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Biennial report of the Bureau of Labor Statistics of the ..., Volumes 16-17 online

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cated on their portion of the premises. Shower baths were loeated in
rooms at each corner of this block, and were supplied with cold water
only. The dining-rooms had screens on the windows, but the doors
were not screened. Tree« and vines have been planted on the premises
and the place had been made as attractive as possible.

Not far away are two frame buildings, 20 feet by 100 feet in size.
Each building has a room 20 feet by 60 feet equipped with ten steel
bunks, for the use of the men, principally Austrians. Sanitary toilets



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THE PORTLAND CEMENT INDUSTRY IN CALIFORNIA. 157






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158 REPORT OF THE BUREAU OF LABOR STATISTICS.

and three cement washtubs are at each place. The Austrians i»ny $1,
every two weeks, for laundry work and housing.

Armenians, employed by this company, live in a city not far distant.
An investigation of their living conditions showed that some of the
unmarried men would cooperate in renting a house, or rent from &
lessee. Two or three men were occupying each room and doing their
cooking in a primitive manner, usually in the kitchen, or together in
some other room of the house. Their diet was principally bread and
meat, but fruit, butter, eggs and other ordinary necessities are bought
by them only occasionally.

In this discussion of the housing and living conditions of foreigners,
it should be borne in mind that they are desirous of living as eeonoin-
ieally as possible. For this reason, whether they get fifty or a hiuulred
dollars or more, per month, many of them do their own cooking and
other work, and purchase only the plainest of food, instead of patroniz-
ing boarding houses or hotels, like their fellow employees do, and where
better living conditions prevail.

Two companies have recently completed first class emergency hos-
pitals, fully equipped, constructed of cement, and each costing about
$10,000, without the equipment. They are a credit to the plants where
they are located.

The plants are operated throughout the year, depending on business
conditions, and they average around three hundred working days, each,
per year.

The process of making cement has been aptly described as the ''grind-
ing of a mixture of limestone and clay together to a fine powder and
heating this mixture to incipient fusion ; this partly fused mixture when
ground to a flour and mixed with a retarder, forms Portland cement."

The raw materials used are chiefly limestone, clay, shale and gypsum.
The limestone from the quarries, and the elay from clay pits, iwr con-
veyed by cars to the plants and are placed in separate bins.

The general mode of cement manufacture in the various mills is
essentially the same. The operations are divided into two departments,
i. e., the '*raw'' mill, and the ** finishing'' mill.

In the *'raw'' mill, the ingredients pass through the crushers, ball
mills, tube mills, and into kilns where the heated mixture is brought to
incipient fusion, which forms a *^ clinker."

After cooling on the clinker pile, in the open air, this clinker is con-
veyed into the *' finishing" mill, where it is reground by ball mills, and
tube mills, gypsum is added as a retarder, and then the product, as
cement, is ready for the packing machines which are used to sack the
cement.

In one representative plant in California, the cars containing the
limestone from the quarry are run over track scales to check the gross

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THE PORTLAND CEMENT ES^DUSTRY IN CALIFORNIA. 159

tonnage. The cars are then dumped and the limestone discharged into
two No. 6 Gates gyratory crushers operated by one 150-horsepower
motor. This constitutes the second reduction, the first reduction hav-
ing been completed in the crusher at the quarry.

The two crushers are arranged so as to discharore their product on to
one twenty-four inch 15 degree inclined belt, 200-feet centers, which
conveys the product into a rock storage capable of holding 16,000 tons.
Three belts with three Robins automatic trippers serve to distribute the
crushed limestone over the rock-storage area. By means of a system
of tunnels and belting, the limestone is drawn out from underneath the
rock storage onto a cross belt into two six by sixty-foot dryers. From
the discharge end of the drj'ers, the limestone is elevated into a bucket
conveyor, which delivers the material into the ball mill bins. All the
bins are of a steel, hopper type of construction. At the same time, the
clay and shale is dried through similar dryers, and their discharge
delivered into the ball mill bins.

