MECHANICAL ENGINEERING is that branch of the science and art of engineering which relates specially to machinery. It is closely allied to all other classes of engineering, inasmuch as there is hardly an occupation or industry in which machines of some sort are not directly or indirectly concerned, and it is often, for this reason, difficult to draw the line clearly between one class and the other. The civil engineer who plans and supervises the building of a railroad calls to his aid the machinery used. in excavating, blasting, building masonry and numberless other mechanical processes required in the work, all of which are the result of mechanical engineering. Electri cal engineering would accomplish comparatively little in the production of light and transmission of power were it not for the dynamo and other machinery on which dependence is placed for the manufacture and use of electric current. Mining engineering would be of little use in devising means for extracting the coal and mineral treasures buried in the earth if suitable machinery planned by mechanical engineers could not be employed to assist the labor of men. In marine engineering it is the mechani cal engineer who designs the steam plant which produces the motive power for the propulsion of the steamship, and without his assistance there would be no such a thing as a steamship. In dealing with problems relating to water works, the hydraulic engineer would be power less if he could not make use of the pumps and hydraulic machinery which the mechanical engi neer has devised. In every kind of industry where power is required, whether it be con nected with engineering, architecture, chemis try, agriculture or any other subject, the me chanical operations involved are based on the continuous operation of the machine constitut ing the motive power, whether it be a steam engine or water wheel or other motor, and these are the products of mechanical engineer ing. When we come to fully analyze the sub ject, therefore, it appears that mechanical engineering so far underlies engineering of every class, and all kinds of industrial oper ations, that it can almost be said to sustain the whole fabric of modern civilization.
Mechanical engineering, in its strictest sense, relates simply to the design of machines. In its broad sense it covers not only their design hut all matters relating to their proper construction and operation. In its common application it has for its scope both the design and construc tion of machines required for performing cer tain desired operations, and in addition the de sign and operation of the complete industrial plant, of which the individual machines form a part, and the construction of the plant in such a manner as to secure a successfully working whole for whatever purposes the plant is built. A large part of the mechanical engineering re quired at the present day consists in the as sembling of machinery to produce certain de sired ends, rather than in the design of the machinery itself. In many cases, the machinery has already been designed and constructed by engineers of the past and the perfected ma chines can be had by purchase in the market. This class of mechanical engineering covers a wide field. Perhaps its scope in this field can best be shown by referring in some detail to a familiar example. Take the case of the engi neering required in a large modern hotel. The mechanical plant of such an establishment em braces a great variety of machinery, among the most important of which are the machines and appliances required for power, heating, ventila tion, lighting, elevator service, distribution of hot and cold water, fire protection, refrigera tion, ice-making, laundry work and cooking. The work of the engineer, although confined mainly to the mechanical plant, must, at the very outset, be directed to the building itself. The building, no doubt, accords with the mod ern ideas of construction which call for a framework made of iron, in the design and construction of which the architect must have the assistance of the mechanical engineer. Not only this, but there must be, at the outset, a careful consideration of the required location of the various mechanical appliances, so that in working out the details of design relating to the building the architect may provide the necessary amount of room. He must lease a place for the boilers, engines, steam turbines. dynamos, pumps, etc., which make up the steam plant, and room also for the supply and storage of fuel. Provision must be made for the re ception of flues, ducts, pipes and wiring, which pass up through the building and which are dir tributed here and there to the different rooms The character of the structures which may be needed for supporting the machinery, and the location of such structures, must also be planned at the outset so that the building may be prepared for them before it is too late. In the design of the mechanical apparatus, one of the first questions for the engineer to con sider is the size and character of the steam plant. In dealing with this matter he ascer tains all the uses to which steam is applied. embracing the generation of power, the pump ing of water, the supply of steam for all kinds of heating and cooking, and that required for ventilation. With the data thus obtained he determines the total amount of steam required for all purposes and then calculates the boiler capacity needed to furnish the steam. For the next step he decides upon the type of boiler best suited for the purpose, whether fire-tube or water-tube, horizontal or vertical, or whether internally or externally fired, and fixes upon the number and size of the units as well as their location. He then makes a plan showing
