"THE CONSTRUCTION AND OPERATION OF THE PUNT
WASHINGTON BRICK COMPANY AT MUIRKIRK,MD. "
A THESIS PRESENTED AS A REQUIREMENT FOR
MEMBERSHIP IN TAU BETA PI.
The new plant of the "feshington Brick Company is located at Muirkirk,
Maryland twelve miles north of "'ashington D. C. on the TTashington- Baltimore Blvd.
It is of interest because it uses the Circle System which is a revolutionary
design in the construction of brick plants*
The plant is composed of two main structures,the preparations build-
ing and the Circle. The clay is prepared for burning in the preparations build-
ing and is burned in the Circle,
The clay is dug from suooly pits behind the preparations building by
steam shovels and is loaded into dinkey cars. These cars are brought to the top
floor of the preparations building where the clay is dumped into a hopper. The
clay then passes through a series of three sets of rolls. The first breaks up
the clods, the second reduce? theeize of the clay and reoves the rocks, the third
reduces the clay to a fine powder. The clay is then carried to the machine room
by a belt conveyor.
The Sircle is a circular structure 140 ft. in diameter. The inner dia-
meter is 98 ft. The area between these circles is divided into 16 permanent kiln
bottoms. The machine room stands in the center of the Circle. As the clay enters
it is fed to a brick machine and cutter which form and cut the bricks. From the
cutter the bricks are taken by another belt conveyor to the kilns. The machine
room can turn so as to feed bricks to any kiln section.
The burning is done by the two burning units on the Circle. A burning
unit is composed of 4 hoods, drying, preheating, heating and cooling. The hoods
are composed of steel sides on the inner and outer circles and a flat arch acros
the top. These hoods are moved around the circle on rails. Once the bricks are
set in a kiln they are cooled by a fan in the drying kiln f then the hoods are
mov^d and the bricks are preheated in pre-heating kiln by the combustion gases
from the firing kiln. Then the firing kiln is moved up and the bricks are fired
by oil burners. The are then cooled in the cooling kiln. The hoods are then
on and the bricks are left exoosed so that they may be loaded directly into
The Circle System has many advantages over the older type of plant.
The main advantages are in initial cost, simplicity of arrangement, low fuel
requirements, low labor requirements, and flexibility of op ration. The Wash-
ington Brick Company is to be congratulated on having the most modern brick
plant in the country*
"THE CONSTRUCTION AND OPERATION OF THE PLANT OF THE
WASHINGTON BRICK COMPANY AT MUIRKIRK, MARYLAND. "
The new plant of the Tfeshington Brick Company is located at Muirkirk,
Maryland twelve miles north of Wellington D.C. on the ^feshington-Baltimore
Boulevard.lt was built in 1938. The plant is of Bpecial interest because it is
the first olant,and the only one at this date, to be constructed using the
Circle System which is a revolutionary design in the construction of brick
plants. It is an entirely new approach to the solution of the numerous and
varied problems of brick manufacture. It is an attempt to cheapen the manu-
facture of brick, building tile, and similar ware by minimizing the amount of
labor by mechanization as well as by compact arrangement. The system was invent-
ed by John R. Clark, who is at present Sales-Manager of the organisation, and de-
signed by T.W.Garvee.
The essential features of the construction and operation of the new
plant are here presented.
To orient the reader Picture No. 1 has been included.
Picture No. l( Courtesy of ^sh. Brick Co.)
This is an aerial photo which clearly shows the entire plant with
the exceotion of the clay supply pits which are farther to the right than the
view shown. On the far right can be seen the tracks leading from the supply
pits into the white building in which the clay is prepared. From the bottom of
this building can be seen the belt conveyor carrying the prepared clay over the
roof of the Circle.and into the machine room in the center of the Circle. The
machine room contain^ the brick machines and a belt conveyor which transports
the green bricks to the Circle. The circular white-domed structure is the Circle
which contains the kilns. All the heating processes are carried on in this
structure. In addition to these structures, the fuel heating find pumping build-
ing can be seen just to the l&ft and behind the preparations building. The gen-
eral offices of the company are housed in a small brick building located about
where the construction shack is in the lower left hand corner of the photo. This
in brief is^birds-view of the entire plant of the Vfesbington Brick Company.