A third reduction is accomplished through eleven Gates Xo. S ball
mills for limestone, clay and shale, each of which is ground separately
and their product elevated and conveyed into separate bins: six for
limestone, and three, each of a different capacity, for clay and shale.
Automatic samplers are arranged for sampling each of the three raw
materials while their respective bins are filling. When these samples
are analyzed and a raw composition formulated in the laboratory, the
three separate materials are drawn out simultaneously into a battery of
three automatic weighing machines, which again simultaneously dis-
charge into a huge double-screw-cut flight mixer. From the mixer, the
raw composition is elevated and conveyed into the tube mill bins.

The tube mills, giving the final grinding to the raw composition, are
of the Gates ^\e and one half foot by twenty-two foot type and are
fourteen in number, operated in pairs by a 250-horsepower Westing-
house motor. The tube mill product, 73 per cent of which passes a
200-me8h screen, is discharged into one long continuous screw c<»nveyor,
where the raw composition is again automatically sampled and cheeked
from the laboratory. The raw composition is then elevated and con-
veyed to the kiln bins.

In the kiln-room are twenty-four 7^ foot by 7 foot by 125 foot kilns,
which lie on an incline of a three fourths of an inch pitch, and are
indi\'idually operated by a 30-horsepower speed motor, with a ccnit roller
at the burner end of the kilns. Each kiln is provided with a stack, five
feet by eighty feet, at the far end of the kiln. Fourteen of tlie kilns
are now in daily operation, each of which easily produces its 500 barrels
of clinkers in twenty-four hours.

The raw composition is fed into the stack end of the kiln by means
of screw conveyors from the hopper base of the kiln bins, w^hieh, under



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160 REPORT OF THE BUREAU OF LABOR STATISTICS.

the rotation of the kiln, is carried onward and downward through the
heat zone, where it is calcined to incipient fusion and discharges into a
pit as clinker. The burning is accomplished with crude oil and com-
pressed air. The oil is of 17 degrees Beaume gravity and the air pres-
sure is eighty pounds at the burner. Approximately 2,000 barrels of
oil are consumed per day.

From the clinker pit the clinker is delivered into coolers, which finally
discharge into a portable steel skip on a narrow gauge track, to be takoi
to an open air clinker storage.

The clinker now in the steel skips, which hold thirty barrels, is deliv-
ered to the clinker storage pile. One of the chief assets to a cement
plant lies in a large clinker storage. It not only gives the plant flexi-
bility, but gives an aging to the clinker which favorably aflPects its
quality as well as the final grinding. The clinker storage at this plant
covers an area of 80,000 square feet, on which approximately 500,000
barrels of clinker can be stored.

The clinker storage has fourteen tunnels underneath into which the
clinker is drawn through chutes directly onto belts which convey the
clinker to a cross belt running into the finishing mill.

In the ** finishing'* mill, the clinker is received in a steel bin directly
over the stack end of the dryer, provided with an adjustable rocker
feed, which delivers the clinker into the dryer. While the clinker
passes through the dryer a low heat is applied, when necessary, to drive
off any water absorbed by the clinker through rains or damp atmos-
phere, thereby avoiding any clogging of the ball mill screens. To
retard the setting time of the cement, about 2^ per cent of gypsum is
added in the dryer discharge pit from a bin controlled by an adjustable
rocker feed.

The gypsum is fed into the pit by a continuous belt, which delivers
a continuous stream simultaneously with the clinker stream discharged
from the dryer. This assures a thorough distribution of the gypsum
and a well regulated setting time of the cement.

From the dryer discharge pit the stream of combined clinker and
gypsum is elevated and conveyed into the ball mill bins. Through the
hopper of the bins the material is fed into the ball mills, eighteen in
number, similar in type and size to those in the raw mill building.
From the ball mill discharge, the stream passes through elevators and
conveyors into the tube mill bins. From these bins the material passes
on into the tube mills for its final grinding. The tube mill installation
consists of twenty-four mills, twenty of which are in constant operation.
The tube mill product, which is the cement, is an impalpable powder,
80 per cent of which passes a 200-mesh screen. The product is elevated
and automatically sampled while conveyed into a large stockhouse.



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THE PORTLAND CEMENT INDUSTRY IN CALIFORNIA. 161






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162 REPORT OF THE BUREAU OF LABOR STATISTICS.

