Document 10DO48ger5OaYEo7zkM48ryJm

American Society of Heating and Ventilating Engineers Guide iq - Chapter 21--Pipe, Fittings and Valves Commercially wrought iron, though essentially made direct fro ore, is usually made from cast iron by such removal of its carboTM1 * gsielitch_o_en_r_ai_ns__ta_o_b_ca_o_tnhkvioelofrtcpiitnadsinetytropopar artssilcatlyegspi,naatrotnicdlaebsmc,yohahspneqrdrupeenbetyzimnsgaqsutshe,ees-wzeinh>t.-gHi*c**h-tUhUereQesse*ta3af^"iinj!l permanently an important quantity of that slag* T^e featuTM! of wrought iron is the presence, in a finely divided, and uniformly l(jgJ tributed state, of a quantity of silicate slag. f* The chief advantage claimed for wrought iron is to resist corrosion toll greater degree than does steel. This is held to be due to the high degree! of purity of the iron base and to the purely mechanical resistance to ti# progress of corrosive action offered by the slag veins. The exact degree 5 superiority has never been determined. f"' " I to be bent readily, so that no elbow fittings are ordinarily un.enoug11 * PI0' ue run in building walls very much as BX cable is installed. makes it particularly valuable for new installations or as rejn existing buildings as it will save much cutting and patching. IS&P??6!'able too, where flexible connections are required and limited W^lbite the usual construction in which several elbows are used, diator runouts. This material is available in sizes of % in. to r a due to the ease with which it may be worked around obstruc- t0 ^,e reduced number of fittings required, it often costs less tf,an ordinary threaded pipe, and is of course more permanent. Identification of Wrought Iron and Steel Pipe. There is little difference* torrorion Rin the appearance of wrought-iron and steel pipe but there are several '- The electrolytic theory of corrosion, as formulated in 1903 by Dr. tests which readily identify the materials. The fracture of wrought-iroh iivVtney led to the development of certain protective methods for closed ttphhipeeeffrriaasccrttauugrrgeeeccdaa, nnduuueenaallssggiillrrvyaayybb,,eeaaonnbdd^sefnirbbvrreooduu.ss..'TruhBBe-yyrf--rh,haaacmm-t-u-mm-r-eeerro.iinnfggstaaeepplii.eeiscce.ee..voo..e.ff.npp6,i1ip*pbeecrf-iWvirhoinl^^p;-iVi:4'WwSaeWftajwur`atSsJVtyets'etre.trernnCts-,awrehfiuclhtheoaexvrpneaewbmriiamm0spueeandnntttossnoiifnnttnhcevvoaarrrenoiomsuioos>vnarel,soefadrrcci.shhsinollalavs-mbbeuoodcrrshaootxolsyunygtiseeotsnenm,fhrsaaovnmieds carnudmcbrlyesdta_cl_hli_nip_e_,. duW_e_r_ot_ou.gt.hhet-ifriobnro(uvpisippces,,trwuwrchieteunnretnt.hrreSeaataedseslaapreripeecc,u--uwtt'oh--onennitit,th,gregivaivedeses'd^ . '-M'drmeiTonst^ra^te-dL,thramt tnhnertioanmaol utont tohte caomrrosuinotn wuuyu iU OULU wvv--w '/ -almost directly proportional to the amount of oxygen in solution, and gives a long spiral chip. A microscopic examination of polished and * etched specimens is an infallible test. The presence of slag in the wrought lilies rweliitahbtlehedtaetma poenrathtuisres. ubject indicate that the composition of the iron is unmistakable, while the steel is almost without slag. f :f- Fwan--i-C; the varying amount of carbon, phosphorous, manganese, sul- Seamless Pipe. Steel pipe or tubing without the lap or butt weld i$1 frequently used for high-pressure work. Its advantages are its somewhat^ silicon, oxides, slag and copper usually found in wrought iron and l"-*'ffift steel--makes very little difference in the amount or character of greater strength, permitting the use of a thinner wall, and in the smallfl ^^chnbsion under water, although under atmospheric exposure the influence sizes its freedom from the tendency of welded pipe to split at the weldti occasionally when bent. Furthermore, the inherent physical properties^ of the steel used in its manufacture are somewhat better and a variety of? : S^?TOmposition is more marked. V :Sln practice, oxygen removal has been accomplished in two ways, -V;namely; by de-aerating the water mechanically; and by fixing the free combinations of carbon content and heat treatment are available. ' -O'oxygen by chemical combination. Suitable apparatus for this purpose is Seamless pipe is made by either of two different processes, depending-; upon the size. The piercing process is used in the smaller sizes and the cupping process is sometimes used for tubing of 6 to 9 in. diameter. Cast Ferrous Pipe. There are now available several types of cast ferrous metal pipe made of a good grade of cast iron with additions of nickel, chromium, etc. This pipe is available in sizes from in. to 6 in. and ^v\.. nbw on the market. Another expedient sometimes resorted to in domestic supply systems ps^is the use of zinc pockets in the supply line, An enlarged section is installed the line and filled with pieces of zinc and the corrosive action of the :;;-cwater is expended on the zinc. As the zinc is consumed it must be re;V]jnewed from time to time. The best way to deal with a corrosive water standard lengths of 5 or 6 ft with external and internal diameters closely approximating those of extra strong wrought pipe. Cast ferrous pipe 1 may be had coupled, bevelled for welding or ends plain or grooved for the several types of couplings. It is readily cut, and threaded, as well t as welded. The fact that it is readily welded enables the manufacturers v to supply the pipe in any lengths practical for handling. Alloy Metal Pipe. Steel pipe bearing a small alloy of copper is some what more resistant to corrosion than plain steel pipe. It is recommended usually for atmospheric corrosive conditions, i.e., for corrosion caused by alternate exposure to air and water. Non-Ferrous Pipe. A type of non-ferrous pipe is now marketed in which the weakness of threading the pipe is eliminated. Instead of thread ing the tubing, the ends are flared or expanded so as to fit against smoothfinished spherical or bevelled surfaces in the fittings, and are clamped there by a sieve nut screwed over the fitting, similar to a union. The tube '^'--supply is to treat it at the sofirce. The introduction into piping systems of various chemical compounds, Usually for forming a protective coating of thin deposit has apparently ''L-j been rewarded with some success. Piping exposed to elements dr buried i in the ground is quite successfully protected by coatings of the asphaltic y.A type, usually applied hot. Pipe Welding . The application of welding on,the job gives to the heating industry an ;>; improved method of joining pipes. Arc welding and oxy-acetylene welding are used with equal success in piping work. To date welded piping has i\F been found practicable and less expensive than piping made with screwed - or flanged joints on sizes down to 2 in. Smaller sizes are difficult to weld r,. due to the thinness of the material. 7r~ Fittings often cause so much friction as to impair seriously the smooth 320 321