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Tuesday, November 3, 2015
Asbestos cement pipe production history, methods, & properties Los Angeles and Orange County California
Asbestos cement pipe & transite pipe product history, production & properties: this article describes the manufacturing process used for production of cement-asbestos pipe.
Asbestos-cement pipe was widely used world-wide for water supply piping, sewer piping, even some chimney applications as well as in various industrial processes. Built and installed more than 50 years ago, asbestos-cement pipes remain in use in some locations today.
A variety of manufacturing processes were used for making asbestos-cement pipe and are described here, including the Mazza process, the Magnani Process, the Dalmine Process, and the Hiamanit Process used for Making Asbestos-Cement Pipes. Some of these methods were used and may also still be used to produce reinforced concrete pipes that do not contain asbestos.
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Cement asbestos materials: this article series describes asbestos cement products & materials and the history of their production and use.
[Click to enlarge any image]
This article includes text & data Adapted from Rosato (1959 out of print) on the production and use of asbestos-containing materials, adding photographs, inspection, repair and maintenance advice, and updates on asbestos hazards involved in the installation, repair, or demolition of asbestos cement products such as roofing and siding or asbestos millboard that remain in place on buildings.
Transite Asbestos pipes: a cement-asbestos product, were widely used for warm air heating ducts, especially embedded in floor slabs, also for gas fired heating appliance chimneys, and for water transport in some cities as well.
Asbestos-cement pipes have been used for many years. The comforts and conveniences of family dwellings and business establishments have required many thousands of miles of water pipes.
. Government and private enterprises use asbestos-cement pipes for such applications as fresh and sea water mains, gas mains, sewerage, mining operations, agriculture, electrical cables, venting flues, etc. See Figure 3.4 (above left) and also
see Transite Pipes, Chimneys & Flues
see Transite Pipes, Chimneys & Flues
and TRANSITE PIPE AIR DUCTS for identifying photographs and advice
Figure 3.4. Asbestos-cement in transit.
(Courtesy Johns-Manville Corp.)
The experimental manufacture of asbestos-cement pres-sure pipes was started in Italy in 1913. Progress was rapid and by 1921, asbestos-cement pipes had been accepted in Europe.
At that time, the British Ministry of Health ap-proved the use of the pipe for water-mains. They provided for loans for these pipes, with a repayment period of 30 years; this period represented the same period allowed for cast iron pipes.
This type of pipe gradually superseded both metal and ceramic piping in a large number of applications because of the fact that they are resistant to corrosion, impervious to and free from electrolytic action when buried in the earth, light weight, elastic, strong, resistant to compression, eco-nomical to install, and unaffected by temperature changes.
They are unaffected by the ordinary corrosive agents en-countered in soils and waters which attack metal pipes and cause their destruction in a few years.
Tests have been conducted on pipes after 30 years in serv- ice with the conclusion that they had retained their original properties. These pipes have a smooth, glossy, cylindrical internal surface, and offer very low hydraulic frictional resistance to the flow of liquids.
The Italit Mazza asbestos-cement pipes manufactured by Eternit, Genoa, Italy, are still in operation throughout the world. Their experimental data show that the carrying capacity of pipe is on an aver-age of 25 per cent greater than that of new cast iron pipes and 30 to 60 per cent greater than that of old cast iron pipes, all being of the same internal diameter.*
Manufacturing Processes used for Making Asbestos-Cement Pipes.
There are three principal processes for making asbestos-cement pipes; i.e., the Magnani, Dalmine and Mazza Processes, with each process having been named for its originator. A more recent process is referred to as the Hiamanit. This process was developed by the Hiamanit HÃ¼ttenwerke A.G., Duisburg, Germany.
The initial steps in the process of making pipe and conduits are similar to those employed in the wet mechanical process. Engineering progress provided for the development of pipe after the sheets and shingles had been manufactured.
* "Asbestos-Cement Pressure Pipes and Low Pressure Pipes," London, Eng. Asbestos Cement Products Ltd. (Italit Mazza).
Asbestos-cement pressure pipes are generally manufactured on costly and complex machines which are automati-cally operated by means of hydraulic and electrical controls. The pipes are built up of a continuous, uniformly thin and highly compressed film of asbestos-cement. See Figure 3.5.
From mechanical stirrers located above the pipe manu-facturing equipment, a mixture of asbestos and cement of low viscosity flows through specially prepared conveyors which are endless felt blankets. See Figure 3.6.
Mazza Process used for Making Asbestos-Cement Pipes.
The Adolfo Mazza process is the most important commercial process used in the manufacture of pipes. High production equipment permits recirculation of cutoffs. The Mazza machine is similar to other machinery for wet processing. The basic difference is that the Mazza machines are wider.
The accumulator roll which is a feature of the oher machines is replaced by a mandrel. The diam-eter of r ndrels varies from 6 to 250 in.
Because of their weight, the larger diameter mandrels are more difficult to handle. These large mandrels are usually mounted in pairs; one attached to each side of the machine. The machine per-mits wrapping on one mandrel, as the previously wrapped pipe is withdrawn from the other mandrel.
