Valves four-port

Figure 4.2. Typical gas-flow experimental setup used in electrochemical promotion studies (4 PV) Four-port valve.

The experimental apparatus consists of a gas flow system with a four-port valve, a multi-reflection Attenuated Total Reflection (ATR) accessory (Pike Technologies), and a custom reactor manifold mounted to the ATR top plate, shown in Fig. 45.1. The ATR reactor manifold consists of (i) a Cap2 window for UV irradiation, (ii) an inlet and outlet port, and (iii) an injection port for the liquid phase reactant. 

For smaller samples, four port valves with an internal loop can be used. In these, the sample loop is an engraved slot in the body of the valve. With both types, the volume of sample that has to be used to flush out and fill the loop is about ten times the loop volume. Fig. 2.2g shows the operating principle of each type. 

Figure 7.7. Schematic diagram of the continuous flow hydride generation system, showing the two positions of the four-port valve (A) for analysis of the test solution and (B) for blank integrations used for changing the test solution. From [115]...

The gas oil injector system included a l(X)0 tL glass syringe connected to the injection needle and to a m gas oil reservoir by means of a two-way valve (sample/inject). It was also equipped with electrically actuated switches which controlled the timer/actuator assembly on the four-port valve as well as the data acquisition system. The data acquisition system allowed for collecting the pressure proriles in the reactor and vacuum system as a function of time during the reaction and post-reaction evacuation periods. 

An electrical mass flow controller was used to control the flow rate of HCl. The gas flow through the reactor could be switched to nitrogen or HCl by a four-port valve. 

The sampling cell is formed by the sampling column I + l and the diffusion column L, which is connected perpendicularly to the middle of the sampling column. The ends, Di and D2, of the sampling column are connected through a four-port valve to the carrier gas inlet and the detector, as shown in Fig. 1. 

Fig. 6 Design and fabrication of four-port microGER valve, (a) Design of four-port valve chip. Right, cross-section of the different layers forming the flow valve LI is the GER channel layer, L2 the controlled flow channel layer, and L3 the cover layer, (b) Optical photograph of fabricated microGER valve chip. Right, top-view image of the planner electrodes and the GER channel, (c) Experimental setup for microvalve testing [74]...

Figure 5.13 Multiport switching valves (a) loading sample loop and injecting sample onto the column (b) two loop sample injection system (c) four port valve for column or solvent switching...

The experimental setup of RF-GC for the study of catalytic processes comprises -the sampling cell, formed by the sampling column I + I and the diffusion column L, which is connected perpendicularly to the middle of the sampling column. The ends Di and D2 of the sampling column are connected through a four-port valve to the carrier gas inlet and the detector, as shown in Fig. 1. A conventional gas chromatograph is equipped with the appropriate detector (e.g., flame ionization, thermal conductivity). A separation column L may also be incorporated in the GC oven. This column can be filled with the appropriate material for the separation of the carrier gas constituents due to the reactants and possible reaction products, and it can be heated at the same or at a temperature different from that of the sampling cell. 

The flows are switched using a four-port valve (1) with pneumatic or electric drive. The switching time should be minimal to avoid noticeable flow disturbance and cannot exceed the gas response time of the mass spectrometer. This response time is generally equal to 0.1-0.2 s. Another four-port valve (2) commutes the flows analyzed by mass spectrometry (MS), but is not necessary in the scheme shown. 

Note that the two flows exist in rather different conditions. The first flow passes through a catalyst bed with definite hydraulic resistance, whereas the second flow is discharged to the atmosphere. Without equalization of the pressure drop values on both feed lines, the output Ar-normalized response of the He-He/Ar step change can be strongly distorted (Figure 51.2). Tlierefore, needle valve (3) should be installed between the four-port valve (1) and the four-port valve (2) on the line, bypassing the reactor (Figure 51.1) to avoid flow disturbance after the switch. 

The connections of the reaction gas container to the source of the gas, and to the trap bottles, are shown on Fig. 9 (an arrangement with two reaction gas containers is shown). Wetted parts of the valves are made of Teflon, and 1/4 Teflon tubing is used for connections. Two ports of the three-port valve V1 are connected the source of an inert gas (nitrogen) and a reagent gas (HF, HCl, or NH3). The third port is linked to the four-port valve V2. The outlet and inlet of the reaction gas container are connected to the neighboring ports of the four-port valve V2. A second four-port valve is used for the arrangement shown in Fig. 9 that uses two reaction gas containers. A check valve is attached to the outlet of the reaction gas container. The last port is connected to the four-port... 

Fig. 138. Diagram of CC-MIP-MS system (1) four-port valve, (2) transfer line, (3) three-port gas inlet, TMoio cavity, (5) discharge tube, (6) waveguide, (7) magnetron tube, (8) electrical feedthrough, (9) skimmer cone, (10) extraction lenses, (11) swing gate valve, (12)...

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