tailieunhanh - Mechanical Engineer's Reference Book 2011 Part 9

Tham khảo tài liệu 'mechanical engineer's reference book 2011 part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Lubricants oils and greases 9 11 Conditions MlL-L-46152 US Military test procedures Engine type Oil quality Additive treatment level SHPD Super High Performance Diesel PO Passenger Car Diesel Figure 9 5 Approximate refationship between classifications and test procedures MIL-L-45199 Delisted Withdrawn Jan 90 Withdrawn Jan 90 pressure pumps have been developed. Additionally systems have to provide increased power densities more accurate response better reliability and increased safety. Their use in numerically controlled machine tools and other advanced control systems creates the need for enhanced filtration. Full flow filters as fine as 1-10 Aim retention capability are now to be found in many hydraulic systems. With the trend toward higher pressures in hydraulic systems the loads on unbalanced pump and motor components become greater and this coupled with the need for closer fits to contain the higher pressures can introduce acute lubrication problems. Pumps one of the main centres of wear can be made smaller if they can run at higher speeds or higher pressures but this is only possible with adequate lubrication. For this reason a fluid with good lubrication properties is used so that hydraulics is now almost synonymous with oil hydraulics in general industrial applications. Mineral oils are inexpensive and readily obtainable while their viscosity can be matched to a particular job. The hydraulic oil must provide adequate lubrication in the diverse operating conditions associated with the components of the various systems. It must function over an extended temperature range and sometimes under boundary conditions. It will be expected to provide a long trouble-free service life its chemical stability must therefore be high. Its wear-resisting properties must be capable of handling the high loads in hydraulic pumps. Additionally the oil must protect metal surfaces from corrosion and it must both resist emulsification and rapidly release entrained air that on