Good temperature control by ProQuest

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[...] abrupt changes in coolant or steam flow can shock equipment and upset other utility users. [...] it is also important to monitor the controller output and use methods (e.g., set point velocity limits and split-range, criss-cross prevention logic) to prevent rapid changes or oscillations. Since you typically achieve temperature control by the direct or indirect manipulation of heat flow into or out of the system, a reduction in the overshoot and oscillation of temperature loops can also correspond to a decrease in energy consumption.

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									                                                                                           Temperature | automation basics



Good temperature control



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         emperature is one of the four most      furnace firebrick) by preventing excursions      rate) of temperature loops.
         common types of loops. While the        beyond the temperature rating. However,           Once you properly implement and tune
         other common loops (flow, level,         abrupt changes in coolant or steam flow          a temperature loop, the control error is
pressure) occur more often, tempera-
ture loops are generally more difficult
and important.                                   Tight temperature control can extend the life of
   Temperature is a critical condition for
reaction, fermentation, combustion, dry-
                                                 process equipment by preventing excursions beyond the
ing, calcination, crystallization, extrusion,    temperature rating.
or degradation rate and is an inference of
a column tray concentration in the process
industries.                                      can shock equipment and upset other             often less than the tolerance (error limits)
   Tight temperature control translates to       utility users. Thus, it is also important to    of the sensor. If you consider the accumu-
lower defects and greater yields during          monitor the controller output and use           lated error of an installed thermocouple or
seeding, crystal pulling, and rapid thermal      methods (e.g., set point velocity limits and    RTD system is about five times larger than
processing of silicon wafers for the semi-       split-range, criss-cross prevention logic) to   the error limits of the sensor, you realize
conductor industry.                              prevent rapid changes or oscillations. Since    system measurement error seriously limits
   For boilers, temperature is important         you typically achieve temperature control       temperature loop performance.
for water and air preheat, fuel oil viscosity,   by the direct or indirect manipulation of
and steam superheat control. For incinera-       heat flow into or out of the system, a re-       Sensor, tuning, strategy options
tors, an optimum temperature often exists        duction in the overshoot and oscillation of     The user can reduce errors significantly by
in terms of ensured destruction of haz-          temperature loops can also correspond to        changing installation or by using a break-
ardous compounds and minimum energy              a decrease in energy consumption.               through in technology. Control loop analyz-
cost. For heat transfer fluids, such as cool-                                                     ers, auto tuners, and self-tuning controllers
ing tower, chilled water, brine, or Thermi-      Control problems, sources                       can alleviate most of the tuning problems.
nol, good temperature control minimizes          The slowness of the response of the tem-           You can also develop quantitative rela-
upsets to users.                                 perature process is the biggest source of       tionships for tuning temperature loops to
   Temperature control in cold rooms re-         problems and opportunities for tight tem-       see use with signal characterization
								
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