Electric, Forge and Thermit Welding
Together with Related Methods and Materials Used in Metal Working
And
The Oxygen Process for Removal of Carbon
By
HAROLD P. MANLY
CONTENTS
CHAPTER I
METALS AND ALLOYS--HEAT TREATMENT:--The Use and Characteristics of the
Industrial Alloys and Metal Elements--Annealing, Hardening, Tempering and
Case Hardening of Steel
CHAPTER II
WELDING MATERIALS:--Production, Handling and Use of the Gases, Oxygen and
Acetylene--Welding Rods--Fluxes--Supplies and Fixtures
CHAPTER III
ACETYLENE GENERATORS:--Generator Requirements and Types--Construction--Care
and Operation of Generators.
CHAPTER IV
WELDING INSTRUMENTS:--Tank and Regulating Valves and Gauges--High, Low and
Medium Pressure Torches--Cutting Torches--Acetylene-Air Torches
CHAPTER V
OXY-ACETYLENE WELDING PRACTICE:--Preparation of Work--Torch Practice--
Control of the Flame--Welding Various Metals and Alloys--Tables of
Information Required in Welding Operations
CHAPTER VI
ELECTRIC WELDING:--Resistance Method--Butt, Spot and Lap Welding--Troubles
and Remedies--Electric Arc Welding
CHAPTER VII
HAND FORGING AND WELDING:--Blacksmithing, Forging and Bending--Forge
Welding Methods
CHAPTER VIII
SOLDERING, BRAZING AND THERMIT WELDING:--Soldering Materials and Practice--
Brazing--Thermit Welding
CHAPTER IX
OXYGEN PROCESS FOR REMOVAL OF CARBON
INDEX
ACETYLENE GENERATORS
Acetylene generators used for producing the gas from the action of water on
calcium carbide are divided into three principal classes according to the
pressure under which they operate.
Low pressure generators are designed to operate at one pound or less per
square inch. Medium pressure systems deliver the gas at not to exceed
fifteen pounds to the square inch while high pressure types furnish gas
above fifteen pounds per square inch. High pressure systems are almost
unknown in this country, the medium pressure type being often referred to
as "high pressure."
Another important distinction is formed by the method of bringing the
carbide and water together. The majority of those now in use operate by
dropping small quantities of carbide into a large volume of water, allowing
the generated gas to bubble up through the water before being collected
above the surface. This type is known as the "carbide to water" generator.
A less used type brings a measured and small quantity of water to a
comparatively large body of the carbide, the gas being formed and collected
from the chamber in which the action takes place. This is called the "water
to carbide" type. Another way of expressing the difference in feed is that
of designating the two types as "carbide feed" for the former and "water
feed" for the latter.
A further division of the carbide to water machines is made by mentioning
the exact method of feeding the carbide. One type, called "gravity feed"
operates by allowing the carbide to escape and fall by the action of its
own weight, or gravity; the other type, called "forced feed," includes a
separate mechanism driven by power. This mechanism feeds definite amounts
of the carbide to the water as required by the demands on the generator.
The action of either feed is controlled by the withdrawal of gas from the
generator, the aim being to supply sufficient carbide to maintain a nearly
constant supply.
Generator Requirements.--The qualities of a good generator are
outlined as follows: [Footnote: See Pond's "Calcium Carbide and
Acetylene."]
It must allow no possibility of the existence of an explosive mixture in
any of its parts at any time. It is not enough to argue that a mixture,
even if it exists, cannot be exploded unless kindled. It is necessary to
demand that a dangerous mixture can at no time be formed, even if the
machine is tampered with by an ignorant person. The perfect machine must be
so constructed that it shall be impossible at any time, under any
circumstances, to blow it up.
It must insure cool generation. Since this is a relative term, all machines
being heated somewhat during the generation of gas, this amounts to saying
that a machine must heat but little. A pound of carbide decomposed by water
develops the same amount of heat under all circumstances, but that heat
can be allowed to increase locally to a high point, or it can be equalized
by water so that no part of the material becomes heated enough to do
damage.
It must be well constructed. A good generator does not need, perhaps, to be
"built like a watch," but it should be solid, substantial and of good
material. It should be built for service, to last and not simply to sell;
anything short of this is to be avoided as unsafe and unreliable.
It must be simple. The more complicated the machine the sooner it will get
out of order. Understand your generator. Know what is inside of it and
beware of an apparatus, however attractive its exterior, whose interior is
filled with pipes and tubes, valves and diaphragms whose functions you do
not perfectly understand.
It should be capable of being cleaned and recharged and of receiving all
other necessary attention without loss of gas, both for economy's sake, and
more particularly to avoid danger of fire.
It should require little attention. All machines have to be emptied and
recharged periodically; but the more this process is simplified and the
more quickly this can be accomplished, the better.
It should be provided with a suitable indicator to designate how low the
charge is in order that the refilling may be done in good season.
It should completely use up the carbide, generating the maximum amount of
gas.
Overheating.--A large amount of heat is liberated when acetylene gas
is formed from the union of calcium carbide and water. Overheating during
this process, that is to say, an intense local heat rather than a large
amount of heat well distributed, brings about the phenomenon of
polymerization, converting the gas, or part of it, into oily matters, which
can do nothing but harm. This tarry mass coming through the small openings
in the torches causes them to become partly closed and alters the
proportions of the gases to the detriment of the welding flame. The only
remedy for this trouble is to avoid its cause and secure cool generation.
Overheating can be detected by the appearance of the sludge remaining after
the gas has been made. Discoloration, yellow or brown, shows that there has
been trouble in this direction and the resultant effects at the torches may
be looked for. The abundance of water in the carbide to water machines
effects this cooling naturally and is a characteristic of well designed
machines of this class. It has been found best and has practically become a
fundamental rule of generation that a gallon of water must be provided for
each pound of carbide placed in the generator. With this ratio and a
generator large enough for the number of torches to be supplied, little
trouble need be looked for with overheating.
Water to Carbide Generators.--It is, of course, much easier to
obtain a measured and regular flow of water than to obtain such a flow of
any solid substance, especially when the solid substance is in the form of
lumps, as is carbide This fact led to the use of a great many water-feed
generators for all classes of work, and this type is still in common use
for the small portable machines, such, for instance, as those used on motor
cars for the lamps. The water-feed machine is not, however, favored for
welding plants, as is the carbide feed, in spite of the greater
difficulties attending the handling of the solid material.
