U.S. ARMY INTELLIGENCE CENTER AND SCHOOL DOCUMENTS

SupR 62810-11

January 1976

INDUSTRIAL TARGET ANALYSIS
SUPPLIMENTAL READING

U.S. ARMY INTELLIGENCE CENTER AND SCHOOL

FORT HUACHUCA, ARIZONA

INDUSTRIAL ANALYSIS

1. INTRODUCTION. Whatever the current status, peace or war, and if war, limited or world wide, the intelligence officer, regardless of his primary function within his field, has a vital role to play. No modern weapon can be accurately deployed without adequate intelligence on the target. No target, once attacked, should be ignored. An assessment of the damage must be made to enable further attacks to be planned or to calculate the effect of the target's destruction on the enemy. Accurate, timely intelligence is vital to all stages of military planning and operations, both strategic and tactical. It has been frequently said that aerial reconnaissance and the resultant analysis were responsible for 80% of the valid intelligence collected during WW II. Although this figure may be disputed, it is undoubtedly true that aerial reconnaissance is one of the most important and reliable systems in use today. And remember, the system and aircraft in use are only as good as the man who exploits the imagery obtained. Thus, the 11 and his report are vital parts of the intelligence collection effort and may have a decisive effect on the progress of the battle and the war. To be fully effective in his job, the imagery interpreter must have a detailed knowledge of many and varied subjects. Anything manmade or natural, on the surface of the earth, can be the subject of sensor surveillance and, therefore, the subject of a report. In the purely tactical situation, military equipment (tanks, guns,, etc.) will predominate; however, their progress and ability to fight effectively will be dependent on the country's economy; namely, the industrial structure and transportation networks required to support such a situation or operation. In peacetime a large portion of the intelligence collection effort will be directed against static targets in the industrial and transportation fields. From information so obtained, an accurate assessment of the subjects' potential to wage war can be made. Strategic and tactical deployments can be watched on their transportation systems and development of new and sophisticated weapons can be assessed from industrial analysis. New industrial and transportation developments will tend to reflect changes in national policy and should be closely watched. It is the purpose of this block of instruction to provide instruction in military support subjects, a vital area in the knowledge required by the imagery interpreter. The basic principles of construction and an analysis of the electric power and coke, iron and steel industries will be covered. This SupR gives an outline of the subjects covered during the industrial analysis portion of 62810.

2. TARGET ANALYSIS CYCLE.

The Target Analysis Cycle provides a logical sequence for the analysis of any target. There are 4 distinct phases in the cycle, each requiring specific studies or events within that phase. The phases of the cycle should not be considered as time frames. They are, instead, a sequential ordering of activities which establishes the priority of work performed by the an imagery interpreter d all other personnel involved in the Target Analysis Cycle.

The 4 phases of the Target Analysis Cycle are the PLANNING PHASE, the PRE-ATTACK PHASE, the ATTACK PHASE, and the POST-ATTACK PHASE. Each single target may go through all 4 phases. If several targets are under study at the same time, each may be in a different phase. One target, for instance, may be in the planning phase while another is in the post-attack phase.

a. Planning Phase.

In this phase, the broad target system is developed. In the development, large areas are studied, and industrial complexes rather than individual industries are considered in order to determine their importance. This is done by trained analysts, and the imagery interpreter does not, contribute materially during this phase, other than by interpretation of existing imagery. Source material for the analyst will include all available information, such as statistical reports, economic studies, technical publications, and information obtainable from industrial experts. As a result of the analyst's studies, targets are selected for further study, and target priorities are assigned.

b. Pre-attack Phase.

It is during this phase that the imagery interpreter will be busiest. The necessary imagery for targets selected during the planning phase either will be available or will be procured. Using all material available as reference and the imagery of a given target or group of targets, the will imagery interpreter conduct various types of studies as required by the particular situation. The studies will deal with either industrial targets or urban areas, and in some cases both. The specific requirements and contents of the studies on industrial targets and urban areas will be discussed further on a separate basis.

When completed, the studies will be utilized primarily by personnel trained in weaponeering. It is then that weapon type, ordnance type, and ordnance quantity will be specified, based on the characteristics of the particular target and the end result desired.

c. Attack Phase.

The imagery interpreter has no responsibility during, the attack phase. As the, name, implies, in the attack phase the weapons/ordnance designated by the weaponeering specialist are delivered to, the target by a unit having that capability.

d. Post-attack Phase.

During the post-attack phase, the imagery interpreter will conduct various types of studies on industrial targets subjected to attack. Normally, urban areas will not come under study during this phase unless a specific requirement exists.

3. URBAN AREAS.

Analysis of urban areas will occur principally in the pre-attack phase. There are numerous types of studies which may be prepared in the analysis of an urban area, and when considered together these studies show the relationship which exists between the urban area and any industrial targets within the area. -References to be used in the prepa-ration of urban area studies include NAVAER 10-35-573, Urban Area Analysis, and TM 30-268, Building Structure Analysis. Some of the most important of the urban area studies are discussed briefly in the following paragraphs.

a. Zone Analysis (Zoning).

The zoning procedure consists essentially of resolving an urban area into zones according to the major categories of building occupancy or function. The zoning information will be presented in the form of an annotated map, color coded overlay, or an overprinted mosaic. Depending upon specific requirements, the study may be limited to show- ing only the industrial zones or the military zones, etc. Unless such requirements do exist, the study will contain a complete breakdown of all zone types in the area of consideration. The following zone cate-gories, along with the recommended color code for each, will be used in the preparation of a zone analysis.

(1) Residential Zone (Red).

This zone consists of districts having 85% or more residential occupancy. It includes nonadministrative public buildings such as museums, schools, and hospitals. The zone also includes household (invisible) industry and small elements of other types of occupancy which are intricately intermixed.

(2) Commercial Zone (Light Blue).

This, zone consists of districts having 35% or more commercial occupancy. Commercial occupancy includes shops, offices, banks, administrative public buildings, etc. The zone may also include small amounts of other types of occupancy which are intricately intermixed.

(3) Industrial Zone (Dark Blue).

This zone consists of districts having virtually pure industrial occupancy. It includes plant administrative buildings and plant storage. Public utilities are also included in this zone, but trans-portation is not.

(4) Mixed Zone (Purple).

The mixed zone will consist of an area where two or more types of occupancy occur in approximately equal proportions with no one type making up more than 75% of the occupancy. The different types of occupancy in the mixed zone will be so intermixed that they cannot be separated. Such an area will be reported as a mixed zone, and the occupancy types will be designated; e.g., m4xed commercial and residen-tial zone.

