No. 431 THE DURABILITY OF MATERIALS CONVEYING STEAM, AIR AND WATER BY ARTHUR K. OHMES, NEW YORK Member B PREFACE Y far the greater part of papers presented to the Society treat the design of any particular apparatus which aids to secure stipulated results at a minimum cost of operation. Comparatively few papers treat the durability of the apparatus itself, despite the fact that the durability of the apparatus (in other words, the life of the plant) will seriously affect the amounts making up the cost of operation, such as the cost of supplying a certain building with heat and ventilation. It is questionable whether the importance of the durability of heating and ventilating plants is sufficiently appreciated by the owners themselves or by the chosen advisers of the owner, may they be architects, builders or engineers. We seem to be confronted, however, with a condition that will make the durability of our plants a more important matter to the owner than heretofore, because in years gone by we were building mostly "temporary" structures in our fast growing cities and communities. The temporary nature of our buildings is very forcefully illustrated in Fig. 1 reproduced from the letter head of a prominent steam heating concern in New York City. Frequently the character of a neighborhood would change so rapidly, that permanent buildings (in the sense of the old world) were seldom a good investment and consequently scarcely ever built. If a certain district of a city was developed for homes, there would soon spring up business and pleasure buildings and then factories, always, of course to the detriment of the better classes of buildings. Presented at the Annual Meeting of THE AMERICAN SOCIETY OF HEATING AND VENTILATING ENGINEERS, New York, January, 1917. There is scarcely a city where the amalgamation of all kinds of buildings into one district, became in certain localities a greater nuisance, if not a greater calamity, than in New York City. All real estate classes generally realized this condition and the enactment of building zone ordinances resulted, establishing districts for homes, factories, etc. There is no question but that New York City has taken one of the most far sighted steps in enacting these new building zone ordinances. A number of reports from other cities. would indicate that similar ordinances will be enacted by other communities, giving therefore to the New York City ordinances the color of national importance. Before these ordinances were enacted, some prospective builder of a fine house (as a distinct point in question, we might quote Mr. Andrew Carnegie when building his New York City home), would buy up an amount of property, far in excess of his own needs, then sell his surplus property to desirable neighbors in order to protect his own grounds from what he considered undesirable neighboring buildings. This should not now take place under our new ordinances and the supposition is in order that we may have more permanent building districts, and that means automatically more permanent buildings, viz:-we are approaching the settled. building policies of the old countries. Architects and heating engineers should realize that if these surmises become facts, greater responsibilities than ever for the installation of the most durable apparatus will rest upon them when they design apparatus. While it is needless to say that the results to be secured in heating effect are still and will always be the most important, still the length of life, and repair and maintenance costs must not be forgotten, because they enter vitally into the total cost. of operating any heating apparatus. We are in the habit of making allowances for these factors in determining the cost of a pound of steam, of pumping a gallon of water, or of generating a kilowatt of electricity! Why then should these items not appear in determining the cost of providing our buildings with heat? Suppose on one hand we had an ordinary house in which a durable heating apparatus would cost $1,000 and its life would be 10 years, and on the other hand we had a less durable apparatus costing $840 and its life would be only 20 years. This approximate increased cost of 20 per cent. would be a considerable amount of money in case of a large installation. Both plants, however, would secure the same excellent results; both would use the same amount of fuel and both would require the same amount of labor for oper ating the plant. We will assume the latter to be $150 per year. The total cost of providing the building with heat after a period of 40 years time, if we make allowances for a charge of 6 per cent. interest for each apparatus, also for incidental work in the way of decoration, in case the 20 year apparatus is overhauled or put in new, would then be as follows: FIG. 1. THREE DIFFERENT BUILDINGS ON THE SAME SITE, COR. WALL AND BROAD STREETS, NEW YORK CITY. Expensive Inexpensive Fuel, Labor, Ash Removal, etc., (40 x $150) .$6,000 $6,000 Installation costs of plants in 40 years time... Incidental costs of new apparatus after 20 years time in the way of repairs to Building. 