TUBERCULATION AND THE FLOW OF WATER IN PIPES

In a paper read before the Toronto convention of the American Water Works association, Nicho las S. Mill, jr., dealt with the subject of “Tuberculation and the blow of Water in Pipes,” with special reference to the deposits and growth in water mains. He divided into three classes the various deposits which lessen the carrying capacity of water pipes and conduits as follows: (1) Incrustations, commonly known as tuberculation or rust on unprotected or imperfectly protectod iron pipes; (2) deposits, growths on the inner surface of iron pipes, whether protected or unprotected, and of conduits, rock tunnels and other channels; the nature of the deposits dc pending on the chemical constituents or biology of the water or both; (3) accumulation of debris and mud in inverts, hollows and dead-ends. As to tuberculation: A pipe of small diameter is sometimes completely choked by the incrustation , while in large pipes the thickness the deposit seems to be limited to about one inch or one inch and a half--the increase, if any, being slight, owing to the density of the incrustation acting as a protection. This tuberculation will not oc cur when the iron is effectively protected by any means from contact with the water. As to the conditions under which tuberculation takes place : These are affected by the character of the pip coating, source of the water supply and the chem ical constituents of the water, separately and it' dividually, iu different localities. Tuberculation arising from rust, or oxidation of the iron in the pipes, and forming the characteristic limpets or nodules may be affected to some extent by microorganisms or the chemical constituents of the water. Highly alkaline waters, containing calcium and magnesium, may form deposits which seem to prevent tuberculation; but those deposits may in themselves be almost as objectionable as the rust nodules. No chemical treatment what ever prevents the corrosion of iron pipes. I he only effective treatment is to provide a coating for the iron which will preclude oxidation and with stand the .solvent action of certain waters upon the coating. It is perfectly possible, however, to remove the incrustation as it forms by scraping. The accompanying illustration shows the space occupied by rust in an iron pipe. Cleaning by scraping will remove that, as it will also remove incrustation due to alkalinity and biological for mat ions due to organisms, while flushing-scraping will do away with sedimentary deposits. Pipecoatings may somewhat prevent tuberculation; but only temporarily. Wherefore, to maintain pressures, as well as the quantity and quality of the sitpplv, periodical removal of the incrustation is necessary. The pipes must be attended to regularly and systematically. It may also be noted that, so far as Mr. Hill knows, “no pipecoating will prevent the development of slime, pipe-moss, sponges, etc " As to cleansing mains by scraping. “This method of removing incrustations and deposits has not been largely resorted to in this country up to the present time, although, in England, scrapers for cleaning mains have been in vogue for thirty years. In some places, where the crenothrix is encountered, the mains arc scraped annually. Spasmodic efforts have been made on this side of the water in past years—notably at Halifax, St. Johns, Boston, and a few other places in New England.” The gain in delivery reported at different places in Great Britain and Ireland as a result of scraping mains has varied from 300 per cent, to seven per cent. In several instances cleaning by scraping has been instrumental in saving costly new construction. In Boston the pipes cleaned were not the supply mains, but the 6-in. ami 12-in. distributing pipes. The scraping machine was “very successfully used, * The discharge of 6-in. tuberctilated pipes (says Mr. Dexter Brackett) was from twenty-five per cent, to thirty-five per cent, of the quantity which a clean-coated pipe might be expected to deliver, under the same head, and the discharging capacity of the pipes was more than doubled by the removal of the tubercles,” as has since been proved in many similar cases. The process of scraping is perfectly feasible. The cleaning of a section of 8-in. main at Far Rockawav. Queens borough. New York, showed a gain of thirty-three per cent. In the case of this main the incrustation was not continuous or oyer J/&-in. to 14-in. It was thick and covered a small area of the surface. In another case, that of a 48-in. main forming part of the Sudbury conduit in Boston after sixteen years’ use. a comparative test on the pipe before and after cleaning showed an increase of thirty per cent, in capacity. There were “no serious conditions, and it is well known the effect of surface roughness is much less in large than in small pipes. It was found possible to remove tubercles without injuring materially the original coating underneath them, and the original condition of the pipe was practically restored. The cleaning in this case was done by hand with old round pointed shovels and wooden scrapers made of oak.” It will lie found that the “rust tubercles so often occur separately or in combination with organic growths, that it is possible no treatment of water, of which, we now possess knowledge, will obviate an ultimate serious depreciation in the discharge of mains, and. hence, some process of removal or else reinforcement will have to be restored to. until such time as the interior of all our mains are enameled, or coated by some process which will preclude rust. Besides, it is sometimes impractical to use filtration or more expensive than securing a supply from another source, The development of these nodules in small embntities is sufficient to effect a startingly large reduction in capacity." How greatly the effective bead must be increased per square inch to