(5) Transportation Zone (Green).

This zone consists of the facilities devoted to the repair, maintenance, operation and storage of railroad, trolly, and bus systems. It also includes ferry terminals and waterfront transshipment facilities but not storage buildings used to house goods awaiting shipment.

(6) Storage Zone (Yellow).

This zone includes all structures devoted to anv type of storage, but factory site storage or storage incidental to commercial activity is not included. Petroleum and POL product storage is classified in the storage zone.

(7) Military Zone (Orange).

This zone includes installations or structures which are used by the military, such as barracks, ammunition dumps, artillery and vehicle parks. All airfields are classified as military zones regardless of ownership or occupancy.

b. Steps in Zoning Procedure.

Initially, the imagery interpreter should plot all available ground information which relates to the location and extent of the various types of occupancy in the area under study. This information should be plotted on the aerial photo cover so that it can be verified by stereoscopic examination of the photography. Stereoscopic examination is also used to determine the types of occupancy in those areas for which ground information is unavailable. Once the zone determinations have been completed, the information is transferred to an overlay or other selected form of graphical representation, and each zone is appropriately color coded.

(1) Open Areas.

During the zoning process, it would become evident that open areas may exist which are not accounted for in the zones given. Such open areas will be left uncolored, provided they meet the following criteria. The areas must be no less than 500,000 square feet and measure no less than 500 feet on any one side.

(2) Firebreaks.

Many open spaces in urban areas (not to be confused with open areas defined in paragraph 3.b.(l)), whether natural or manmade, may be classified as firebreaks. In addition to arresting the spread of fire, firebreaks may serve as avenues of approach for firefighters and as islands of safety for the population. Examples of some features typically found in urban areas which might serve as firebreaks include parks, waterways, marshaling yards, wide streets and cleared railroad right-of-ways.

Firebreaks are classified as either PRIMARY, SECONDARY, or TERTIARY. The physical parameters for placing a firebreak into one of these categories depend upon numerous variables and should be determined for each area based on the physical characteristics prevalent within that area. Some of the variables to be considered are the density, 'height and construction of buildings within an area. Obviously, the establishment of firebreak parameters requires a great deal of research and study beyond the normal scope of the cap imagery interpreter's abilities.

Even when parameters for firebreak classification are established, they must be used only as guidelines rather than hard and fast rules. In reality, there are numerous factors which will influence the spread of fire that cannot be predicted with complete accuracy. Consider, for example, the influence of weather conditions prior to an attack (extended periods of rain versus drought). Equally important are the weather conditions at the time of attack; for example, rainy versus dry and windy versus calm.

The following parameters for the classification of firebreaks are recommended for use in the School.

(a) Primary Firebreaks.

These provide less than 40% chance of fire spread and are 130 feet or more in width. Plot these as solid black lines on the zone analysis overlay.

(b) Secondary Firebreaks.

These give between 40% and 50% chance of fire spread and are between 90 and 130 feet in width. Plot these as dashed black lines on the zone analysis overlay.

(c) Tertiary Firebreaks.

These give between 50% and 60% chance of fire spread and are between 50 and 90 feet in width. Plot these as dotted black lines on the zone analysis overlay.

c. Other Urban Area Studies.

The zone analysis is usually the first of the urban area studies prepared. It forms the basis for the other studies which may be required, including all of those discussed in this paragraph. Each zone as identified in the zone analysis is further analyzed and broken down into subzones according to the criteria selected. An overlay presenting the information in graphical form is then prepared. The overlay must be prepared at the same scale as the zone analysis so that it may be superimposed over it.

(1) Building Density Analysis.

The must imagery interpreter resolve each of the occupancy zones into subzones according to building density. Basically, the term building density refers to a ratio between total roof area and total ground area.

Total Roof Area Building Density = Total Ground Area

Recommended density divisions for use in the preparation of the building density overlay are:

(a) Subzone 1 - 40% and over.
(b) Subzone 2 - 20-40%.
(c) Subzone 3 - 5-20%.
(2) Height Analysis.

In this analysis, the must resolve imagery interpreter each of the occupancy zones into subzones according to building height. An overlay is prepared which graphically presents average building heights. Usually, the buildings within given areas are considered to be of equal or near equal heights (for example, housing developments). Depending on the detail required, the imagery interpreter may be allowed to use approximations. Single story structures are usually about fifteen feet high with an additional ten feet for each additional floor. Isolated buildings or especially tall buildings need not interfere with the building height groupings. An asterisk on the overlay with an explanation in the legend will over-come this problem.

(3) Structural Content Analysis.

In this study, the urban area is divided into districts in which buildings of one particular structural type predominate, or where buildings of several structural types are inextricably mixed. The following categories are considered to be the basic structural types for analysis of the structural content of urban areas.

(a) Buildings of wooden or predominantly wooden construction.
(b) Buildings with framework of steel or concrete.
(c) Buildings with load bearing walls of brick, stone or concrete.

Buildings which are a composite of the load bearing wall and frame construction may be classed with steel or concrete framed buildings for purposes of general structural analysis. Stressed skin structures are encountered so infrequently that they will generally not require a special category. If an area being studied has mixed structural content, it should be identified as such and the approximate percentage of each type given.

d. Transportation Analysis.

The transportation network which serves as urban area or industrial-ized area is, in many respects, the very lifeblood of the region, pro-viding for the movement of raw materials, goods, services and people. For this reason, the study of an urban area, or an industrial center, cannot be considered complete without an accompanying study of the existing transportation network. Such an analysis would include road, rail, air, and waterway facilities of the area. Essentially, this study provides an assessment of the capabilities of the transportation network, and it forms the basis for designating vulnerable points as targets which when damaged will result in the disruption of activity in the area.

4. INDUSTRIAL TARGETS.

During the planning phase, various industrial installations con-sidered important to an enemy's war effort are nominated by analysts for further study. Those installations selected are assigned priorities and then enter the pre-attack phase of the Target Analysis Cycle.

A Functional Analysis must be conducted on each of the installa-tions studied in the pre-attack phase, identifying tae overall function of the site, dividing it into functional areas, and giving other assorted information required by the Functional Analysis Report. The more important installations and key buildings may require a Structural Analysis in addition to the Functional Analysis.

a. Identification of Industries.

Unless the imagery interpreter immediately recognizes a particular industry appear-ing on photography as to its overall function, the initial problem will be the determination of an industrial installation's function (steel production, reduction of aluminum, etc.). In such a case, the imagery interpreter must resort to the use of reference material such as (C) TM 30-260, Industrial Components (U).

