Hydraulic valve

SEPARATE TRIP THROTTLE VALVE Hydraulic Mech ... 

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. 

ON/OFF normal-opened solenoid valve, hydraulic torque converter locking increase the efficiency of medium speed run. ... 

Reactivity control system X Reactor scram function RPS, scram valves, hydraulic insertion of control rods (non-safety scram backup via el mech drives), boron mjection system... 

Valves, hydraulic, pneumatic, e.g., rollover gas shutoff valves... 

Hydraulic power is typically used where high-motive force is required, such as very large valves. Hydraulic power checklist ... 

Shutoff nozzles are used to prevent nozzles from leaking into empty molds or when the nozzle is retracted from the sprue bushings. Valves of all kinds —i.e., spring-loaded ball check valves, hydraulically and mechanically operated needle valves, and rotary valves —have been incorporated into nozzles. 

A more refined version of the nozzle type of centrifuge has valved nozzles, in which each nozzle is individually closed by a valve, hydraulically opened when the solids level in the bowl reaches a pre-defined level. 

Modern subsea trees, manifolds, (EH), etc., are commonly controlled via a complex Electro-Hydraulic System. Electricity is used to power the control system and to allow for communication or command signalling between surface and subsea. Signals sent back to surface will include, for example, subsea valve status and pressure/ temperature sensor outputs. Hydraulics are used to operate valves on the subsea facilities (e.g. subsea tree and manifold valves). The majority of the subsea valves are operated by hydraulically powered actuator units mounted on the valve bodies. 

As most throttling control valves are still operated bv pneumatic actuators, the control-valve device descriptions that follow relate primarily to devices that are used with pneumatic actuators. The function of hydraulic and electrical coimteiparts are very similar. Specific details on a particular valve-control device are available from the vendor of the device. 

A duplex outside-end-packed plunger pump with pot valves, of the type used with hydraulic presses and for similar service, is shown in Fig. 10-49. In this drawing, plunger A is direct-connec ted to rod B, while plunger C is operated from the rod by means of yoke D and tie rods. 

Fluid-pressure distribution tends to close the valve. For this reason, the smaller manually operated valves have a latching device on the handle, and the larger manually operated valves use worm gearing on the stem. This hydraulic unb ance is proportional to the pressure drop and, with line velocities exceeding 7.6 m/s (25 ft/s), is the principal component in the torque required to operate the valves. Compared with other valves for low-pressure drops, these valves can be operated by smaller hydrauhc cylinders. In this service butterfly valves with insert bodies for bolting between existing flanges with bolts that... 

The slide is located in the compressor casting below the rotors, allowing internal gas recirculation without compression. Slide valve is operated by a piston located in a hydraulic cylinder and actuated by high-pressure oil from both sides. When the compressor is started, the slide valve is fuUy open and the compressor is unloaded. To increase capacity, a solenoid valve on the hydraulic hne opens, moving the piston in the direction of increasing capacity. In order to increase partload efficiency, the slide valve is designed to consist of two parts, one traditional shde valve for capacity regulation and other for built-in volume adjustment. 

Sieve plates usually have negligible hydraulic gradient. Bubble-cap plates can have significant gradient because of the blockage by the caps. Valve plates presumably are intermediate, with hydraulic-gradient characteristics approaching those of sieve plates. 

At the start of the leaf test run, the hose between the test leaf and filtrate receiver should be crimped by hand to bring the filtrate receiver to the operating vacuum level. The use of a valve at this point is not only less convenient but very frequently results in a hydraulic... 

Basically a tube with hydraulic water fed near bottom to produce hindered settling. Underflow withdrawn through valve at base. Column maybe filled with network to even out flow. 

Coarse solids are discharged by siphons extending to the bottom of the hindered-settling zone. Siphon control is obtained by a novel hydrostatically actuated valve which makes or breaks the siphon to flow only when the teeter zone is in correct condition. Discharge by an intermediate fraction from the upper column is by means of additional siphons. Hydraulic-water consumption is considerably lower than required for multipocket sizers. 

Pneumatic and hydraulic vibrating conveyors have as their greatest asset ehmination of explosion hazards. If pressurized air, water, or oil is available, they can be extremely practical since their drive design is relatively simple and pressure-control valves can be used to vaiy capacity either manually or automatically. 

Special Arrester Types and Alternatives Several types of unlisted arresters (water seals, packed beds, velocity-type devices, and fast-acting valves) mentioned in API 2028 are described more fully in Howard (1982). There are few design or test data for hydraulic and packed-bed arresters some types are designed and used by indiviciual companies for specific applications, while others are commercially available. Figure 26-27 shows some special arrester types. 

Decomposition Flame Arresters Above certain minimum pipe diameters, temperatures, and pressures, some gases may propagate decomposition flames in the absence of oxidant. Special in-line arresters have been developed (Fig. 26-27). Both deflagration and detonation flames of acetylene have been arrested by hydrauhc valve arresters, packed beds (which can be additionally water-wetted), and arrays of parallel sintered metal elements. Information on hydraulic and packed-bed arresters can be found in the Compressed Gas Association Pamphlet G1.3, Acetylene Transmission for Chemical Synthesis. Special arresters have also been used for ethylene in 1000- to 1500-psi transmission lines and for ethylene oxide in process units. Since ethylene is not known to detonate in the absence of oxidant, these arresters were designed for in-line deflagration application. 

Speed-Control Systems The most common sensing element is mechanical some systems are hydraulic or electronic. For valve positioner they all have a hydrauhc servo as first choice, with an occasional choice of pneumatic for lighter loads. 

Figures 29-19 and 29-20 illustrate two different mecbanical-hydraulic systems. Figure 29-19 is a bar-lift steam chest with a heavy-duty hydraulic seivo. The speed-sensing element is a flyball assembly attached to a rotating pilot. This rotating pilot sends a control-pressure signal that is proportional to speed to a bellows on the seivo. A change in control pressure initiated through the rotating pilot by either speed or speed changer deflects the bellows and seivo pilot valve. The seivopiston position is proportional to the control pressure.

According to the Standards of the Hydraulic Institute, a suction lift test is performed on the pump and the pressure in the suction vessel is lowered to the point where the pump suffers a 3% loss in total head. This point is called the NPSHr of the pump. Some pump manufacturers perform a similar test by closing a suction valve on a test pump and other manufacturers lower the suction elevation. 

Flue gas line hydraulics to the expander, including the regenerator pressure control valve... 

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