The stockhouse, which consists of ten separate bins, is of concrete con-
struction throughout, and has a capacity of 128,000 barrels of cement.
The base is of the hopper and tunnel-type construction, two of which
run longitudinally through the entire length of the stockhouse. By
means of screw conveyors, the cement is conveyed through these tunnels
into the packing bins, adjacent to the stockhouse. Eight Howe packing
machines mechanically fill the sacks, which are carefully weighed and
tied and passed on trucks into cars.*

A portion of every plant is devoted to the receiving, cleaning, count-
ing, patching, repairing, and storage of returned cement sacks, and this
place is referred to as the ''bag house.'*

The cleaning of sacks is generally done by revolving a number of
them in a cylinder, which is operated in a closed room. The slatted
perimeter allows the cleanings to drop through to the floor. The bags
are removed from the cleaner through a door provided in one section
of the slats. No one remains in this closed room during the operation
of cleaning the sacks.

It is evident that in a manufacturing process, which produces a pul-
verized mineral product, as cement, there is likely to be a leakage at
various stages of the operation. The result of this leakage is that dust
is distributed throughout the plant, while the air becomes heavily
charged with the most minute particles.

The siliceous character of the limestone necessitates the use of metal
machinery and containers to withstand the constant friction. In none
of the plants were the metal conveyors, or the machinery, boxed in
with lumber to restrict the dissemination of dust. Such a procedure
would tend to precipitate and control much of the dust ; to prevent its
dissemination, and to admit of its removal as required.

The kiln rooms were affected the least, and the grinding, packing,
and bag cleaning rooms the most, by the leakage of dust, thoujjh com-
parisons are difficult to make when dust is found everywhere.

The dust problem is a mechanical difficulty, which varies with the
individual plants — ^their machinery, mode of operation and construction
arrangement.

One plant was walled off longitudinally, dividing the building into
zones, in each of which a particular process was performed. The in-
tent, and the result, of this plan was to retain in each department, the
dust which was disseminated there by leakage from machinery.

In no plant was vacuum apparatus or any other dust collecting
machinery used to eliminate or to dispose of the dust.

One plant had, however, installed a dust collecting plant at an
expense of $10,000, but it failed to operate satisfactorily.



•Llewellyn T. Bachman, "Cement and Engineering News." March, 1913.

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THE PORTLAND CEMENT INDUSTRY IN CALIFORNIA.



163



Regarding the dust problem in English cement plants, it is stated
that:

Provision is made in well-arranged works for the withdrawal and collection of
the suspended dust, which was formerly so objectionable a characteristic of cement
works, leading not only to unhealthy conditions within the buildings, but poisoning
and disfiguring the whole neighborhood in which the industry was carried on.

By the aid of exhaust fans and dust-collecting apparatus, the air is now kept
free from dust, and a considerable quantity of cement, which was formerly wasted,
is now saved to the manufacturer.*

Most of the superintendents have been engaged in manufaeturing
cement for many years, and their experience has convinced them that,
generally speaking, cement dust is harmless to employees. Acting on
this theory, it is not remarkable that they have done so little to reduce
the dust problem to a minimum.

One manager submitted the following statement of the term of

service of some of his employees, for the purpose of showing their

preference for, and their ability to perform, the work required in

this industry.

For your information, we give the actual time of service of our employees in the
packing house and bag house, as follows :





Ye»ra of senrlcc of employees


FUet of Work


0-1


1-S


2-3 3-4


4-5 5-6 6-7 7-8 T.Ual


Packing boose

Bair house


3

3


5
1


8 5

4 5


3 2 3 29

! 13







The following figures show employees* time of service on the job, and do not
necessarily mean the length of their service in the respective departments :



•C. H. Desch. "The Chemlatry of Cement." p. 32.



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164 REPORT OF THE BUREAU OF LABOR STATISTICS.



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THE PORTLAND CEMENT INDUSTRY IN CALIFORNIA. 165



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166 REPORT OF THE BUREAU OP LABOR STATISTICS.

The above figures show that of a total of three hundred eighty-five
men on the pay roll of this company, a large proportion of them had
remained with the company for many years.

Of the men who had left this factory, some had gone to other
plants to continue with the same line of work ; others had made their
** stake,'* and had gone into farming, or business, or had returned to
their native land.

Though the mill men do not work as hard as those outside, they
have longer hours and receive proportionately more wages.

It is diflBcult to secure Americans to remain in some of the ocatmpa-
tions in the mills, and therefore foreigners are greatly in the majority.

