Asbestos, a Johns-Manville Film

Johns-Manville Corporation made this film, probably in the early 1970s. After an account of how asbestos formed in the earth and the Greek name for it, it describes chrysotile and J-M's mine at Asbestos, Quebec, the open pit, and the mill's crushing, screening and aspirating stages. It then shows the grading and laboratory tests of the fibre at the J-M Research Center and the products made from it, such as asbestos-cement pipe, shingles, floor tile, friction materials, paper and insulation.

What it says about asbestos and health

It does not mention disease. It notes that dust is aspirated away and air is filtered in the mill, describing this as part of the process of recovering the fibre.

About this copy

Our copy is a transfer of a print from Johns-Manville's own film archive (box 04-03391), shown in full, 18:36 long.

Transcript

A machine transcript of the soundtrack, not yet checked against the film; names and technical words may be wrong.

It's still fresh and new looking after more than four and a half billion years in space. But we know if we travel back far enough in time that the seemingly ageless planet Earth has seen many changes. It had an especially violent beginning. So violent, in fact, that any solid minerals existing in the first billion years have long since vanished. Probably they were melted down in the heat, lost in the mists of early creation. Throughout the Earth's lifetime, the cooler surface has often yielded to the seething forces below.

Over hundreds of millions of years during which the surface formed a relatively thin crust, the continents and sea beds shifted thousands of miles in response to the upheavals of the underlying mantle and core. In one dramatic example of volcanic activity, molten minerals violently forced their way to the surface, then cooled and hardened into rock so far a well-known geological story but then during further disturbances the hardened rock became fissured later scientists believe hot mineral bearing water flowed through the fissures dissolving some of the surrounding rock this solution crystallized into a network of fibrous veins from this unusual geological event came a A most unusual mineral. Even before the dawn of the Iron Age, it was already proving highly useful to man. The ancient Greeks, with their well-known curiosity, investigated it and found its fine fibers could be spun into yarn, and it resisted fire. The Greek word for this unique mineral was asbestos. Today, at Johns-Manville, we call it asbestos the indispensable mineral asbestos fibers are flexible and soft yet the individual strands have greater tensile strength than many types of steel aside from small amounts produced in laboratories man has never been able to duplicate its unique combination of physical chemical and textile properties in one mineral several types of asbestos ore are found throughout the world.

Three are commercially important. Of these, the most useful is chrysotile. It is found in abundance in Canada in J-M's principal asbestos mine located at Asbestos Quebec. This huge open pit mine is one of the world's largest sources of chrysotile asbestos fiber. It is expected to go on producing through most of the 21st century. The fiber is processed here at the world's largest, most modern asbestos mill.

In a little more than 35 years, annual asbestos fiber production has been increased from 90,000 to more than 600,000 tons. A long-term recovery and expansion plan is in effect to meet the needs of the future. Enlarged facilities will be built at new locations as the perimeter expands. At present, the open pit is almost a mile wide and nearly 900 feet deep. Three shifts work around the clock six days a week to maintain the current level of production. Ten million tons of asbestos bearing ore mined and processed annually.

In its natural state, chrysotile asbestos is found in irregular crystalline veins. The The name crude is applied to this cross-vein material before the fibers have been opened or separated. Both crude and milled grades are subdivided into groups according to fiber length. The fibers have a chemical composition similar to the rock in which they are embedded. This means they cannot be separated chemically as by leaching or electrolysis, but must be extracted by mechanical means. The first and biggest step in fiber recovery is removing overburden, the barren rock, dirt, and low quality material.

In order to expose the underlying ore, more than three times as much overburden and waste, 30 million tons, is removed annually. When the asbestos-bearing rock has been exposed, it is broken up by drilling and blasting with modern liquid explosives. Giant power power shovels remove the ore-bearing rock. On the average, a twelve and a half ton bucket of this ore yields about three-fourths of a ton of usable asbestos fibers. A fleet of giant trucks transports the ore from the pit. The startling change from this original load of asbestos-bearing rock to the carefully graded fibers which result later is made possible through special fiber recovery methods.

Here, starting with the rock being dumped, are some highlights. First the ore falls down a chute into the jaws of the primary crusher. Next it moves to screens and secondary crushers. The finer fractions are conveyed to dryers and then to dry rock storage until needed at the mill. The asbestos-bearing rock is moved on shielded conveyors to the distribution point at the top of the mill. Inside this massive 14-story structure the asbestos fiber is recovered from the ore in a semi- automated operation in a series of crushing, screening, and aspirating stages.

Asbestos fiber recovery is a mechanical process. Here is the basic flow line. After the rock has been crushed to loosen the fibers, the crushed ore goes to the primary rock screen. The unseparated ore passes over the screen as the fines fall through. The released fibers are sucked up by the aspirator in a stream of air moving at 4,000 cubic feet per minute. The fibers are removed from the stream in the cyclone collector.

Here, the clean air stream moves out the top. The fibers, losing velocity, move downward. Meanwhile, the screened rock containing unreleased fibers is further broken up in the fiberizer. This is a vertical type hammer mill used to prepare the ore for further fiber release. In the fiber cleaning circuit, the paddle trommel screens out fine grit and de-dusts the fiber in the same operation. The dust is aspirated away, airborne, as the fibers fall down to the fiber screen.