A water-feed generator is made up of the gas producing part and a holder
for the acetylene after it is made. The carbide is held in a tray formed of
a number of small compartments so that the charge in each compartment is
nearly equal to that in each of the others. The water is allowed to flow
into one of these compartments in a volume sufficient to produce the
desired amount of gas and the carbide is completely used from this one
division. The water then floods the first compartment and finally overflows
into the next one, where the same process is repeated. After using the
carbide in this division, it is flooded in turn and the water passing on to
those next in order, uses the entire charge of the whole tray.
These generators are charged with the larger sizes of carbide and are
easily taken care of. The residue is removed in the tray and emptied,
making the generator ready for a fresh supply of carbide.
Carbide to Water Generators.--This type also is made up of two
principal parts, the generating chamber and a gas holder, the holder being
part of the generating chamber or a separate device. The generator (Figure
10) contains a hopper to receive the charge of carbide and is fitted with
the feeding mechanism to drop the proper amount of carbide into the water
as required by the demands of the torches. The charge of carbide is of one
of the smaller sizes, usually "nut" or "quarter."
Feed Mechanisms.--The device for dropping the carbide into the water
is the only part of the machine that is at all complicated. This
complication is brought about by the necessity of controlling the mass of
carbide so that it can never be discharged into the water at an excessive
rate, feeding it at a regular rate and in definite amounts, feeding it
positively whenever required and shutting off the feed just as positively
when the supply of gas in the holder is enough for the immediate needs.
The charge of carbide is unavoidably acted upon by the water vapor in the
generator and will in time become more or less pasty and sticky. This is
more noticeable if the generator stands idle for a considerable length of
time This condition imposes another duty on the feeding mechanism; that is,
the necessity of self-cleaning so that the carbide, no matter in what
condition, cannot prevent the positive action of this part of the device,
especially so that it cannot prevent the supply from being stopped at the
proper time.
The gas holder is usually made in the bell form so that the upper portion
rises and falls with the addition to or withdrawal from the supply of gas
in the holder. The rise and fall of this bell is often used to control the
feed mechanism because this movement indicates positively whether enough
gas has been made or that more is required. As the bell lowers it sets the
feed mechanism in motion, and when the gas passing into the holder has
raised the bell a sufficient distance, the movement causes the feed
mechanism to stop the fall of carbide into the water. In practice, the
movement of this part of the holder is held within very narrow limits.
Gas Holders.--No matter how close the adjustment of the feeding
device, there will always be a slight amount of gas made after the fall of
carbide is stopped, this being caused by the evolution of gas from the
carbide with which water is already in contact. This action is called
"after generation" and the gas holder in any type of generator must
provide sufficient capacity to accommodate this excess gas. As a general
rule the water to carbide generator requires a larger gas holder than the
carbide to water type because of the greater amount of carbide being acted
upon by the water at any one time, also because the surface of carbide
presented to the moist air within the generating chamber is greater with
this type.
Freezing.--Because of the rather large body of water contained in
any type of generator, there is always danger of its freezing and
rendering the device inoperative unless placed in a temperature above the
freezing point of the water. It is, of course, dangerous and against the
insurance rules to place a generator in the same room with a fire of any
kind, but the room may be heated by steam or hot water coils from a furnace
in another building or in another part of the same building.
When the generator is housed in a separate structure the walls should be
made of materials or construction that prevents the passage of heat or
cold through them to any great extent. This may be accomplished by the use
of hollow tile or concrete blocks or by any other form of double wall
providing air spaces between the outer and inner facings. The space between
the parts of the wall may be filled with materials that further retard the
loss of heat if this is necessary under the conditions prevailing.
Residue From Generators.--The sludge remaining in the carbide to
water generator may be drawn off into the sewer if the piping is run at a
slant great enough to give a fall that carries the whole quantity, both
water and ash, away without allowing settling and consequent clogging.
Generators are provided with agitators which are operated to stir the ash
up with the water so that the whole mass is carried off when the drain cock
is opened.
If sewer connections cannot be made in such a way that the ash is entirely
carried away, it is best to run the liquid mass into a settling basin
outside of the building. This should be in the form of a shallow pit which
will allow the water to pass off by soaking into the ground and by
evaporation, leaving the comparatively dry ash in the pit. This ash which
remains is essentially slaked lime and can often be disposed of to more or
less advantage to be used in mortar, whitewash, marking paths and any other
use for which slaked lime is suited. The disposition of the ash depends
entirely on local conditions. An average analysis of this ash is as
follows:
Sand....................... 1.10 per cent.
Carbon..................... 2.72 "
Oxide of iron and alumina.. 2.77 "
Lime....................... 64.06 "
Water and carbonic acid.... 29.35 "
------
100.00
GENERATOR CONSTRUCTION
The water for generating purposes is carried in the large tank-like
compartment directly below the carbide chamber. See Figure 11. This water
compartment is filled through a pipe of such a height that the water level
cannot be brought above the proper point or else the water compartment is
provided with a drain connection which accomplishes this same result by
allowing an excess to flow away.
The quantity of water depends on the capacity of the generator inasmuch as
there must be one gallon for each pound of carbide required. The generator
should be of sufficient capacity to furnish gas under working conditions
from one charge of carbide to all torches installed for at least five hours
continuous use.
After calculating the withdrawal of the whole number of torches according
to the work they are to do for this period of five hours the proper
generator capacity may be found on the basis of one cubic foot of gas per
hour for each pound of carbide. Thus if the torches were to use sixty cubic
feet of gas per hour, five hours would call for three hundred cubic feet
and a three hundred pound generator should be installed. Generators are
rated according to their carbide capacity in pounds.
Charging.--The carbide capacity of the generator should be great
enough to furnish a continuous supply of gas for the maximum operating
time, basing the quantity of gas generated on four and one-half cubic feet
from each pound of lump carbide and on four cubic feet from each pound of
quarter, intermediate sizes being in proportion.
Generators are built in such a way that it is impossible for the acetylene
to escape from the gas holding compartment during the recharging process.
This is accomplished (1) by connecting the water inlet pipe opening with a
shut off valve in such a way that the inlet cannot be uncovered or opened
without first closing the shut off valve with the same movement of the
operator; (2) by incorporating an automatic or hydraulic one-way valve so
that this valve closes and acts as a check when the gas attempts to flow
from the holder back to the generating chamber, or by any other means that
will positively accomplish this result.