These are principally Italians, Greeks, and Armenians. They live as
economically as possible, and either send their wages home, or return
when they have accumulated enough to enable them to live there com-
fortably.

One manager reported that Greeks are prone to retain their brass
identification checks when returning to Europe, and give them to
friends, who bring the checks back in the expectation of securing the
vacant positions, or a chance to work elsewhere about the plant.

Much data on the personal habits of the foreigners employed in this
industry was obtained, which indicates that their standards of living
are far below what they should be.

Since the beginning of the agitation regarding cement dust, sev-
eral of the companies require their physicians to make physical exam-
inations of the employees in order to reject those who are unsuited
to the work, and at different times to note the effect, if any, of the
work and dust upon them.

Records of these examinations are made, and the doctors are
thereby enabled to report more intelligently upon the physical effects
of the industry on the workers than they could heretofore.

Several company doctors reject applicants who have any defect in
their nasal passages, or have bronchitis, or lung trouble. They now
pass, as a rule, none but sound men between the ages of twenty-one
and fifty years.

One doctor resides in a cement company town, though all the com-
panies have retained doctors who live within convenient access of the
plants.

The dust problem in its relation to the health of the employees, may
be considered from several standpoints as follows :

1. Bacteriological. AMien the finely groimd mixture of limestone
and clay is brought to incipient fusion in the kilns, the temperature
registered there, by pyrometers, ranges from 2,700° F. to 3,500° F.



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THE PORTLAND CBMENT INDUSTRY IN CALIFORNIA.



167



Any organic material is broken down chemically, and any bacteria
would, of course, be destroyed.

Bacteria that might be found in the finished Portland cement would
be acquired while the clinker is on the clinker pile, or subsequent
thereto, during the regrinding operations. It is very improbable that
any bacteria would be thus combined with the cement.

Respirators are seldom used and then only by packing and bag house
employees. It is possible that their continued use, without being
cleaned or sterilized, affords a greater menace to the health from bac-
teria exhaled with the breath and lodged in them, than the sterilized
cement dust does.

2. Chemical. Analyses of American Portland cements indicate some
variations in the proportion of their constituents, and the following
table gives some representative determinations :

Analysis of American Portland Cements.*





PerceatAges of compotltlon


ElemenU


••


n.


III.


rv'. 1 V.


VI,


VII.


SlOt


21.99
7.24
3.39

62.53
2.37
1.19
1.29


20.75
7.72
2.59

62.75
2.61
1.66
1.92


20.88
7.91
2.69

62.98
2.85
1.46
1.23


21.61
7.88
3.18

62.56
2.37
1.52
0.88


23.25
5.32
S27

63.14
3.01
1.32
0.69


22.14
7.32
3.02

63.14
1.61
1.58
1.97


22.47


AliO»


6.94


Fet 0»

CaO

MgO

SO«


2.79

60.42

3J23

1.67


rndetermined —


2.48






Totals


100.00


100.00


100.00


lOO.OO


100.00


100.00


lOJ.CO



•Bulletin No. 331. U. S. Geol. Survey, 1908.

Any injurious effects from the mineral elements above enumerated
would be dependent upon their chemical or mechanical action on the
men.

At one plant, a notice is posted requesting employees to wash their
hands before eating. The inference is that cement dust, absorbed with
food, would be injurious to the men, causing intestinal and other
troubles.

II Fumes. These are expelled from the kilns, through chimneys,
during the process of incipient fusion in the formation of clinker.
Several companies have been defendants in lawsuits instituted by own-
ers of adjacent property, who alleged that the fumes were injurious
to crops.

In order to overcome such objections, two companies have, at consid-
erable expense, installrd dust collectors, or fume houses, in connection
with the chimneys, at their plants. Here the dust and fumes are treated
by different processes in order to minimize their injurious effects upon
the neighborhood.



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168 REPORT OF THE BUREAU OF LABOR STATISTICS.

Fumes ordinarily contain sulphur trioxide (SOg), carbon dioxide
(COo), and carbon monoxide (CO), in varying quantities. The action
of the first named is well illustrated when it comes in contact with
barbed wire fences, or other iron surfaces, in the presence of moisture,
as it corrodes the metal. Any of these fumes, in quantity, are injurious
to human beings.