In the use of this type of key, the imagery interpreter must first place the industrial installation in question into one of several broad cate-gories based upon the general features noted. There are very few industries which cannot be easily categorized.

Once the industry has been categorized, the imagery interpreter must then go to the section of the key dealing with that category of industries. Examining each stereopair, the one which most nearly matches the appearance of the image of the unknown industry is located. Assuming that the imagery interpreter has not made an error in previous steps or in his final selection, the selected stereopair will give the function of the installation shown, and con-sequently the function of the unknown industry.

The imagery interpreter may be required to identify industries from existing imagery during the planning phase to provide input to the analyst. This input, along with all other information, would then be used in designating the targets requiring further study and the assignment of target priorities. If there is no existing imagery at the time of the planning phase, or if for some reason the imagery interpreter is not required to provide input, it will be essential that industries be identified in the pre-attack phase in preparation for the functional analysis of individual installations.

b. Other References.

Once an industrial installation enters the pre-attack phase, imagery interpreter 's requirements far exceed simply the identification by function. In order to meet these requirements, which will be reported in the Functional Analysis Report and possibly a Structural Analysis Report, the imagery interpreter must usually resort to the use of reference material other than (C) TM 30-260 (U).

For many of the basic industries and industries essential to the waging of war, II keys and reference materials have been compiled and are readily available. An example of one of these keys would be (C-NOFORN) TM 30-274, Aluminum Industry (U) which is concerned solely with the aluminum industry, to include the extraction of bauxite,. the production of alumina, and the reduction of alumina into aluminum metal. A key of this type generally includes background information about the industry, information about the various processes utilized within the industry, photography and stereograms showing the equipment and facilities used within the industry, and not the least important, a flow chart for the particular industry. By using this reference material carefully, the imagery interpreter can easily identify functional areas within an industrial installation and can identify the function performed by specific equipment or within specific buildings.

Because of the rapid spread of industrial technology, the key for a specific industry has worldwide application. That is, an installation for the production of steel in China or the USSR will basically be the same as a similar facility in the United States. Granted, there may be variations in equipment and layout, but these will generally be minor, and the processes employed in production will be identical in most respects.

c. Industrial Flow Chart.

The flow chart for a particular industry will in many cases be one of imagery interpreter 's most valuable items of reference. Looking at a flow chart, the imagery interpreter can, at a glance, gain an overall appreciation of that particular industry. The chart provides information as to the raw materials and intermediate products necessary to the industry, the various processes or steps of production which are employed, and the sequence in which these processes or steps of production must take place. As is the case with the industry key, a flow chart for an industry is universal in application. To use the flow chart effectively, the imagery interpreter must realize that it is a guide and that minor variations may occur. The basic flow chart, however, will aid the imagery interpreter in detecting any variations and in making an accurate, definitive analysis.

Examine the flow chart an steelmaking on page 46 of this SupR. Notice that iron ore, limestone, and coal are the basic raw materials required in steelmaking. Each of these materials is subjected to intermediary processing for subsequent use in the production of molten pig iron. The iron ore is either sintered or pelletized, the limestone is crushed, and the coal is converted into coke. These three intermediate products are then combined and processed in a blast furnace, the result being another intermediate product, molten pig iron. The molten pig iron is further processed as shown to produce steel, and so on. Those raw materials and processes must be used regardless of the geographic location of an in-dustrial installation whose function is steelmaking.

As you should have noticed from the flow chart for the steelmaking industry, the final product is steel which has been fabricated into a wide variety of forms. All of those items are actually semi-finished products in that they serve as raw materials used in other industrial functions in the final production of consumer items.

d. Research by the Imagery Interpreter.
.

In some cases, the imagery interpreter may be required to make an analysis of an industrial installation having a function for which a flow chart is unavailable or using a unique series of processes for which a basic industry flow chart would not be applicable. Examples might include a newly established industry or a pilot facility employing experimental methods of production. When confronted with a situation of this type, the imagery interpreter may find it necessary to conduct research on that industry.

Such research should strive to touch upon all possible sources of useful information. Some possible sources might include industrial experts such as industrial engineers and process engineers employed within the industry, scientific and technical publications, industrial journals and publications, and textbooks dealing with the industry or industrial processes. The list of sources which might be of value is limited only by the imagery interpreter's ingenuity and imagination.

5. STRUCTURAL ANALYSIS.

The more important priority targets are selected for structural analysis, which is made up of 2 parts, the preparation of the target plan and the building construction analysis. The imagery interpreter is concerned only with the building construction analysis, and only those targets that have been identified as vital to the enemy will be selected for this type of study.

a. Building Construction Analysis.

If an industrial installation is selected for building construc-tion analysis, the characteristics of every building within the In-stallation must be studied. The physical characteristics which must be determined include length, width, area, number of floors, type of construction and material. This information, when combined with the target plan, may be used by an individual trained in weaponeering in order to designate the weapon type and size required to achieve the desired degree of damage. In order to successfully perform the build-ing construction analysis, the imagery interpreter must have a general knowledge of roof types and construction support systems. See pages 18 thru 20.

6. DAMAGE ASSESSMENT.

During the post-attack phase, the imagery interpreter is required to prepare various types of studies and reports from post-strike photography. Pre-strike photography will generally be required for comparison purposes. The damage assessment information generated by the 11 may be used to determine whether the target has been sufficiently neutralized or whether another strike will be required to evaluate. weapon effective-ness and to make estimates of production loss.

a. Post-Attack Studies.
(1) Limited Damage Assessment.

The limited damage assessment is conducted immediately after the attack and is usually reported verbally because of the time requirement. This assessment provides a near immediate determination of the need to reattack the target.

(2) Detailed Damage Assessment.

This assessment consists of a detailed analysis of damage inflicted on the target. The analysis is conducted from post-strike photography, using pre-strike photography as a basis for comparison. A tabular record of damage noted during the analysis is prepared and is referred to as a Damage Schedule. The Damage Schedule and any other information reported in the detailed damage assessment allows for a very careful determination of possible need to reattack the target, and in the case of an industrial target, it provides the industrial analyst with essential information required to make an estimate of the effects of the attack on production.

(3) Repair Studies.

Repair studies are conducted on a periodic basis after a target has been attacked. The compilation of these studies over a period of time indicates the rate of repair within an industrial facility. The most important structures and functional areas within a complex will be reconstructed first if repairs are undertaken. On the other hand, A complete lack of repair activity may be equally revealing to the analyst.

(4) Weapons Analysis.

