MAINTAINABILITY DESIGN TECHNIQUES METRIC - AcqNotes.com

Downloaded from http://www.everyspec.com on 2011-10-29T14:56:01.Figure 6-3. Placement of Labels forHazardous Tasks (Ref. 11)Figure 6-4. Examples of Informative Labels(Ref. 11)DOD-HDBK-791(AM)manufacturer and or National Stock Number (see par.3-6.9) uniquely defines the item for ordering from themanufacturer. supply, and inventory control.When parts cannot be physically marked because oflack of space, e.g., too small, or because marking wouldhave a deleteriouss effect. the information specified in par.6-3.2 should be marked on the container (Ref. 3) in additionto the identification marking information specified inMIL-STD-129 (Ref. 12). Where polarity or impedancerating are critical, the identification should so indicate.Some parts, because of their small size, e.g., resistors, arecolor coded to reveal their ratings and quality. For example,a gold marking on a resistor indicates ±5% of its ratedvalue, a silver marking, ±10%.A part number and the drawing number detailing thepart are the same. As a drafting practice, each part on thedrawing or schematic should be keyed to the descriptionof the part shown elsewhere on the drawing or schematic.A wiring diagram prepared in accordance with the schematicshould carry identification for wire, sockets, plugs,receptacles, resistors, transistors, capacitors, etc. Terminalson all assemblies and parts should be suitablymarked, and the wiring should have all terminal markings.Circuit cards should show the part number or a codeto assure the correct positioning of parts to be affixed tothe card. Each mechanical part that will require repair orreplacement must be identified by a unique name andnumber.6-4 METHODS OF LABELINGThere are numerous marking processes available, andeach one has advantages and limitations. A marking processshould be selected only after a review of the partdesign (material, type of construction, marking spaceavailable, and environment in storage and use); the typeof surface to which it will be applied; the best location forvisibility or durability; and any remarking requirementsthat may result from engineering changes. Markings anddesignations are applied either directly to the item—i.e.,part, framework, panel, chassis, or end item—or by attachmentof separate plates bearing the desired designations.The commonly used methods of applying the charactersare ink stamping, steel stamping, engraving, molding-in,decalcomania transfer, stenciling, photoetching,metal plates, tags, photocontact, screen printing, andadhesive-backed labels of metal or plastic. Special featuresthat pertain to each of these processes, their limitations,and preferred types of applications are described inthe subparagraphs that follow.Despite the fact that this is a maintainability handbook,the production advantages and disadvantagesassociated with the various application methods areincluded because—since labeling is such a seeminglyunimportant consideration—they may not be wellknown.This information will enable the maintainability6-5