Energized seals

In seals which are not pressure-energized, sealing force is provided by the residual stress in the compressed seal, so that stress relaxation becomes an important factor. Even for more common simations using pressure-energized seals, residual stress is required at initial start-up—or after a... 

As a common alternative, metallic pressure energized seal systems such as the Grayloc cormection are used. Since it only requires a relatively small axial pretension to realize the initial seal effect, the size of the mechanical holding elements can be reduced and the handling of the closure can be simplified by using a clamp mechanism in heu of a bolted connection (Figure 12.17). 

Electrode insulators must also be designed for a particular service. The properties of the dust or mist and gas determine their design as well as the physical details of the installation. Conducting mists require specif lowances such as oil seals, energized shielding cups, or air bleeds. With saturated gas, steam coils are frequently used to prevent condensation on the electrodes. 

When the vacuum valve closes, its auxiliary contacts open causing interruption of the cir-cnits to the recirculation pump and pressure control pump motor starters. Auxiliary contacts in the starters open, intermpting the circuit to the seal flushing water solenoid valve and the remotely mounted control relay. The control relay is de-energized stopping the feed pump and macerator. 

Divers are an extension of the hydrometer technique. They act as miniature hydrometers in which each diver is calibrated to a particular density. Several divers of different densities are added to the fully dispersed suspension and each will settle to a height where its density is equal to the suspension around it. A copper ring sealed in each diver interacts with an external search coil (energized by high frequency alternating current), and thus the location of the diver can be monitored. 

Self-energizing types O rings, metallic, elastomer or other gasket types considered as self-sealing ... 

A safety instrumented function has a valve energized and open. The valve must close when a demand is detected. The valve is fitted to a piston type pneumatic actuator that has an O-ring seal around the piston. This seal degrades with time and gets sticky. If it is left in position a long period of time, it will cause the actuator to stick in place. How would this failure mode be classified ... 

Figure 8 shows a similar bimetallic microvalve which was fabricated by Messner et al. [9]. In contrast to the microvalve shown in Fig. 7, it has another port (port 2) which is always open at the edge of the membrane. When the microvalve is de-energized, the center boss seals... 

In 1992, Doring proposed using the bimetallic microcantilever stmcture to direct a fluid jet. Later, on the basis of this idea, Trah et al. [14] fabricated a micromachined normally closed valve using an Al — Si cantilever, as shown in Fig. 12. When the cantilever is in its de-energized state, the cantilever is slightly bent upward and directs the fluid to the room above the membrane. Thus, the pressure in the upper room is a little larger than that in the lower room. The pressure difference presses the boss down to the valve seat and seals the valve. When the cantilever is heated and thus bends downward, the fluid jet also deflects downward and flows into the lower room to lift up the boss. Thus, the valve opens. The size of the valve is 14.5 x 8.5 x 1.43 mm. 

Self Energized This type is utilized for high pressure apphcations. The surface exposed to the highest pressure, usually the inner periphery, is vented with small holes or slots. The pressure inside the vessel enters the o-ring and reduces the differenhal pressure across the seal. 

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