Steam flow recorder controller

) For most evaporative units, the steam flow is directly proportional to the production rate and to the temperature rise in the recirculation system and the AT in the heat exchanger. Both of these values have an important influence on the scaling rate in cases where materials of inverted solubility are being handled or where there are scale-forming components within the system. In systems where this value is critical, the AT can be monitored and used to reset the steam rate. An interlock should be provided that will cut off the steam flow to the system if the circulating pump or propeller circulator in a draft tube baffle unit is off due to motor overload or power failure. 

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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 ...

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 ... 

The hot section (Fig. 5) is controlled by a cascade loop which is based on a selected pumping rate (150 gpm) and sterilization temperature set in the TIC. Changes in the feed temperature are monitored at TTl which will automatically override the steam supply to keep the temperature at set point. Steam flow rate is monitored (by FE) and flow is automatically compensated should a large drawdown of steam occur elsewhere in the plant. Temperature is recorded at the beginning and end of the hot section. The hot section should be well insulated and special care should be given to the pipe supports for expansion. (Instrumentation symbols used here and in Figs. 3, 5, 6 and 7, conform to the standard symbols of the Instrument Society of America.)... 

The steam jacket is supplied with steam at a controlled pressure and the flow of jacket condensate is measured to allow calculation of the heat transferred in the test section. Jacket condensate may also be passed to a measuring tank and a continuous record of level in the tank used to estimate the average heat transfer rates over hourly or longer periods. 

Instruments used on steam boilers included pressure and flow indicators and controllers, carbon dioxide recorders, speed controls for mechanical stokers and liquid level indicators and controllers. As chemical manufacturers began to abandon batch processing in favour of continuous processing plants and also paid greater attention to fuel efficiency the possible uses of the type of instruments employed in steam raising plant must have become apparent. ... 

The flow rate can be determined by means of an orifice meter. Prior to beginning the measurement, the fan is started and the desired airflow adjusted by a throttle valve the tan-perature and moisture content of the air are controlled by means of an electric heater and a steam valve. In the next section the development of an adequate value of flow rate may be ensured by means of screens. The time-varying mass of the sample to be dried is measured continuously and recorded. 

Figure 2.14 is a record of temperature and flow of a product stream leaving a heat exchanger. Temperature was being controlled by manipulating the flow of steam to the exchanger. Notice that the temperature record at 80 percent flow is overdamped, whereas at 40 percent flow. 

There are also block valves in the auxiliary feedwater lines to the steam generators. These block valves are required to be open while the plant is operating. Records indicated that the valves had been reopened following maintenance completed 2 days earlier however, they were not open at the time of the accident. It took the operators 8 min to discover the valves were closed, in part, because tags on the control room panel inadvertently covered the valve position indicator lights. As a result, there was no flow of auxiliary feedwater from the condensate storage tank to the steam generators until an operator opened the block valves at 8 min 18 s. 

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