber.
Please send testing results, comments, suggestions, and
requests
for further information to:
VITA
1600 Wilson Boulevard, Suite 500
Arlington, Virgnia 22209 USA
Tel: 703/276-1800 * Fax:
703/243-1865
Internet:
pr-info@vita.org
ISBN 0-86619-164-X
Revised April 1984
WASTE OIL-FIRED OVEN
INTRODUCTION
The development of small-scale industries in many countries
has
been hampered by the scarcity and cost of high-grade fuels.
This is particularly true for bakeries in small villages,
which
must presently rely on the use of low-grade fuels such as
peat
or dried dung for economical operation.
At the same time, large
amounts of used automotive crankcase oil are discarded.
Waste
motor vehicle oil is usually dumped into the nearest field
or
river. However,
waste oil is a refined petroleum product, which
with special handling has considerable potential as an
alternative
fuel source.
The oven design in this bulletin makes use of waste oil
without
preheating or mixing with other, more expensive fuels.
The cost
range for building this oven is from $25 to $60 (US, 1980).
<Figure 1>
45p02.gif (600x600)
TOOLS
* Acetylene
torch *
Metal shears
* Drill and
bits *
Metal punch (3.175cm)
* Saw for cutting
wood *
Hacksaw
* Pliers
*
Scribe
* Hammer
*
Screwdriver
MATERIALS
* Drum, steel,
55-gallon (1)
* Drum, steel,
42-gallon (1)
* Tin can,
one-gallon (1)
* Sheet metal,
medium (26) gauge, about .058cm thick (approximately
122cm x 122 cm)
* Steel angle iron,
2.54cm (183cm long), 122.04cm left for
trough
* Threaded steel
rod, .95cm dia. (25.4cm long)
* Steel strap, .63cm
wide x 15.24cm long x .32cm thick
* Galvanized pipe,
.31cm, each end threaded 5.08cm (38cm long)
* Galvanized
reducers, 1.27 to .63cm (2), or fittings to serve
as nuts to hold
above galvanized pipe to tin can fuel tank
* Galvanized
coupler, .63cm (1)
* Petcock (auto
radiator drain valve), .63cm (1)
* Wood lathe, 2.54 x
1.27 (25.4cm long)
* Cheesecloth or
other loosely woven cloth (183 sq cm)
* Rubber or plastic
washers, flat, .63cm (2)
* Screws, wood,
2.54cm (2)
* Screws, metal,
.31cm (8)
* Nuts, .95cm x
.15cm (8)
CONSTRUCTION
Step One:
Using the acetylene torch, cut the top off of the 55-gallon
drum.
Step Two:
Turn the drum upside down and, starting with any diameter
across the bottom, scribe the locating lines as shown in
Figure 2.
45p05a.gif (486x486)
Continue the diameter line on the side of the drum to locate
the ventilation and drain holes, as shown in Figure 3.
45p05b.gif (540x540)
Step Three:
Place the 42-gallon drum on top of the upside down 55-gallon
drum
so that the edge of the 42-gallon drum lines up with the
locating
lines scribed in Step Two (as shown in Figure 2).
Scribe a line around the circumference of the 42-gallon
drum.
Remove the 42-gallon drum and set aside.
Step Four:
Using either a hacksaw or an acetylene torch, cut a hole in
the
55-gallon drum on the line scribed in Step Three.
Make the cut as neat and accurate as possible as the piece
cut
out will be used as the door of the oven.
Step Five:
Using either the 3.175cm punch or the torch, cut a drain
hole
as close to the bottom of the 55-gallon drum as possible.
Center this hole on the locating line scribed on the side of
the drum, as shown in Figure 3.
Step Six:
Using the punch or the torch, cut six or seven evenly spaced
ventilation holes along the side locating line as shown in
Figure 3.
Step Seven:
Using Figure 4 as a suggested locating guide, cut out the
sheet
45p07.gif (600x600)
metal pieces for the front and rear trough supports as shown
in
Figure 5.