PREPARATION OF TH3 MATERIAL
The clay or shale from the manufacture of the bricks is dug from the
ground behind the plenty Here the company owns an area of land sufficient to su~
pply eoft clay for an indefinite period.
Picture No. 2
This area is shown in Picture No. 2 which was taken from the tracks
immediateiy behind the preparations building. The area extends all the way to
woods shown in the picture. The clay is dug by steam shovels and dumpeu into
side- dump cars or dinkeys which run upon light tracks which can be moved ab-"
out so as to stay near the immediate source of supply. The steam shovels and &
a line of dinkeys can be seen in the left-center of Picture No. 2. Also the area
of clay already cut out can be seen. The dinkeys are pulled by a small gasoline
engine into the top floor of the preparations building. It is interesting to
note at this point that only one man is necessary to dig the clay and bring it
to the preparations building. This Is under ordinary conditios of course but
more men can be added as needs increase.
In the prenarations building the cars are dumped from either side into
a hopper which leads the clay through a granulator. The granulator is merely a
set of screw-shaped rolls which break ud the big clods of clay and reduce it all
to a uniform siie. The clay then passes downward through a set of conically-
shaped rolls which further reduce the size of th'; clay and kick out any stones
which nay be present. The clay now passes through a third set of rolls. These
are smooth mils running at different speeds and serve to reduce the clay to a
fine powder. The path of the material is downward through the rolls by gravity.
All rolls are run by electricity,suitable machinery h-ving been installed for
that purpose. A pit under the smooth rolls accommodates the tail end of a belt
conveyor which carries the clay to the Circle.
Picture No. 3
Pietura No* 3 shows the preparations building and the belt conveyor
carrying the clay from the pit beneath the smooth rolls into the Circle. Pic-
ture No. 5 gives another view of the conveyor. This picture was taken during
construction an > the belt has not been put on yet. This leaves the rollers
uncovered so that they may be clearly seen. The light steel structure which
supports the rollers and the belt is also clearly visible. This structure
connects to the top of the machine room as will be explained more fu lly later.
Here again it is interesting to note that only one man is necessary to run the
whole system of three sets of rolls and the conveyor.
DESIGN OF TIE CIRCLE
Kilns and Honds
The Circle is 140 feet in diameter, outer edge to outer edge. The inner
disjueter is 98 fe«t. The area between these two circles is divided into 16 perm-
anent kiln bottoms each 21 feet in width and 27 ft. 6 in. in length center to
center of partitions along the outer circumference. The kiln sections accommo-
date approximately 105,000 bricks set 33 high or about 12 feet.
Picture No. 4
Picture No.4 is a view of the Circle from the outside. The supporting
columns of the roof are not the kiln divisions f the kilns being about one anti
one-half times the distance between these columns*
The kilns are designed as a downdraft kiln system. The downdraft kiln
is used instead of the updraft kiln, despite its greater fuel consumption, be-
cause of the excellence of the results due to the effective control it provides
over the kiln atmosphere. This effective control insures the production of every
colour effect by oxidizing and reducing conditions and also soecial colors by
the use of minerals or salts in the final stages of firing such as zinc to pro-
duce green, manganese for black, and common salt for glazing etc.
Picture No.5(Countesy of 7fesh. Brick Co.)
Picture No. 5 has been included because having been taken during con-
struction it reveals many features of the Circle which could not be seen on a
photo taken after completion. This picture will be referred to from time to
3ach kiln bottom contains parallel 9 inch flues and a connecting flue
in the center leading to the circular main draft flue which runs completely aro-
und the circle. Picture No. 5 shows the kiln bottoms with the 9 inch flues runn- r € /
ing parallel to the radius of the circle. Bach kiln collecting flue has a damper
before its entrance into the main circular flue. The circular main draft flue
has a damper between each 2 kiln section. All dampers are flat and sloping and
are operated by a transportable hoisting frame equipped with a suitable winch.
