Chapter 2 Drawings and Specifications

CHAPTER 2 DRAWINGS AND SPECIFICATIONS The Naval bases, advance bases, Seabee camps, and equipment of the Navy were built from plans drawn on blueprints. They are operated, checked, and maintained according to information found on these same blueprints. When the equipment fails in service or is damaged in battle, blueprints are used to aid the repairman. When new parts are to be made or a facility is expanded, blueprints provide the necessary information Planning, scheduling, and manpower and material estimating are based on the information contained in these blueprints. This chapter discusses the function and care of blueprints and the importance of being able to read and work from them. This chapter will also discuss electrical diagrams and schematics. Diagrams and schematics are maps that indicate the configuration of circuits and circuit connections and components of electrical equipment. When properly used, they are an invaluable aid in installation, troubleshooting, and repair of an electrical component. Understanding and being able to use blueprints and schematics will be some of the most important work assignments you will have as a Construction Electrician. BLUEPRINTS Blueprints are reproduced copies of mechanical or other types of technical drawings. The term blueprint reading means interpreting the ideas expressed by others on drawings whether the drawings are actually blueprints or not. Drawing or sketching is the universal language used by engineers, technicians, and skilled craftsmen. Whether this drawing is made freehand or with drawing instruments, it is used to convey all the necessary information to the individual who will then fabricate and assemble the mechanical device. PARTS OF A BLUEPRINT Military blueprints are prepared as to size, format, location, and information included in the various blocks according to the Military Standards (ML-STD-100) (latest revision) Engineering Drawing Practices. American National Standard Institute (ANSI) is the mandatory publication used by the Navy for the graphic symbols (ANSI Y32.2—1975) and electrical wiring symbols (ANSI Y32.91—1972). These standards are used on electrical diagrams and electrical drawings. The various parts of a blueprint are described briefly in the following paragraphs. Title Block The requirements that determine what information must be included in a title block (fig. 2-1) vary. The title block, however, will contain the title of the drawing, the signature of the approving authority, the drawing number, the sheet number (when the drawing is one of a set of several sheets), and the number of sheets in the project set. The Naval Facility Engineering Command (NAVFACENGCOM) also requires the following information in title blocks: the name and location of the activity; the specifications and contract numbers (if any); the preparing activity, including the architect- engineer (A-E) firm, if applicable; and the surnames of the personnel concerned in the preparation of the drawings. The code identification number 80091 is to appear in the title block of all NAVFACENGCOM drawings as well as a sheet designation letter (I—Index, C—Civil, A—Architectural, S—Structural, M—Mechanical, P—Plumbing, E—Electrical, and W—Waterfront). Drawing Number All blueprints are identified by a drawing number that appears in a block in the lower right-hand comer of the title block. The drawing number is especially important, both for purposes of filing the blueprint and for locating the correct drawing when it is specified on another blueprint. 2-1