Steam:
Its Generation and Use

__________________ __________________ ______ COVERING FOR BOILERS, STEAM PIPES, ETC. The losses by radiation from unclothed pipes and vessels containing steam is considerable, and in the case of pipes leading to steam engines, is magnified by the action of the condensed water in the cylinder. It therefore is important that such pipes should be well protected. The following table gives the loss of heat from steam pipes, naked and clothed with wool or hair felt, of different thickness, the steam pressure being as _____ sumed at 75 lbs. and the extreme air at 6o°. There is a wide difference in the value of differ- ent substances for protection from radiation, their value varying nearly in the inverse ratio of then- conducting power for heat, up to their ability to transmit as much heat as the surface of the pipe will radiate, after which they become detrimental, rather than useful, as covering. This point is reached nearly at baked clay or brick. _______________________________________________ experiments, made at the Mass. Institute of Tech- nology in 1871, showed the condensation of steam in a pipe covered by one of them, as com- pared with a naked pipe, and one clothed with hair felt, was 100 for the naked pipe, 67 for the “cement” covering, and 27 for the hair felt. Table of Relative Value of Non-Conductors, (FROM CHAS. E. EMERY, PH. D.) Non-Conductor. I Value. Wood Felt........ Mineral Wool No. 2 Do. with tar.... Sawdust.......... Mineral Wood No. 1 Charcoal_________ Pine Wood, across fibre........__ i .000 .832 ■7'5 .680 .676 .632 • 553 Non-Conductor. Loam, dry and open Slacked Lime_____ Gas House Carbon. Asbestos.......... Coal Ashes_______ Coke in lumps... Air space undivided______ Value. •55° .480 .470 • 363 •345 • 277 .136 “Mineral wool,” a fibrous material made from blast furnace slag, is a good protection, and is incombustible. __________________ be C TABLE OF LOSS OF HEAT FROM STEAM PIPES. __________________________ ______________________________________________ Outside Diameter of Pipe, without Felt. 6 •— c 2 in. diameter. 4 in. diameter. 6 in. diameter. 8 in. diameter. 12 in. diameter. Loss in units per foot run per hour. Ratio of Loss. Feet in length per H. P. lost. Loss in units per foot run per hour. Ratio of Loss. Feet in length per H. P. lost. Loss in units per foot run per hour. Ratio of Loss. Feet in length I per H. P. lost. Loss in units per foot run per hour. Ratio of Loss. Feet in length per H, P. lost. Loss in units per foot run per hour. Ratio of Loss. j Feet in length 1 per H. P. lost. 219.0 100.7 65-7 43-8 28.4 19.8 1.00 .46 • 30 .20 •13 .09 132 288 441 662 1020 1464 390.8 180.9 117.2 73-9 44-7 28.1 23 4 1.00 .46 • 30 .18 •07 .06 75 160 247 392 648 1031 1238 624. i 187.2 in .0 66.2 41.2 33-7 1.000 .300 . 178 . 106 .066 .054 46 $ 438 7°3 860 729.8 219.6 128.3 75-2 46.0 34-3 i .000 .301 . 176 .103 .063 • 047 4° 132 225 385 630 845 IO77-4 301.7 185.3 98.0 60.3 45-2 1.000 .280 .172 .091 •p50 .042 26 92 157 294 486 642 A smooth or polished surface is of itself a good protection, polished tin or Russia iron having a ratio, for radiation, of 53 to 100 for cast iron. Mere color makes but little difference. Table of Conducting Power of Various Substances. (from PÉCLF.T.) „ , ' Conducting Substance. Power. Substance. Conduct’^ Power. — Blotting Paper.. .274 Eiderdown j -3T4 Cotton or Wool) 1 2_ any density .. 1 j Hemp, Canvas... -4l8 Mahogany Dust.. .523 Wood Ashes 531 Straw -563 Charcoal Powder. . 636 Wood, across fibre .83 1.15 Coke, pulverized. India Rubber.... Wood, with fibre. Plaster of Paris.. Baked Clay 1.29 1-37 1.40 3-86 4-8.3 6.6 13-68 Hair or wool felt has the disadvantage of bt - coming soon charred from the heat of steam at high pressure, and sometimes of taking fire there- from. This has led to a variety of “cements” for covering pipes —composed generally of clay mixed with different substances, as asbestos, paper fibre, charcoal, etc. A series of careful Cork chips cemented together with water-glass make one of the best coverings known. A cheap jacketing for steam pipes, but a very efficient one, may be applied as follows : F irst, wrap the pipe in asbestos paper —though this may be dispensed with ; then lay slips of wood lengthways, from 6 to 12 according to size of pipe—binding them in position with wire or cord; and around the framework thus con- structed wrap roofing paper, fastening it by paste or twine. For flanged pipe, space may be left for access to the bolts, which space should be filled with felt. If exposed to weather, use tarredpaper — or paint the exterior. A French plan is to cover the surface with a rough flour paste mixed with sawdust until it forms a mod- erately stiff dough. Apply with a trowel in lay- ers of about (X inch thick — give 4 or 5 layers in all. If iron surfaces are well cleaned from grease, the adhesion is perfect. For copper, first apply a hot solution of clay in water. A coating of tar ren- ders the composition impervious to the weather. ___________ ________________ _________________________________________________ 77