Record control

Control System. For quaUty control, a complete record of the control and operation of the HTST is kept with a safety thermal-limit recorder—controller (Fig. 9). The temperature of product leaving the holder tube, ahead of the FDV, is recorded and the forward or diverted flow of the FDV is determined. Various visual iadicators, operator temperature caUbration records, and thermometers also are provided. 

Fig. 2. Process flow sketch where CW = cooling water, FRC = flow recorder controller, and Cond = condensate. See Figure 3 for other definitions.

Fig. 1. Flow diagram of production of sulfur dioxide from oleum 1, 30% oleum exchanger 2, SO vaporizer 3, reactor 4, coolant surge tank 5, coolant ckculatkig pump 6, coolant exchangers 7, sludge and acid pump 8, scmbber 9, SO2 cooler 10, gas cleaner 11, SO2 compressor 12, pulsation damper and 13, SO2 condenser. CM is the condensate FRC, flow recording controller PIC, pressure kidicatkig controller SM, steam TC, temperature recorder ...

Fig. 1. Fat sphtter. TRC, temperature recorder controller FLIC, Hquid level indicator controller PCV, pressure control valve and HCV, heat control valve.

Column Bottom Temperature. The bottom temperature is often controlled on the reboiler outlet line with a control valve in the heating medium line. The control point can also be on a bottom section tray. Care must be exercised in location of the temperature control point. It is recommended, especially for large columns, that a cascade arrangement be used. The recommended scheme has a complete flow recorder/controller (FRC) in the heating medium line including orifice and control valve. The set point of this FRC is manipulated by the temperature recorder/controller (TRC). This eliminates the TRC from manipulating the control valve directly (recall that temperature is the most difficult parameter to control). This makes for smoother control for normal operations. Also, it is handy for startup to be able to uncouple the TRC and run the reboiler on FRC for a period. 

Tips on Instrument Troubleshooting Recorders and Recorder-Controllers... 

Use maintenance records to inspect HVAC equipment and make sure that it is in good operating condition. Identify items of equipment that need to be repaired, adjusted, or replaced. Record control settings and operating schedules for HVAC equipment for comparison to occupancy schedules and current uses of space. 

Two furnaces were each fitted with a temperature recorder controller and high-temperature trip. The two recorders were side by side on the instrument panel in the control room, with the recorder for A furnace on the left (Figure 3-2). 

Teniperaturo recording controller, board mounted (electric measurement)... 

Pressure recording controller, pneumatic transmission with board niotmted receiver... 

Pressure recording controller (differential), pneumatic transmission with pressure recorder, combined instrument board mounted... 

Level recording controller external type, pneumatic transmission... 

Ann. Assistant Records Control OfFiccr TSilO Sfandish Place Rockville. MD208SS... 

Property First Indicating Recording Controlling Indicating Recording... 

Tanks with vent hlters must be designed for pressures of -20 kPa and +100 kPa and must be equipped with a rupture disk. Tanks for hot loop and steam sterilizable line must be designed to withstand steam sterilization (121°C). A steam jacketed sterile vent hlter must be used to avoid condensation in the hlter and the vent hlter housing temperature controlled. The tank for hot storage is steam jacketed and insulated for temperature maintenance. Minimum instrumentation shall include level indication, temperature recording controller, pressure gauge, and pressure relief valve. 

Instrumentation on the solvent extraction equipment will usually consist of recording flow and recording temperature controllers on the feed stream, a pressure controller on the raffinate exit line, temperature recorders on the column intercoolers, and a liquid level recording controller at the liquid-liquid interface to set the extract layer withdrawal rate. 

Documentation is critical for assessment. Standard protocols provide directions for what must be documented and how the documentation is to be done, including how to record information in notebooks. For labs that rely on manuals of standard practices, it is imperative that tasks done to comply with the manuals be monitored and recorded. Control charts (Box 5-1) can be used to monitor performance on blanks, calibration checks, and spiked samples to see if results are stable over time or to compare the work of different employees. Control charts can also monitor sensitivity or selectivity, especially if a laboratory encounters a wide variety of matrixes. 

To lower the tower pressure, the hot-vapor bypass pressure recorder controller (PRC) valve is closed. This forces more vapor through the condenser, which, in turn, lowers the temperature in the reflux drum. As the liquid in the reflux drum is at its bubble point, reducing the reflux drum temperature will reduce the reflux drum pressure. As the stripper tower pressure floats on the reflux drum pressure, the pressure in the tower will also decline. 

There are two ways to answer this question. Let s first look at the reboiler. As the tower-top temperature shown in Fig. 4.1 goes down, more of the lighter, lower-boiling-point alcohol is refluxed down the tower. The tower-bottom temperature begins to drop, and the steam flow to the reboiler is automatically increased by the action of the temperature recorder controller (TRC). As the steam flow to the reboiler increases, so does the reboiler duty (or energy injected into the tower in the form of heat). Almost all the reboiler heat or duty is converted to vaporization. We will prove this statement mathematically later in this chapter. The increased vapor leaving the reboiler then bubbles up through the trays, and hence the flow of vapor is seen to increase, as the reflux rate is raised. 

The statement that the mass, or weight flow of vapor through the trays, increases as the refluxed rate is raised is based on the reboiler being on automatic temperature control. If the reboiler were on manual control, then the flow of steam and the reboiler heat duty would remain constant as the reflux rate was increased, and the weight flow of vapor up the tower would remain constant as the top reflux rate was increased. But the liquid level in the reflux drum would begin to drop. The reflux drum level recorder controller (LRC) would close off to catch to falling level, and the overhead product rate would drop, in proportion to the increase in reflux rate. We can now draw some conclusions from the foregoing discussion ... 

H)-F10 RECORDING CONTROLLER FLAKE FLO KCOWHNC COITROLLU VALVE aS4-FL0 RECOIOER TO -F10 RECORDER FUKC pT OU-FLOf INDICATOR plQ -FLOi INDICATOR FUiCE... 

FRC flow recorte controller TBC lemperaMe recorder controller UC level indicator corn roller PIC pressure Indicator controler... 

FRC flow recorder controller TRC temperature recorder controller LIC level indicator controller PIC pressure indicator controller... 

Supervisory control and data acquisition Solid-state relay Self-tuning regulator Temperature recorder controller Transistor-transistor logic Zero order hold element... 

It consists of a rail-mounted carriage, which carries rows of sample beakers past three stations where each sample receives an aliquot of extractant (usually water), is thoroughly stirred, and has an electrode or electrodes lowered into it. The electrical output from the electrode(s) is passed through an amplifier to a flatbed recorder. Control of the sequence of operations is completely automatic, involving a system of three interlocking motor-driven cam timers, thereby ensuring that each sample receives identical treatment. 

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