This study is not conducted by the imagery interpreter but by a trained weapons analyst. The detailed damage assessment will provide information used by the analyst in arriving at his conclusions. In the study, the analyst will assess the weapons used against a target from both an economic and effectiveness standpoint.

b. Damage Classification.
(1) Total Damage.

Total damage is the total effect of an attack. It includes physical damage to structures and equipment, loss of contents such as stock and material in process, and the loss of manpower. Obviously, it is far beyond the capability of the imagery interpreter to assess total damage. This will normally be done by the analyst using input from all sources, including the detailed damage assessment made by the imagery interpreter.

(2) Visible Damage.
Visible damage is that portion of the total damage which can be detected from aerial photography. Reports on visible damage will include damage to structures and physical plant facilities. In essence, the limited damage assessment and the detailed damage assessment are both assessments of visible damage.
(3) Structural Damage.

Structural damage, in framed buildings, is defined as damage in-volving the collapse, sagging, or lateral distortion (exceeding 12 inches) of the main framework. Any part of the main framework which is visibly out of alignment should be considered structurally damaged. In order to classify any damage to the framework as structural damage, the evidence of distortion must be real.

(4) Superficial Damage.

Superficial damage in a framed building is the stripping of roof material or damage to those parts of the frame not considered as being a part of the main framework.

Roof disturbance is widespread minor damage to the roof without actual stripping. It includes groups of small holes which are indi-vidually too small co mark on an overlay. Although this type of damage is not normally measured in routine reporting, its mention in the Remarks Column of the Damage Schedule may be helpful to the analyst.

(5) Destroyed Damage.

Destroyed damage is descriptive of damage which is so severe that it is beyond the normal expectancy of repair.

(6) Gutted.

Gutting is extensive, severe fire damage to the contents of a building, with only superficial damage to the containing structure.

If doubtful of the severity of damage, it should be placed in the lesser category. An assignment must be made in all cases. Doubts and inferences can be fully expressed in the remarks.

c. Causes of Damage.

Assessment of the causes of damage completes the picture desired by the economic analyst, and it is of primary interest to the weapons analyst. For reporting purposes, the causes of damage may be classi-fied into 4 categories.

(1) HE (high explosive).

HE damage is caused by explosion regardless of how initiated.

(2) Fire.

Fire damage is caused by combustion, however ignited.

(3) HE plus Fire.

This is damage caused by a combination of both HE action and fire. Visible evidence of both forces must be present regardless of the weapons involved.

(4) Causes not Assigned.

This describes damage which is real in severity and extent, but the evidence for classifying the destructive force is insufficient or lacking.

PRINCIPLES OF CONSTRUCTION

7. CONSTRUCTION SUPPORT SYSTEMS. The fundamental problem in building construction is using a structural system which will support the loads caused by materials and external forces. The system selected attempts to reconcile the peculiar requirements of a building (functional and aesthetic) at the least possible cost. It is important to understand that the engineer designs the support for the loads essentially created by the weight of the building which in turn is a function of the purpose of the building. The exception ' to this generality is when the building houses overhead cranes and other lift equipment. The following are examples of support systems commonly used in industrial building construction:

(1) Simple Support. This category includes most of the frame and truss support systems in which loads are transferred through a system of vertical and horizontal members to the ground. This system is some-times referred to as the post and lintel system. Probably the most effective and common system is the truss which distributes the load of the building over a number of structural support elements thus reducing the load on the main column and increasing the load capacity of the frame. Occasionally, for light structures, walls will support the load. In this case the walls are called "load bearing walls" which have a high tendency to crash or buckle. In addition, earthwork and structural buttresses are sometimes used to reinforce the support system of a building, especially in the case of load bearing walls. The structures that use the support system outlined in this paragraph may range from Gothic cathedrals to the warehouse type of building.

(2) The Arch. The arch provides a relatively low cost support system when large open volume is required. Examples of the arch support system can be found in single level structures such as auditoriums, factory assembly areas, shops, hangers and warehouses. The arch supports its own weight and the weight of the roofing material continously through-out its span. This is different from the simple support system mentioned in paragraph (1). Because of the load carrying limits, this system is rarely used for multilevel construction.

(3) Cantilever. The cantilever is a frame support moment arm. This means that one end is supported by the other. it is most often used in the construction of overhead passages, corridors, cranes, and bridges. Today, there are examples of cantilever construction at some airports. It can sometimes be detected by the fact that part of the frame extends outside the roof covering. Its industrial application in building construction is limited. by its load bearing capacity.

(4) The Dome. With the discovery of new plastics, fibers, glass -and metal alloys, new systems of support have been developed to utilize the unique characteristics of these materials. A variety of unconven-tional geometric shapes (spheroids for nuclear reactors and new domes) are being produced to more closely complement the functional specifi-cations of industrial plants while attempting to minimize the cost of construction.

(5) Composite. When the simple support system the load bearing wall are combined, a composite support system is established. This type of construction is becoming less popular.

(6) The Rigid Frame. The rigid frame is the most important type of construction. In the rigid frame, all loads are concentrated at specific points in posts or columns and carried to the ground. The wall in this type of construction provides protection from the elements and privacy only. In short the wall performs no structural function.

(7) There are many changes which occur in this field and it is the responsibility of the image interpreter to keep abreast of the changes. One system not mentioned that may play an important role in industrial construction in the future is called the stressed skin type of construction. In this system all the loads and forces are carried by cohesion in a very thin shell. The American pavilion at EXPO 67 utilized this system. An egg incorporates this principle.

8. ROOF TYPES.

a. Roofs may assume many and varied shapes and it would be difficult to categorize each specifically. A knowledge of the more commonly seen types is necessary because the construction materials used play a part in the assignment of a combustibility classification. For examples of the more common roof types see pages 18, 19 and 20.

b. An additional consideration when assigning a combustibility class-ification is the number of trusses within a structure. A truss is defined as an assemblage of light members to form a rigid framework for spanning long distances.

c. Trusses are divided into four types: (1) Triangular. (2) Curved. (3) Flat. (4) Rigid and hinged arch.

Roof Supports (See Above Illustration)
Beam:
A horizontal membr supported at each end desinged to carry a load over an opening.
Truss:
An assemblage of light members

to form a rigid framework for spanning long distances.
Purlin:
A horizontal member spanning from truss to truss supporting the rafters.
Rafter:
Light member to carry roof material.
Chord:
The upper and lower members of a truss.
Brace:
An inclined member which forms a triangle thereby adding stiffness.
Span:
The distance from support to support in the direction of the main framing members.
Spacing:
The distance from support to support in the direction perpendicular to the main framing members.