45p08.gif (600x600)
Still using Figure 4 as a guide, cut out the sheet metal
pieces
for the upper and lower covers as shown in Figure 6.
45p09.gif (600x600)
Step Eight:
Braze the support brackets to the sides of the front trough
support (see Figure 5).
Step Nine:
Locate the front trough support inside the 55-gallon drum so
that the "V" cut in the support is on the same
line as the
center of the drain and ventilation holes.
Weld this assembly to the drum about 7.62cm behind the drain
hole.
Step Ten:
Support the 42-gallon drum on a level surface so that when
the
55-gallon drum is placed over it, the top edge of the
42-gallon
drum just lines up with the hole cut in the bottom of the
55-gallon
drum as shown in Figure 7.
45p10a.gif (486x486)
Step Eleven:
Carefully weld the top edge of the 42-gallon drum to the
bottom
of the 55-gallon drum as shown in Figure 8.
45p10b.gif (437x437)
Step Twelve:
Cut a 30.48cm length of angle iron from the 183cm piece.
Step Thirteen:
Turn the drums over (55-gallon drum top side up) and weld
the
angle iron cut in Step Twelve to the bottom of the 42-gallon
drum and the sides of the 55-gallon drum as shown in Figure
9--this
45p11.gif (486x486)
forms the rear support for the 42-gallon drum.
Step Fourteen:
Place the drum with the ventilation holes facing down.
Using
either the sabre saw or the torch, cut a 10.16cm diameter
hole
for the chimney in the top rear of the 55-gallon drum,
located
approximately as shown in Figure 10.
45p12.gif (437x437)
Step Fifteen:
Cut out a 10.16cm x 34.29cm piece of sheet metal (#4 in
Figure 4) and form it into a 10.16cm diameter tube.
Place this piece
45p07.gif (600x600)
into the hole cut in Step 14 and weld around the
circumference
as shown in Figure 10.
45p12.gif (393x393)
Step Sixteen:
Cut out the remaining chimney pieces (#1 and #2, as shown in
Figure 4). Form
these pieces into 10.16cm diameter tubes with a
slight taper so the ends can be fitted together to form the
chimney.
Step Seventeen:
Weld the seams of the chimney pieces formed in Step Sixteen.
Step Eighteen:
Cut the threaded rod into two 12.70cm lengths.
Step Nineteen:
Cut out a 30.48cm x 2.54cm section of sheet metal and drill
two
1.12cm holes in it as shown in Figure 11.
45p13.gif (437x437)
Step Twenty:
Weld this piece inside the 55-gallon drum approximately
5.08cm
from the top (refer to Figure 9).
Assemble the rear trough
support as shown in Figure 11 above.
Step Twenty-One:
Cut the top off the one-gallon tin can.
Drill a .95cm hole in
the bottom of the can so that when feed pipe is inserted it
will be clear of upper cover.
Step Twenty-Two:
Assemble the components of the drip feed system as shown in
Figure 9 and Figure 12.
45p14a.gif (437x437)
Step Twenty-Three:
Cut two 15.24cm lengths of angle iron and form the reservoir
support as shown in Figure 13.
Half of bottom part of each
45p14b.gif (437x437)
piece needs to be cut away before bending.
Weld the supports to
the 55-gallon drum as indicated in Figure 13.
Step Twenty-Four:
Cut out a 30.48cm x 2.54cm piece of sheet metal (#9 in
Figure 4) and form the door handle. Cut
two pieces of wooden lathe to
fit inside and outside of the formed handle as shown in
Figure 13. Weld the completed handle
assembly to the door.
<Figure 14>
45p15a.gif (393x393)
Step Twenty-Five:
Cut off three 5.0 8cm lengths of .63cm strap and form as
shown
in Figure 15.
45p15b.gif (486x486)
Step Twenty-Six:
Weld the formed strap pieces to the 55-gallon drum as shown
in
Figure 16.
45p16.gif (486x486)
Step Twenty-Seven:
Using .31cm sheet metal screws, secure the top cover to the
rear of the oven by bending the mounting tabs over and
drilling
four holes through both the tabs and the side of the drum.
