The subject of the fire-hazard of organic coverings has been pretty thoroughly investigated and can be pretty well-known, when there is any inclination to get out of ruts which long years of travelling in has deepened. How many fires (cause unknown?) have really originated from the slow carbonizing of organic material on steam-pipes? It is but recently that the hair-felt covering on the steam end of a Worthington pumping-engine, within ten miles of us, not only burnt itself but destroyed some thousands of dollars worth of walnut lagging. Cases of the combustion of these organic coverings are numerous and are well-known.
Few appreciate the great loss of heat from uncovered or imperfectly covered pipes. Many have an indistinct impression that there may possibly be some slight loss. But there is in many cases an absence of knowledge upon this subject where it should be complete. The most correct data available show that the radiation from uncovered two-inch steam-pipe, with 60 pounds steam-pressure, is 391.83 kilo. centigrade heat-units one foot one hour, or 21,739.78 kilos. of coal for 100 feet per year of 300 days of 10 hours each; one kilo. equals 2,205 pounds. Properly combining these figures we see that there are 23.97 tons of coal lost by radiation from that uncovered pipe. If the coal costs $4 per ton, the radiation from this 100 feet of pipe will amount to $95.87. From the same pipe covered with Wm. Berkefield's fossil meal composition, 32/100-inch thick, the most powerful inorganic non-heat conductor used as a covering at the time these investigations were made, there was radiated 24,109 kilo. cent. heat-units one foot one hour, or 1,337.63 kilos. of coal for the year. This would be 1-474/1000 tons of coal at $4 per ton, amounting to $5.89. Then $95.87 less $5.89 equals $89.98, the saving effected by covering this pipe with William Berkefield's fossil-meal composition 92/106 of an inch thick. Or, in other words, the saving effected was over 93 per cent of the total possible radiation, using a thickness of one inch this loss would be reduced to $5.50.
From the same data we find (page 44) it stated that while the radiation through 25 m.m. of Wm. Berkefield's fossil meal was 7.7 heat-units, through 25 m.m. of carb. magnesia it was 6.7 heat-units, therefore the proportions 7.7: 6.7 = $5.50: $4.80 gives us the coal value of heat lost by radiation through the magnesia covering. To put this in another form: From the running-foot of two-inch pipe uncovered the loss is 96 cents, while, from the same pipe covered with the magnesia, the loss is less than five cents; or a saving of over 91 cents per year. To accomplish this saving the cost of the covering should be taken into account. This was 27 cents. Therefore, the investment in the magnesia covering is paid back in less than four months. The data which we have used were obtained by the use of a calorimeter measuring the quantity of heat passing through covering. The other possible method of arriving at this knowledge would be to accurately measure the condensation of the steam. In these experiments, owing to several reasons, it was not deemed advisable to rely upon the second method. Recently, however, I have seen in the American Engineer of June 12, a report of the proceedings of the Michigan Engineering Society containing a paper by Professor Cooley, of Ann Arbor, Mich., in which he says:
"The benefits of covering steam-pipes to prevent radiation are strikingly illustrated by the following example: The Thomson-Houston electric-light plant in Ann Arbor has about 60 feet of seven-inch pipe connecting the boilers with the engines and two large steam-drums above the boilers: in March, 1887, the steam at the far end of this pipe was tested to determine the amount of entrained water, the pipes and drums at the time being uncovered. An average of nine experiments gave 31.01 per cent moisture. In June of the same year, after the pipes were covered with magnesia sectional-coverings, the quality of the steam was again tested, the average of five experiments giving 3.61 per cent moisture; the tests were made by the same men from the same connections, and in the same manner. The pipes and steam-drums in March were subjected to a draught, which, of course, aided the condensation. Enough water passed into the cylinders to retard the engines, producing a disagreeable noise. In June the weather was warmer and the pipes and steam-drums were well protected. The quality of steam at the boilers was tested in June, and showed about three per cent moisture. Assuming that 100 incandescent horse-power were being developed at the time, and that each horse-power required 30 pounds of steam; if the steam is assumed to have 25 per cent entrained water due to condensation in the pipes and connections, then 4,000 pounds steam will need be produced in the boilers, or 1,000 pounds more than necessary. To produce this steam will require about 125 pounds of good coal per hour, or 1,000 pounds per day of eight hours. One-half ton per day at $3 per ton for 300 days, $450. The actual cost of the covering put on complete probably did not exceed $150."
An interesting verification of the remarkable non-heat condensing quality of the magnesia covering occurred at Lynn, Mass. In the heart of the district in that city, recently the scene of the disastrous conflagration, there was located the machine-shop of Messrs. Rollins & Glozier. A two-inch steam-pipe there was covered with this material. The heat of the fire at this place has been curiously determined to have been between the minimum extreme of 2,756° Fah. and the maximum extreme of 2,950° Fah., in this way: Cast-iron melts at 2,756° Fah.; wrought-iron at 2,950° Fah. A portion of the cast-iron bed of a lathe was fused into an irregular mass, and on it, partly imbedded, was a wrought-iron nut not melted. The steam-pipe spoken of fell a distance of 20 feet, and some of the magnesia covering was broken by the fall, but so effective was its heat-resisting and non-heat-conducting power that the pipe was found to be uninjured, and it is being used again in the building which is being erected to take the place of the one burned. That the magnesia should have endured the ordeal successfully was not unexpected, for we know that it is used by the Herreshoff Manufacturing Company as a lining to the shells of its coil boilers, and it is there subjected to a very intense heat resulting from the forced draught used in this type of boiler. Instances could be multiplied indefinitely, but I refrain from occupying further time with them, citing, however, one recent pertinent case.
The trial trip of the new cruiser "Baltimore" took place in the middle of September. It is reported to have been in many ways eminently satisfactory. The report goes on to state: "Another noteworthy fact was the comfortable condition of the fire and engine rooms. A duplicate crew had been provided with the expectation of relieving the firemen in two-hour turns; but after the first two hours of the run the first watch refused to quit work and insisted in running the ship throughout the entire four hours' trial." Boilers and all steam-surfaces were covered with the magnesia covering.
So it appears that not alone is the man who pays for the coal interested in this question of most perfect insulation, but also the men who operate the plant as well. In time, those architects, those mechanical engineers, those engine-builders and those other advisers, who are paid to advise soundly and correctly, and who are represented by our figure with the re-entering angles, will, of necessity, change their form and begin to assimilate these new facts, or ossification will so spread throughout the whole figure that they will be relegated to the shelf for curiosities as showing what strange geometrical forms the intellectual life of man may take.
THE COST OF A SMALL MUSEUM.