In generators having no separate gas holding chamber but carrying the
supply in the same compartment in which it is generated, the gas contained
under pressure is allowed to escape through vent pipes into the outside
air before recharging with carbide. As in the former case, the parts are
so interlocked that it is impossible to introduce carbide or water without
first allowing the escape of the gas in the generator.
It is required by the insurance rules that the entire change of carbide
while in the generator be held in such a way that it may be entirely
removed without difficulty in case the necessity should arise.
Generators should be cleaned and recharged at regular stated intervals.
This work should be done during daylight hours only and likewise all
repairs should be made at such a time that artificial light is not needed.
Where it is absolutely necessary to use artificial light it should be
provided only by incandescent electric lamps enclosed in gas tight globes.
In charging generating chambers the old ash and all residue must first be
cleaned out and the operator should be sure that no drain or other pipe has
become clogged. The generator should then be filled with the required
amount of water. In charging carbide feed machines be careful not to place
less than a gallon of water in the water compartment for each pound of
carbide to be used and the water must be brought to, but not above, the
proper level as indicated by the mark or the maker's instructions. The
generating chamber must be filled with the proper amount of water before
any attempt is made to place the carbide in its holder. This rule must
always be followed. It is also necessary that all automatic water seals
and valves, as well as any other water tanks, be filled with clean water
at this time.
Never recharge with carbide without first cleaning the generating chamber
and completely refilling with clean water. Never test the generator or
piping for leaks with any flame, and never apply flame to any open pipe or
at any point other than the torch, and only to the torch after it has a
welding or cutting nozzle attached. Never use a lighted match, lamp,
candle, lantern, cigar or any open flame near a generator. Failure to
observe these precautions is liable to endanger life and property.
Operation and Care of Generators.--The following instructions apply
especially to the Davis Bournonville pressure generator, illustrated in
Figure 11. The motor feed mechanism is illustrated in Figure 12.
Before filling the machine, the cover should be removed and the hopper
taken out and examined to see that the feeding disc revolves freely; that
no chains have been displaced or broken, and that the carbide displacer
itself hangs barely free of the feeding disc when it is revolved. After
replacing the cover, replace the bolts and tighten them equally, a little
at a time all around the circumference of the cover--not screwing tight in
one place only. Do not screw the cover down any more than is necessary to
make a tight fit.
To charge the generator, proceed as follows: Open the vent valve by turning
the handle which extends over the filling tube until it stands at a right
angle with the generator. Open the valve in the water filling pipe, and
through this fill with water until it runs out of the overflow pipe of the
drainage chamber, then close the valve in the water filling pipe and vent
valve. Remove the carbide filling plugs and fill the hopper with
1-1/4"x3/8" carbide ("nut" size). Then replace the plugs and the
safety-locking lever chains. Now rewind the motor weight. Run the pressure
up to about five pounds by raising the controlling diaphragm valve lever
by hand (Figure 12, lever marked E). Then raise the blow-off lever,
allowing the gas to blow off until the gauge shows about two pounds; this
to clear the generator of air mixture. Then run the pressure up to about
eight pounds by raising the controlling valve lever E, or until
this controlling lever rests against the upper wing of the fan governor,
and prevents operation of the feed motor. After this is done, the motor
will operate automatically as the gas is consumed.
Should the pressure rise much above the blow-off point, the safety
controlling diaphragm valve will operate and throw the safety clutch in
interference and thus stop the motor. This interference clutch will then
have to be returned to its former position before the motor will operate,
but cannot be replaced before the pressure has been reduced below the
blow-off point.
The parts of the feed mechanism illustrated in Figure 12 are as follows:
A, motor drum for weight cable. B, carbide filling plugs.
C, chains for connecting safety locking lever of motor to pins on
the top of the carbide plugs. D, interference clutch of motor.
E, lever on feed controlling diaphragm valve. F, lever of
interference controlling diaphragm valve that operates interference clutch.
G, feed controlling diaphragm valve. H, diaphragm valve
controlling operation of interference clutch. I, interference pin
to engage emergency clutch. J, main shaft driving carbide feeding
disc. Y, safety locking lever.
Recharging Generator.--Turn the agitator handle rapidly for several
revolutions, and then open the residuum valve, having five or six pounds
gas pressure on the machine. If the carbide charge has been exhausted and
the motor has stopped, there is generally enough carbide remaining in the
feeding disc that can be shaken off, and fed by running the motor to
obtain some pressure in the generator. The desirability of discharging
the residuum with some gas pressure is because the pressure facilitates
the discharge and at the same time keeps the generator full of gas,
preventing air mixture to a great extent. As soon as the pressure is
relieved by the withdrawal of the residuum, the vent valve should be
opened, as if the pressure is maintained until all of the residuum is
discharged gas would escape through the discharge valve.
Having opened the vent pipe valve and relieved the pressure, open the
valve in the water filling tube. Close the residuum valve, then run in
several gallons of water and revolve the agitator, after which draw out the
remaining residuum; then again close the residuum valve and pour in water
until it discharges from the overflow pipe of the drainage chamber. It is
desirable in filling the generator to pour the water in rapidly enough to
keep the filling pipe full of water, so that air will not pass in at the
same time.
After the generator is cleaned and filled with water, fill with carbide and
proceed in the same manner as when first charging.
Carbide Feed Mechanism.--Any form of carbide to water machine should
be so designed that the carbide never falls directly from its holder into
the water, but so that it must take a more or less circuitous path. This
should be true, no matter what position the mechanism is in. One of the
commonest types of forced feed machine carries the carbide in a hopper with
slanting sides, this hopper having a large opening in the bottom through
which the carbide passes to a revolving circular plate. As the pieces of
carbide work out toward the edge of the plate under the influence of the
mass behind them, they are thrown off into the water by small stationary
fins or plows which are in such a position that they catch the pieces
nearest the edges and force them off as the plate revolves. This
arrangement, while allowing a free passage for the carbide, prevents an
excess from falling should the machine stop in any position.
When, as is usually the case, the feed mechanism is actuated by the rise
or fall of pressure in the generator or of the level of some part of the
gas holder, it must be built in such a way that the feeding remains
inoperative as long as the filling opening on the carbide holder remains
open.
The feed of carbide should always be shut off and controlled so that under
no condition can more gas be generated than could be cared for by the
relief valve provided. It is necessary also to have the feed mechanism at
least ten inches above the surface of the water so that the parts will
never become clogged with damp lime dust.