DEFINITION AND USE OF TERMS FOR INDUSTRIAL INTERPRETATION

The definitions contained in this Supr should not be considered as precise definitions which are universally applicable. When reading the definitions, consider them from the standpoint of an imagery intepreter engaged in industrial analysis.

BASIC INDUSTRY:
A basic industry is one which is within the primary level of production and which is engaged in the extraction and/or initial processing of raw materials derived from natural resources. In some cases, a basic industry may produce finished products for final consumption. The majority of the products of a basic industry, however, are semifinished products which are consumed by other industries. The products of a basic industry are unique in that either substitutes for them do not exist, or potential substitutes are not economically feasible for use. Excellent examples of basic industries are those which produce metals, such as the steel, aluminum, and copper industries.

ESSENTIAL INDUSTRY:
An essential industry is one which is engaged in production essential in some particular aspect to a nation or national effort. Industrial target analysis is primarily concerned with those industries essential to the prosecution of war. An essential industry may be a basic industry, or it may be within a higher level of production.

FLOW CHART:
A flow chart is a graphic illustration which shows the raw materials, processes, and sequences of operations involved in production. A flow chart may deal with an overall industry, such as the aluminum industry (extraction of bauxite, production of alumina, reduction of aluminum metal), or it may deal with some defined segment of the overall industry, such as the production of alumina. The term flow diagram is a frequently encountered synonym for flow chart.

FUNCTIONAL AREA:
A functional area is a physical area within an industrial installation in which all equipment and facilities are devoted to performing a major function essential to industry.

INTEGRATED INDUSTRY:
An integrated industry is one in which a single industrial installation has the capability to process all raw materials into the completed product, whether a semifinished product or a finished product. This definition is not in complete accordance with the classical definition of an integrated industry as used by the economic geographer, but it is a useful working definition from the standpoint of the IT engaged in industrial target analysis.

NONINTEGRATED INDUSTRY:
A nonintegrated industry is one in which a single installation performs one or more processes which contribute to the industry's product, but which cannot produce the completed product at a single installation. In many cases, the final process consists of the assembly of components or subassemblies into a finished product at a separate industrial installation having as its sole purpose the performance of the assembly function.

INDUSTRIAL CATEGORIES

1. EXTRACTION INDUSTRIES

  • Excavations, mine headframes, ponds, and derricks.
  • Piles of waste.
  • Bulk materials stored in piles, ponds, or tanks.
  • Handling equipment such as conveyors, pipelines, bulldozers, power shovels, or mine cars:
  • Buildings few and small in size.

    2. PROCESSING INDUSTRIES

  • Facilities for storage of large quantities of bulk materials in piles, ponds, silos, tanks, hoppers, and bunkers.
  • Facilities for handling bulk materials such as conveyors, pipelines, cranes, and mobile equipment.
  • Large outdoor processing equipment such as blast furnaces, cooling towers, kilns, and chemical processing towers.
  • Provision for large quantities of heat or power as evidenced by boiler houses, oil tanks, coal piles, large chimneys, many stacks or transformer yards.
  • Large or complex buildings. Piles or ponds of waste.

    a. Mechanical Processing Industries

  • Few pipelines or closed tanks.
  • Little, fuel.
  • Few stacks.
  • No kilns.

    b. Chemical Processing Industries

  • Many closed or tall tanks, including gasholders.
  • Many pipelines.
  • Much large outdoor processing equipment.

    C. Heat Processing Industries

  • Few pipelines or tanks.
  • Large chimneys or many stacks6
  • Large quantities of fuel.
  • Kilns.

    3. FABRICATION INDUSTRIES

  • Rarely facilities for storing or handling bulk materials.
  • Little outdoor equipment other than cranes.
  • Little or no waste.
  • Large or small buildings.

    a. Heavy Fabrication Industries

  • Heavy steel-frames, one-story buildings.
  • storage yards with heavy lifting equipment.
  • Rail lines entering buildings

    b. Light Fabrication Industries

  • Light steel- and wood-frame buildings and Vall bearing (load-bearing wall) multi-story buildings.
  • Lack of heavy lifting equipment.
  • Open storage rare.

    ELECTRIC POWER INDUSTRIES

    1. Types of Power Stations.

    a. Thermal powerplants.

    (1) Fuel. Coal, gas, oil, wood, or peat are burned under a boiler to create steam. Coal, being the cheapest, is the most widely used fuel. Stockpiles of coal are easily seen on photos. They often appear as dark- toned heaps close to a railway or other means of transportation. Some type of conveyer system will bring the coal from the stockpile to the boiler house. Where oil or gas is used as fuel, large storage tanks will appear in the vicinity.

    (2) Cooling water. Where the supply of water is limited, water must be cooled before it is used again. This is done by a spray pond or cooling tower. River, canal, or sea water is used to condense steam, for re-use in the boilers. Cooling towers are used where natural running water is not available; in this process, a continuous cloud of steam is emitted. Cooling ponds are recognized by the dividing walls, spraying systems, and pump houses.

    (3) Boiler house. Here the fuel is burned, converting water into steam. Almost without exception, the boiler house is the tallest and largest building in the power station. Smokestacks are either adjacent to or extending through the top of the boiler house.

    (4) Generator house. This is a long, narrow building which is smaller and lower than the boiler house and usually adjacent to it. Here the steam is piped to the turbines which, when activated, rotate the generator. Thus, the latent energy of the fuel is converted into electrical energy.

    (5) Pump houses. These small rectangular buildings, sometimes difficult to recognize, are located near the cooling water inlet or cooling ponds.

    (6) Gas engine (internal combustion) power stations. These are usually found at blast furnaces and steel works. Gasoline engines are used to drive generators which supply electric power for the works. Little can be obtained from photographs. In some cases the pipelines carrying the gas from the cleaners or the pump house can be seen enter-ing the building and sometimes the narrow exhaust chimneys can be distinguished.

    b. Hydroelectric plants. Hydroelectric plants may be generally classified in two broad types: consolidated and separated.

    (1) Consolidated hydroelectric plants are those with the power-house located adjoining or at the base of the dam.

    (2) Separated hydroelectric plants are those with the powerhouse located downstream or at a considerable distance from the dam.

