Pressure ports

Pressure manifold - This distributes the air to the various pressure ports. 

FIGURE 2.36 A schematic diagram of port interface showing both the pressure port and electrical connection [295]. Reprinted with permission from Springer-Verlag. 

Fig. 10.66 Schematic representation of the mode of numerical determination of pressure at the apex and side pressure port. [Reprinted by permission from V. L. Bravo, A. N. Hrymak, and J. D. Wright, Numerical Simulation of Pressure and Velocity Profiles in Kneading Elements of a Co-TSE, Polym. Eng. Set, 40, 525-541 (2000).]...

The mercury porosimetry experiments were carried out using an Autopore 9220 apparatus (Micromeritics). Around 4 g of sample were placed into the penetrometer. The initial results were obtained on a low pressure port between 0.004 and 0.1 MPa. The high pressure curve was obtained up to 400 MPa before extrusion and reintrusion. A contact angle of 130° was used to interpret the results using the Washburn equation. 

This particular FloJet could be enclosed in a positive pressure vessel, as was done with the process controller for this project. It could easily be slipped into standard PVC pipe fitted with screw-on pipe caps and a pressurization port. Also, an air driven pump and/or pulley driven pump could be used instead, or purchase a pump that is rated for hazardous environments. 

There is one more pressure port - the inlet for the pressure sensor for the box. This consists of a small drilled hole in the box. Ours is located on the side of the box (port 5), but it can be anywhere convenient for attaching the pressure sensor hose. 

This is just one design for pressurized ports. You may well be able to come up with a more elegant approach. 

There is a pressure drop through the pressure ports causing an unequal distribution of flow through the plate stack. Solids then begin to accumulate in the plates with the lowest pressure drop until plugging results. Gaskets often leak or rupture... 

Safety procedures are given in Appendix 2 however, it could be summed up by the sentence There is no such thing as a safe high-pressure window . This means that operators should treat all high-pressure ports as though they might fail at any pressure, even at pressures well below the safe working pressure. A sapphire window may well hold at, say, 1.2 GPa, and then fail at... 

The design of optical cells with high-pressure ports... 

Caution For safety procedures see Appendix 2. High-pressure windows for measurements up to 1.5 GPa should be used in the unsupported-area (Poulter) geometry. Sapphire, diamond, and, in a few cases float glass are the preferred materials. The high-pressure ports should always be shielded. 

There are four actuator ports located on the nozzle with a pressure port before and after each actuator port. The jet was operated at the same conditions... 

The actuators that were used in this experiment were high-pressure jets with an exit diameter of 2.3 mm. The pressure of the jets was varied from 300 to 700 psia. The jets were operated in two modes continuous and pulsed. In the pulsed mode, the jets were operated, in phase, at 2000 Hz using a proprietary high-speed valve. A Kulite high-temperature pressure transducer was used in the pressure port following one of the actuators to detect any change in the pressure inside the nozzle. An arc of eight microphones at a distance of 65 nozzle diameters was used to measure the far-field noise. One microphone was placed five diameters downstream of the nozzle exit at a distance of 20 diameters from the jet centerline. 

For the pressure drop measurements, a differential pressure meter Comark C9555 (range 0- 200 kPa, accuracy 0.2 %) was used, connected to two pressure ports before and after the microchannel, as illustrated in Fig. 3.5. To measure the pressme drop in the glass microchannel, two side channels (referred as t2 in Fig. 3.5), with a length of 5 cm each, were added to connect the main channel to the pressure ports. For pressure drop measurements in the Teflon microchannels the pressure ports... 

A mixing zone B, E pressure port CD test section BC 5cm DH 5 cm... 

By dividing the plungers or pressure ports into two sets and alternatively activating them, two different flow paths are created across the diaphragm, thereby connecting different combinations of ports via the circular groove. 

Prior to the measurement, the sample is introduced into a sample cell that allows for degassing under vacuum. Usually the same port also provides the coimections to the low pressure system of the mercury porosimeter, where air pressure is applied onto the pool of mercury to force it into the sample in contrast, the high pressure port uses a hydraulic system to provide pressure up to 400 or even 600 MPa. The amount of mercury vanishing from the mercury reservoir, AVmercury. is recorded together with the net applied pressure and converted into a pore size distribution. 

Figure 1. A sketch of the basic Fast Thermolysis/FTIR cell. The pressure ports and gauge are drawn in abstraction.

Figure 7 Effect of tube diameter, dpp, on pressure fluctuations. Particles 68 /zm FCC, purge gas velocity 1 m/s, pressure port length 2 m dead volume, 450 mm. (Xie and Geldart, 1997.) (With permission of Elsevier Science)...

In Figure 3.5, a double-sided pressurised machine is described. It possesses two inter casings with suction and pressure ports, so that an exchange of the medium to be compressed can take place via both front faces of the compressor stage. This type of arrangement is necessary if large suction capacities are to be realised with comparatively long impellers. 

But to some extent, one also guides the medium to be pumped from one to the other front face of the compressor stage. In addition, one inter casing with a suction port and another inter casing with a pressure port are needed. 

If the counterpressure at the fixed pressure port is less than the pressure achieved by the volume reduction between the blades, then the compressed medium to be pumped is released via the pressure port. 

Similar to greater counterpressure, the gas is released first at the pressure port into the blade area and it pushes out again in the further course of the rotary motion. The losses arising as a consequence of the restriction at the pressure port must be counterbalanced by an increased energy input. Consequently, with a pressure port corresponding to Figure 3.6, the fiquid ring machine works optimally only with a specific pressure ratio. 

The so-called variable pressure ports can be used for the reduction of the restrictor losses. These are generally drillings and slots covered by mobile plates and balls, which open or close depending on the difference of pressure at the valve. The valves are not opened until the pressure, which depends on the angle of rotation and suction pressure in the blade area, is greater than the counterpressure. One can thereby substantially reduce the restrictor losses. 

For reasons of economy and also for reasons that are historically developed, primary vacuum pumps with inter casings have prevailed in the industry up to now. Deformations of the impeller and inter casing rotationally symmetrical to the shaft centre are conceivable for the enlargement of the working openings. Conical and cylindrical hubs are already completed constructions (Figure 3.7). The possibilities of the medium conveyance discussed in the earlier details as well as the design of the pressure ports are also transferable to the employment of these control bodies. 

LRVPs in closed coupled design with variable pressure ports for covering the entire pressure ranging from approximately 40 to 1013 mbar represent at present the most frequently used design with new installations due to their good price-performance ratio. But even these vacuum pumps do not meet all the requirements. Thus, deposits in the dead spaces and drUHngs as well as defects of the valves ofthe variable pressure ports rank among the most frequent causes of failure. 

What had actually happened was, however, far more prosaic. Debris recovered from the seabed showed that the Pitot tubes (used for airspeed indication) and also the static pressure ports (used for barometric altitude measurement) had been covered by masking tape. This tape was used when the aircraft was polished. Quahty control checks should have taken place to confirm the tape was removed - a (unnamed) duty supervisor and line chief were responsible. One of the pilots should also have carried out visual checks as part of pre-flight checks. 

Three-way valves contain a pressure port, cylinder port, and return or exhaust port (see Figure 9.11). The three-way directional control valve is designed to operate an actuating unit in one direction. It is returned to its original position either by a spring or the load on the actuating unit. 

The typical four-way directional control valve has four ports pressure port, return port, and two cylinder or work (output) ports. The pressure port is connected to the main system-pressure line, and the return port is connected to the reservoir return line. The two outputs are connected to the actuating unit. 

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