Th^ partitions or end walls which separate the kiln sections are perm-
anent being made of brick 12 inches thick. The dimensions of these radial walls
are slightly smaller in width and height than the kiln hoods than the inside
measurements of the kiln hoods so that these hoods can pass over.
The kiln hoods are in the shape of an inverted "U" having side walla
on the inner and outer circles and a flat arch across the top. Picture No. 5
shows a hood in the process of construction. The hood appears to the left of
the conveyor. The walls of the kiln can be clearly seen but the arch across
the top has not been constructed as yet.
There are two complete burning units in the circle, oach unit contain-
ing a drying hood, a preheating hood, a firing hood, and a cooling hood. All hoods
may be recognized by their outer steel shells and their rigid top and side bra-
ping to maintain the guage.
Picture No. 6
outside of burning unit.
Picture No.fi is a view of the Circle with the burning unit visible.
The heavy side bracing can be clearly seen. The burning unit ta.kes up a quart-
er of the Circle. The other burning unit is on the opposite side of the Circle.
The drying hood is lightest in design and consists of a light guage ou
ter steel shell and an inner shell of asbestos-cement plates with a 3" space of
diatomaeeous earth. The ceiling is provided with nuroerois outlets permitting
regulation of the drying processes.
The preheating, firing, and cooling hoods differ from the drying hoods
by their insulating refractories. These refractories consist of light weight
refractory brick secured to the housing along the sides and suspended from a
structural steel bracing in the top by means of pipes, hooks and rods.
The firing hood has a 9" brick lining and the other hoods have a 4.5"
lining. There is no steel plate back of the refractories at the crown of the
hoods so that the inside of the hood may be inspected. The firing hood has a
special working platform provided below the burners on each side of the hoods,
adequate openings in the hood side being made for the adjustment of burners and
observation through peep-holes. The hood shown in Picture No. 5 is a firing hood
and the soecial platform and Deep-holes are claarly visible.
Picture No. 7
Picture No. 7 is a view of the burning unit from the inside of the
Circle . This shows the firing kiln in the center with its special platform.
On the kiln to the right may be seen the pyrometers which are on each kiln so
that the heating processes may be accurately regulated.
The firing of the brick is done with oil burners. The fuel used is
heavy Bunker oil.and has to be heated* This is done in the little building
shown in Picture No. 1. which contains steam coils which heat the oil to 200°F.
Tanks behind the building provide for storage of 30,000 gallons of oil. The
building also contains two pumps .one of which is an auxiliary, for pumping the
oil to the Circle. The oil burners are arranged above the brick setting with-
in t^e upper cart of the hoods, approximately 13"below the crown. The firing
hood carries the special high speed air fan and piping and oil apparatus. Th-
ere are oil and electrical connections opposite each kiln.
The kilns travel around the circle on wheels which roll on circular
tracks, The outer wheels are double flanged, guiding the hoods around a circu-
lar path while the inner wheels are flangeless, permitting some variation due
to steel fabrication or exDansion. The wheel trucks are not visible since
they are located within shallow circular rail pits. These rail pits are clea-
rly visible in Picture So. 5. The total weight of each firing hood is about
60 tons or 120,000 pounds, so there is a load of 30,000 pounds on each wheel.
Along the sides, inside of the circular rails along the kiln bottom
all hoods are provided with steel plates or side aprons dipping into a cont-
inuoa sand trough. There is a recess in the kiln wall and a corresponding pro-
jection of the hood refractories at the bottom which acts as an additional
seal. The drying hoods do not have the refractories nor the seal projections
at the bottom. However, they do havo the sand seal aprons which line up with
those of the other hoods.
The sealing between the ends of the hoods against the permanent
partition walls is made by a string of brick attached to an "H" steel beam
in their rear. The uooer ends of the "H" beams are attached to standard rollers
which are separate from the hoods at the junction and are easily rolled in and
out the few inches needed for clearance while the hoods are being moved. The top
seals are made by filling the gap between the hoods and the partitions with
sand. The pre-heating ( firing and cooling hoods travel together and are coupled
together by a suitable coupling on each side of the hood permitting play for
operating the seals.
