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DESCRIPTIONRotor weighfeeder FRW/SRW/VRW
Rotor Weighfeeder Pfister
FRW / SRW
Highly accurate and reliable gravimetric feeding of
Whether kiln feeding, additive feeding to the raw or finish mill or cement pre-loading, the robust design
of the Pfister FRW is ideal for dosing powdered bulk materials such as raw meal, fly ash, bypass dust or
cement products with high dosing constancy and precision. Due to the integration of weighing and dos-
ing the system is easy to operate and thus extremely reliable.
Pfister FRW + ProsCon: the innovative solution for metering powdered materials.
FLSmidth Pfister has more than 110 years of
experience in manufacturing industrial weigh-
ing equipment and is part of the FLSmidth
group since 1998.
The Rotor Weighfeeder technology was invented
by FLSmidth Pfister in 1984 to feed pulverised
coal to the cement burning process and it is
now time tested and state of the art technol-
ogy. More than 1,700 systems are in operation
Out of the long experience, FLSmidth Pfister
developed the Pfister FRW for non-explosive
pulverised material. Since the first installation
in 1997, more then 200 systems have been
installed world-wide for different applications
How does the system work?
What are the benefits?
What are the dimensions?
How ist the system installed?
What are the technical facts?
Is there further information?
All Pfister weighfeeders are
The usual applications kiln feed
mill feeding (fine grained materials)
The Pfister FRW is used for extracting fine
grained bulk material out of a storage silo and
feed it with high accurate feedrate on an
airslide or any other transport media.
The usual bulk materials raw meal
other fine or pulverised materials
What applications are there? Pages 11-14
Mill feeding and Kiln feeding. The application for rotor weighfeeder FRW.
Historic Pfister scale. Ludwig Pfister,
founder of the company in 1894.
The Function Principle
The pulverised material is transported in
the chambers of the rotor wheel (1) inside
the feeder from the inlet (2) towards the
outlet (3) . At the outlet, the chambers are
completely emptied. The rotor is driven by
a variable speed drive (4) . The rotor hous-
ing (5) cover the rotor and provides a com-
pletely closed and dust tight system. It is
suspended on a eccentric weighing axis (A-
A) through the middle of inlet and outlet.
The third point is suspended with a tow-
bar (6) at a load cell which weighs the gra-
vimetric bulk material content inside the
rotor. That means that the rotor weigh-
feeder measures real kilograms and is
therefore a true scale. At the outlet, the
material falls out of the feeder by gravity.
The gravimetric measuring value provides infor-
mation on the bulk material mass in the rotor
weighfeeder before the material leaves the
feeder. The loading of the rotor in relation to
the angular section is stored by the weighing
electronics. The speed of the rotor is controlled
inverse to the loading of the rotor at the outlet.
The Weighing Electronics ProsCon
The electrical controller calculates the required
speed of the motor for the time of the dis-
charge. It uses the set feedrate and the meas-
ured bulk material mass for the calculation of
the angular speed of the rotor (see chart). Less
material in the rotor results in a higher angular
speed, more material in a lower speed.
With this principle, so-called prospective control
ProsCon, the rotor weighfeeder achieves a
highly accurate compensation of variation in
rotor loading and material density. This results
in an extremely accurate feedrate with varia-
tions of less then 0.5% for short- and long-
Pfister FRW. A-A eccentric weighing axis. 1: rotor wheel, 2: bulk material inlet, 3: outlet, 4: variable speed drive, 5: rotor housing, 6: tow-bar to load cell, 7: Pfister CPI control box, 8: air-supply for purge air, 9: weighing bearing, 10: suspension frame.
How does the system work?
To achieve high accurate feeding, angular speed of rotor is controlled invers to rotor weighfeeder loading.
4 5process interface
Motor Control Center
2 3 Power supply
To plant control system
Pfister Rotor Weighfeeder Controller
All data are collected in the:
Pfister CPICan Process Interface (at feeder (5))
and transferred via CAN-Bus to the:
Pfister CSCCan System Controller (in MCC (6))
The communication between the Pfister CSC
and the plant control system can either be via:
Serial-Interface (ModBus RTU).
(Profi-Bus DP, Device Net)
Analog/Digital-Hardwired Interface. Electronic control 1: pre-bin, 2: shut-off gate, 3: flow-control gate or star-feeder, 4: rotor weighfeeder FRW, 5: Pfister CPI, 6: Pfister CSC
Reactive, Follow-up Control.
Reactive Control Compared to Pfis-
ters Proactive Control Strategy
Other feeders are based on a reactive control
(follow-up) rather then a proactive control.
Deviations in feedrate is measured and the pre-
feeding is adjusted. The measured deviation is
already sent to the process. This also requires a
very fine and sensitive pre-feeding device.
With the proactive Pfister rotor weighfeeder, the
material mass is measured before it leaves the
rotor weighfeeder. That means that the speed
of the rotor is adjusted before the material gets
discharged into the system, not the other way
Pfister Prospective Control ProsCon (Forward looking / pro-active)
What are the benefits?
Less Maintenance and Longer Opera-
tion Hours Because of...
Smart design with only one moving part, the
rotor wheel inside.
Completely dust tight.
Less wear because of slow speed of the ro-
tor. 4 to 8 rounds per minute.
Only one bearing which is additionally purge-
air sealed. No rollers or idlers.
All measuring parts and the motor are lo-
cated on the outside of the system.
Because of the minimal amount of parts, the
system is extremely reliable and problem
free. Less parts reduce maintenance work.
Only steel in contact with bulk material.
It is not necessary to clean the rotor weigh-
feeder since no spillage is possible.
Benefits in Installation Because of...
Compact design with minimal installation
It is not necessary to have a highly accurate
and constant pre-feeding.
Less necessary height of the pre-bin. The
special installation shown on the right is run-
ning since 7 years without any problems. It
is designed for a feedrate of 160 t/h with a
total height of only 5.1 meters. Pleas see
standard under chapter Installation.
It is no additional dedusting necessary.
Simple and intuitive operation.
The rotor weighfeeder is an advanced
mechatronic system. However it is very sim-
ple to operate. The communication to the
local plant control system is flexible and
works absolutely reliable.
Optional remote process display RPD.
Special pre-bin and Pfister FRW. Feedrate 160 t/h, total height 5.1m. 1: pre-bin filling, 2: pre-bin, 3: pre-bin content measuring, 4: material extraction devices, 5: rotor weighfeeder, 6: aeration bottom.
High Accuracy in Dosing Because of
No influence of pre-bin extraction property
on the dosing quality.
Air-flow or the flow characteristics of the
bulk material have no influence on the dos-
Proactive rather then reactive dosing and
feeding. The feedrate gets adjusted before
material leaves the feeder, not the other
High measuring load.
The design enables a high material layer
and therefore a high measuring load in the
weighing section. The material mass in the