MAINTAINABILITY DESIGN TECHNIQUES METRIC - AcqNotes.com

More documents

Recommendations

Info

Downloaded from http://www.everyspec.com on 2011-10-29T14:56:01.DOD-HDBK-791(AM)stateside. Let us take climatic hardening as an example.Do we need to harden the entire Army inventory ofequipment to withstand an arctic climate when only 10%of the equipment is ever used there? Why not harden the10% that is supposed to endure the environment or providesupplemental environmental protection in the formof kits or shelters? Accordingly, the maintainabilityengineer—before developing a maintainability plan --should ascertain the decision of the Materiel AcquisitionReview Board, Army Materiel Command, and the ArmyTraining and Doctrine Command relative to the degree ofhardness required.Of the natural environmental factors, temperature andhumidity represent the most severe environment formaintenance in the field. Extreme cold affects the technicians’ability to handle parts, and the heavy gloves makesmall parts virtually impossible to handle or manipulate.Heavy clothing interferes with access and impairs visibility.Cold temperatures also have a deleterious effect onmany materials.Hot climates also create poor working conditions.Extremely hot temperatures, particularly if associatedwith high relative humidity, have a debilitating effect onpersonnel. Hot climates also may create difficult workingconditions. Hot, dry areas usually produce dust, whichpenetrates mechanical equipment and causes prematurewear in moving parts. Where dust accumulates, it canabsorb water; this may result in corrosion and electricalproblems. Hot, wet areas—such as the tropics causefungous growth in and on equipment.Warfare, although not an induced environmental factorin the classical sense, is an important factor. Warfareneglecting increased materiel damage—causes severemaintenance problems because of the mental stress on thetechnician; he is concerned with both his position and theurgency to return equipment to a serviceable condition asrapidly as possible. The conditions of war may also makeit difficult to obtain required repair parts and thusaggrevate the situation.Of the induced environmental factors, shock and/orvibration represent the most severe environment.Personnel performance—operator and maintenance—isadversely affected by the degree of the shock and/orvibration. These factors also can produce mechanicaldamage to materiel. Materiel experiences a variety ofdynamic mechanical loads during movement i.e., fromthe origin of manufacture to the stockpile and from thestockpile to target. Some of these loads are intrinsic to thetype of transport and handling; others are characteristicof the system itself or associated with inadvertentmishandling.10-2 ENVIRONMENTS10-2.1 NATURAL, INDUCED, ANDCOMBINEDThe components, or descriptors, of the environmentare referred to as factors. The factors (see Table 10-2 (Ref.4)) are divided into natural and induced, defined asfollows:1. Natural. Those factors primarily natural in origin.It is notable that the importance of each of these factorsmay be altered by man and. in fact, of often is whenprotection is provided.2. Induced. Those factors for which man’s activitiesconstitute the major contribution. These factors, resultingfrom man’s activity, may be controlled to any extentdeemed necessary and practical.Table 10-2 also identifies the environmental factors as toclass.The term “combined environmental factors" is used insituations to identify combinations of environrnental factorsthat frequently are observed arid that are associatedby natural coupling. In their effects on materiel, manyenvironmental factors act in conjunction or in synergism.In the conjunctive case are found examples of factors inpairs or in multiple combinations that are characteristicof geographic regions or other circumstances. Thus hightemperature and high humidity often cooccur its do hightemperature and airborne sand and dust. In the synergisticcase two or more environmental factors act together toproduce effects that are more important than the separateeffects of either constituent. An example of synergism isthe effect obtained with low temperature and vibration.With this combination of factors, rubber shock mountsthat can survive either the severe cold or the severe vibritionsreadily are destroyed by the combined action of thetwo envronmental factors. In similar fashion, the appearanceof one environmental factor may inhibit theaction of another e.g., high temperature inhibits solidprecipitants, and low temperature inhibits attack bymicrobiological organisms. Time of exposure is an importantfactor when considering the effects of combinedenvironmental factors. Table 10-3 (Ref. 2) summarizesthe qualitative relationships between pairs of environmentalfactors.For a detailed and sophisticated treatment of environmentalfactors