Three position valve

It can easily be seen tbat the event X7 (three-position valve not placed in operation position on start-up) dominates the unavailability with a contribution of 89 %. It represents a good starting point for system improvements. 

In a two-position valve, the flow path is always directed to one of the work ports (A or B). In a three-position valve, a third or neutral position is added. In this figure, a Type 2 center position is used. In the neutral position, all ports are blocked, and no flow through the valve is possible. 

Double-solenoid, spring-centered, three-position valve... 

The direction and flow rate of the test and hydraulic fluids are determined by nine three-way valves and six a1r-dr1ven hydraulic pumps that must be sequenced 1n the proper order. The position of the valves 1s determined by six air-driven actuators. Two of the pumps are miniaturized, air-driven, hydraulic pumps used for sample loading and pressurization. One of the remaining four pumps 1s a high-pressure, constant volume, positive displacement, piston metering pump to provide hydraulic pressure, and the other three are positive displacement syringe pumps for In-line addition of additives. 

The cell is made up of one glass tube and three metal valves. The valves are open when they are in vertical position and are closed when in the horizontal position and allow maximum flow at the 45 position. When the three valves are closed, the liquid automatically flows into the solution compartment of the cell when the right-hand valve (solvent-inlet valve) is open, the liquid will be directed from the solution in-let tube into the solvent compartment of the cell by passing the solution compartment. The left hand valve is the solvent drain valve, and the near valve, the solution-drain valve. 

Vacuum is provided by a continuously running two-stage rotary vacuum pump (P). A three-way valve M) connects the bell jar either to the vacuum line or to the pressure line. Inserted into the vacuum line is a valve (N) which has a permanent bypass consisting of a coil of long, narrow steel tubing. In order to prevent the liquid in the cup from boiling, caused by too sudden fall in pressure, the system is evacuated first through the bypass with valve (IV) in the closed position. This valve is opened after a predetermined delay period. 

Aldstadt et al. described the determination of U in groundwater using a FI system with a TRU-Resin column coupled on-line to an ICP-MS. The system used three 2-position valves and a flow-reversal scheme to load the sample in one direction and elute in the reverse direction. The system provided an enrichment factor on the order of 30-fold compared to direct groundwater analysis. Separate elution of Pu and Th in a group prior to eluting U was also discussed. 

A positioner will be helpful on most slow loops that are controlling analytical properties, temperature, liquid level, blending, slow flow, and large-volume gas flows. A controlled process can be considered "slow" if its period of oscillation is three times the period of the oscillation of the positioned valve. 

In the case of fast loops (fast flow, liquid pressure, small-volume gas pressure), positioners are likely to degrade loop response and cause limit cycling, because the positioner (a cascade slave) is not faster than the speed at which its set point (the control signal) can change. A controlled process is considered "fast" if its period of oscillation is less than three times that of the positioned valve. 

The burner tip has no moving part, then its adjustment is done by three butterfly valves installed on the cold end of burner. The main burner concept of the burner tip is to have the PF channel located in between two streams of swirling air (Figure 31.13). The multi-channels are positioned as follows ... 

For removing water floating on a chlorinated hydrocarbon bottom layer, two or three drain valves at easily accessible positions should be provided. The valves should be fitted close to the tank sides to avoid the danger of the drain lines freezing up. Product tanks should be fitted with pressure-vacuum valves and with self-closing dip and sample hatches. 

Two liquid phases are separated using the continuous decanter shown in Figure 21.40. The output variables, which must be controlled, are F, the volumetric feed rate, Pj, the operating pressure, and 7, the dispersion interface level in the decanter. The positions of the three control valves, m, m2, and m3 are the manipulated variables. A linear model is available to describe the proeess ... 

In this section, we describe the operation of the DAB method. With the bed isolated by the four way valve and the three way valve set to the position such that the adsorption cell (C) is connected to the desorption bomb (B). These two are cleaned by either vacuum or heating or a combination of them. 

After the bed is cleaned, the three way valve is set to the position to isolate the cell from the reservoir B, and the adsorption cell is brought to the adsorption temperature with an aid of a flowing inert gas. Once this has been done, the cell is isolated from the flowing gas by using the four way valve F. 

The methods for the collection and introduction of gas samples in gas chromatography (GC) are described. Containers for samphng gases, sorption pipes, two- and three-position multiport valves and chambers capable of changing pressure with a mobile piston are presented. The methanizer in which the catalytic reduction of carbon monoxide and carbon dioxide to methane occurs is also presented. 

Fig. 8 Three-position, ten-port valve with two sample loops, taking sample from two gas tracks.

This shortcoming is absent in the three-position, ten-port valve having two sample loops, which is used for taking samples from two gas tracks (Fig. This valve can be used to analyze two gases in any order. The constructional solution of this valve makes it possible to simultaneously take two samples of different gases into two sample loops and perform their chromatographic analyses. 

Fig. 9 Three-position, six-port valve with expansion chamber, taking sample from one gas track.

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