The entire kiln bottom and all hoods are housed under a suitable
light steel structure. The roof is supported by Fink roof trusses with a mon-
itor added on top to permit the escape of combustion gases. The roofing is
light corrugated metal laid on purlins which are in turn supported by the
trusses. The whole roof is supported on suitable light steel columns which
are braced against wind with light portal bracing. Each part of the roof con-
struction is splendidly shown in Picture No. 5.
DESIGN OF THE MACHINE ROOM
The center of the open space within the Circle is occupied by the
Picture No. 8
Picture No.S was taken whils standing in one of the empty kilns. It
shows the machine room as it occupies the center of the stage. The building
is constructed of corrugated steel plates. At the top of the picture the belt
conveyor may be seen delivering the prepared clay to the machine room. The
belt conveyor delivers the clay into a pipe hopper 3 ft. in diameter. This
hopper convoys the clay into a screw feeder which forces the clay under pre^
s'sure into a combination brick machine. The feeder pipe also acts as a support
for the belt conveyor frame. Since the conveyor is fixed, whereas the machine
room turns around its center, the feeder pipe is provided at the bottom with a
flange to which are bolted a series of casters which in turn with their rol-
lers are standing on a steel plate ( the latter mounted on the turntable. Thus
the machine room can rotate independently of the conveyor frame.
Picture No. 9
Picture No .9 is a close- up of the machine room. It shows clearly the
connection between the belt conveyor and the machine room* The feeder pipe raav
be seen extending out of the roof of the machine room and supporting the belt
convevor. The circular nlate at the ,1 unction of the two is the flange plate
which permits the machine mom to rotate independently of the conveyor frame.
This connection is made rather loosely so that slight variations in the length
of the convevor frame due to expansion and contraction from heat and cold can-
nnt cause any disturbance.
The entire machine rpom is supported by a turntable composed of two
main girders and suitable cross-beams. The turntable is supported by four wh-
eels, one at each end of a girder. These wheels along with the girders and cross-
beams were designed to carry safely in excess of sixty tons. The turntable
turns on a circular rail 38 feet in diameter. All rails t including the hood rails
weigh 60 lbs. per yard and are bent true to their respective circles.
The machine room is kept centered by a shaft or coner bearing under
the platform. This stubbv shaft does not carry any load and so is made hollow
to serve for the admittance of a water line and a steam line. Three contact
rings are attached to the lower castings for the admission of electric power,
contact being made by brushes attached to and revolving with the turn-table.
An off-bearing belt which acts as a brick delivery conveyor extends
from the end of the machine room into the kiln. Its outer end is supported half-
way its length, permitting up and down movement to accommodate the setting of
the brick. A job crane is used to take care of this movement as well as of the
shifting of the conveyor back to clear the inner building columns when the turn-
table is revolving to the next kiln section. The vertical boom to this jib crane
is attached to the end of the platform.
Picture No. 10
Picture No. 10 shows the off-bearing belt carrying the bricks from
the machine room to the kiln. The little chute at the side is catching the
bad bricks which are returned by the brick-setters. These bad bricks are re-
ground and the clay is used again so there is no waste,
OPERATION OF TH£ MACHINE ROOM AND THE CIRCLS
As the clay is delivered to the machine room by the belt conveyor
it drops into the previously mentioned pipe hopper and thence into a screw
feeder. This screw feeder forces the clav through a combination brick machine
which is merely a die of a rectangular shape, its dimensions being slightly
larger than those of a normal brick to allow for shrinkage. This die there-
fore extrudes a column of clay the cross-section of which is the size of a
brick. This column is cut into bricks by a cutter which is merely a line of
wires spaced a brick si2e apart. These wires descend upon the column of clay
and lop off 15 bricks at a time. From the cutter the green bricks automatic-
ally picked up by the off-bearing belt which takes them,properly spaced, due
to a belt speed greater than the speed with which thoy leave the cutter, into
the kiln. Here a crew of 5 or 6 setters or hackers take the bricks off the belt
and set them properly in the kiln. The machine room is turned at intervals to
keep in stap with the setting. The bricks, of course,may be fed into any kiln.
