MAINTAINABILITY DESIGN TECHNIQUES METRIC - AcqNotes.com

Downloaded from http://www.everyspec.com on 2011-10-29T14:56:01.DOD-HDBK-791(AM)CHAPTER 10ENVIRONMENTAL FACTORSThis chapter emphasizes the importance of the environment in which equipment will be operated or storedas a factor in establishing design criteria and evaluating maintainability features. The environmental factors—natural and induced—and combined environ mental factors as they affect maintenance personnel and materielare discussed.10-1 INTRODUCTIONEnvironment is defined in MIL-STD-1165 (Ref. 1) as“the totality of natural and induced conditions occurringor encountered at any one time and place”. The naturaland induced conditions (factors) are presented in par.10-2. The description of the environment must be tailoredfor particular consideration according to the particularmateriel type and to the challenge the materiel presents topersonnel who must operate and maintain it. In differentclimates, the environmental factors vary in importance.For example. solid precipitant comprise an importantfactor in Alaska, but this factor is of no importance in thePanama Canal Zone. Similarly, rain is an important factorin the outdoor envrironment in the temperate zone butis unimportant inside a warehouse. The interior of awarehouse, however, is an important region of the environmentfor materiel. Table 10-1 (Ref. 2) indicates therelationship of environmental factors to climatic types.Certain combinations of environmental factors andclimates exert various levels of effects on materiel andpersonnel—some more severe, others less severe. In thepast it was considered impractical to design equipment tomeet a specific climatic condition, i.e., equipment wasdesigned to be operated and maintained in a worldwideenvironment. This philosophy is being challenged (Ref. 3)when nondevelopmental items (NDI) could satisfy anexisting requirement. It is necessary to examine the practiceof designing to the “worst case” scenario for allequipment. The design for all environmental conditions isa necessary approach for front-line combat materiel butmay not make sense for materiel used in rear echelons orTABLE 10-1. RELATIONSHIP OF ENVIRONMENTAL FACTORS TO CLIMATE (Ref. 2)Factor Intermediate Arctic Hot-Dry Hot-WetTerrainLow temperatureHigh temperatureLow humidityHigh humidityPressureSolar radiationRainFogSolid precipitationWhiteout and ice fogSalt, salt fog, salt waterWindOzoneMicrobiological organismsMicrobiological organismsAtmospheric pollutantsSand & dustShockVibrationAccelerationAcousticsElectromagnetic radiationNuclear radiation+++ Key factor++ Important factor+ Active factor0 Unimportant or absent factor* Little or no climatic relationship++++++0++0+++++++0++*++*+******++++++00+0+++++++++++ +*00*0******+++0+++++00++++000++*00*+++******+++0++0++++++++000+++*++++*+******10-1