Hydraulic machine

The cavitation phenomenon offers at present considerable technical interest, first of all, in connection with the destruction of materials and energy losses that arise in hydraulic machines, propellers, etc., when the velocity is increased. 

Tensile tests involve either stretching a sample and monitoring the load or loading it while monitoring the extension. The simplest test uses a tensile testing machine (e.g. an Instron) where the sample is stretched at a constant rate while the load is measured using a (usually hard) load cell. Variations on this test allow the specimen to be extended at a constant strain rate or to be loaded at a constant load, or stress rate. These latter tests are usually carried out on servo hydraulic machines. 

Cyclic tension-tension fatigue tests were conducted on a computer controlled MTS servo hydraulic machine. The load ratio R (the ratio of minimum load to the maximum... 

PCB hydraulic machines containing >50 ppm PCBs and in which all free flowing liquid has been removed PCB-Contaminated Electrical Equipment... 

In CD production for example, toggle lever and fully hydraulic machines can sometimes be found side by side. 

Reduced maintenance. The hydraulic machine has fewer moving parts. Having less wear points, there is less worry about linkage maintenance and also fewer replacement parts. 

Improved controls. Hydraulic machines have ram control for up or down travel with a foot switch either on or off. Circuits are in use, so that with the foot control in the off position, the ram immediately returns to the top of the stroke. 

It appears that the use of drag-reducing additives in hydraulic machines and hydraulic power stations is quite feasible. The additional investment is negligible- The power gain may be several hundred kW per kg of polymer at very low injection rates, hence, it may be economical at peak demands. 

Bilgen/ E., Vasseur/ P. Feasibility of utilization of drag reducing additives in hydraulic machines. 2nd Int. Conf. Drag Reduction/ Paper B4/ Cambridge 1977... 

These tests were carried out in a hydraulic machine provided with perfectly hinged platens. Oil pressure was servo-controlled by measurement of the overall vertical displacement. 

An injection-molding screw is rotated using an electric drive motor coupled with a reducer or gear box or a direct hydraulic drive. Electric drive motors are usually employed with larger hydraulic machines [clamp force > 15,000 kN (1700 tons)]i and in all-electric molding... 

The maximum injection pressure is the maximum available pressure for injection. In hydraulic machines, the injection cylinders are rated for a maximum hydraulic pressure, typically 14 to 21 MPa (2000 to 3000 Ib/in ). Pressure on the melt increases because the screw diameter is usually smaller than the diameter of the injection cylinder. Thus, injection pressure Pinj is given by... 

A typical molding cycle will not start until a number of interlock conditions are satisfied. While the interlock conditions vary with the machine, the machine will not enter semiautomatic or automatic mode in the absence of these interlock conditions. Generally, the gate (operator guard door) must be closed and the gate safety (interlock) switches tripped. In hydraulic machines, the front gate has three switches (electrical, mechanical, and hydraulic) whereas the rear gate usually has one or more electrical limit switches. The electrical interlocks are usually electrical limit switches. When tripped, the hydrauHc interlock pre-... 

The granite used in the current study was obtained from the Lingyan Mountain, located in Suzhou City, Jiangsu Province, China. The rock was sliced and polished into the cubic specimens with the size of around 50 mm x 50 mm x 50 mm. The uniaxial compression tests for the specimens were employed using the YE-2000 type of hydraulic machine, produced by the Zhejiang Jingyuan Machinery Company Limited, China. The distances from the camera to the specimens were about 5.0 m. The video camera was placed normal to the rock specimen surface in order to eliminate the perspective errors and lens distortion. 

Bernoulli s Theorem. When friction is neghgible and there are no hydraulic machines, the conservation of energy principle is reduced to Bernoulli s equation, which has many applications in pressurized flow and open-channel flow when it is safe to neglect the losses. 

Use of advanced guarding systems interlocks and trip devices for pneumatic and hydraulic machines application of risk assessment methodologies and reliability engineering principles to complex guarding systems. 

Over 90% of the hydraulic machine producers currently do not report plastic pressure on the controller or gauges. Hydraulic pressure is the standard. Production scheduling often forces a mold to be run in several different presses, each with a potentially different intensification ratio. Processors need to control this plastic pressure variable for consistent parts. Many molders reproduce hydrauhc pressures (a machine variable) and not the critically important molten plastic pressures (the key plastic variable). With the advent of all electric machines this issue may resolve itself Electric injection-molding machines use plastic pressure values for set points and reported pressures on their controllers. Injection pressure is sensed through a transducer moimted on the thrust bearing pushing on the screw, and it must read in plastic or injection pressure. 

The whole aim behind present ERF developments is to provide a means of control/adaptronics (that is easy to apply and economical) to a mechanism that has to be by its nature flexible in force, displacement or speed and hydraulically operated. Electronic solid-state semiconductor devices and computers are powerful, inexpensive and adequate for many applications in control, and yet their interface with hydraulic machines usually involves a bulky solenoid or an expensive servo-valve, often with a pilot stage and a power su > ply. The aim of ER research is to be able to influence a hydraulic mechanism directly with a current low enough to allow the integration of a system made up of electronic transducing and signal-conditioning equipment, computer processors and feedback monitoring, solid-state controllable field-excitation... 

The subject of cavitation has stimulated the interest of engineers and scientists since the early experiments of Sir Charles Parsons in the late 19th Century, so eloquently described by Burrill. Since that time research effort has been roughly divided between that concerned with the effects of cavitation in fluid flow on the efficiency of hydraulic machines such as turbines, pumps and propellers, and that concerned with the problems of material erosion resulting from the collapse of the vapour bubbles. Several major texts have been publishedand excellent reviews have dealt with specific areas. The latter will be identified in the relevant sections. 

TPUs can be blow molded, and the requirements for the screw design are the same as for extrusion. Both injection molded and blow molded parts should be heated at 100 °C for 24 hours to reach the equihbrium structure and minimize creep and compression set. The main field of application of thermoplastic urethanes is for various casters, rollers, wheels, flexible clutches, seals and gaskets for hydraulic machines, shoe soles, printing rolls and machine parts. 

HUFFENUS, 3.P. and KHALETZKY, D. "Theoretical study of heat transfer in thrust bearings of hydraulic machines. Application to the cooling of the oil film". Proc. of the 6th Leeds-Lyon Symposium, 1980, 117-126. 

Khurmi, R. S. 1970. Hydraulics and hydraulic machines. Delhi S. Chand Co. 

Performance degradation when cavitation occurs in a hydraulic machine. 

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