In the asbestos-cement sheet machine, the accumulator roll is weighed against the breast roll below it; the woven felt passes between them.
The full density of the stock is obtained at this contact point. In the Mazza machine, there is a pair of press rolls above the mandrel which is hydrau-lically loaded. They apply a much heavier pressure on the pipe being formed than would be possible with the usual arrangement.
A second woven felt runs between these rolls and the mandrel in order to distribute the pressure and to provide a cushion to prevent damage of the pipe as it is formed. The result is that a higher density asbestos-cement product is obtained. Generally, a one or two cylinder vat is used in manufacturing pipes as compared to multi-vat arrangements for sheet producing equipment.
Figure 3.5. Front view of large asbestos-cement pipe machine.
Completed 13-ft. length of pipe is shown on mandrel at left of machine. Empty mandrel has just been swung into position against felt blanket. Cradle in foreground contains newly-made pipe.
(Courtesy Johns-Manville Corp.)
Magnani Process used for Making Asbestos-Cement Pipes.
In the Magnani process, a plastic paste mix rather than a slurry is used. It requires the lowest capital investment of the various methods.
It is necessary that the mixture flow slowly under gravity, but it must not be too thin in order to eliminate running.
The mixing of the cement and asbestos is performed by a number of different conven-tional procedures which includes those used in the wet mechanical process.
The stock is usually fed to the head box above the forming machine after it has been prepared.
Figure 3.6. Rear view of pipe machine. Slurry tank is in view.
(Courtesy Johns-Manville Corp.)
The machine consists of three separate units; the stock manufacturing unit, the compression operation unit, and the unit that is concerned with removal of the mandrel from the pipe. The first unit consists of a stock slightly wider than the length of the pipe.
The trough used is a shallow "17," with the side toward the mandrel almost horizontal. A steel backer roll is located below the lip of the trough, and moves horizontally in relationship to the mandrel. This procedure permits the increasing thickness of stock on the mandrel while maintaining pressure against it.
The mandrel serves the same function as the accumulator roll in the wet me-chanical process. It is a hollow steel or cast iron tube, perforated over its entire surface. Its ends are closed and fitted with vacuum tube connections. The trough is filled with the stock in the first operation. A mechanical or manual spreader is used to distribute the stock evenly.
The mandrel is wrapped with a strong filter cloth. After the vacuum has been drawn on the mandrel, the mandrel is rotated at a slow speed; the stock is hoed into the nip between the mandrel and the backer roll. Because of the suction, stock builds up on the mandrel, and it is partially dewatered. The backer roll smoothes the surface and compresses the stock as it is deposited. Buildup continues to a predetermined thickness.
A mandrel with its formed asbestos-cement pipe is then removed from the machine. It is placed in a compression unit which contains two rollers. One of the rollers is in a fixed position and the second roller is the pressure roll. Vacuum is applied to the mandrel during this operation.
A combination of pressure, rotation, and suction will compress the material and release more water from the stock. The rolling of the tube continues after the vacuum has been removed in order to permit the pipe to enlarge slightly. It is then transferred to the third unit and the mandrel is with-drawn. Wooden forms are usually inserted in the pipe in order to maintain its true shape until the cement has com-pletely set. The final product is smooth on its exterior, uni-form in wall thickness, and straight.
Dalmine Process used for Making Asbestos-Cement Pipes.
The Dalmine process is made up of one or more banks of parallel narrow wet mechanical machines each having a width of approximately 50 in. and operating simultaneously. This complex process permits manufacture of long pipe, independent of machine width.
In this process, the accumulator roll is replaced by a smooth tubular steel mandrel. It is angled to the axis of the small wet machine and it is removable. The roll moves across the machine as the pipe is built up. The stock is placed on the mandrel in a spiral form with each successive layer overlapping the pre-vious one. Presure is applied against the mandrel during this operation. After the desired thickness has been obtained, it is calendered and the mandrel is withdrawn.
Hiamanit Process used for Making Asbestos-Cement Pipes.
The Hiamanit process can be used for the manufacture of concrete and reinforced concrete pipes, as well as for asbestos-cement pipes. The equipment is such that any type of pipe can be made without modification. Its distinctive characteristic is the use of a rolling process which consists of a system of rollers. Lightweight-high burst pipes can be manufactured. A cloth belt is stretched over the roller. Te roller system is hydraulically actuated.
The pipe mandrel is perforated and covered with a thin fabric to prevent the cement mixture from entering the per-forations. The core is connected to a vacuum pump which is similar to the Magnani process. A quantity of the thick stock sufficient for the required length and thickness of the pipe is spread out on the belt in the form of a fiat sheet.
The pipe is formed immediately when the rolling opera-tion starts. It is compressed to the desired density by the hydraulically actuated pressure roller. Water is removed from the inside of the pipe by means of a vacuum and from the outside surface through the cloth belt. When the rolling is completed, the core is removed and an auxiliary core is inserted; it remains in the pipe until it sets.
