【文章內(nèi)容簡介】 be done through use of a hydraulic cylinder which converts hydraulic energy into linear motion and work, or a hydraulic motor which converts hydraulic energy into rotary motion and work. As with hydraulic pumps, hydraulic cylinders and hydraulic motors have several different subtypes, each intended for specific design applications. Key Lubricated Hydraulic Components There are several ponents in a hydraulic system, that due to cost of repair or criticality of mission, are considered vital ponents. Pumps and valves are considered key ponents. Several different configurations for pumps must be treated individually from a lubrication perspective, including: Vane Pumps There are many variations of vane pumps available between manufacturers. They all work on similar design principles. A slotted rotor is coupled to the drive shaft and turns inside of a cam ring that is offset or eccentric to the drive shaft. Vanes are inserted into the rotor slots and follow the inner surface of the cam ring as the rotor turns. The vanes and the inner surface of the cam rings are always in contact and are subject to high amounts of wear. As the two surfaces wear, the vanes e further out of their slot. Vane pumps deliver a steady flow at a high cost. Vane pumps operate at a normal viscosity range between 14 and 160 cSt at operating temperature. Vane pumps may not be suitable in critical highpressure hydraulic systems where contamination and fluid quality are difficult to control. The performance of the fluid’s antiwar additive is generally very important with vane pumps. Piston Pumps As with all hydraulic pumps, piston pumps are available in fixed and variable displacement designs. Piston pumps are generally the most versatile and rugged pump type and offer a range of options for any type of system. Piston pumps can operate at pressures beyond 6000 psi, are highly efficient and produce paratively little noise. Many designs of piston pumps also tend to resist wear better than other pump types. Piston pumps operate at a normal fluid viscosity range of 10 to 160 cSt. Gear Pumps There are two mon types of gear pumps, internal and external. Each type has a variety of subtypes, but all of them develop flow by carrying fluid between the teeth of a meshing gear set. While generally less efficient than vane and piston pumps, gear pumps are often more tolerant of fluid contamination. 1. Internal gear pumps produce pressures up to 3000 to 3500 psi. These types of pumps offer a wide viscosity range up to 2200 cSt, depending on flow rate and are generally quiet. Internal gear pumps also have a high efficiency even at low fluid viscosity. 2. External gear pumps are mon and can handle pressures up to 3000 to 3500 psi. These gear pumps offer an inexpensive, midpressure, midvolume, fixed displacement delivery to a system. Viscosity ranges for these types of pumps are limited to less than 300 cSt. Hydraulic Fluids Today’s hydraulic fluids serve multiple purposes. The major function of a hydraulic fluid is to provide energy transmission through the system which enables work and motion to be acplished. Hydraulic fluids are also responsible for lubrication, heat transfer and contamination control. When selecting a lubricant, consider the viscosity, seal patibility, base stock and the additive package. Three mon varieties of hydraulic fluids found on the market today are petroleumbased, waterbased and synthetics. 1. Petroleumbased or mineralbased fluids are the most widely used fluids today. The properties of a mineralbased fluid depend on the additives used, the quality of the original crude oil and the refining process. Additives in a mineralbased fluid offer a range of specific performance characteristics. Common hydraulic fluid additives include rust and oxidation inhibitors (Ramp。O), anticorrosion agents, demulsifies, antiwar (AW) and extreme pres