Motor Feed.--The feed mechanism itself is usually operated by power
secured from a slowly falling weight which, through a cable, revolves a
drum. To this drum is attached suitable gearing for moving the feed parts
with sufficient power and in the way desired. This part, called the motor,
is controlled by two levers, one releasing a brake and allowing the motor
to operate the feed, the other locking the gearing so that no more carbide
will be dropped into the water. These levers are moved either by the
quantity of gas in the holder or by the pressure of the gas, depending on
the type of machine.
With a separate gas holder, such as used with low pressure systems, the
levers are operated by the rise and fall of the bell of the holder or
gasometer, alternately starting and stopping the motor as the bell falls
and rises again. Medium pressure generators are provided with a diaphragm
to control the feed motor.
This diaphragm is carried so that the pressure within the generator acts
on one side while a spring, whose tension is under the control of the
operator, acts on the other side. The diaphragm is connected to the brake
and locking device on the motor in such a way that increasing the tension
on the spring presses the diaphragm and moves a rod that releases the brake
and starts the feed. The gas pressure, increasing with the continuation of
carbide feed, acts on the other side and finally overcomes the pressure of
the spring tension, moving the control rod the other way and stopping the
motor and carbide feed. This spring tension is adjusted and checked with
the help of a pressure gauge attached to the generating chamber.
Gravity Feed.--This type of feed differs from the foregoing in that
the carbide is simply released and is allowed to fall into the water
without being forced to do so. Any form of valve that is sufficiently
powerful in action to close with the carbide passing through is used and is
operated by the power secured from the rise and fall of the gas holder
bell. When this valve is first opened the carbide runs into the water until
sufficient pressure and volume of gas is generated to raise the bell. This
movement operates the arm attached to the carbide shut off valve and slowly
closes it. A fall of the bell occasioned by gas being withdrawn again opens
the valve and more gas is generated.
Mechanical Feed.--The previously described methods of feeding
carbide to the water have all been automatic in action and do not depend
on the operator for their proper action.
Some types of large generating plants have a power-driven feed, the power
usually being from some kind of motor other than one operated by a weight,
such as a water motor, for instance. This motor is started and stopped by
the operator when, in his judgment, more gas is wanted or enough has been
generated. This type of machine, often called a "non-automatic generator,"
is suitable for large installations and is attached to a gas holder of
sufficient size to hold a day's supply of acetylene. The generator can then
be operated until a quantity of gas has been made that will fill the large
holder, or gasometer, and then allowed to remain idle for some time.
Gas Holders.--The commonest type of gas container is that known as a
gasometer. This consists of a circular tank partly filled with water, into
which is lowered another circular tank, inverted, which is made enough
smaller in diameter than the first one so that three-quarters of an inch is
left between them. This upper and inverted portion, called the bell,
receives the gas from the generator and rises or falls in the bath of water
provided in the lower tank as a greater or less amount of gas is contained
in it.
These holders are made large enough so that they will provide a means of
caring for any after generation and so that they maintain a steady and even
flow. The generator, however, must be of a capacity great enough so that
the gas holder will not be drawn on for part of the supply with all torches
in operation. That is, the holder must not be depended on for a reserve
supply.
The bell of the holder is made so that when full of gas its lower edge is
still under a depth of at least nine inches of water in the lower tank. Any
further rise beyond this point should always release the gas, or at least
part of it, to the escape pipe so that the gas will under no circumstances
be forced into the room from, between the bell and tank. The bell is guided
in its rise and fall by vertical rods so that it will not wedge at any
point in its travel.
A condensing chamber to receive the water which condenses from the
acetylene gas in the holder is usually placed under this part and is
provided with a drain so that this water of condensation may be easily
removed.
Filtering.--A small chamber containing some closely packed but
porous material such as felt is placed in the pipe leading to the torch
lines. As the acetylene gas passes through this filter the particles of
lime dust and other impurities are extracted from it so that danger of
clogging the torch openings is avoided as much as possible.
The gas is also filtered to a large extent by its passage through the water
in the generating chamber, this filtering or "scrubbing" often being
facilitated by the form of piping through which the gas must pass from the
generating chamber into the holder. If the gas passes out of a number of
small openings when going into the holder the small bubbles give a better
washing than large ones would.
Piping.--Connections from generators to service pipes should
preferably be made with right and left couplings or long thread nipples
with lock nuts. If unions are used, they should be of a type that does not
require gaskets. The piping should be carried and supported so that any
moisture condensing in the lines will drain back toward the generator and
where low points occur they should be drained through tees leading into
drip cups which are permanently closed with screw caps or plugs. No pet
cocks should be used for this purpose.
For the feed pipes to the torch lines the following pipe sizes are
recommended.
3/8 inch pipe. 26 feet long. 2 cubic feet per hour.
1/2 inch pipe. 30 feet long. 4 cubic feet per hour.
3/4 inch pipe. 50 feet long. 15 cubic feet per hour.
1 inch pipe. 70 feet long. 27 cubic feet per hour.
1-1/4 inch pipe. 100 feet long. 50 cubic feet per hour.
1-1/2 inch pipe. 150 feet long. 65 cubic feet per hour.
2 inch pipe. 200 feet long. 125 cubic feet per hour.
2-1/2 inch pipe. 300 feet long. 190 cubic feet per hour.
3 inch pipe. 450 feet long. 335 cubic feet per hour.
When drainage is possible into a sewer, the generator should not be
connected directly into the sewer but should first discharge into an open
receptacle, which may in turn be connected to the sewer.
No valves or pet cocks should open into the generator room or any other
room when it would be possible, by opening them for draining purposes, to
allow any escape of gas. Any condensation must be removed without the use
of valves or other working parts, being drained into closed receptacles. It
should be needless to say that all the piping for gas must be perfectly
tight at every point in its length.
Safety Devices.--Good generators are built in such a way that the
operator must follow the proper order of operation in charging and cleaning
as well as in all other necessary care. It has been mentioned that the gas
pressure is released or shut off before it is possible to fill the water
compartment, and this same idea is carried further in making the generator
inoperative and free from gas pressure before opening the residue drain of
the carbide filling opening on top of the hopper. Some machines are made so
that they automatically cease to generate should there be a sudden and
abnormal withdrawal of gas such as would be caused by a bad leak. This
method of adding safety by automatic means and interlocking parts may be
carried to any extent that seems desirable or necessary to the maker.