overenjue the friction, needs no demonstration. It "increases inversely as the diameter. In addition, in a main of given size, a larger surface is exposed to friction. As the area of cross-section is diminished, the velocity for the same discharge must be greater, 'flic loss of head increases as the square of the velocity. Add to these the eddies caused by protuberances in the pipe and the concomitant energy expended in impact, caused by the unsteady motion of the particles of water, thus creating additional loss of head, and we see the cumulative effect produced. * * * It is now generally recognised that the loss of head caused by the friction iti pipes, increases with age, and, inversely, the discharge or capacity decreases.” The three causes of the variation of resistance and. more particularly, that arising from tht condition of the interior surface of a pipe, are: (i) The variation in velocity: (2) the variation in diameter; (3) the variation in the roughness of surface—i. c., the physical condition of the interior of the pipe. Tt must, also, be born in mind that, while filtration will retard further developments after the pipes have been cleaned, and may reduce all forms of organic growth, and certainly will reduce them materially, there are no data to confirm or deny the development of other forms in time. Filtration will not prevent the formation of rust-nodules. The subject of tuberculation and deposits in pipes has, therefore, a practical side of vital concern to the waterworks superintendent, since incrustation and deposits in water mains (generally classified as tuberculation) affect not only the aesthetic and potableness of a water supply, but. also, the earning capacity of a plant, The water is physically depreciated, and that depreciation can be expressed in dollars and cents. That being so, “it is surprising how little is spent on the upkeep and maintenance of distribution systems" "A diminution of pressure or capacity in the distribution and supply mains is continually met with supplementary extensions. There are very many instances where more money spent in maintenance would have saved heavy outlay for new construction, which, if paid for from revenues, forestalled other needed improvement or dividends, and. if paid for by bond issues, increased the fixed charges of the plant by an amount greater than the proper maintenance costs,” and it may well be asked how much at tention is paid to the pipe or distribution system. When once the water has been turned into a pipe-system, little more is paid to the condition of the pipes. Sometimes, it is true, small pipes fill up entirely, and then specimens are exhibited showing the growth of tuberculation. Again, the water becomes bad in one street, while it is good iti the adjoining neighborhood, and the result is attributed to “some mysterious agency." One of the great steps in advance, therefore, that lias been made in the designing of pipe-systems is the introduction of facilities for cleaning out the pipes at stated intervals of time—something necessary, not so much for the purpose of restoring the normal capacity of the pipes as for maintaining the purity of the water. Mr. Mill suggests, as a means, the advisability of equiping pipe-systems with manholes for the purpose of test, inspection and cleaning. An effective arrangement would be to tap ordinary 3-in. connections on either sid of a gate-valve located in these manholes. A small Venturi meter could always be inserted in the 3-in. line by means of flanged connections and set in gate-boxes, at a proper distance from the the connection, the flow in the pipe could be bypassed and measured through the meter, and the loss of head in a given section of main obtained by readings from the pressure gauges located in the various manholes. By means of adjustable throat-pieces the rate of flow could be adjusted at will. Another arrangement would be to have corporation-cocks for the pitometer connections, set in gateboxes, at a proper distance from the hatch-boxes, thereby avoiding any possible influence which the eddies caused by change in cross-section at the hatch-box might produce in the readings. The valves, too, might be placed in the manholes. Four-way hatch-boxes could be built for street intersections. Their form should be such as to create as slight a change in crosssections as possible. The cost of such arrangements would not be great. The question of deposits in mains seriously affects the estimates of the per-capita consumption based on infrequent gaugings or a single gauging made when a conduit or pipe-line is new. The effect of tuberculous growths in old conduits, such, for instance, as the old Hemlock lake conduit at Rochester, X. V., is certainly to retard the delivery. In 1876 gaugings were made on the then new conduit, whose daily capacity was given as 9.000,000 gal-. A water famine threatened in the summer 1890. when it was found that the delivery was only 7,142.000 gals.—twenty-one per cent, in fourteen years. Subsequent gaugings showed steady diminution up to 1895, when the deliveryhad fallen to 6,660,000 gals. It may be added that such reductions in delivery often begin very soon after a pipe line is put in service -even one or two years. It is also worth mentioning that estimates of consumption based upon the plunger-displacement of pump may be greatly excess of the actual use of water. Mr. Mill con eludes by pointing out that on the condition of the mains depends the value of a waterworks plant. “In some cases, where certain rules arc applied to hard water, this modification may cause an excessive reduction. On the other hand, the same formula may be inapplicable to waters conducive to heavy deposits. Thus still another argument is added to show how essential proper inspection is to the whole range of problems presented in the distribution of water in cities and towns.”

