This is a reproduction of a library book that was digitized by Google as part of an ongoing effort to preserve the information in books and make it universally accessible. http://books.google.com Their CONSTRUCTION CARE and OPERATION "With Questions and Answers ..I STEAM BOILERS THEIR CONSTRUCTION, CARE AND OPERATION With Questions and Answers A RELIABLE UP TO DATE TREATISE, CONTAINING FULL DESCRIPTIONS, WITH ILLUSTRATIONS OF THE VARIOUS TYPES OF BOILERS, INCLUDING ALL THE LEADING TYPES OF WATER TUBE BOILERS IN USE TODAY. A LARGE SECTION IS DEVOTED TO BOILER CONSTRUCTION, GIVING RULES AND FORMULA FOR ASCERTAINING THE STRENGTH OF RIVETED SEAMS: ALSO METHODS OF BRAC ING. INSTRUCTIONS FOR SETTING BOILERS, EITHER BY THE ORDINARY METHOD. OR BY SUSPENSION. RULES FOR EINDING SAFE WORKING PRESSURE; ADJUSTMENT OF SAFETY VALVES, ASCERTAINING HEATING SURFACE, MAKING EVAPORATION TESTS, ETC. COMBUSTION CLEARLY EXPLAINED. ALL LEADING TYPES OF ME CHANICAL STOKERS DESCRIBED AND ILLUSTRATED. By CALVIN F. SWINGLE, M. E. AUTHOR OF "ENCYCLOPEDIA OF ENGINEERING," "EX AMINATION QUESTIONS AND ANSWERS FOR MARINE AND STATIONARY ENGINEERS," "MODERN LOCOMOTIVE ENGINEERING." ETC. ILLUSTFAJFD V * .1 CHICAGO FREDERICK J. DRAKE & COMPANY PUBLISHERS Copyrighted 1905 BY FREDERICK J. DRAKE & CO. Copyrighted 1912 BY FREDERICK J. DRAKE. Copyrighted 1913 FREDERICK J.lJDRAKE & CO. INTRODUCTION Inestimable benefits have been conferred upon the human race through the medium of steam in its varied applications to the needs of men, but too often the steam generator itself is neglected, through ignorance or carelessness, and allcwed to deteriorate until it becomes an actual source of danger instead of a useful agent. There is a constant and growing demand in the manufacturing world for more power from steam, and as the boiler is the source of this power, too much attention cannot be paid to its construction, care and management. It cannot be denied that a great responsibility rests upon any man who has charge of a boiler or battery of boilers, and it should be the chief aim of a man in such a position to thoroughly acquaint himself with his boilers, their construction, care, and the safest and most economical method of operating them. It has been the aim of the author, in compiling the following pages, to place before the student some facts regarding steam boilers- which he believes will be helpful to engineers. Boiler construction has been dwelt upon at consider able length, especially the strength and efficiency of riveted joints. The staying of flat surfaces, including all the various kinds of stays, receives particular attention also, for the reason that in the opinion of the author a man taking charge of a boiler should first of all be compe 3 4 INTRODUCTION tent to ascertain, by means of certain standard rules and formulas, what is the safe working pressure of his boiler, also the proper area of the safety valve in pro portion to grate area, and many other details of brac ing, riveting, etc. Boiler settings and appurtenances, feed pumps and injectors, boiler operation, washing out, etc., all receive due attention. Combustion, the nature of steam and correct rules for mak'ng evaporation tests are all treated upon at length, also the subject of firing, both by hand and by the use of mechanical stokers. The highest authorities have been consulted in the make-up of the book, and this fact, coupled with the author's practical experience of thirty five years as an engineer, it is believed, will make the book of great value to its readers. C. F. S. Steam Boilers CHAPTER I THE BOILER Importance of correct knowledge of the construction and strength of steam boilers — Tensile strength of steel boiler plates — Dr. Thurston's specifications — Specifications of U. S. board of inspectors of steam vessels — Punched and drilled plates — Rivets and rivet iron and steel — Efficiency of the joints — Proportions of double riveted butt joints — Lloyd's rules for thickness of plate and diameter of rivets — Cor rect design of triple riveted butt joints — Calculations for efficiency of different forms of joints — Discussion of various ways in which failure may occur in different styles of joints — Necessity for higher efficiencies in riveted joints — Quad ruple and quintuple butt joints — Staying flat surfaces — Different methods of staying a boiler — Correctly designed stays — Stay bolts for fire box boilers — The Belpaire boiler — Vanderbilt Locomotive with Morison fire box — Gusset stays — Through stay rods — Calculating strength of stayed surfaces — Area of segments — Proper spacing of stays — Strength of un stayed surfaces — Dished heads — Welded seams. As it is of the highest importance, not