All generators should be provided with escape or relief pipes of large size
which lead to the open air. These pipes are carried so that condensation
will drain back toward the generator and after being led out of the
building to a point at least twelve feet above ground, they end in a
protecting hood so that no rain or solid matter can find its way into them.
Any escape of gas which might ordinarily pass into the generator room is
led into these escape pipes, all parts of the system being connected with
the pipe so that the gas will find this way out.
Safety blow off valves are provided so that any excess gas which cannot be
contained by the gas holder may be allowed to escape without causing an
undue rise in pressure. This valve also allows the escape of pressure above
that for which the generator was designed. Gas released in this way passes
into the escape pipe just described.
Inasmuch as the pressure of the oxygen is much greater than that of the
acetylene when used in the torch, it will be seen that anything that caused
the torch outlet to become closed would allow the oxygen to force the
acetylene back into the generator and the oxygen would follow it, making a
very explosive mixture. This return of the gas is prevented by a hydraulic
safety valve or back pressure valve, as it is often called.
Mechanical check valves have been found unsuitable for this use and those
which employ water as a seal are now required by the insurance rules. The
valve itself (Figure 13) consists of a large cylinder containing water to a
certain depth, which is indicated on the valve body. Two pipes come into
the upper end of this cylinder and lead down into the water, one being
longer than the other. The shorter pipe leads to the escape pipe mentioned
above, while the longer one comes from the generator. The upper end of the
cylinder has an opening to which is attached the pipe leading to the
torches.
The gas coming from the generator through the longer pipe passes out of the
lower end of the pipe which is under water and bubbles up through the water
to the space in the top of the cylinder. From there the gas goes to the
pipe leading to the torches. The shorter pipe is closed by the depth of
water so that the gas does not escape to the relief pipe. As long as the
gas flows in the normal direction as described there will be no escape to
the air. Should the gas in the torch line return into the hydraulic valve
its pressure will lower the level of water in the cylinder by forcing some
of the liquid up into the two pipes. As the level of the water lowers, the
shorter pipe will be uncovered first, and as this is the pipe leading to
the open air the gas will be allowed to escape, while the pipe leading back
to the generator is still closed by the water seal. As soon as this reverse
flow ceases, the water will again resume its level and the action will
continue. Because of the small amount of water blown out of the escape pipe
each time the valve is called upon to perform this duty, it is necessary to
see that the correct water level is always maintained.
While there are modifications of this construction, the same principle is
used in all types. The pressure escape valve is often attached to this
hydraulic valve body.
Construction Details.--Flexible tubing (except at torches), swing
pipe joints, springs, mechanical check valves, chains, pulleys and lead or
fusible piping should never be used on acetylene apparatus except where the
failure of those parts will not affect the safety of the machine or permit,
either directly or indirectly, the escape of gas into a room. Floats should
not be used except where failure will only render the machine inoperative.
It should be said that the National Board of Fire Underwriters have
established an inspection service for acetylene generators and any
apparatus which bears their label, stating that that particular model and
type has been passed, is safe to use. This service is for the best
interests of all concerned and looks toward the prevention of accidents.
Such inspection is a very important and desirable feature of any outfit and
should be insisted upon.
Location of Generators.--Generators should preferably be placed
outside of insured buildings and in properly constructed generator houses.
The operating mechanism should have ample room to work in and there should
be room enough for the attendant to reach the various parts and perform the
required duties without hindrance or the need of artificial light. They
should also be protected from tampering by unauthorized persons.
Generator houses should not be within five feet of any opening into, nor
have any opening toward, any adjacent building, and should be kept under
lock and key. The size of the house should be no greater than called for by
the requirements mentioned above and it should be well ventilated.
The foundation for the generator itself should be of brick, stone, concrete
or iron, if possible. If of wood, they should be extra heavy, located in a
dry place and open to circulation of air. A board platform is not
satisfactory, but the foundation should be of heavy planking or timber to
make a firm base and so that the air can circulate around the wood.
The generator should stand level and no strain should be placed on any of
the pipes or connections or any parts of the generator proper.
WELDING INSTRUMENTS
VALVES
Tank Valves.--The acetylene tank valve is of the needle type, fitted
with suitable stuffing box nuts and ending in an exposed square shank to
which the special wrench may be fitted when the valve is to be opened or
closed.
The valve used on Linde oxygen cylinders is also a needle type, but of
slightly more complex construction. The body of the valve, which screws
into the top of the cylinder, has an opening below through which the gas
comes from the cylinder, and another opening on the side through which it
issues to the torch line. A needle screws down from above to close this
lower opening. The needle which closes the valve is not connected directly
to the threaded member, but fits loosely into it. The threaded part is
turned by a small hand wheel attached to the upper end. When this hand
wheel is turned to the left, or up, as far as it will go, opening the
valve, a rubber disc is compressed inside of the valve body and this disc
serves to prevent leakage of the gas around the spindle.
The oxygen valve also includes a safety nut having a small hole through it
closed by a fusible metal which melts at 250° Fahrenheit. Melting of this
plug allows the gas to exert its pressure against a thin copper diaphragm,
this diaphragm bursting under the gas pressure and allowing the oxygen to
escape into the air.
The hand wheel and upper end of the valve mechanism are protected during
shipment by a large steel cap which covers them when screwed on to the end
of the cylinder. This cap should always be in place when tanks are received
from the makers or returned to them.
Regulating Valves.--While the pressure in the gas containers may be
anything from zero to 1,800 pounds, and will vary as the gas is withdrawn,
the pressure of the gas admitted to the torch must be held steady and at a
definite point. This is accomplished by various forms of automatic
regulating valves, which, while they differ somewhat in details of
construction, all operate on the same principle.
The regulator body (Figure 14) carries a union which attaches to the side
outlet on the oxygen tank valve. The gas passes through this union,
following an opening which leads to a large gauge which registers the
pressure on the oxygen remaining in the tank and also to a very small
opening in the end of a tube. The gas passes through this opening and into
the interior of the regulator body. Inside of the body is a metal or rubber
diaphragm placed so that the pressure of the incoming gas causes it to
bulge slightly. Attached to the diaphragm is a sleeve or an arm tipped
with a small piece of fibre, the fibre being placed so that it is directly
opposite the small hole through which the gas entered the diaphragm
chamber. The slight movement of the diaphragm draws the fibre tightly over
the small opening through which the gas is entering, with the result that
further flow is prevented.