definitions, concentrations or severityworldwide, methods of measurement, and effects on personneland materiel refer to Refs. 2, 4, 5. and 6.10-2.2 WARTIME ENVIRONMENTSWarfare—ignoring a worst case scenario of a “nuclearwinter”—will have no effect on the naturally occurringenvironmental factors presented in par. 10-2.1. Theinduced environmental factors may be increased in intensityand effects due to the employment of nuclear and orchemical munitions. Enemy and friendly fire with theattendant noise although not classical envrironrnentalfactors– must be considered in the total environrnent ofwarfare.Maintenance operations. following a nuclear or chemicalattack. will include decontamination. The guidance inthe previous chapters as to permanent labels and thedesign of doors and external fixtures so as to drain readilyand not act as liquid reservoirs will facilitate decontamination.Radiation that has been induced in materiel by anuclear explosion cannot be removed by decontamination.Accordingly, to avoid possible overexposure of personnel,speed of repair is of the essence. The guidance in10-2
Downloaded from http://www.everyspec.com on 2011-10-29T14:56:01.DOD-HDBK-791(AM)TypeNaturalInducedTABLE 10-2. MAJOR ENVIRONMENTAL FACTORS (Ref. 4)ClassTerrainClimaticBiologicalAirborneMechanicalEnergyFactorTopographyHydrologySoilsVegetationTemperatureHumidityPressureSolar radiationRainSolid precipitantFogWindSaltOzoneMicrobiological organismsMicrobiological organismsSand and dustPollutantsVibrationShockAccelerationAcousticsElectromagnetic radiationNuclear radiationthe previous chapters relative to simplicity, accessibility,and module replacement is, therefore, apropos.Decontamination and working in a contaminated areawill require a protective ensemble. The wearing of theprotective mask, hood. overgarment, and gloves posesserious problems in functional efficiency and degradation.The overall ensemble imposes the problems of heatstress, loss of visual field and visual acuity, lens foggingwith attendant loss of vision, and reduced tactility. Thebulk of the protective ensemble must be evaluated as afunction of the operators’ and technicians’ task (Ref. 7).10-2.2.1 ChemicalA chemical (pollutant) environment can be created bythe introduction of lethal and nonlethal chemical agentsand riot control chemical agents. The chemical environmentmay result in the deposition of corrosive materialson materiel; if inhaled or deposited on bare skin, physiologicaland psychological changes to personnel will result.10-2.2.2 NuclearThe nature and severity of the contamination resultingfrom a nuclear detonation are a function of weapon yieldand type of burst i.e.. air, ground, or underwater. Thefire and blast effects, except for magnitude, are identicalwith those associated with conventional weapons; theeffects of the nuclear radiation are unique. Salvageableequipment immediately after the event will be radioactivedue both to induced nuclear radiation and fallout. Thefallout can be removed by decontamination techniques,but the induced radiation will persist. The persistence ofthe radiation is a function of the material in which theradiation was induced. An electromagnetic pulse (EMP)—which has the potential for severely damaging electroniccomponents and circuits—is associated with a nucleardetonation. Nuclear effects on materiel are presented inpar. 10-3.2.1.7.10-2.2.3 Electromagnetic RadiationRef. 6 is a thorough, scholarly presentation of electromagneticradiation—sources, detection, measurement,and effects on man and materiel. Electromagnetic radiationis present in many maintenance environments andmay be introduced by equipment related to the functionsbeing performed or under the control of the techniciansubject to exposure. Basically, the electronic environmentconsists of two categories of radiation (Ref. 6), i.e., naturallyoccurring radiation and radiation generated by manmadeequipment. The very low frequency band, i.e., lessthan 10 4 Hz, is not considered to be environmentallyimportant because (1) the radiated power densities arerelatively low and (2) at the long wavelengths, the energyabsorption by materiel is negligible.Although the electromagnetic environment is composedof emanations from a multiplicity of sources, only a10-3
Page 3 and 4:
Downloaded from http://www.everyspe
Page 6:
Page 9 and 10:
Page 11 and 12:
Page 13 and 14:
Page 15 and 16:
Page 17 and 18:
Page 19 and 20:
Page 21 and 22:
Page 23 and 24:
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
Page 69 and 70:
Page 71 and 72:
Page 73 and 74:
Page 75 and 76:
Page 77 and 78:
Page 79 and 80:
Page 81 and 82:
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134: Downloaded from http://www.everyspe
Page 183: Downloaded from http://www.everyspe
show all

MAINTAINABILITY DESIGN TECHNIQUES METRIC - AcqNotes.com

Create successful ePaper yourself

Delete template?

Save as template?