Actuators hydraulic

FIG. 10-99 High-pressure, low-capacity compressor having a hydraulically actuated diaphragm, (Pressure Products Industries.)... 

All valves are equipped with hydraulic actuators, electronic positioning controllers for precise positioning, and solenoid valves for rapid (trip) opening of bypass valves and emergency closure tripping of trip and inlet control valves. 

Fig. 4.21 Free-body diagram of load on hydraulic actuator.

Liner hanger. This special tool is installed on the top of the liner string. The top of the liner hanger makes up to the drillpipe on which the entire liner assembly is lowered into the well. Liner hangers can be either mechanically or hydraulically actuated. 

Speed and load governing with electro-hydraulic actuators... 

Pneumatic actuators are normally used to control processes requiring quick and accurate response, as they do not require a large amount of motive force. However, when a large amount of force is required to operate a valve (for example, the main steam system valves), hydraulic actuators are normally used. Although hydraulic actuators come in many designs, piston types are most common. 

A typical piston-type hydraulic actuator is shown in Figure 37. It consists of a cylinder, piston, spring, hydraulic supply and return line, and stem. The piston slides vertically inside the cylinder and separates the cylinder into two chambers. The upper chamber contains the spring and the lower chamber contains hydraulic oil. 

The principles of operation of a hydraulic actuator are like those of the pneumatic actuator. Each uses some motive force to overcome spring force to move the valve. Also, hydraulic actuators can be designed to fail-open or fail-closed to provide a fail-safe feature. 

A major advantage of solenoid actuators is their quick operation. Also, they are much easier to install than pneumatic or hydraulic actuators. However, solenoid actuators have two disadvantages. First, they have only two positions fully open and fully closed. Second, they don t produce much force, so they usually only operate relatively small valves. 

Hydraulic actuators use fluid displacement to move a piston in a cylinder positioning the valve as needed for 0-100% fluid flow. This type actuator is incorporated when a large amount of force is necessary to operate the valve. 

An extrusion is comprised of a basket (cylinder) to contain the mix and a hydraulically actuated piston to press the mass through multiple extrusion dies. The baskets are jacketed for temperature control and contain internal screens to retain large agglomerates. Since the casting powder strands are unperforated, the dies are simple cylindrical barrels with conical lead-in sections. Extrusion rates are normally controlled by orifices in the hydraulic supply line however, constant-rate positive displacement devices are also used. As they extrude, the strands are collected separately in suitable containers. 

Fig. 4.2-7. In-line safety- and side-stream valve (PN 2500, DN 60/32, adopted from BOHLER). 1, Tubular reactor train 2, In-line valve 3, Hydraulic actuator 4, Side outlet (inlet).

The LDPE production with tubular reactors (see Section 5.1) requires some sophisticated control valves [45]. The let-down valve (Fig. 4.2-6 B) controls the polymerization reaction via the pressure and temperature by a high-speed hydraulic actuator (9) together with an electronic hydraulic transducer. The position of the valve relative to the stem is determined by a high-resolution electronic positioner (7). The cone-shaped end of the valve stem (2), as well as the shrunk valve seat (3) are made from wear-resistant materials (e.g., sintered tungsten carbide) in order to tolerate the high differential pressure of around 3000 bar during the expansion of the polymer at that location. 

Air to hydraulic actuator regulates, pressure exerted on rolls... 

These control rods thus control the overall reactor power level and provide the principal means of quickly and safely shutting down the reactor. The rods are vertically moved by hydraulically actuated, locking pislou Lype drive mechanisms. The drive mechanisms perform both a positioning and latching function, and a scram function with the latter overriding any other signal (scram signifies prompt shutdown). 

The rocket motor has two levels of thrust to achieve rapid acceleration. The guidance system computes a collision course, then steers to intercept by means of four hydraulically actuated tail fins... 

PMTC liquids are used in hydraulic actuators of membrane compressors and as operating liquids in hydraulic systems. 

This evaluation does not consider the advantage of the hermetical sealing, the system s safeguarding ability of the PDP and the fact that hydraulically actuated Diaphragm Pumps are saving energy due to their better overall energy efficiency. 

Hydraulic The design of typical hydraulic actuators is similar to double-acting piston pneumatic types. One key advantage is the high pressure (typically 35 to 70 bar [500 to 1000 psi]), which leads to high thrust in a smaller package. The incompressible nature of me... 

Compaction simulators (Fig. 20) were designed to mimic the compression cycle of any prescribed shape by using hydraulic control mechanisms that are driving a set of two punches (upper and lower) in and out of the die. All hydraulic compaction simulators are similar in design and construction. A compaction simulator consists of several main units the load frame (column supports and crossheads with punches), the hydraulic unit (pumps and actuators that move the crossheads), and the control unit (electronic console and computer). Usually, a simulator accepts F tooling only, but can be retrofitted to use standard IPX B tooling. Under computer control, the hydraulic actuators maintain load, position, and strain associated with each punch. 

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