600 Interest at 6 per cent. per annum in 40 years. Cost of apparatus at end of 40 years.. $9,400 $10,296 This shows the more expensive apparatus, if durable, would still be considerably cheaper after a period of 40 years than the less expensive apparatus, if not durable. It is true that many owners will frequently not wish to look ahead for more than 20 years time if it means a greater initial cost of building, but it should be pointed out to them that the investment value of any building is certainly greatly enhanced if the mechanical plant may be considered permanent and will last as long as a cheap wooden clapboard construction would last, not to speak of the more permanent brick, stone or concrete construction. The writer hopes that the members will freely contribute to this paper in the form of discussion, because only time can teach and prove valuable experience; if they will do so it might prove a boon to our younger members, inasmuch as they will be enabled to avoid mistakes made by others. SCOPE OF PAPER It is not the intention to discuss the various causes of corrosion as encountered in chemical factories, in which we may include dyeing establishments, laboratories, color factories, etc., but to confine the discussion to conditions met with in our houses, office buildings, ordinary factories, churches, schools, theatres, etc. Nor is it desired. to settle or discuss the question of whether wrought iron or steel is most durable, or also the question of the supremacy of cast iron over both of these, not to mention lead, brass and copper. OUTSIDE CORROSION Where Within the limits of the paper, outside corrosion is seldom encountered for the reason that there are few pipes in places which could be subjected to outside corrosion. Generally speaking, it is also comparatively simple to protect pipes from outside corrosion, because protecting coats of paint are easily applied in most cases. piping is concealed in floors, furring, etc., no trouble need ever be feared as long as it lays in a dry place. On the other hand, I have seen pipes completely corroded in a few years time (in supposedly absolutely dry places) due to very simple causes. As an example, I might mention pipes carrying water or steam and laying in concrete. Due to improper installation, or perhaps because the expansion of the pipe line was not properly taken care of, the pipe springs a leak; not enough to be noticed in the heavy floor construction but still enough to thoroughly wet cinderconcrete around it. The wet cinder-concrete forms an acid which will rapidly destroy the pipe. Similarly, covered pipes laying in poorly waterproofed trenches which become wet several times a summer, will be destroyed rapidly. If there is heat on the pipe and the covering can dry out, nothing serious will happen for a long time, but, if the pipes do not thoroughly dry out, then in a few years time the pipe will fail. in water-proofed trenches, all piping must be kept away so far from the asphalt that it will not melt away gradually, because this would result in leaky construction and corrosion. Pipe lying in trenches or in conduits underground must be kept dry by proper underdrains, if durability is desired. The drains must be ample, particularly in swampy low ground, to take off spring floods, etc. Finally, no covering should be accepted which might seriously affect iron, when becoming moist, as it will more or less in any cellar during the summer months. INSIDE CORROSION For various reasons, the causes for inside corrosion are much more complicated. The causes are difficult to detect, because only complete dismantling of pipe system allows for thorough inspection. It is as yet not possible to apply positively protecting coats on the inside; then again there are always some weak spots left, due to threading of pipes and fittings. Pipes Conveying Water: A pipe may carry water from exactly the same sources, but it may be hot or cold. If hot, it may be always fresh water (domestic hot water supply) or it may be the same water circulated over and over again for years and years, as in the case of hot water heating. Again it may be condensed water, or a mixture of condensed water, vapor and air; both of these apply to steam heating systems. It is surprising to find the number of educated people who still consider that all kinds of water will have substantially the same corrosive effect on pipe and other material. To illustrate the corrosive effects of different water, I will quote a personal experience I have had within the last year, the absolute accuracy of which I can readily prove. A hot water heating apparatus was changed and altered after eight years of service. All pipes and fittings could be easily taken apart; they were not rusted in. Where the threads were in the metal of the fittings, they were in almost all cases as bright as the day they were cut. Threads outside the fitting, but protected by covering, were covered with the finest layer of rust. All material was in perfect shape and could be used again. A radiator with the so-called "soft steel" push nipples was taken apart. The push nipples did not show any sign of corrosion and their contact surfaces were still bright. The large threaded bushings on a number of radiators could be easily removed. All brass valves with their soft seats were in perfect shape. The boiler of this same hot water heating system was provided in the rear with a so-called hot water back of cast-iron, connected up as shown in Fig. 2, for heating a small quantity of domestic hot |