4. Mechanical. The dust, which is distributed throughout the plants,
varies in size from that which will pass through a 200 mesh screen to
that of larger size. At one plant the chemist stated that 96 per cent
of the cement would pass a 100 mesh screen, while 84 per cent would
pass a 200 mesh screen.

The dust may be an impalpable powder, or larger and somewhat angu-
lar in shape. In the latter form it is more irritating, as it causes an
abrasion of the skin and mucuous membranes. The heavier granular
particles are precipitated more quickly than the lighter ones.

In the packing-rooms, particularly, the atmosphere is charged Anth
cement dust. This is due to mechanical defects in the machinery ; the
lack of effective boxing around conveyors and machinery, and the modus
operandi of the packing and tying operations.

Occasionally cement dust lodges in the eyes, causing conjunctivitis.
The doctors uniformly state that the number of office visits of employees
due to dust troubles is very small, and they are not aware of any disease
that is peculiar to this industry. It is claimed that cement dust will
imickly cure a cold in the head — presumably because of its strong atfinity
for moisture.

When inhaled in the nasal passages, the dust is irritating and annoy-
ing to many people. It may penetrate into the clothing or shoes and
cause skin irritation. For this reason packers and truckers often hind
up their shoes with gunny sacking while employed in the packing
departments.

With reference to the effects of cement dust on employees, an English
government publication states as follows :

Investigations by Dr. Hcim. of Paris, and by tlie Factory Department of tho
Home Office, made two or three years ago. have also shown that men enRau:ed in
the manufacture of plaster of Paris and cement are free from any excessive iuoidence
of phthisis.

We may also refer to a valuable pai)er read by Dr. Collis at the XVIIth Interna-
tional Congress of Medicine, London, 1013, on *'The effects of dust in producing
diseases of the lungs." in which the whole subject is summarized.

The investigations briefly summarized above, while indicating that dust inhalation
predisposes to respiratory diseases, the mortality from which may attain terrible
proportions, show certain uuexjjccted excejjtions, notably in the case of slate miners
and of men employed in the manufacture of cement and of plaster of l*aris. Evidence,
b.owever. has been placed before us which by indicating one, and probably the most
imi>ortant injurious element in dust. will, we consider, materially assist in the pre-
vention of mortality from pueumonoconiosis.



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THE PORTLAND CEMENT INDUSTRY IN CALIFORNIA. 169

It is desirable to explain by what steps this element has been isolated. The term,
pneamonoeoniosis or dustlung, is used to describe the damage caused to lungs by
dust Inhalation ; this damage may manifest itself in various diseases, such as phthisis,
asthma, pleurisy, chronic pneumonia, or bronchitis. These diseases occur in the gen-
eral population, and difficulty, therefore, arises in establishing for each individual ease
the predisposing influence of occupation ; and we feel confident that if this influence
could have been demonstrated with the same certainty as in the case of lead poison-
ing among workers who manipulate materials containing lead, of anthrax among wool
sorters, and of other such specific occupational diseases, the existence of this widely
distributed evil would have been ere now recognized and dealt with. Of these
diseases, as regards men employed in metalliferous mines and quarries, phthisis or
consumption is the most important. Other diseases of the lungs appear always to
occur in excess among those who suffer a heavy mortality from phthisis induced by
dust inhalation, and such diseases may also be unduly prevalent even when an exces-
sive death rate from phthisis is absent, as, for example, pneumonia among slate-
workers whose death rate from phthisis is low. No relation, however, has yet been
established between such forms of pneumonoconiosis, as e. g., pneumonia, asthma,
and bronchitis, and the inhalation of particular forms of dust.

F'or our present purpose phthisis mortality may usefully be taken as the com-
parative index of the injury dust causes, at least among those employed in metal-
liferous mines and quarries, regard being had to the fact that the figures which ex-
press the mortality from phthisis do not express the total mortality in these indus-
tries from pntumonoconiosis.

The sequence of events which follows inhalation of injurious dust — the formation
of fibrous tissue in the lungs which lose their spongy texture and become tough and



Online LibraryDeutsche Numismatische GesellschaftBiennial report of the Bureau of Labor Statistics of the ..., Volumes 16-17 → online text (page 13 of 46)