Page 240 - Wastewater Solids Incineration Systems

202 Wastewater Solids Incineration Systems

monitor basic conditions of temperature, flow, pressure, voltage, current, weight,
level, speed, and position. It is illustrative to consider the very beginnings of instru-
ment systems and the concepts of remote viewing and remote control, such as for a
steam boiler installation.
In their most fundamental form, these instruments provide direct information to
the operator but no one else. Even to the operator, their usefulness can be compro-
mised because they cannot see more than one process condition at one location or at
one time. To remedy this drawback, higher-level components were added to provide
the capability to transmit or provide remote readings to one central area, or co-locate
the readings of these process conditions to a more convenient location, typically the
control room. This allowed the operator to be many places at once. When chart
recorders were added, the operator was allowed to be other places and still have a
record of what occurred. But, more importantly, the operator was able to view infor-
mation, trends, and responses to previous operational changes and apply judgment
to make sound decisions about operations. From a management perspective, the
components increased both the quality and quantity of work an operator could
undertake and complete.
The next level of sophistication entailed use of “controllers” in conjunction with
the instruments. They can be open- or closed-loop and use feedback control. When
process conditions vary, the controller takes corrective actions to vary (increase, slow)
a process condition, further freeing the operator from repetitive tasks and allowing
increased attention to higher level decision-making. For example, turning your home
furnace on if the outdoor temperature is low and off when it is warm involves an
open-loop system; measuring the temperature in the house (the controlled space) and
tuning the furnace on or off to maintain a desired temperature based on feedback
from a thermostat involves a closed-loop system.
Once these instruments, controllers, and recorders were co-located in one place,
it was but a short step to recognize that they could be located nearly anyplace. Thus
primitive instrument and control systems were born, incorporating remotely located
control rooms, remote-control of local systems, remote information, and remote
sharing of information.

6.0 PROCESS AUTOMATION
The focus of instrumentation and control systems is changing. The initial focus on
labor savings has been essentially supplanted by the opportunity to increase safety
and quality, minimize process deviation, and eliminate process inconsistencies.