MIL-STD-1365C
4.4.7 Human factors engineering (HFE). HFE is the application of the knowledge of human capabilities and characteristics to the development of engineered equipment and systems. By applying this knowledge, human performance, and therefore system performance, can be improved dramatically. Man/machine systems designed with the human as the key element are inherently safer and more reliable than those that are not.
4.4.7.1 HFE design criteria. The designer shall consider safety, comfort, ease of use, and productivity/performance during development of equipment or a system. The methodology presented in ASTM F1166 shall be followed to mitigate potential deficiencies in human/equipment interfaces.
4.5 Hydraulic systems.
4.5.1 General. Hydraulic systems and parts shall be designed to operate satisfactorily under all conditions which the equipment may be expected to encounter. They shall conform to sound design practice with respect to flow constriction, structural design, and strength. Consideration shall be given to baffles, fluid connectors, sumps, drains, vents, filters, inlet filter units, and heat exchangers. Unless otherwise specified in the applicable specification or by the procuring activity (see 6.2), hydraulic systems shall conform to the best commercial practices.
4.5.2 Materials.
4.5.2.1 Metals. Metals shall be compatible with the hydraulic fluid used and intended temperature extremes, and shall conform to the functional, service, and storage conditions to which the components and system will be exposed. Magnesium shall not be used.
4.5.2.2 Plastic parts. Plastic parts shall be used only when allowed by the developmental specification or with the approval of the procuring activity. When used, they shall be suitable for the system environment and the fluid used.
4.5.2.3 Plating. The applicable developmental specification shall define the environment in which the equipment will operate. Metal coatings which have been demonstrated to be satisfactory for commercial applications or by the government shall be used to protect the equipment in the specified environment. When used, aluminum alloys shall be anodized or treated with a chemical coating suitable to resist corrosion. Ferrous alloys shall be internally and externally protected against corrosion. Further, cadmium plating shall not be used, and zinc
plating shall not be used for any internal parts or on internal surfaces in contact with hydraulic fluid or exposed to its vapors.
4.5.2.4 Hydraulic fluid. Hydraulic fluids should be selected in accordance with best commercial practice, except that for systems exceeding 600 psi (see 4.5.3.3).
4.5.3 Pressure limitations.
4.5.3.1 Gauges. Red-lined gauges shall be provided to indicate safe limits of operation.
4.5.3.2 Emergency pressure backup. When hydraulic pressure is supplied by a powered primary source, a manual hand pump and check valve circuit shall be provided for emergency pressure backup in the event of a failure to the primary source. The manual system shall be capable of providing sufficient power to operate the lift mechanism to raise or lower the rated load; however, it may be at a reduced rate of motion as specified by the applicable developmental specification. Levers to operate the manual hand pump shall be designed so that the force required by one hand does not exceed 30 pounds. For two-hand operation, the force shall not exceed 50 pounds. Maximum fore-aft displacement of the lever shall not exceed 14 inches.
4.5.3.3 Safety hydraulic fluid. When system pressure is greater than 600 psi, a water-based safety type hydraulic fluid shall be used.
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