    Dams will vary in design and size according to the purpose or pur-poses, drainage area, variations in flow of the body of water, and the topography of the site. Dams may be categorized as high or low dams, with approximately 100 feet as the dividing line between the two. The distance the water falls is related to the force exerted on the turbine. This relationship is termed "head" or "head of water. " Usually a plant at a high dam, using a high head of water, is a high head plant. Where the plant is associated with a low dam, the plant is usually called a low head plant. Although this is the usual terminology, there are exceptions.

    c. Nuclear generating plants. There are not enough full-scale, commercial-type nuclear electric plants in existence to establish a definite set of recognition characteristics. The Atomic Energy Commission conducted a Reactor Development Program under which at least five different types of reactors were constructed. Except for the reactor at Shippingport, PA., these units are of pilot-plant size. These pilot plants are just large enough to test principles and design data for future scaling up.

    One of these pilot plants is at Lement, Ill. This plant uses the "direct boiling" type reactor. The unique feature of this boiling water reactor is that live steam is actually generated in the uranium core by nuclear heat and piped directly to the turbine. In effect, it operates very much like the coal-fired boiler in a conventional powerplant. Based on a knowledge of the electric power industry in general and the existing pilot nuclear generating power plants it is possible only to theorize on the recognition characteristics of a full-scale, commercial nuclear generating plant.

    2.Transformers and Switching Stations. Transformers are rectangular, solid-appearing objects difficult to detect because of their small size. The switching gear and the necessary wiring for the transformers and switches are supported on a framework, usually steel, which gives a lace- like effect. Their object is to step down voltage for distribution at a lower voltage or to step it up for distribution at a higher voltage. On photographs of open air stations, the interpreter can gain information on the origin and destination of overhead powerlines leading from the station. They present an open lattice-work, appearance. The closed type, housed in a building, is more difficult to detect, although powerlines may indicate its presence.

    If a local community consumes this power, a transformer station is not necessary because the consumer will have a transformer situated near him. Cooling systems for the large transformers are required be-cause of the amount of heat produced. They are often so close to the transformer that they appear to be a part of it, and an overestimation of the length of the transformer is quite possible. The transformer station may be protected by blast walls in wartime.

    3. Grid and Transmission Lines. Electric current is transported by means of buried cables or overhead powerlines. Newly-laid cables can be traced by the disturbed earth of the cable trenches seen and traced on good, large-and medium-scale photos. Given good shadow, the type and number of insulators and the type of pylon can also be determined. At times special pylons are needed and appear heavier in design.

    4. Flow of Power. On the following pages are schematic charts which illustrate the flow of power: Electric power flow chart, hydroelectric ,generating plant and distribution system, thermal and internal combustion electric plants, industrial coolers, and unloading and conveying.

    COKE, IRON, AND STEEL INDUSTRIES

    1. Steel is essentially a combination of iron and carbon. Iron alone does not possess enough strength and hardness for the tools and machinery that must be made from a strong, hard material. When iron is combined with a small amount of carbon (usually less than 1 percent), the result is a useful metal called carbon Steel. Carbon alone cannot give steel all of the special properties demanded by modern industry. Special elements must be added to molten steel to obtain these improved properties. Almost every type of steel must be treated by heat or by working to achieve its improved qualities.

    2. The five basic materials used in the manufacture of steel are iron ore, coal, fluxes (primary limestone), oxygen, and refractories.

    a. Iron ore is the term applied to iron bearing material in which the content of iron is sufficient to be commercially usable. After the continuous drain of high grade iron ore had depleted the supply by the end of the Second World War, efforts were made to upgrade ore quality by crushing, screening, and washing the ore to make it more suitable for the manufacture of iron (ore having in excess of 60 percent iron). This whole process is known as "beneficiation." Beneficiation of iron ore takes two forms:

    (1) Sintering: Particles of iron ore too small for use in the blast furnace (furnace used to smelt iron ore into iron). are fused together and then broken into pieces of ore of usable size.

    (2) Pelletizing: Low grade iron ore is crushed and then ground into a very fine powder. This powder is passed over a series of magnetic separators that collect the magnetic iron ore. A suitable binding agent is added to the powder, which is then formed into pellets. These pellets are then baked and are ready for the blast furnace. To pelletize non-magnetic ore, the same process is used except that the finely ground ore is added to a solution which separates the iron ore from the waste materials.

    b. Coal supplies more than 80 percent of the iron and steel industry's total heat, requirements. Additionally, coke (bituminous coal heated in the almost complete absence of air) is used in blast furnaces to manufacture iron. For each ton of pig iron produced, 1300 pounds of coke. are needed.

    c. Fluxes. Additives used in metallurgical operations which separate the impurities in the ore by fusing, such as chemically combining or physically mixing, is the process called smelting. Many impurities associated with iron ores are difficult to melt. If these should remain unmelted, they would retard the smelting operation and interfere with the separation of the metal and the impurities. These substances make the impurities more fusible. Flux also acts as a substance with which these impurities combine in preference to the metal. Either limestone or dolomite may be used as a blast furnace flux. Availability and cost are the most important factors in choosing between them. Limestone is also used in smaller quantities as a flux in furnaces where iron is refined into steel.

    d. Oxygen is used in most of the standard mill processes from the blast furnace through the finished product. Essentially, oxygen is directed on the surface of molten iron to support combustion and to oxidize the undesirable elements (carbon, silicon, manganese). Almost, 2000 cubic feet of oxygen is consumed per ton of steel. The introduction of oxygen to furnaces has become important in substantially increasing production rates (over 100 percent in some instances) from existing equipment. Some steel companies own their own oxygen production facilities, and others have a supplier's production plant on, or adjacent to, their property.

    e. Refractories can be defined as nonmetallic materials that will withstand severe or destructive conditions at high temperatures. They must withstand chemical attack, molten metal and slag erosion, thermal shock, and physical impact. Refractories are the chief materials used by the steel industry in the construction of furnaces and in the lining of retaining vessels, as well as in flues or stacks through which hot gases are conducted. Raw materials for refractories are crushed, ground, and screened to the proper size for use in brickmaking. The materials are then blended in the proper proportions, thoroughly mixed (often with binders added), and prepared in batches for making brick. The most common methods of making brick are power pressing (clay pressed into prepared molds under pressure), extrusion (clay forced through a die and then cut to desired lengths), and hand molded (for specially shaped bricks). After one of these processes, they are kiln dried and are then ready for use.

