Archive for May, 2010

Hydraulic Vane Motor Efficiency

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Hydraulic Vane Motor Efficiency

A Vickers Model 25M (65) vane motor was chosen for the comparison. This motor is rated for 3000 rpm at 2500 psi maximum pressure. It has a displacement of 4.19 in3/rev. Efficiencies were calculated for a 35 GPM input flow. As shown in Fig. 5.4, the torque efficiency for this design is higher than for […]

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Hydraulic Gear Motor Efficiency

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Hydraulic Gear Motor Efficiency

The gear pump design can also be used as a motor. The Hydreco Model 1919 motor has a theoretical displacement of 4.53 in3/rev, a maximum pressure rating of 2500 psi, and 3000 rpm maximum speed rating. Efficiencies were calculated for a 36 GPM input flow to the motor (Fig. 5.3). Volumetric efficiency decreases linearly as […]

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Sources of Hydraulic Contamination

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Sources of Hydraulic Contamination

There are four sources of contamination in hydraulic fluid. 1. Built-in contamination. This is contaminate that was left in the system when it was assembled. It can range from a piece of teflon tape to a piece of welding slag. 2. Contaminated new oil. Contaminate is introduced during the manufacture and subsequent handling of oil. […]

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Hydraulic Contamination Control

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There are three types of failure in a fluid power system. 1. Degradation. The performance of the component degrades over time as surfaces wear, clearances increase, and leakage increases. 2. Intermittent. Valves stick and then break loose such that operation is intermittent. 3. Catastrophic. Catastrophic failure occurs when a major component breaks apart. Often, debris […]

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Methods for Cooling Hydraulic Oil

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Methods for Cooling Hydraulic Oil

Two types of heat exchanger are used to cool hydraulic oil: (1) shell-and-tube and (2) finned tube. The shell-and-tube (Fig. 8.1) has a series of tubes inside a closed cylinder. The oil flows through the small tubes, and the fluid receiving the heat (typically water) flows around the small tubes. Routing of the oil can […]

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Hydraulic Temperature Control

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Operating temperatures consistently above 160°F promote chemical reactions that change the properties of the oil. Effects of high temperature are listed below: 1. Oxidation of the oil 2. Formation of insoluble gums, varnishes, and acids 3. Deterioration of seals (they harden and leakage begins) 4. Loss of lubricity 5. Changes in viscosity The gums and […]

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Hydraulic Cylinder Construction

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Hydraulic Cylinder Construction

Typical construction for cylinders used in industrial applications is shown in Fig. 7.18. The seals are a key feature, as is the rod wiper. Dirt from the environment settles on the rod and will ingress into the hydraulic system if it is not removed. Some small particles do escape the wiper, and these must be […]

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Hydraulic Cylinder Failure

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Hydraulic Cylinder Failure

Standard cylinders are not designed to take a side load. Care must be taken to ensure that binding does not occur during extension or retraction. A designer will use one of the mounting methods shown in Fig. 7.15 to prevent binding. Also, it is often necessary to provide guides to ensure that the load follows […]

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Hydraulic Cylinder Selection

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Cylinder manufacturers typically classify their products as heavy duty, medium duty, and light duty. Pressure ratings up to 6000 psi are available. Some manufacturers build an agricultural-grade cylinder. These cylinders are satisfactory for applications where annual use is limited. A manufacturing application, where the cylinder cycles thousands of times per year, requires an industrial-grade cylinder.

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