Pumps and Control Valves

Design the control valve and pump so that both the maximum and minimum flow rates can be handled with the valve never less than 10 percent open. 

Fig. 6.1.4 Components of the high-performance liquid chromatography (HPLC) system for oxidized pterins with column switching. The autosampler starts the chromatography software, which controls valves and pumps. Pump 3 is used only for rinsing the precolumn. Details of the three valves and their different positions are explained in Fig. 6.1.5...

Fig. 6. The experimental setup for performing automated flow injection-ELISA measurements. FI, excess flow of main buffer F2, main buffer flow F3, washing buffer F4, excess flow of washing buffer F5, substrate solution F6, sample solution F7-F9, waste streams PI and P2, peristaltic pumps VI and V2,3-way valves V3 and V4, injector valves. The computer logs and evaluates the data and controls the flow through the whole system by controlling valves and pumps. (From Nilsson et al. (143).

The control valve and pump sizing procedure proposed above is not without its limitations. The two design equations for the maximum and minimum conditions in general terms are ... 

If it is decided to write procedures at this level, a valve/pump checklist such as that shown in Table 6.7 can be useful, and often has to be developed anyway when working out instrument logic. It shows the status of each control valve and pump on the unit at the conclusion of each operation for each P ID. Even if this type of list is not included in the final product, it is useful for the procedures writers to develop one as a check on their own work. Table 6.7 is also handy for catching oversights, such as forgetting to turn on a pump before filling a vessel. 

The model outlined is particularly suited for treating the failure of passive components. Such components fiilfil their function by their mere presence, for example vessels, pipes and walls. Contrary to this active components have to move in order to fulfil their function. Examples are control valves and pumps. Yet, active components usually have a passive ancillary function. Thus, the pump casing serves as well to contain the transported medium. 

All the pieces of a distillation column will be specified (column, control valves, and pumps) so that we can perform a dynamic simulation after the steady-state simulation is completed. If we were only interested in a steady-state simulation, pumps and control valves would not have to be included in the flowsheet. However, if we want the capability to do simultaneous design (steady-state and dynamic), these items must be included to permit a pressure-driven dynamic simulation. 

Select the number of degrees of subcooling so that the sensible heat load will be at least 5 percent of the total heat load. This will have a secondary advantage of reducing the probability of cavitation in control valves and pumps. 

It is to be noted that a spurious trip generally, but not always, results in spurious shutdown of the ongoing process. More clearly, in regard to process equipment failures, a spurious closure/stop of non-SIS equipment, like control valves and pumps that interact with the ongoing process, may lead to spurious shutdown. The spurious closure of control valves or the spurious stop of pumps may be due to factors such as element internal failures, automatic control system errors, and human errors. 

V ri ble Frecjuency Drives. An important energy by-product of soHd-state electronics is the relatively low cost variable speed drive. These electronic devices adjust the frequency of current to control motor speed such that a pump can be controlled direcdy to deUver the right flow without the need for a control valve and its inherent pressure drop. Eigure 11 shows that at rated load the variable speed drive uses only about 70% as much power as a standard throttle control valve system, and at half load, it uses only about 25% as much power. 

The process controller is the master of the process-control system. It accepts a set point and other inputs and generates an output or outputs that it computes from a rule or set of rules that are part of its internal configuration. The controller output seiwes as an input to another controller or, more often, as an input to a final control element. The final control element is the device that affects the flow in the piping system of the process. The final control element seiwes as an interface between the process controller and the process. Control valves and adjustable speed pumps are the principal types discussed. 

FIG. 8-85 Pressure, flow, and power for a throttling process using (1) a control valve and a constant speed pump and (2) an adjustable speed pump. 

Switch on and off and control the speed of pump and fan motors. Control valves and dampers. 

Backflow from the delivery side of the pump was prevented by a check (nonreturn) valve. In addition, a control valve and a hand valve well away from the fire were closed (Figure 7-5). 

If the maximum flow-rate required is 20,000 kg/h, calculate the pump motor rating (power) needed. Take the pump efficiency as 70 per cent and allow for a pressure drop of 0.5 bar across the control valve and a loss of 10 velocity heads across the orifice. 

Four different types of tasks are performed by automation. Two involve the sequencing of valves and pumps Involved 1n the setup and completion of the designed experiment through the operation of the test and hydraulic fluid systems. The other tasks involve the control of the temperature bath and data collection. To perform these tasks, a1r-actuated solenoids and optically coupled sol Id-state relays are used. These devices are controlled by an electrical circuit consisting of the device connected 1n series with a power supply and a channel on the actuator card In the HP 3497. The power supply 1s either 24 VDC for use with the solenoids or 5 VDC for the solid-state relays. The actuator output channel acts as a simple on/off switch which allows power to be supplied to the solenoid or relay when closed. The logic of the circuit 1s controlled by application programs running on the local HP 1000. 

A liquid with a viscosity of 25 cP and an SG of 0.87 is pumped from an open tank to another tank in which the pressure is 15 psig. The line is 2 in. sch 40 diameter, 200 ft long, and contains eight flanged elbows, two gate valves, a control valve, and an orifice meter. 

In some situations it is very important to be able to increase the flow rate above the design conditions (for example, the cooling water to an exothermic reactor may have to be doubled or tripled to handle dynamic upsets). In other cases this is not as important (for example, the feed flow rate to a unit). Therefore it is logical to base the design of the control valve and the pump on having a process that can attain both the maximum and the minimum flow conditions. The design flow conditions are only used to get the pressure drop over the heat exchanger (or fixed resistance part of the process). 

Calculate the C value of the control valve, the pump head at design rate, the size of the motor required to drive the pump, the fraction that the valve is open at design, and the pressure drop over the valve at design rate. 

The exchange-quenched solution is then injected onto the protein processing system which includes injection loops, protease column(s), a trap column, an analytical column, electronically controlled valves, and isocratic and gradient pumps. 

Table S.4 shows the preconcentration programme that was used in this investigation. Sample volumes of 10, 20 and SO ml were used successfully and the enriched metals were in all three instances eluted with S ml of HNO3 (2 M). The control unit is equipped with a CRT display to simplify the input of the desired preconcentration parameters. During the preconcentration, the current settings of valves and pumps are displayed.

The catalyst preparation area is positioned between the two polyethylene production units with 60 feet separating each one. The aluminum alkyls storage canopy and isopentane horizontal storage tank are located at a remote area at an approximate distance of 250 feet away from the production and utility areas. The isopentane is transported to the catalyst preparation area through a 3-inch pipeline. A remote actuated isolation valve on this supply line that fails closed is located at the isopentane storage tank. This control valve and an associated isopentane feed pump are managed by the operator in the control room. 

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