Figure 17 shows a view of the completed oven.
45p17.gif (486x486)
OPERATING PROCEDURES
The beauty of this particular waste oil oven lies in its
simple
design and ease of operation.
Following just a few mandatory
operating procedures will allow the oven to be used to its
fullest cooking capabilities.
To ensure safe operation, before starting up the oven it is
important that:
* The oven is in a
semi-enclosed area with adequate ventilation
for combustion.
* No combustible
materials are within eight meters of the oven.
* The chimney and
combustion chamber between the two drums is
free of
obstructions, carbon build-up, and remaining oil
drippings from
previous operation.
* The drip-feed
system is free of obstructions for easy adjustment
of the fuel flow
rate.
* An oil collection
container is carefully placed to catch all
oil overflow from
the oven.
Once all of the above precautions are met, begin preparing
to
start the oven.
First, make sure that the drip feed valve is
completely closed and that the reservoir is full of oil.
Next, open the drip feed valve, just slightly, to allow a
drop
of oil to form on the nozzle.
This will prime the system for
immediate operation at the time of firing.
The most critical of all the start-up procedures involves
the
preparing of the wick and combustion trough.
It is essential
that the next sequence of steps is carefully followed.
* Remove the trough
from the oven. Clean both the trough
and
the metal rod
completely. Any remaining ash or oil
build-up
will impede the
fuel flow thus severely reducing the oven's
efficiency.
* Wrap the entire
length of the metal rod in the wick material.
* Place the wrapped
rod in the trough.
* Liberally douse
the rod and wick with fuel oil so that it is
fully soaked.
* Place the trough
halfway into the oven combustion chamber so
that
it is resting on the bracket.
* Light with a match
the endmost portion of the soaked wick.
* Place the trough
completely into the oven.
* Begin a very slow
drip feed into the trough at about one drop
per second.
This will allow the flame to burn clown the
trough, which in
turn will raise the combustion chamber
temperature to the
point of flashing.
* Once the trough is
burning down its entire length, increase
the fuel flow rate
to the point where the single drops are no
longer
distinguishable and a steady fluid stream has not yet
been completely
established.
* At this point your
oven is operational. Wait fifteen
minutes
before using so
that the peak temperature may be reached.
Once the operating temperature has been reached, make frequent
checks upon the drip-feed system and the troughs.
It is important
that the fuel reservoir be kept at least one-half full to
maintain a constant fluid flow rate.
It is also necessary to prevent fouling in the trough.
Fouling
could lead either to flame burnout or fuel overflow
flashing.
Fuel overflow flashing will cause uneven and sometimes
uncontrollable
combustion processes.
In this case, it is best
to turn off the fuel supply and to allow the internal
burning
to die out. Then
start again.
In closing down the oven, it is best if the fuel supply is
turned off and the troughs immediately smothered.
This
avoids the annoyance of incomplete combustion and its
accompanying smoke.
When the oven is cool, it is best if the troughs are then
cleaned. This avoids
complications such as gumming up or
hardening of the oil in the trough.
It also facilitates
start-up procedures the next time the oven is to be used.
WARNING!
Waste oil from engine crankcases or gear boxes can
be a useful, low-cost fuel in certain applications.
However, users of waste engine oil are
warned that the oil might contain lead from leaded
gasoline. The lead
would be released into the air
as the oil burned.
It could be a hazard to people
working around the oven.
Users of waste engine oil should have the oil
tested to find out if it contains lead.
The baking
chamber of the oven should be sealed tightly to
keep combustion products away from the food being
baked. The oven
should be used out of doors or in
a well-ventilated place.
The chimney should be
high enough to carry combustion products well away
from the work area.
Do not use engine oil to fire space heaters or
food dryers. Waste
oil from electric transformers
should not--repeat, not--be used as fuel in any
circumstances.
Transformer oil contains poly
chlorinated biphenol (PCB) compounds.
PCB is highly
toxic and should not be burned at all.
It
should not even be handled at all.
If you think
your waste oil supply might come from electric
transformers, do not take chances.
Do not burn the
oil.
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