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 | Split-Range Controllers, Part 2
In part 1 of this brief series (April 2008), I looked at the most common application for split-range controllers -- the heating and cooling of the barrel zones of plastics extruders. This month, I will continue the discussion and look at managing heat/cool processes using control valves.
by Arthur Holland
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 | Split-Range Controllers
The most common split-range application is the heating and cooling of the barrel zones of plastics extruders (figure 1).
by Arthur Holland
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 | Hazards to People and Plant, Part 3
In
this brief series, I’ve described three industrial incidents that demonstrate
the potential cascading effects that failing to consider the human
factor and to ensure equipment reliability
can have. What
can we learn from incidents such as these?
by Arthur Holland
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 | Hazards to People and Plant, Part 2
In
Part 1 of this brief series, I described three industrial incidents
demonstrating the potential cascading effects that failing to consider the
human factor and ensure equipment reliability can have. What can we learn from
incidents such as these?
by Arthur Holland
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 | Thermocouple Wiring Revisit, Part 2
Last
month, I started a brief series about the inaccuracies and instabilities caused
by misuse of thermocouple extension cable on temperature control systems. I’ll
continue by looking at other traps you can fall into when color confusion leads
to the wrong thermocouple wiring use.
by Arthur Holland
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 | Thermocouple Wiring Revisit
It has been some six years since I wrote about the inaccuracies and
instabilities caused by misuse of thermocouple extension cable on
temperature control systems. In 1989, the International
Electrotechnical Commission (IEC) published IEC 584-3. Yet even now, some 18 years on, the standard is virtually invisible in North America.
by Arthur Holland
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 | Helplines for Users of Process Heating Controls
A helpline or hotline, or a telephone line providing customers or clients with direct access to a company or professional service, can be a useful resource when used in an effective, efficient manner.
by Arthur Holland
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 | Thermocouples: A Thousand Shapes and Sizes
Every different application of thermocouples demands that you choose a shape, size and material to match the process. That’s all this column deals with. Matters of temperature, environment, thermocouple alloys and construction materials are largely outside this month’s topic and are for another day.
by Arthur Holland
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 | Infrared Thermometers, Part 2
When you point and shoot most infrared thermometers, you need to be sure that you are on target and that your sensor is capturing the radiated energy from all of the field of view.
by Arthur Holland
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 | Infrared Thermometers, Part 1
When you have to measure the temperature of the untouchable and have ruled out
using the thermocouple and the RTD, your best choice is usually one of the many
infrared thermometers (also known as optical pyrometers). The
sensing technology is the same for hand-held as for fixed-position units that
monitor continuously.
by Arthur Holland
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 | Nickel/Chrome and Comparable Heaters, Part 2
Heaters that incorporate one or other of the many nickel/chrome alloy wires and ribbons are widely popular, due to attributes such as low cost; a wide choice of size and shape; versatility of construction; robust performance; easily controlled due to minimal resistance change with temperature and service life; and tolerance to thermal cycling.
by Arthur Holland
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 | Nickel/Chrome and Comparable Heaters, Part 1
There is no limit to the ways in which you can deliver resistance heating to the
material in your process. Chances are you will be looking for a heater that
incorporates one or other of the many nickel/chrome alloy wires and ribbons.
by Arthur Holland
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 | Troubleshooting Extruders, Part 6
In my last column, I began to review how the controller varies power to the heater. I’ll conclude this series with power feedback, heat and cool cycle times, balancing heat and cool, and controlling cooling zones.
by Arthur Holland
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 | Troubleshooting Extruders, Part 5
In my last column, I reviewed the elements of a controller that can throttle back the power well ahead of the temperature reaching setpoint and provide a way to defeat temperature overshoot and cycling: a PID (proportional + integral + derivative) controller. Among the parameters that you adjust to optimize (or tune) your controller are the proportional band, integral time and derivative time. I’ll pick up with tuning your PID controller.
by Arthur Holland
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Trends in Temperature Control Equipment
Walk round a few process plants and you will see some 20 years of evolution, says controls guru Arthur Holland. Starting from the tried-and-true using discrete instruments all the way up to SCADA systems with color monitors and operator interfaces, rich in control, protection and data analysis capability, Holland offers a review of control technology.
by Arthur Holland
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Ratio Control
Take a look at some of ratio control's applications
and imperfections with Arthur Holland.
by Arthur Holland
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Protective Devices for Control Equipment, Part 3
In Part 3, Arthur Holland continues his look at transient overload protection; then, a few comments on flow failure protection, thermal cutoffs and arc-fault circuit breakers.
by Arthur Holland
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 | How Should I Calibrate? Part 2
Control signals are put out by controllers and expect to be obeyed by
such final control devices as motorized valves, electropneumatic
valves, motor drives and SCR heater controllers. How well they are
obeyed is often pretty rough and nonlinear. Checking at this stage --
while not called calibration -- is important to control performance.
by Arthur Holland
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How Should I Calibrate? Part 1
You want your processing to be accurate, consistent and reproducible
over the long term. You want to be ready when ISO compliance or your
customer's quality control calls for proof of the integrity of your
operation. So, make sure all your process-critical signals are checked
and recorded once or twice per year.
by Arthur Holland
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Power Factor
Arthur Holland debunks two myths and gives some words of comfort.
by Arthur Holland
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Negative Feedback, Part 2
Arthur Holland looks at specific and simpler cases of feedback usage in components of the process.
by Arthur Holland
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Cascade Control
Handle Processes that Challenge Regular PID Control
by Arthur Holland
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Signal Conditioners
What are these little hidden boxes that manipulate your process signals?
by Arthur Holland
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