Here, medium gritty material and short fibers are screened out. The longer fibers move on to the Bauer air separator which further separates grit from the fibers in a fast-moving stream of air at 8,000 cubic feet per minute. The cleansed fibers are again separated from the air stream by cyclone collectors. Then they move to the grater which screens out long or short fibers as required before final mixing. The overall The overall asbestos fiber recovery process requires the circulation and filtration of huge volumes of air for aspirating, cleaning, and de-dusting. This is accomplished in the huge fan room occupying the upper floor of the mill.

Here, three million cubic feet of air move through the bag filters each minute. Some or all of the steps in this basic process may be repeated, depending on the grades to be collected. The milled asbestos fibers are classified into some 60 standard grades. Other special grades are processed to meet the needs of particular industries. This, then, is the basic flow line of the asbestos fiber recovery process. As the last major component, the mixer helps form an homogenous, consistently uniform product prior to packing.

The packing operation is also automated. Packing methods include pressure packing, in which the fiber is accurately weighed, compressed, and extruded into bags. The user is assured that each bag shipped will meet specifications. Bulk shipments are also carefully controlled. The rigid standards are maintained by continuous quality control. For example, the Quebec standard screen test is used to determine fiber length and grade.

A 16-ounce sample is subjected to a controlled dry screening in a series of boxes with successively finer meshes. The prepared sample is placed in the top box, then shaken down during a standard time interval. After shaking, the amount of each fiber length caught on each screen is measured. The more long fibers caught on the top screens, the higher the grade of the sample. The Ro-Tap test is another method of measuring fiber length distribution. The quantity of fibers retained on each mesh is recorded as a percentage of the original sample by weight.

A color test may also be used to establish the relative whiteness of a fiber sample. The McNett test utilizes a wet screen technique to measure fiber length distribution. A weighed sample is washed down through four successively finer screens. After the water is drained, the fibers retained on each screen are recovered, dried, and weighed. The proportional amounts of each fiber length recovered are then expressed as percentages. The relative surface area of a fiber sample is obtained by the Blaine-Dyckerhoff apparatus.

A predetermined volume of air is automatically drawn through the fibers, which are loosely tamped into a cell attached to the equipment. The time required for the air to pass through the sample gives its air permeability as a basis for calculating its surface area. The crudy test separates spicules and bundles of crude fiber from a milled fiber sample. The well-opened fibers are carried upwards by a controlled flow of water, while the unopened fibers remain in the glass cylinder to be dried and weighed. The strength unit test evaluates the capacity of a milled asbestos fiber to impart strength to a steam cured asbestos cement product by breaking test pieces under flexure as a simply supported beam. The TAPPI test for drainage is important to the asbestos cement and asbestos paper industries.

A fiber sample is placed in a test slurry. The mixture is then added to a column of water and the water is pumped out. The rate of removal is timed, giving an indication of the drainage characteristics. The mill houses the fiber development department, which tests and evaluates new equipment and milling techniques. To help customers with grade selection and problem solving, sales service representatives are available throughout the world. At the J-M Research Center, the characteristics and uses of asbestos fibers are studied.

Facilities include this apparatus which calculates surface area based on the amount of nitrogen gas removed from the sample at the extremely low temperatures provided by liquid nitrogen coolant. This muffle furnace removes moisture from fibers at thousands of degrees Fahrenheit. The x-ray spectrograph is used to measure traces of other elements found in proportions greater than 1% of a given an asbestos sample. The apparatus relies on the digital timer, which gives results at electronic speeds. The emission spectrograph is a means of analyzing element traces less than one percent of a sample. Spectrograph alignment is accurate to within one millionth of an inch.

Other apparatus, such as the electron microscope, reveal hidden secrets that can can lead to product improvement and new uses. Here, a typical fiber grade is magnified thousands of times, clearly showing the strong fibers that are so effective as a reinforcement for other materials. As the needs of modern industry have expanded, asbestos has appeared in a wide range of applications suitable to its unique combination of properties. Long fibers are spun into yarn to lend strength and fire resistance to textiles asbestos combines easily with many other materials for example with cement it is formed and cured to make strong corrosion free pipe large diameter conduits tap water resources and convey wastewater the smaller diameters are installed for such uses as underground irrigation and sprinkler systems asbestos cement can also be extruded to form a variety of shapes it is highly suitable as a building material particularly for architectural siding asbestos cement shingles are dimensionally stable they provide fire and termite resistance as well as strength and beauty for the roofs and siding of quality homes many of today's caulking compounds contain asbestos some fiber grades are combined with plastics to make floor tiles for brighter interiors. Other J-M fiber grades have been developed for the asphalt industry, lending strength and bulk to roofing materials. Adding asbestos to asphalt paving in airport runways, highways, and bridge decks gives numerous benefits when a thin overlay of asbestos reinforced resurfacing asphalt is used.

Asbestos is almost irreplaceable in friction materials. Brake linings in in particular, depend on its strength and heat resistance. Asbestos reinforcement improves gasket materials. Asbestos is used to make many grades of paper, including fine papers for electrical insulation, protecting large generators, high voltage transformers, and everyday home appliances. This special asbestos paper is impregnated with a phenolic resin. later the paper is rolled into pipe to form a unique type of pipe used in the petrochemical industry asbestos is a principal ingredient in a wide variety of thermal insulating products such as the pipe insulation on this Arctic tanker because it is best known for its high resistance to extreme heat and fire it is hard to imagine modern industry without it new uses are constantly being developed. Here an insulation containing asbestos is being applied to a high-gain antenna for use in outer space.

On the surface of the earth or voyaging towards a distant planet, asbestos plays a unique role no other material can equal. As in past ages, so in the future that lies ahead. Asbestos will will remain the indispensable mineral in the service of mankind.