Against the opposite side of the diaphragm is the end of a plunger. This
plunger is pressed against the diaphragm by a coiled spring. The tension on
the coiled spring is controlled by the operator through a threaded spindle
ending in a wing or milled nut on the outside of the regulator body.
Screwing in on the nut causes the tension on the spring to increase, with a
consequent increase of pressure on the side of the diaphragm opposite to
that on which the gas acts. Inasmuch as the gas pressure acted to close the
small gas opening and the spring pressure acts in the opposite direction
from the gas, it will be seen that the spring pressure tends to keep the
valve open.
When the nut is turned way out there is of course, no pressure on the
spring side of the diaphragm and the first gas coming through automatically
closes the opening through which it entered. If now the tension on the
spring be slightly increased, the valve will again open and admit gas until
the pressure of gas within the regulator is just sufficient to overcome the
spring pressure and again close the opening. There will then be a pressure
of gas within the regulator that corresponds to the pressure placed on the
spring by the operator. An opening leads from the regulator interior to the
torch lines so that all gas going to the torches is drawn from the
diaphragm chamber.
Any withdrawal of gas will, of course, lower the pressure of that remaining
inside the regulator. The spring tension, remaining at the point determined
by the operator, will overcome this lessened pressure of the gas, and the
valve will again open and admit enough more gas to bring the pressure back
to the starting point. This action continues as long as the spring tension
remains at this point and as long as any gas is taken from the regulator.
Increasing the spring tension will require a greater gas pressure to close
the valve and the pressure of that in the regulator will be correspondingly
higher.
When the regulator is not being used, the hand nut should be unscrewed
until no tension remains on the spring, thus closing the valve. After the
oxygen tank valve is open, the regulator hand nut is slowly screwed in
until the spring tension is sufficient to give the required pressure in the
torch lines. Another gauge is attached to the regulator so that it
communicates with the interior of the diaphragm chamber, this gauge showing
the gas pressure going to the torch. It is customary to incorporate a
safety valve in the regulator which will blow off at a dangerous pressure.
In regulating valves and tank valves, as well as all other parts with which
the oxygen comes in contact, it is not permissible to use any form of oil
or grease because of danger of ignition and explosion. The mechanism of a
regulator is too delicate to be handled in the ordinary shop and should any
trouble or leakage develop in this part of the equipment it should be sent
to a company familiar with this class of work for the necessary repairs.
Gas must never be admitted to a regulator until the hand nut is all the way
out, because of danger to the regulator itself and to the operator as well.
A regulator can only be properly adjusted when the tank valve and torch
valves are fully opened.
Acetylene regulators are used in connection with tanks of compressed gas.
They are built on exactly the same lines as the oxygen regulating valve and
operate in a similar way. One gauge only, the low pressure indicator, is
used for acetylene regulators, although both high and low pressure may be
used if desired. (See Figure 15.)
TORCHES
Flame is always produced by the combustion of a gas with oxygen and in no
other way. When we burn oil or candles or anything else, the material of
the fuel is first turned to a gas by the heat and is then burned by
combining with the oxygen of the air. If more than a normal supply of air
is forced into the flame, a greater heat and more active burning follows.
If the amount of air, and consequently oxygen, is reduced, the flame
becomes smaller and weaker and the combustion is less rapid. A flame may be
easily extinguished by shutting off all of its air supply.
The oxygen of the combustion only forms one-fifth of the total volume of
air; therefore, if we were to supply pure oxygen in place of air, and in
equal volume, the action would be several times as intense. If the oxygen
is mixed with the fuel gas in the proportion that burns to the very best
advantage, the flame is still further strengthened and still more heat is
developed because of the perfect combustion. The greater the amount of fuel
gas that can be burned in a certain space and within a certain time, the
more heat will be developed from that fuel.
The great amount of heat contained in acetylene gas, greater than that
found in any other gaseous fuel, is used by leading this gas to the
oxy-acetylene torch and there combining it with just the right amount of
oxygen to make a flame of the greatest power and heat than can possibly be
produced by any form of combustion of fuels of this kind. The heat
developed by the flame is about 6300° Fahrenheit and easily melts all the
metals, as well as other solids.
Other gases have been and are now being used in the torch. None of them,
however, produce the heat that acetylene does, and therefore the
oxy-acetylene process has proved the most useful of all. Hydrogen was used
for many years before acetylene was introduced in this field. The
oxy-hydrogen flame develops a heat far below that of oxy-acetylene, namely
4500° Fahrenheit. Coal gas, benzine gas, blaugas and others have also been
used in successful applications, but for the present we will deal
exclusively with the acetylene fuel.
It was only with great difficulty that the obstacles in the way of
successfully using acetylene were overcome by the development of
practicable controlling devices and torches, as well as generators. At
present the oxy-acetylene process is the most universally adaptable, and
probably finds the most widely extended field of usefulness of any welding
process.
The theoretical proportion of the gases for perfect combustion is two and
one-half volumes of oxygen to one of acetylene. In practice this proportion
is one and one-eighth or one and one-quarter volumes of oxygen to one
volume of acetylene, so that the cost is considerably reduced below what it
would be if the theoretical quantity were really necessary, as oxygen costs
much more than acetylene in all cases.
While the heat is so intense as to fuse anything brought into the path of
the flame, it is localized in the small "welding cone" at the torch tip so
that the torch is not at all difficult to handle without special protection
except for the eyes, as already noted. The art of successful welding may be
acquired by any operator of average intelligence within a reasonable time
and with some practice. One trouble met with in the adoption of this
process has been that the operation looks so simple and so easy of
performance that unskilled and unprepared persons have been tempted to try
welding, with results that often caused condemnation of the process, when
the real fault lay entirely with the operator.
The form of torch usually employed is from twelve to twenty-four inches
long and is composed of a handle at one end with tubes leading from this
handle to the "welding head" or torch proper. At or near one end of the
handle are adjustable cocks or valves for allowing the gases to flow into
the torch or to prevent them from doing so. These cocks are often used for
regulating the pressure and amount of gas flowing to the welding head, but
are not always constructed for this purpose and should not be so used when
it is possible to secure pressure adjustment at the regulators (Figure 16).
Figure 16 shows three different sizes of torches. The number 5 torch is
designed especially for jewelers' work and thin sheet steel welding. It is
eleven inches in length and weighs nineteen ounces. The tips for the number
10 torch are interchangeable with the number 5. The number 10 torch is
adapted for general use on light and medium heavy work. It has six tips and
its length is sixteen inches, with a weight of twenty-three ounces.