only to the engineer in charge of the plant, but also to his assist ants, and in fact to all persons whose business com pels them to be in the vicinity of the boiler-room, that there should be absolutely no doubt as to the safe construction of the boilers and their ability to with stand the pressures under which they are operated, the 5 6 STEAM BOILERS author has compiled the following additional data regarding the construction and strength of boilers. The deductions and reports of tests and experiments made by such eminent authorities as Dr. Thurston, Prof. Wm. Kent, Dr. Peabody, D. K. Clark, Hutton and many other experts have been consulted, and the author has also added the results of his own obser vations, collected during an experience of thirty-five years as a practical engineer. When steel was first introduced as a material for boiler plate, it was customary to demand a high tensile strength, 70,000 to 74,000 lbs. persq. in., but experience and practice demonstrated in course of time that it was much safer to use a material of lower tensile strength. It was found that with steel boiler plate of high tenacity there was great liability of its cracking, and also of certain changes occurring in its physical properties, brought about by the variations in tem perature to which it was exposed. Consequently present-day specifications for steel boiler plate call for tensile strengths running from 55,000 to 66,000 lbs., usually 60,000 lbs. per sq. in. Dr. Thurston gives what he calls "good specifications" for boiler steel as follows: "Sheets to be of uniform thickness, smooth finish, and sheared closely to size ordered. Tensile strength to be 60,000 lbs. per sq. in. for fire box sheets and 55,000 lbs. per sq. in. for shell sheets. Work ing test: a piece from each sheet to be heated to a dark cherry red, plunged into water at 60° and bent double, cold, under the hammer. Such piece to show no flaw after bending. The U. S. Board of Supervising Inspectors of Steam Vessels prescribes, in Section 3 of General Rules and Regulations, the following method for ascertaining the tensile strength of steel plate for STEAM BOILERS r boilers: "There shall be taken from each sheet to be used in shell or other parts of boiler which are sub ject to tensile strain, a test piece prepared in form according to the following diagram: yfboi/tz' TEST PIECE. The straight part in center shall be 9 in. in length and 1 in. in width, marked with light prick punch marks at distances 1 in. apart, as shown, spaced so as to give 8 in. in length. The sample must show, when tested, an elongation of at least 25 per cent in a length of 2 in. for thickness up to ^ in. inclusive; in a length of 4 in., for over % in. to T\ in. inclusive; in a length of 6 in., for all plates over ^ in. and under 1%. in. in thickness. The samples shall also be capable of being bent to a curve of which the inner radius is not greater than I times the thickness of the plates, after having been heated uniformly to a low cherry red and quenched in water of 82° F." Punched and Drilled Plates. Much has been written on this subject, and it is still open for discussion. If the material is a good, soft steel, punched sheets are apparently as strong and in some instances stronger than drilled, especially is this the case with regard to the shearing resistance of the rivets, which is greater with punched than with drilled holes. Concerning rivets and rivet iroh and steel Dr. 8 STEAM BOILERS Thurston has this to say in his "Manual of Steam Boilers": "Rivet iron should have a tenacity in the bar approaching 60,000 lbs. per sq. in., and should be as ductile as the very best boiler plate when cold. A good f£-in. iron rivet can be doubled up and hammered together cold without exhibiting a trace of fracture." The shearing resistance of iron rivets is about 85 per cent and that of steel rivets about 77 per cent of the tenacity of the original bar, as shown by experiments made by Greig and Eyth. The researches made by Wohler demonstrated that the shearing strength of iron was about four-fifths of the tensile strength. The tables that follow have been compiled from the highest authorities and show the results of a long and exhaustive series of tests and experiments made in order to ascertain the proportions of riveted joints that will give the highest efficiencies. The following Table 11 gives the diameters of rivets for various thicknesses of plates and is calculated according to a rule given by Unwin. TABLE 11 Table of Diameters of Rivets* Thickness of Plate Diameter of Klvet Thickness of Plate Diameter of Rivet V4 inch V2 inch 9/id inch 7/s inch ■/ie " 9/l6 " 5/8 " 15/.« " 3/s " "/ie " *U " lVw " 7/16 " ,f .