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DFD INSTRUMENTATION OPERATING
SYSTEM
Overview:
The DFD (Disc pump-FloDirector) Thick Stock Pumping System is a new
technology that radically differs from all other technologies in
mechanical operation. Its unique PLC operating system compliments and
supports the mechanical operation. The DFD system is the first
technology to offer a complete and comprehensive instrumentation package,
resulting from a 5-year research program that tested many different
instruments for both accuracy and quality. Only the most accurate and
reliable instruments are incorporated into our final design. Siemens
Energy & Automation developed the PLC operation control program with
state-of-the-art computer technology. The final system is the most
sophisticated of its type ever produced for a stock pumping system.
Features and Benefits:
Manufacturers of other medium- and high-density stock pumping technologies
offer instrumentation if requested by the customer. The general industry
practice is for the customer to install various unrelated instruments tied
to a central DCS. Our approach is to integrate an instrument package and
the mechanical equipment into a complete, high-quality operating system.
With inputs of inter-related monitoring instruments connected to a Siemens
PLC, the system generates comprehensive information outputs. A mill can
connect its DCS to the integral Modbus communication port of the PLC to
obtain all operating data required for complete monitoring and control of
the DFD system either centrally or locally.
SECTION I: THE OPERATING SYSTEM
The operating system consists of two parts - the motor
control center and the PLC. Siemens Energy & Automation designed and
wrote the operating software for the PLC and combined the input signals of
all instruments and gauges to generate a comprehensive range of output
information.
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Motor Drive Center: The Siemens Motor Drive Center
package contains VFD drives for both the rotary disc pump motor and the
FloDirector motor. It houses the Siemens PLC with display screen, and
DIN rail mounting of flow monitor, level monitor, consistency monitor,
temperature monitor, and pump discharge pressure monitor. Both VFD
drives are custom, high-performance units, and are matched to the
Siemens inverter-duty motors mounted on the rotary disc pump and
FloDirector. Available in 25 HP to 600 HP, they can be driven from 0 Hz
to 90 Hz. They are preprogrammed for control by the Siemens PLC
software. Siemens MDC units are optionally housed in a NEMA enclosure.
- PLC: The Siemens PLC is a self-contained logic
controller with microprocessor CPU. This device is programmed with a
custom software package designed to receive inputs from each monitoring
instrument – Siemens VFD drives, Krohne flowmeter, Kay-Ray consistency
meter, Kay-Ray temperature gauge, WIKA pressure gauge, and Drexelbrook
level gauge – and integrate them into the software package.
This software continuously adjusts the operation of
the DFD system to maintain control set points and display all
operating data related to the system operation (see sketch of operating
system on back of this brochure). The software displays the current
stock flow rates and calculates totalized throughput of stock in BDTPD.
When constant level in the dropleg is desired, the system makes
continuous adjustments in rotary disc pump and FloDirector speeds
to maintain dropleg level while maintaining the fluidized state of the
stock. When constant flow is desired, the speed of primary equipment
(washer, etc.) can be adjusted to provide constant flow of stock into
the dropleg and the DFD system will maintain a constant flow rate
from the dropleg.
This powerful software program can be used in a wide variety of ways to
monitor and improve the entire process of handling thick stock. A Modbus
communication port is provided for connection to customer’s DCS system.
This provides for local or remote monitoring and control of the DFD
system, as well as operational convenience for system and instrument
tuning and calibration.
SECTION II: THE MONITORING
INSTRUMENTS
The Siemens PLC
receives 4 – 20 mA input from the following instruments and generates
the DFD system information as shown on the back of this brochure.
All information generated is transmitted via the optional Modbus
communication port to the customer’s DCS. The PLC contains two
additional ports that may be used for other instruments, if desired by the
customer.
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Level Measurement: The Drexelbrook
Smart Level Transmitter is designed with Hart Protocol to provide ease of
calibration "on the bench" or from anywhere on the two-wire
loop. It uses a cable running the length of the dropleg to detect the
stock level in the dropleg and transmit a 4 – 20 mA signal back to the
meter. The cable is coated with a special material that, along with
admittance technology, rejects the effects of stock clinging to the cable,
foaming in the dropleg and entrained air. The system is calibrated with
either a hand-held calibrator or laptop computer. The computer software
option has the advantage of saving the transmitter data, seeing all the
configuration data on the screen, and outputting the data to a standard
printer. After the system is calibrated for stock, it is unaffected by
changes in density, temperature, pressure of the stock or any background
noise. This is an accurate and reliable method of monitoring stock level
in the dropleg.
- Flow Measurement: The Krohne
electromagnetic flowmeter provides excellent flow measurement with no
intrusion into the piping system. The IFS 4005 primary head is PFA lined
for long-term stability with high measuring accuracy. The SC150 signal
converter uses bipolar, pulsed DC field excitation,
microprocessor-controlled signal generation and processing, and features
high zero and long-term stability. It displays actual flowrate, forward,
reverse and sum-totalizers, each adjustable for continuous or sequential
display, and output of error messages. Its pulsed DC field excitation
requires no zero-point adjustment and provides accurate measurement. The
periodic phase shift ensures accuracy, zero, long-term and temperature
stability, even at high field frequencies, the same as the electromagnetic
flowmeter with low-frequency pulsed DC field. It is an exceptionally
accurate flow meter and easily the best we tested in our R&D program.
- Consistency Measurement: The Kay-Ray
Gamma Consistency Meter measures pulp consistency on a non-intrusive
and non-contacting basis. It consists of a gamma source (Cesium 137)
mounted on one side of the process pipe and a detector mounted on the
opposite side. It works on the principle that pulp fibers block out or
attenuate a transmitted gamma beam in direct proportion to the pulp
consistency. The system is referenced with pulp in the pipe under stable
process conditions. The amount of gamma energy that is received at the
detector during this reference condition is calibrated to a single set
point to establish a measurement curve for the desired consistency range.
The device has proved to be the most accurate and reliable method of
realtime consistency measurement.
- Temperature Measurement: The Kay-Ray
temperature probe is mounted in the dropleg just above pump suction. There
are two outputs: the first connects to the consistency meter for
temperature compensation of the calibration curve; the second is a 4 –
20 mA output transmitter to the Siemens PLC. A remote gauge is mounted in
the Siemens MCC to provide a continuous display of realtime stock
temperature. This device provides accurate temperature input to the PLC.
- Pressure Measurement:
The WIKA Pressure Sensor displays
pump discharge pressure with an oil-filled gauge and with a 4 – 20 mA
output pressure transmitter. A diaphragm between the gauge and pipe
interior isolates the device against stock contamination. The 4 – 20
mA electronic signal is transmitted to the Siemens PLC where it is
displayed on the PLC screen. The PLC combines the pump discharge
pressure, the flow rate and pump motor power consumption to calculate
pumping efficiency. This has proved to be an accurate method for
monitoring pump pressure.
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