The number 15 torch is designed for heavy work, being twenty-five inches in
length, permitting the operator to stand away from the heat of the metal
being worked. These heavy tips are in two parts, the oxygen check being
renewable.
Figures 17 and 18 show two sizes of another welding torch. Still another
type is shown in Figure 19 with four interchangeable tips, the function of
each being as follows:
No. 1. For heavy castings.
No. 2. Light castings and heavy sheet metal.
No. 3. Light sheet metal.
No. 4. Very light sheet metal and wire.
At the side of the shut off cock away from the torch handle the gas tubes
end in standard forms of hose nozzles, to which the rubber hose from the
gas supply tanks or generators can be attached. The tubes from the handle
to the head may be entirely separate from each other, or one may be
contained within the other. As a general rule the upper one of two
separate tubes carries the oxygen, while this gas is carried in the inside
tube when they are concentric with each other.
In the welding head is the mixing chamber designed to produce an intimate
mixture of the two gases before they issue from the nozzle to the flame.
The nozzle, or welding tip, of a suitable size are design for the work to
be handled and the pressure of gases being used, is attached to the welding
head and consists essentially of the passage at the outer end of which the
flame appears.
The torch body and tubes are usually made of brass, although copper is
sometimes used. The joint must be very strong, and are usually threaded and
soldered with silver solder. The nozzle proper is made from copper, because
it withstands the heat of the flame better than other less suitable metals.
The torch must be built in such a way that it is not at all liable to come
apart under the influence of high temperatures.
All torches are constructed in such a way that it is impossible for the
gases to mix by any possible chance before they reach the head, and the
amount of gas contained in the head and tip after being mixed is made as
small as possible. In order to prevent the return of the flame through the
acetylene tube under the influence of the high pressure oxygen some form of
back flash preventer is usually incorporated in the torch at or near the
point at which the acetylene enters. This preventer takes the form of some
porous and heat absorbing material, such as aluminum shavings, contained in
a small cavity through which the gas passes on its way to the head.
High Pressure Torches.--Torches are divided into the same classes as
are the generators; that is, high pressure, medium pressure and low
pressure. As mentioned before, the medium pressure is usually called the
high pressure, because there are very few true high pressure systems in
use, and comparatively speaking the medium pressure type is one of high
pressure.
With a true high pressure torch (Figure 20) the gases are used at very
nearly equal heads so that the mixing before ignition is a simple matter.
This type admits the oxygen at the inner end of a straight passage leading
to the tip of the nozzle. The acetylene comes into this same passage from
openings at one side and near the inner end. The difference in direction of
the two gases as they enter the passage assists in making a homogeneous
mixture. The construction of this nozzle is perfectly simple and is easily
understood. The true high pressure torch nozzle is only suited for use with
compressed and dissolved acetylene, no other gas being at a sufficient
pressure to make the action necessary in mixing the gases.
Medium Pressure Torches.--The medium pressure (usually called high
pressure) torch (Figure 21) uses acetylene from a medium pressure generator
or from tanks of compressed gas, but will not take the acetylene from low
pressure generators.
The construction of the mixing chamber and nozzle is very similar to that
of the high pressure torch, the gases entering in the same way and from the
same positions of openings. The pressure of the acetylene is but little
lower than that of the oxygen, and the two gases, meeting at right angles,
form a very intimate mixture at this point of juncture. The mixture in its
proportions of gases depends entirely on the sizes of the oxygen and
acetylene openings into the mixing chamber and on the pressures at which
the gases are admitted. There is a very slight injector action as the fast
moving stream of oxygen tends to draw the acetylene from the side openings
into the chamber, but the operation of the torch does not depend on this
action to any extent.
Low Pressure Torches.--The low pressure torch (Figure 22) will use
gas from low pressure generators from medium pressure machines or from
tanks in which it has been compressed and dissolved. This type depends for
a perfect mixture of gas upon the principle of the injector just as it is
applied in steam boiler practice.
The oxygen enters the head at considerable pressure and passes through its
tube to a small jet within the head. The opening of this jet is directly
opposite the end of the opening through the nozzle which forms the mixing
chamber and the path of the gases to the flame. A small distance remains
between the opening from which the oxygen issues and the inner opening into
the mixing passage. The stream of oxygen rushes across this space and
enters the mixing chamber, being driven by its own pressure.
The acetylene enters the head in an annular space surrounding the oxygen
tube. The space between oxygen jet and mixing chamber opening is at one end
of this acetylene space and the stream of oxygen seizes the acetylene and
under the injector action draws it into the mixing chamber, it being
necessary only to have a sufficient supply of acetylene flowing into the
head to allow the oxygen to draw the required proportion for a proper
mixture.
The volume of gas drawn into the mixing chamber depends on the size of the
injector openings and the pressure of the oxygen. In practice the oxygen
pressure is not altered to produce different sized flames, but a new nozzle
is substituted which is designed to give the required flame. Each nozzle
carries its own injector, so that the design is always suited to the
conditions. While torches are made having the injector as a permanent part
of the torch body, the replaceable nozzle is more commonly used because it
makes the one torch suitable for a large range of work and a large number
of different sized flames. With the replaceable head a definite pressure of
oxygen is required for the size being used, this pressure being the one for
which the injector and corresponding mixing chamber were designed in
producing the correct mixture.
Adjustable Injectors.-Another form of low pressure torch operates on
the injector principle, but the injector itself is a permanent part of the
torch, the nozzle only being changed for different sizes of work and flame.
The injector is placed in or near the handle and its opening is the largest
required by any work that can be handled by this particular torch. The
opening through the tip of the injector through which the oxygen issues on
its way to the mixing chamber may be wholly or partly closed by a needle
valve which may be screwed into the opening or withdrawn from it, according
to the operator's judgment. The needle valve ends in a milled nut outside
the torch handle, this being the adjustment provided for the different
nozzles.
Torch Construction.--A well designed torch is so designed that the
weight distribution is best for holding it in the proper position for
welding. When a torch is grasped by its handle with the gas hose attached,
it should balance so that it does not feel appreciably heavier on one end
than on the other.
The head and nozzle may be placed so that the flame issues in a line at
right angles with the torch body, or they may be attached at an angle
convenient for the work to be done. The head set at an angle of from 120 to
170 degrees with the body is usually preferred for general work in welding,
while the cutting torch usually has its head at right angles to the body.
