Typical Oil-fired Furnaces

: FURNACES
: The Working Of Steel

Several types of standard oil-fired

furnaces are shown herewith. Figure 92 is a lead pot furnace, Fig.

93 is a vertical furnace with a center column. This column reduces

the cubical contents to be heated and also supports the cover.





A small tool furnace is shown in Fig. 94, which gives the construction

and heat circulation. A larger furnace for high-speed steel is

given in Fig. 95. The steel is supported above the heat, the lower

flame passing beneath the support.



For hardening broaches and long reamers and taps, the furnace shown

in Fig. 96 is used. Twelve jets are used, these coming in radially

to produce a whirling motion.





Oil and gas furnaces may be divided into three types: the open

heating chamber in which combustion takes place in the chamber

and directly over the stock; the semimuffle heating chamber in

which combustion takes place beneath the floor of the chamber from

which the hot gases pass into the chamber through suitable openings;

and the muffle heating chamber in which the heat entirely surrounds

the chamber but does not enter it. The open furnace is used for

forging, tool dressing and welding. The muffle furnace is used for

hardening dies, taps, cutters and similar tools of either carbon

or high-speed steel. The muffle furnace is for spring hardening,

enameling, assaying and work where the gases of combustion may

have an injurious effect on the material.







Furnaces of these types of oil-burning furnaces are shown in Figs.

97, 98, and 99; these being made by the Gilbert & Barker Manufacturing

Company. The first has an air curtain formed by jets from the large

pipe just below the opening, to protect the operator from heat.





Oil furnaces are also made for both high- and low-pressure air,

each having its advocates. The same people also make gas-fired

furnaces.



Several types of furnaces for various purposes are illustrated

in Fig. 100 and 101. The first is a gas-fired hardening furnace

of the surface-combustion type.



A large gas-fired annealing furnace of the Maxon system is shown

in Fig. 101. This is large enough for a flat car to be run into

as can be seen. It shows the arrangement of the burners, the track

for the car and the way in which it fits into the furnace. These

are from the designs of the Industrial Furnace Corporation.



Before deciding upon the use of gas or oil, all sides of the problem

should be considered. Gas is perhaps the nearest ideal but is as a

rule more expensive. The tables compiled by the Gilbert & Barker

Manufacturing Company and shown herewith, may help in deciding

the question.



TABLE 27.--SHOWING COMPARISON OF OIL FUEL WITH VARIOUS GASEOUS FUELS

Heat units

per thousand

cubic feet

Natural gas 1,000,000

Air gas (gas machine) 20 cp 815,500

Public illuminating gas, average 650,000

Water gas (from bituminous coal) 377,000

Water and producer gas, mixed 175,000

Producer gas 150,000



Since a gallon of fuel oil (7 lb.) contains 133,000 heat units, the

following comparisons may evidently be made. At 5 cts. a gallon,

the equivalent heat units in oil would equal:



Per thousand

cubic feet

Natural gas at $0.375

Air gas, 20 cp at 0.307

Public illuminating gas, average at 0.244

Water gas (from bituminous coal) at 0.142

Water and producer gas, mixed at 0.065

Producer gas at 0.057



Comparing oil and coal is not always simple as it depends on the

work to be done and the construction of the furnaces. The variation

rises from 75 to 200 gal. of oil to a ton of coal. For forging

and similar work it is probably safe to consider 100 gal. of oil

as equivalent to a ton of coal.



Then there is the saving of labor in handling both coal and ashes,

the waiting for fires to come up, the banking of fires and the dirt

and nuisance generally. The continuous operation possible with

oil adds to the output.



When comparing oil and gas it is generally considered that 4-1/2

gal. of fuel oil will give heat equivalent to 1,000 cu. ft. of

coal gas.



The pressure of oil and air used varies with the system installed.

The low-pressure system maintains a pressure of about 8 oz. on the

oil and draws in free air for combustion. Others use a pressure

of several pounds, while gas burners use an average of perhaps

1-1/2 lb. of air to give best results.



The weights and volumes of solid fuels are: Anthracite coal, 55 to

65 lb. per cubic foot or 34 to 41 cubic feet per ton; bituminous

coal, 50 to 55 lb. per cubic foot or 41 to 45 cubic feet per ton;

coke, 28 lb. per cubic foot or 80 cubic feet per ton--the ton being

calculated as 2,240 lb. in each case.



A novel carburizing furnace that is being used by a number of people,

is built after the plan of a fireless cooker. The walls of the

furnace are extra heavy, and the ports and flues are so arranged

that when the load in the furnace and the furnace is thoroughly

heated, the burners are shut off and all openings are tightly sealed.

The carburization then goes on for several hours before the furnace

is cooled below the effective carburizing range, securing an ideal

diffusion of carbon between the case and the core of the steel

being carburized. This is particularly adaptable where simple steel

is used.