the location of the boilers in the building; the style of the brick setting, if externally fired; the arrangement and location of the smoke flues and of the stack or chimney to which they connect. Having done this and settled all matters relating to the accessories which form a part of the boiler plant, he takes up, in due course of time, the remaining portion of the work relating to the boiler plant, which may be described at this point because it is representa tive of much of the work which requires to be done in relation to the other departments of the plant. He draws up specifications describ ing in full detail the character of the boiler plant desired and what is expected of it as regards capacity and economy. These specifi cations are submitted to boiler manufacturers who are asked to furnish proposals for the construction of the plant in the manner de scribed. When the proposals of the different bidders have all peen received, the engineer examines them, and after consulting with the owner of the property, selects one of the par ties with whom to contract for doing the work. Next follows the inspection of the boilers in process of construction in the shop and erection in the building, the object in view being to de termine if all the terms of the specifications are complied with. Finally, when the plant is com pleted and the contractor sets it to work, the engineer submits it to whatever tests may be required, and thereby determines whether the guarantees which have Leer made regardine the capacity and economy are fulfilled, and whether the plant performs its work with that degree of success and satisfaction that is called for by the specifications. Referring now to the con struction of the remaining departments of the mechanical plant, the next thing considered is the motive power. The greater part of the power in :rich a plant is likely to he transmitted by electricity, and, consequently, the motive power is that required for generating electric . (See ELECTRICAL ENGINEERING). After thy on the number, size and type of the generator units, he must then locate them, and make a plan showing their respective locations with reference to the boiler plant and other parts of the building. At the same time there must be laid out on the plan a system of steam piping connecting the boiler to the engines or turbines, and this must he arranged with a view to supplying steam to all other points of use, including the heating of the building. Next in order, the pumping machilliry re quires attention. This embraces the boiler feed pump, the various pumps used for the differ ent classes of hotel work, the elevator pump, if the hydraulic system is employed, and the fire pump. The engineer must determine the proper size of each one according to the amount of water to be pumped, and he must select the type of pump, fix its location, show it on the plan and extend the system of steam piping to furnish each with the proper supply. He must also plan the exhaust piping re quired for each engine, turbine and pump, the necessary vent pipe for carrying the waste steam to the atmosphere, and, if exhaust steam is used for heating, the required connection of the exhaust pipe to the main supply of the building. There must be a heater provided in the exhaust pipe system for heating the feed water before it is pumped to the boilers, and another heater for the supply of hot water to the building, and both of these, in their selec tion, location and connection, require the care ful attention of the engineer. They must be properly laid out and shown on the plan. A complete system of water piping is required, connecting boilers, pumps, hydrants and ele vators, to say nothing of the hot and cold water supply pipes which extend to the various rooms of the hotel, and the location of these must likewise be shown by means of a suitable plan. Not the least important part of the me chanical engineering for the building is the design and construction of the heating and ventilating apparatus. Calculations of the amount of heat and radiating surface needed, the quantity of air required to be changed in a given time and the sizes of the mains and returns are involved in this work. Here, also, the kind of the system to he employed, the location and type of the heating and ventilat ing apparatus, including all the necessary de tails, are questions which the engineer must consider and decide, and the results must be indicated by proper plans. These various parts of the work are made the subject of detailed specifications, in the manner already referred to, and, likewise, proposals for the installation of the work are obtained, contracts awarded, inspection carried on during construction and the work tested for acceptance when it is completed, all of which is done tinder the jurisdiction of the mechanical engineer. In much the same manner, the selection, location, construction and installation of the remaining parts of the mechanical plant, embracing ele vator machinery, laundry machinery, refriger ating machinery, ice-making machines and the many other appliances concerned in the work of the hotel are carried out under his super vision.