Flow-limiting devices

Less of could lead to recognizing the possibility of inadequate cooling water flowrate to part of the plant when the flow is increased elsewhere, with consequent damage to machinery the solution could be to install a flow-limitation device on the alternative user, or an alarm. 

Cassettes Cassette is a term used to describe two different cross-flow membrane devices. The less-common design is a usually large stack of membrane separated by a spacer, with flow moving in parallel across the membrane sheets. This variant is sometimes referred to as a flat spiral, since there is some similarity in the way feed and permeate are handled. The more common cassette has long been popular in the pharmaceutical and biotechnical field. It too is a stack of flat-sheet membranes, but the membrane is usually connected so that the feed flows across the membrane elements in series to achieve higher conversion per pass. Their popularity stems from easy direct scale-up from laboratory to plant-scale equipment. Their limitation is that fluid management is inherently very limited and inefficient. Both types of cassette are very compact and capable of automated manufacture. 

Common immunochemical assay formats to select from include the 96-well microtiter plates, dipsticks, coated test tubes, and membrane-based flow through devices. If the end-user is a trained technician working in a well-equipped laboratory and needs to detect and tentatively identify, for example, antimicrobial residues in hundreds of meat samples per day, a multiwell or other high-through-put format should be chosen. If, on the other hand, the end user is a quality control inspector at a milk factory who has limited time to find out whether the penicillin residues in the milk waiting to be unloaded exceed a certain level, the same reagents used in the first instance may require a more user-friendly format such as dipstick or membrane-based flow through device. 

One device of this type was discussed by Hickam and Witkowski(23). In the diffusion limited devices that have been discussed, the flow rate of the gas is not normally an important factor. In the Hickam device, however, the gas flow is of paramount importance and new possibilities or complications arise. The structure consists of pump (upstream) and sensor (downstream) cells cylindrically surrounding a flowing stream of gas containing oxygen. The sensor cell EMF is fedback to the pump so that oxygen is either added to or subtracted from the stream in the amount required to keep the sensor EMF at a constant value. For a calibrated device, the amount of pump current required measures the oxygen content of the gas at the inlet of the structure provided the flow rate is held constant. Alternately, if a gas of constant composition were employed, the structure could be used to measure flow rate. 

Operating constraints related to the downcomer or solids flow control devices in CFB systems include limitations concerning the maximum available pressure drop across the downcomer and the maximum solids circulation rate, which can be delivered by the downcomer and the solids circulation and control device. 

Unattended operations must be planned with automatic safety switches that prevent serious damage (fire, flooding, explosion) in case of accidental equipment failure or interruption of utility services such as electricity, water, or gas supplies. Of special concern are the constant flow of cooling water and the operation of high-temperature baths. In the case of water flow, a device should be installed in the water line to (1) automatically regulate the water pressure (so as to avoid surges that might disconnect or rupture a water hose), and (2) automatically turn off electrical connections and water-supply valves in case of a total loss of water supply. In the case of hot thermostat baths or ovens, a sensor/control device should be installed that automatically turns off the electrical power to all heaters if the temperature exceeds some preset upper limit. 

The availability of a sanitary sewer near the point of chlorinated water release, and the capacities of the sanitary sewer and the wastewater treatment plant to handle the additional load, are the primary limitations in this method. Potential upset of treatment plant operations due to chlorinated water release must also be evaluated. A back-flow prevention device or an air gap method must he used to prevent cross-connection problems. 

In the manufecture of vinyl acetate, there is some unreacted acetic acid and other compounds that are discharged to the sewer. Your company has been cited as discharging more than the specified limit of several pollutants. It is not possible to measure the discharge directly because no flow measuring devices are in place, but you can take samples of liquid at different places in the sewer line, and measure the concentration of potassium chloride. At one manhole, the concentration is 0.105%. You introduce a solution of 400 g of KCI in IL at a steady rate of 1 L per minute over 5 hr at a manhole 500 ft downstream, and at 1200 ft downstream measure the average steady-state concentration of KCI as 0,281%. What is the flow rate of fluid in the sewer in kg/min ... 

Cytochrome b2 from Hansenula anomala has been employed for lactate determination in the Glukometer GKM 02 analyzer (ZWG, GDR). When immobilized in gelatin or poly(vinyl alcohol) the enzyme was stable for 15 days. Linearity was obtained over the range 10 (jmol/1-2.4 mmol/1, the upper limit being adjustable by the mediator concentration used. With the rate method a sample frequency of 40/h and a CV below 2% were achieved. In a flow-through device the CV was below 1% (Schubert and Weigelt, 1986). 

The turbine exhaust gas/combustion air velocity profile af the duct burner plane must be within certain limits to ensure good combustion efficiency, and in cogeneration applications this is rarely achieved without flow straightening devices. Even in nonfired configurations, it may be necessary to alter the velocity distribution to make efficient use of boiler heat transfer surface. Figure 26.7 shows a comparison of flow variation wifh and without flow straightening. 

On the other hand, the limitations of GC are as follows the sample should be a gas or the vapor pressure of the sample should be more than a few hundred Pa under the temperature set by the control unit of that system. Figures 2 and 3 show a schematic GC system and a photograph of a GC instrument, respectively. As shown in Fig. 2, a GC system consists of (1) sample inlet, (2) separation column, (3) a temperature control unit, (4) a detector with a data handling system and (5) a carrier gas with a flow control device. In this GC system, a carrier gas (in many cases, an inert gas such as nitrogen or helium) flows continuously from (a container) through the sample injection port, the column, and then the detector. The sample is injected into an inlet where it is vaporized and carried into the column. 

All process channels In the active zone of the reactor containing production materials are equipped with v -sssure sensing flow detection devices the trip limits of which are variable depending upon location of the tubes In the reactor and other factors. Set point limits axe set so that flow reductions and/or power level Increases In Individual process tithes will not result In serious fuel element damage. These flow detection devices may also be used to provide a No. 1 Safety Circuit trip for the condition of low reactor coolant pressure. 

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