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ASME Y14.44-2008 pdf download

ASME Y14.44-2008 pdf download.Reference Designations for Electrical and Electronics Parts and Equipment.
1 GENERAL 1.1 Scope This Standard covers the formation and application of reference designations for electrical and electronics parts and equipment. The reference designations of this Standard are intended for uniquely identifying and locating discrete items on diagrams and in a set; for correlating items in a set; graphic symbols on diagrams; and items in parts lists, circuit descriptions, and instructions. This Standard includes three methods forforming and applying reference designations. (a) the unit numbering method (b) the location numbering method (c) the location coding method A complete reference designation may incorporate reference designations formed by the use of any of these methods at any level from basic parts to complete units. The unit numbering method has a long history of satisfactory use in all types of electrical and electronics equipment. The location numbering method and loca- tion coding method have been developed to permit a rapid physical location of items in large, complicated equipment featuring multiple use of many identical or closely similar items. These methods shall be applied in such a way that duplicate complete reference designa- tions do not occur in a piece of equipment or system. Device function designations for power switchgear and industrial control use are not covered by this Standard.
1.4 Changes in Reference Designation Class Letters If changes in the state-of-the-art appear to make changed ornew reference designationclass letters neces- sary, provide the following information: (a) item for which new designation is requested, type or class of item, and frequency of use (per drawing, per set, etc.) (b) present reference designation used (c) proposed reference designation (d) reasons for recommending a change (supply source material, if feasible) (e) graphic symbol Address comments to The American Society of Mechanical Engineers, Secretary, Y14 Standards Committee, Three Park Ave., New York, NY 10016, and refer to this Standard. 1.5 Use of “Shall,” “Should,” and “May” In this Standard, the word “shall” is to be understood as a requirement; the word “should” as a recommenda- tion; and the word “may” as permissive, neither manda- tory nor recommended. 1.6 Reference The following revisions of American National Standards form a part of this Standard to the extent specified herein. A more recent revision may be used, provided there is no conflict with the text of this Standard. In the event of a conflict between the text of this Standard and the references cited herein, the text of this Standard shall take precedence. IEEE Std 315-1975, Graphic Symbols for Electrical and Electronics Diagrams Publisher: Institute of Electrical and Electronics Engineers (IEEE), 445 Hoes Lane, Piscataway, NJ 08855-41412 UNIT NUMBERING METHOD 2.1 Basic Reference Designations A basic reference designation for an item (such as resistor, inductor, electron tube, or subassembly) shall consist of one or more letters identifying the class and a number (e.g., AR14, C3). In some cases a suffix letter may be added (e.g., C7A, C7B). All letters shall be upper- case. The designation shall be written with all characters the same size, on the same line, and without separation. The reference designation for a unit consists of only a number (see para. 2.2.2). The reference designation (generally the basic reference designation) may be used in a parts list in lieu of an item or find number. 2.1.1 Class Letter. The letters identifying the class of an item shall be selected from Section 22 of IEEE Std 315 (see also para. 2.1.8). Special Class Letter Considerations. For reference designation assignment purposes (a) the term “subassembly” as used hereinshall apply equally to an assembly. (b) a group ofparts shall notbe treated as a subassem- bly unless it is one or more of the following: (1) a plug-in item (2) a significant item covered by a separate schematic (3) a multiple-application item (4) likely to be handled as a replaceable item for maintenance purposes See also para. 2.1.2 Number. The number portion of the reference designation differentiates an item from all other items identified by the same class letter. 2.1.3 Sequential Number Assignment. Within each significant item (unit, assembly, subassembly, etc.), for the parts of each class, numbers shall be assigned sequentially on the schematic diagram in a systematic manner beginning with 1.

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