Saturday, May 30, 2015
Guide to Identifying Asbestos Cement Transite Water Pipes & their Hazards in buildings
This article explains the potential health hazards (asbestos exposure by ingestion) as well as practical problems (fragility, collapse, expense of replacement) of cement asbestos transite pipe water piping and we provide citations to authoritative studies of this question. This document assists building buyers, owners or inspectors who need to identify asbestos materials (or probable-asbestos) in buildings by simple visual inspection.
We provide photographs and descriptive text of asbestos insulation and other asbestos-containing products to permit identification of definite, probable, or possible asbestos materials in buildings.
Transite pipe or asbestos-cement pipes were used for water supply systems in some municipalities up into the 1970's in the U.S. and probably in other countries. In some cities (Ellwood PA for example), the transite water mains were found to be unable to reliably withstand high water pressures (up to 225 psi in Ellwood according to one of our readers) and the pipes were easily broken.
Asbestos fibers may be ingested from water supplied through transite water piping. Transite piping deteriorates over time, releasing asbestos fibers from the interior of the pipe into the drinking water flowing through that conduit. The level of health risk from ingested asbestos fibers is uncertain and probably low. An NIH report prepared by industry experts concluded:
The work group believes that the cancer risk associated with asbestos ingestion should not be perceived as one of the most pressing potential public health hazards facing the nation.
However, the work group does not believe that information was sufficient to assess the level of cancer risk associated with the ingestion and therefore, this potential hazard should not be discounted, and ingestion exposure to asbestos should be eliminated whenever possible.
Another study by Millette JR et als reported
Cancer mortality for the population census tracts of Escambia County, FL, which use asbestos-cement (AC) pipe for public potable water distribution, was compared with cancer mortality data collected from census tracts in the same county where other types of piping materials are used. An analysis of covariance was run to test for differences in standard mortality ratios for seven cancer sites among three potential asbestos exposure groups based on AC pipe usage.
Twelve variables representing nonexposure-related influences on disease rates were combined in four independent factors and used as covariates in these analyses.
No evidence for an association between the use of AC pipe for carrying drinking water and deaths due to gastrointestinal and related cancers was found. The limitations on the sensitivity of the analysis are discussed.
- ASBESTOS DUCTS, HVAC - Guide to Identification of Asbestos Materials On or In Heating and Cooling Duct Work: carbon monoxide hazards of transite chimneys and vents
- TRANSITE PIPE AIR DUCTS - Hazards of Asbestos-containing Transite Pipe HVAC Ducts: duct collapse, mold, radon, asbestos fiber release
- TRANSITE PIPE CHIMNEYS & FLUES - Guide to Identifying Asbestos Transite Chimneys & Flues & their Hazards in buildings
- TRANSITE PIPE WATER SUPPLY PIPING - Guide to Identifying Asbestos Cement Transite Water Pipes & their Hazards in buildings
While an expert lab test using polarized light microscopy may be needed to identify the specific type of asbestos fiber, or to identify the presence of asbestos in air dust or water samples, many asbestos-containing building products not only are obvious and easy to recognize, but since there were not other look-alike products that were not asbestos, a visual identification of this material can be virtually a certainty in many cases. Links to U.S. government and other authoritative research and advice are included.
A more immediate water quality hazard has been detected in some vinyl-lined transite water pipes - Tetrachloroethylene. A report on the Sandwich water district on Cape Cod in Massachusetts reported that
"PCE was detected in the distribution system at an annual average of 0.8 parts per billion, which is below the limit set by the U.S. Environmental Protection Agency (EPA). This substance leaches into the water from vinyl lined transite water pipe. In order to address this problem, in 2002 approximately 8,500 feet of water mains were sealed with an epoxy coating resulting in a dramatic decrease in PCE levels. "
Leaks in transite water supply piping underground can result in substantial water losses in districts where this piping was used.
Locating transite water supply mains: We've been informed that excavators complain that its lack of metal makes locating transite water pipes difficult - one cannot use ordinary metal detectors.
Of course a buried pipe of non-metallic material might be located if it is possible to insert a sending probe inside its length but on a water main this procedure is impractical. Contractors joke that they find transite pipe by using the metal bucket of a backhoe as a pipe detector.
Replacement costs for transite water supply piping: because of its age, leaks, fragility, and difficulty of finding transite cement asbestos water supply mains and water piping without also damaging it at the same time, owners of properties and communities served by cement asbestos water pipes (transite) can expect to face increasing costs to replace that piping.
Asbestos fiber release hazards during removal of demolition of transite piping are discussed
at TRANSITE PIPE CHIMNEYS & FLUES.
at TRANSITE PIPE CHIMNEYS & FLUES.
Incorrect spellings of transite piping or transite duct material that we've seen include transit pipe, transit ducts, Transide pipe, transide ducts, tranisite pipe, and transight pipe. "Transite" is the correct spelling.
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