    3. The Making of Coke. Coke (coal heated in the absenceof air) has several advantages over coal as a fuel in ironmaking. Because of its porosity coke burns rapidly, inside as well as outside, and produces a very intense heat. Also, its structure can support the heavy. weight of the iron ore and limestone (flux) on top of it. Therefore, the coke allows air to pass freely through the blast furnace and speeds up com-bustion. The process of making coke is called the "Coal Chemical Process."

    a. Coal chemical coke ovens are rectangular and may be 30 to 40 feet long and 6 to 14 feet high. However., they are only 11 to 22 inches wide. As many as 100 of these may be set in a "battery" for ease in loading (charging) the coal and unloading (discharging) the I coke. These batteries also make possible a concentrated heating plant. Gas is heated in regenerators (located under the ovens) and then ignited in vertical heating flues in the oven walls. The products of the combustion cross over the top of the ovens and down the vertical heating flues of the other side, and from there back to the regenerators. Every 20 to 30 minutes the flow of gas is reversed to obtain uniform heating.

    b. A modern oven can receive a charge of 16 to 20 tons of coal through ports in the top. The ports are sealed off,, and the coal is heated and begins to fuse., When the coking is finished, in about 17 hours, the end doors of the oven are opened, and a rammer forces the entire charge of coal (about 12 tons) into a waiting "quenching can." The load of coke is then taken to a "quenching tower," where it is watered by overhead sprays to prevent further burning.

    c. The volatile products that pass off during the coking process are piped to a chemical plant, where they are treated to yield gas, tar, ammonia liquor, ammonia sulfate, and light oil. Some of the gases produced are returned to the coking ovens and other processes in the steel mill for fuel.

    4. The Making of Iron. The first step in the conversion of iron ore into steel takes place in the blast furnace. in this tall, cylindrical structure iron is freed from most of its impurities. The blast furnace process consists of blowing great quantities of heated air up through a full furnace of descending iron ore, coke, and flux stone. The hot air entering the bottom of the furnace causes the coke to burn with an intense heat. The carbon of the coke unites with the oxygen in the air, forming carbon monoxide. As this gas rises through the charge, part of it combines with the oxygen in the iron ore and carries it off in the form of carbon dioxide, thereby "liberating" the metallic iron from the ore. The limestone flux is also being heated to a molten state. It combines with most of the impurities from the iron ore and coke to form a molten slag. The liberated iron trickles down through the charge, forming a pool at the bottom (hearth) of the furnace. The slag also drips down and forms a scum which floats on the top of the molten iron. This process takes 5 to 8 hours.

    a. Materials to be loaded (charged) are first weighed and then transported to the "top" of the furnace by self-emptying skip cars. The raw materials are fed into the furnace at regular intervals by means of a double bell arrangement, which prevents the escape of large volumes of gas.

    b. Located near the top of the furnace are exits through which the exhaust gases flow as they are generated in the furnace. These gases are cleaned and reused. At least 25 percent of these gases are used to heat the stoves which preheat the air used in the furnace itself. The remainder of the gases are used to heat other operations of the mill.

    c. As the charge descends through the "stack" of the furnace, it is preheated and most of thereduction of the ore takes place.

    d. The charge then arrives at the "bosh." Here the final reduction of the charge is completed and the fusion of both the iron and the slag takes place.

    e. The bottommost portion of the blast furnace is divided into two parts. The "hearth" contains openings for drawing off the molten iron and slag. Directly above the hearth are the "tuyeres." These are nozzles through which superheated air is blown into the furnace. The function of this air is to burn the coke contained in the charge in order to furnish the necessary heat and reducing gases for the process.

    f. Blast furnaces are lined with refractory brick, and this brick must be water cooled to withstand the high temperatures developed in the furnace. As much as 10 to 12 million gallons of water a day may be used to cool a furnace.

    g. The blast furnace process is continuous, with raw materials being continually charged to maintain a filled furnace, while the iron and slag are removed at intervals. As the molten iron is drained (cast) from the furnace, it is channeled through a series of trenches to "sub-marine" rail cars. These cars then carry it to the steel works, or it is cast into molds for future use. The slag is also removed and either dumped as waste or used in other industries (cement block, road construc-tion, etc.).

    h. The heated air supplied to the blast furnace is obtained by pass-ing quantities of compressed air through hot blast stoves before entering the furnace. Each furnace is equipped with three to four stoves (tall, cylindrical-shaped structures). These stoves are alternately fired and placed on blast, with one stove succeeding another in this sequence.

    i. To produce 1 ton of pig iron requires about 1.6 tons of iron ore, 0.65 ton of coke, 0.2 ton of limestone flux, .05 ton of iron and steel scrap, and about 4 to 41 tons of air. In addition to the pig iron, the furnace will yield 700 pounds of slag and nearly 6 tons of gases.

    J. As the water cools the blast furnaces, it picks up many impurities. The water is taken from the blast furnaces to "Dorr Thickeners," where the impurities are removed through sedimentation. Dorr Thickeners are circular tanks normally located close to the blast furnaces.

    5. The Making of Steel. Pig iron consists of the element iron combined with other chemical elements (the most common are carbon, manganese, phosphorus, sulphur, and silicon). In refining pig iron to convert it to steel, these elements must be either removed or their amount drasti-cally reduced. The chemical principle of oxidation is employed to con-vert pig iron into steel. Each steelmaking process has been devised primarily to provide a means of controlling amounts of oxygen supplied to the molten metal (bath) undergoing refining. The oxygen combines with the unwanted elements to form oxides, which either leave the bath as gases or enter the slag. Three basic processes are used to produce steel; the open hearth furnace, the electric arc furnace, and the basic oxygen furnace.

    a. Open Hearth Furnaces. Open hearth furnaces generally run from 100 to 400 ton capacity. Open hearth furnaces are housed in long build-ings designed and arranged to facilitate the loading (charging) of the furnaces, the making of the heat, and the handling of the finished molten steel. The furnaces are installed in a straight row down the center of the building. Designers prefer not to have over 12 furnaces in a row. Limestone and scrap steel are loaded into the furnace while the furnace is being fired. After the scrap starts to melt, molten pig iron is added. The charge then begins to "work" and becomes a uniform mass of metal. Impurities in the iron, primarily carbon, com-bine with oxygen and are carried off as gases. The melted limestone combined with impurities, such as silica and sulfur, forms a slag on top of the bubbling metal.

    (1) The part of the building in front of the row of furnaces is called the charging floor, which in modern mills is elevated about 20 feet above ground level. On the charging side close to the furnaces, a broad gage track has been laid to move "buggies" that carry the charge boxes loaded with raw materials. Parallel to this track is another track with a very wide gage on which the charging machines operate. These machines pick up the charging boxes containing lime-stone and scrap steel and load their contents into the furnaces.

    (2) Most open hearth shops employ a "hot metal mixer," which serves a dual purpose of having a supply of molten pig iron available and mixing successive lots of pig iron so that possible chemical irregularities are averaged. This mixer building is usually located at one end of the charging floor and is provided with either an over-head crane or an electric cradle car for bringing molten pig iron to the furnaces.