Removable nozzles have various size openings through them and the different
sizes are designated by numbers from 1 up. The same number does not always
indicate the same size opening in torches of different makes, nor does it
indicate a nozzle of the same capacity.
The design of the nozzle, the mixing chamber, the injector, when one is
used, and the size of the gas openings must be such that all these things
are suited to each other if a proper mixture of gas is to be secured. Parts
that are not made to work together are unsafe if used because of the danger
of a flash back of the flame into the mixing chamber and gas tubes. It is
well known that flame travels through any inflammable gas at a certain
definite rate of speed, depending on the degree of inflammability of the
gas. The easier and quicker the gas burns, the faster will the flame travel
through it.
If the gas in the nozzle and mixing chamber stood still, the flame would
immediately travel back into these parts and produce an explosion of more
or less violence. The speed with which the gases issue from the nozzle
prevent this from happening because the flame travels back through the gas
at the same speed at which the gas issues from the torch tip. Should the
velocity of the gas be greater than the speed of flame propagation through
it, it will be impossible to keep the flame at the tip, the tendency being
for a space of unburned gas to appear between tip and flame. On the other
hand, should the speed of the flame exceed the velocity with which the gas
comes from the torch there will result a flash back and explosion.
Care of Torches.--An oxy-acetylene torch is a very delicate and
sensitive device, much more so that appears on the surface. It must be
given equally as good care and attention as any other high-priced piece of
machinery if it is to be maintained in good condition for use.
It requires cleaning of the nozzles at regular intervals if used regularly.
This cleaning is accomplished with a piece of copper or brass wire run
through the opening, and never with any metal such as steel or iron that is
harder than the nozzle itself, because of the danger of changing the size
of the openings. The torch head and nozzle can often be cleaned by allowing
the oxygen to blow through at high pressure without the use of any tools.
In using a torch a deposit of carbon will gradually form inside of the
head, and this deposit will be more rapid if the operator lights the stream
of acetylene before turning any oxygen into the torch. This deposit may be
removed by running kerosene through the nozzle while it is removed from the
torch, setting fire to the kerosene and allowing oxygen to flow through
while the oil is burning.
Should a torch become clogged in the head or tubes, it may usually be
cleaned by removing the oxygen hose from the handle end, closing the
acetylene cock on the torch, placing the end of the oxygen hose over the
opening in the nozzle and turning on the oxygen under pressure to blow the
obstruction back through the passage that it has entered. By opening the
acetylene cock and closing the oxygen cock at the handle, the acetylene
passages may then be cleaned in the same way. Under no conditions should a
torch be taken apart any more than to remove the changeable nozzle, except
in the hands of those experienced in this work.
Nozzle Sizes.--The size of opening through the nozzle is determined
according to the thickness and kind of metal being handled. The following
sizes are recommended for steel:
Davis-Bournonville. Oxweld Low
Thickness of Metal (Medium Pressure.) Pressure
1/32 Tip No. 1 Head No. 2
1/16 2
5/64 3
3/32 3 4
3/8 4 5
3/16 5 6
1/4 6 7
5/16 7
3/8 8 8
1/2 9 10
5/8 10 12
3/4 11 15
Very heavy 12 15
Cutting Torches.--Steel may be cut with a jet of oxygen at a rate of
speed greater than in any other practicable way under usual conditions. The
action consists of burning away a thin section of the metal by allowing a
stream of oxygen to flow onto it while the gas is at high pressure and the
metal at a white heat.
The cutting torch (Figure 23) has the same characteristics as the welding
torch, but has an additional nozzle or means for temporarily using the
welding opening for the high pressure oxygen. The oxygen issues from the
opening while cutting at a pressure of from ten to 100 pounds to the square
inch.
The work is first heated to a white heat by adjusting the torch for a
welding flame. As soon as the metal reaches this temperature, the high
pressure oxygen is turned on to the white-hot portion of the steel. When
the jet of gas strikes the metal it cuts straight through, leaving a very
narrow slot and removing but little metal. Thicknesses of steel up to ten
inches can be economically handled in this way.
The oxygen nozzle is usually arranged so that it is surrounded by a number
of small jets for the heating flame. It will be seen that this arrangement
makes the heating flame always precede the oxygen jet, no matter in which
direction the torch is moved.
The torch is held firmly, either by hand or with the help of special
mechanism for guiding it in the desired path, and is steadily advanced in
the direction it is desired to extend the cut, the rate of advance being
from three inches to two feet per minute through metal from nine inches
down to one-quarter of an inch in thickness.
The following data on cutting is given by the Davis-Bournonville Company:
Cubic
Feet Cost of
Thickness of Gas Inches Gases
of Cutting Heating per Foot Oxygen Cut per per Foot
Steel Oxygen Oxygen of Cut Acetylene Min. of Cut
1/4 10 lbs. 4 lbs. .40 .086 24 $ .013
1/2 20 4 .91 .150 15 .029
3/4 30 4 1.16 .150 15 .036
1 30 4 1.45 .172 12 .045
1 1/2 30 5 2.40 .380 12 .076
2 40 5 2.96 .380 12 .093
4 50 5 9.70 .800 7 .299
6 70 6 21.09 1.50 4 .648
9 100 6 43.20 2.00 3 1.311
Acetylene-Air Torch.--A form of torch which burns the acetylene after
mixing it with atmospheric air at normal pressure rather than with the
oxygen under higher pressures has been found useful in certain pre-heating,
brazing and similar operations. This torch (Figure 24) is attached by a
rubber gas hose to any compressed acetylene tank and is regulated as to
flame size and temperature by opening or closing the tank valve more or
less.
After attaching the torch to the tank, the gas is turned on very slowly and
is lighted at the torch tip. The adjustment should cause the presence of a
greenish-white cone of flame surrounded by a larger body of burning gas,
the cone starting at the mouth of the torch.
By opening the tank valve more, a longer and hotter flame is produced, the
length being regulated by the tank valve also. This torch will give
sufficient heat to melt steel, although not under conditions suited to
welding. Because of the excess of acetylene always present there is no
danger of oxidizing the metal being heated.
The only care required by this torch is to keep the small air passages at
the nozzle clean and free from carbon deposits. The flame should be
extinguished when not in use rather than turned low, because this low flame
rapidly deposits large quantities of soot in the burner.