The drying hood is placed over each set of bricks '.luring drying.
Sets are made for each burning unit alternately. The time of. drying
is synchronized with the time firing and every third day preheating, firing, and
cooling hoods are moved one kiln section ahead so that the preheating hood cov-
ers the drying kiln, etc.
The firing is done with the heavy Bunker rt C" oil previously heated in
the heating building. The oil is burnt by 12 burners w'-iich are in each firing
hood. The fuel is introduced over the top of the setting of brick, there being
a space of about 3 feet between the bottom of the crown and the top of the set-
ting. A fan produces a downdraft in the kiln hence drawing the combustion gases
down through the brick setting and out through the kiln bottom* Here, by anot-
her fan, the hot gases are pushed in the adjacent pre-heater kiln from below,
pre-heating the bricks and escaping through an opening in the c 'own and out
through the monitor in the roof. If necessary or desirable the combustion gases
can be split and used partly for pre-heating and partly for drying in the same
For the combustion gases a centrifugal fan is used. The ducts of this
fan are well insulated with a special high temperature alloy which can stand a
temperature up to 1600°F before melting. The drying fan is of more standard cent
, rifugal type. These fans are mounted on movable trucks so that they may be moved
easily and quickly connected where desired.
To summarize, the kiln cycle is as follows. The drying hood is placed
over the bricks immediately after being set. A standard fan dries fnem by creat-
ing a current of air through the kiln. After the period of drying is completed
the pre-heating kiln is moved over the Betting. Here the bricks are pre-heated
by the combustion gases from the heating kiln. Then the heating kiln is moved
up and the bricks areheated. After three days of heating the cooling kiln is
moved up and the cooling of the bricks is controlled.
The advantages of the Circle System begin with the initial cost of
the plant and carry right through to the storage space supplied.
The average brick plant of the older type costs $6000 per 1000 brick
daily capacity. The new plant at Muirkirk cost $210,000 and with a daily output
of 70,000 brick this averages only $3000 per 1000 brick daily capacity. Thus the
initial cost of the plant is reduced by 50/1 which represents a sizable s to.
The arrangement of the plant is such as to promote simplicity as well
as a saving of space. In the old tunnel type, kilns up to 400 feet long were re-
quired. The arrangement of the kilns in a circle is obviously a space saver ana
the saving of handling of the clay by the use of conveyors is nothing short of
ingenious. After once being set in the kilns the bricks are nevar touched again
until ready for shipment, The 16 kiln sections provide ample storage and there
is no need for second handling t the bricks being packed directly into trucks wh-
ich are backed right up to the kilns.
The fuel requirements for the burning of the brick are held to a min-
imumby the use of the insulating refractories in the hoods and also because of
thf? fact that the bricks are previously preheated 1 by the waste combustion gases.
One of the greatest advantages of the system is its small labor re-
quirements. The older type plants average 1500 brick per day per man. This pi*
ant averages 5000 brick per day per man, using only 15 men to produce their daily
output of 70,000 brick.
The whole system of kilnsjflues, etc. is extremely flexible and changes
c?n be made during operation one way or the other by manipulation of a few damp-
The plant of the Washington Brick Company, by dint of being the first
to emoloy the Circle System, isj without a doubt,the most modern brick plant in .
the country. The introduction of the Circle System with its many advantages will
probably revolutionize the design of olants in the brick industry. It is with-.
out a doubt the greatest contribution to the furtherance of the brick industry
in many years.
Inasmuch as the subject of this thesis is a new structure and of
an entirely new design there was no opportunity for the acquisition of material
from existing books or periodicals. All of t'e facts for this thesis were ob-
tained through John R. Clark, originator of the Circle System and Sal-S-lianyger
of the '.lashington Brick Company. Due apDreciation is here accorded Mr« Clark
who so kindly gave freely of his time so that this ifchesis might he completed*