In a paper read before the Toronto convention of the American Water Works association, Nicho las S. Mill, jr., dealt with the subject of “Tuberculation and the blow of Water in Pipes,” with special reference to the deposits and growth in water mains. He divided into three classes the various deposits which lessen the carrying capacity of water pipes and conduits as follows: (1) Incrustations, commonly known as tuberculation or rust on unprotected or imperfectly protectod iron pipes; (2) deposits, growths on the inner surface of iron pipes, whether protected or unprotected, and of conduits, rock tunnels and other channels; the nature of the deposits dc pending on the chemical constituents or biology of the water or both; (3) accumulation of debris and mud in inverts, hollows and dead-ends. As to tuberculation: A pipe of small diameter is sometimes completely choked by the incrustation , while in large pipes the thickness the deposit seems to be limited to about one inch or one inch and a half--the increase, if any, being slight, owing to the density of the incrustation acting as a protection. This tuberculation will not oc cur when the iron is effectively protected by any means from contact with the water. As to the conditions under which tuberculation takes place : These are affected by the character of the pip coating, source of the water supply and the chem ical constituents of the water, separately and it' dividually, iu different localities. Tuberculation arising from rust, or oxidation of the iron in the pipes, and forming the characteristic limpets or nodules may be affected to some extent by microorganisms or the chemical constituents of the water. Highly alkaline waters, containing calcium and magnesium, may form deposits which seem to prevent tuberculation; but those deposits may in themselves be almost as objectionable as the rust nodules. No chemical treatment what ever prevents the corrosion of iron pipes. I he only effective treatment is to provide a coating for the iron which will preclude oxidation and with stand the .solvent action of certain waters upon the coating. It is perfectly possible, however, to remove the incrustation as it forms by scraping. The accompanying illustration shows the space occupied by rust in an iron pipe. Cleaning by scraping will remove that, as it will also remove incrustation due to alkalinity and biological for mat ions due to organisms, while flushing-scraping will do away with sedimentary deposits. Pipecoatings may somewhat prevent tuberculation; but only temporarily. Wherefore, to maintain pressures, as well as the quantity and quality of the sitpplv, periodical removal of the incrustation is necessary. The pipes must be attended to regularly and systematically. It may also be noted that, so far as Mr. Hill knows, “no pipecoating will prevent the development of slime, pipe-moss, sponges, etc " As to cleansing mains by scraping. “This method of removing incrustations and deposits has not been largely resorted to in this country up to the present time, although, in England, scrapers for cleaning mains have been in vogue for thirty years. In some places, where the crenothrix is encountered, the mains arc scraped annually. Spasmodic efforts have been made on this side of the water in past years—notably at Halifax, St. Johns, Boston, and a few other places in New England.” The gain in delivery reported at different places in Great Britain and Ireland as a result of scraping mains has varied from 300 per cent, to seven per cent. In several instances cleaning by scraping has been instrumental in saving costly new construction. In Boston the pipes cleaned were not the supply mains, but the 6-in. ami 12-in. distributing pipes. The scraping machine was “very successfully used, * The discharge of 6-in. tuberctilated pipes (says Mr. Dexter Brackett) was from twenty-five per cent, to thirty-five per cent, of the quantity which a clean-coated pipe might be expected to deliver, under the same head, and the discharging capacity of the pipes was more than doubled by the removal of the tubercles,” as has since been proved in many similar cases. The process of scraping is perfectly feasible. The cleaning of a section of 8-in. main at Far Rockawav. Queens borough. New York, showed a gain of thirty-three per cent. In the case of this main the incrustation was not continuous or oyer J/&-in. to 14-in. It was thick and covered a small area of the surface. In another case, that of a 48-in. main forming part of the Sudbury conduit in Boston after sixteen years’ use. a comparative test on the pipe before and after cleaning showed an increase of thirty per cent, in capacity. There were “no serious conditions, and it is well known the effect of surface roughness is much less in large than in small pipes. It was found possible to remove tubercles without injuring materially the original coating underneath them, and the original condition of the pipe was practically restored. The cleaning in this case was done by hand with old round pointed shovels and wooden scrapers made of oak.” It will lie found that the “rust tubercles so often occur separately or in combination with organic growths, that it is possible no treatment of water, of which, we now possess knowledge, will obviate an ultimate serious depreciation in the discharge of mains, and. hence, some process of removal or else reinforcement will have to be restored to. until such time as the interior of all our mains are enameled, or coated by some process which will preclude rust. Besides, it is sometimes impractical to use filtration or more expensive than securing a supply from another source, The development of these nodules in small embntities is sufficient to effect a startingly large reduction in capacity." How greatly the effective bead must be increased per square inch to overenjue the friction, needs no demonstration. It "increases inversely as the diameter. In addition, in a main of given size, a larger surface is exposed to friction. As the area of cross-section is diminished, the velocity for the same discharge must be greater, 'flic loss of head increases as the square of the velocity. Add to these the eddies caused by protuberances in the pipe and the concomitant energy expended in impact, caused by the unsteady motion of the particles of water, thus creating additional loss of head, and we see the cumulative effect produced. * * * It is now generally recognised that the loss of head caused by the friction iti pipes, increases with age, and, inversely, the discharge or capacity decreases.” The three causes of the variation of resistance and. more particularly, that arising from tht condition of the interior surface of a pipe, are: (i) The variation in velocity: (2) the variation in diameter; (3) the variation in the roughness of surface—i. c., the physical condition of the interior of the pipe. Tt must, also, be born in mind that, while filtration will retard further developments after the pipes have been cleaned, and may reduce all forms of organic growth, and certainly will reduce them materially, there are no data to confirm or deny the development of other forms in time. Filtration will not prevent the formation of rust-nodules. The subject of tuberculation and deposits in pipes has, therefore, a practical side of vital concern to the waterworks superintendent, since incrustation and deposits in water mains (generally classified as tuberculation) affect not only the aesthetic and potableness of a water supply, but. also, the earning capacity of a plant, The water is physically depreciated, and that depreciation can be expressed in dollars and cents. That being so, “it is surprising how little is spent on the upkeep and maintenance of distribution systems" "A diminution of pressure or capacity in the distribution and supply mains is continually met with supplementary extensions. There are very many instances where more money spent in maintenance would have saved heavy outlay for new construction, which, if paid for from revenues, forestalled other needed improvement or dividends, and. if paid for by bond issues, increased the fixed charges of the plant by an amount greater than the proper maintenance costs,” and it may well be asked how much at tention is paid to the pipe or distribution system. When once the water has been turned into a pipe-system, little more is paid to the condition of the pipes. Sometimes, it is true, small pipes fill up entirely, and then specimens are exhibited showing the growth of tuberculation. Again, the water becomes bad in one street, while it is good iti the adjoining neighborhood, and the result is attributed to “some mysterious agency." One of the great steps in advance, therefore, that lias been made in the designing of pipe-systems is the introduction of facilities for cleaning out the pipes at stated intervals of time—something necessary, not so much for the purpose of restoring the normal capacity of the pipes as for maintaining the purity of the water. Mr. Mill suggests, as a means, the advisability of equiping pipe-systems with manholes for the purpose of test, inspection and cleaning. An effective arrangement would be to tap ordinary 3-in. connections on either sid of a gate-valve located in these manholes. A small Venturi meter could always be inserted in the 3-in. line by means of flanged connections and set in gate-boxes, at a proper distance from the the connection, the flow in the pipe could be bypassed and measured through the meter, and the loss of head in a given section of main obtained by readings from the pressure gauges located in the various manholes. By means of adjustable throat-pieces the rate of flow could be adjusted at will. Another arrangement would be to have corporation-cocks for the pitometer connections, set in gateboxes, at a proper distance from the hatch-boxes, thereby avoiding any possible influence which the eddies caused by change in cross-section at the hatch-box might produce in the readings. The valves, too, might be placed in the manholes. Four-way hatch-boxes could be built for street intersections. Their form should be such as to create as slight a change in crosssections as possible. The cost of such arrangements would not be great. The question of deposits in mains seriously affects the estimates of the per-capita consumption based on infrequent gaugings or a single gauging made when a conduit or pipe-line is new. The effect of tuberculous growths in old conduits, such, for instance, as the old Hemlock lake conduit at Rochester, X. V., is certainly to retard the delivery. In 1876 gaugings were made on the then new conduit, whose daily capacity was given as 9.000,000 gal-. A water famine threatened in the summer 1890. when it was found that the delivery was only 7,142.000 gals.—twenty-one per cent, in fourteen years. Subsequent gaugings showed steady diminution up to 1895, when the deliveryhad fallen to 6,660,000 gals. It may be added that such reductions in delivery often begin very soon after a pipe line is put in service -even one or two years. It is also worth mentioning that estimates of consumption based upon the plunger-displacement of pump may be greatly excess of the actual use of water. Mr. Mill con eludes by pointing out that on the condition of the mains depends the value of a waterworks plant. “In some cases, where certain rules arc applied to hard water, this modification may cause an excessive reduction. On the other hand, the same formula may be inapplicable to waters conducive to heavy deposits. Thus still another argument is added to show how essential proper inspection is to the whole range of problems presented in the distribution of water in cities and towns.”

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