    (3) The part of the building behind the furnaces is called the pit area, or pouring floor. Steel and slag are taken from the furnaces at this location.

    (4) Additionally, a stockyard for solid raw materials will be located as close to the open hearth building as is conveniently possible.

    (5) The furnace itself is very low in relation to its length. In modern furnaces, oxygen is usually injected through two roof lances. in these furnaces between 450 and 2000 cubic feet of oxygen are consumed for each ton of steel produced. When oxygen is injected, it takes about 6 hours for a furnace to complete a cycle.

    (6) When the charge is finished, it is drawn off (tapped) into ladles to be poured into molds. The desired steel composition is attained by alloy additions either in the furnace, the ladle, or the mold.

    b. Basic Oxygen Furnaces. In a basic oxygen furnace steelmaking process, a jet of high purity oxygen is directed at high-speed through a lance into the molten iron. This oxidizes the impurities. An additional benefit is that nitrogen, which impairs the formability of steel for some end uses, does not enter the steel in significant amounts, as it would if air pressure were weak. The main advantages of this process are an approximate 50 minute tap-to-tap cycle and a product that is at least equivalent to the open hearth steel in every respect. The furnace can be turned 180 degrees from the vertical to both the charging and pouring, sides to assist in charging and discharging. Some of these furnaces can hold as much as 300 tons.

    (1) Each basic oxygen furnace building contains a charging floor elevated approximately 25 feet from the ground level. On this floor are control booths, and scrap charging cars containing tilting boxes. After these cars are loaded and weighed, they are positioned in front of the furnace which is tilted toward the scrap cars and charged. The furnace is then returned to the vertical and the hot metal added. At this time an oxygen lance is lowered into position. After it is positioned ignition is obtained and the blowing reactions begin. One minute later the flux is added and the process continues uninterrupted.

    (2) On the opposite side of the building and at ground level is the furnace aisle, which contains the ladles and slag pots into which the furnace contents are poured when the temperature and carbon content are correct. As the steel is poured from the furnace, alloys are added to the ladles.

    (3) In the teeming aisle (which is adjacent to the furnace aisle), the steel is transferred from the ladle into ingot molds.

    c. Electric Arc Furnaces. Prior to WWII most production in electric arc furnaces was confined almost entirely to quality steels. The produc-tion of simple carbon grade steels at that time could not compete with the open hearth process. Today a number of furnaces have the capacity of 150 to 200 tons and produce ordinary grades of steel at rates of more than 800 tons per 24 hours.

    (1) Electricity is used solely for the production of heat and does not impart any properties to steel. The electric arc furnaces has two major advantages: the electric arc can generate extremely high tempera-tures (up to 3500'0 F.) very rapidly, and oxygen is not necessary to support combustion. Therefore, the atmosphere within the electric arc furnace causes less oxidizing than in a fuel fired furnace. The quantity of oxygen entering the furnace can be controlled; thus, the presence of oxygen, compounds of oxygen with other elements, or other impurities un-desirable in fine steels can be materially reduced.

    (2) The furnace body is a circular shell mounted so the furnace can be tilted to pour off molten metal and slag. The charging of an electric arc furnace is facilitated by means of a removable top. Through this top are usually passed three large, cylindrical electrodes of carbon or graphite. The electric power for the furnace is supplied through a stepdown trans-former w1th rheostats to allow the operator to adjust the electrical current load.

    (3) The melting cycle is the most expensive in an electric arc furnace process because power and electrode consumption are highest during this time. The electrodes melt their way through the charge until they approach the bottom of the furnace, forming a pool of molten metal on the -furnace bottom (hearth). From this point on the charge is melted from the bottom by radiation, from the roof by heat from the arc, and by the resistance offered to the current by the charge. This continues until the metal is entirely melted

    .

    (4) Before tapping of the furnace,, the electrodes are raised to their, maximum height and the power shut off. A tap hole is opened and the furnace is tilted so the steel is drained off from under the slag into a ladle.

    6. The Fabrication of Steel. After the steel has been poured into molds and substantially solidified, it goes into a "soaking pit." The pit is a kind of furnace in which the metal is made soft and plastic for rolling by heating it to a uniform temperature throughout.

    a. The massive ingots go from the soaking pits to a rolling mill, which reduces them quickly and efficiently into blooms, slabs, or billets (semifinished shapes that can be handled easily by the finishing mills).

    (1) Blooms are generally square or rectangular in cross section, with that area measuring more than 36 square inches. Billets also are either square or rectangular in cross section, but are smaller than blooms. A slab is generally wider and flatter than a bloom.

    (2) Blooming mills are usually "two-high mills; that is, they have two heavy, grooved rolls similar in appearance to an oversized clothes wringer. The two rolls, revolving in opposite directions, grip the approaching ingot and pull it between the rolls, squeezing it thinner and longer. After the ingot has passed through, the rolls are adjusted to a closer tolerance and their direction reversed. The flattened steel is then rolled through in the opposite direction (its second pass), where it becomes still longer and thinner. From time to time betr sides will be "worked." Meanwhile, pairs of vertical rolls on the side also revolve to control the width of the bloom and to keep its edges properly shaped. After about 16 passes (within 5 minutes) an ingot 25 by 27 inches in cross section will be rolled into a bloom 9 inches square. The uneven ends are then sheared-off with sharp blades.

    (3) A "three-high" mill performing the above process has three rolls, but unlike the "two-high" mill these rolls are not reversed after each pass. The ingot is passed first between the bottom and middle rollers. Then it is raised on a table and goes back between the middle and top rollers, alternating back and forth this way until it is reduced to the right shape.

    (4) Some blooms are put through billet mills, where they are further reduced in size. Billet mills are usually continuous rolling mills. Instead of being passed back and forth between rolls, the ' steel moves straight ahead through a series of rollers which squeeze and work it into smaller and longer shape.

    (5) Rolling mills not only shape steel, they make it tougher and stronger. The steel in ingot form is a relatively weak mass of nonuniform crystals. Rolling breaks down these crystals and elongates them so that they become a closely packed group of fibers.

    b. The roughly shaped steel is now ready for the finishing mill. There are numerous types of finishing mills, usually named after the product rolled in that particular mill. The processes used are alike. Blooms, billets, or slabs are heated to the proper rolling temperature,, then passed through a series of rolls until the desired shape is obtained. Some steel, after being hot rolled, is taken to a cold rolling mill where it is again rolled to reduce it to a finished product. The steel is then shipped to a fabrication mill at a different location or within the steel mill complex itself.