Model PF-18L-S Flexure Scale
Loss-In-Weight Screw Feeder
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Unique THAYER® weight sensing
technology provides isolation from
all force vectors except material
weight for superior sensitivity and
accuracy. |
- Volumetric Capacity: Up to 205 ft³/hr (7.08 m³/hr). Consult factory for higher feed
rates.
- Screw Sizes: range from 2.0 Ø. (variable pitch) to 4.0 Ø (variable pitch) solid flight
or open helix with center through shaft.
- Scale Type: "FMSS" Flexure Scale System (dead load is mass- counterbalanced) and
LVDT Load Sensor.
- Scale Capacity (live load): variable up to 500 lbs (227 kg).
- Hopper Capacity: 2.25 fT³ hopper expandable to 11.25 fT³ with hopper extensions.
- Accuracy: 0.25% to 1% of set rate ±2 sigma based on a minimum sample of one (1)
minute, 30 revolutions of the screw or 1% of scale capacity.
- Precise and reliable feeding of cohesive, easily aerated and difficult to control powders.
- Handles a wide range of material bulk densities at low to medium feed rates.
- Patented compound flight feed screw design works in conjunction with patented Utrough feed chamber to eliminate common problems associated with feeding powders
such as screw starvation and binding.
FMSS Mass counterbalanced, electronic weigh scale features high precision measurement,
exceptional durability and excellent long term stability. Scale system weighs only the
material, not the feeder, for minute-to-minute accuracy and sensitivity.
The THAYER Model PF-18L-S is a low to medium capacity Loss-In-Weight Feeder designed to assure uniform,
non-pulsating accurate feeding of a wide range of materials, from free flowing to friable to cohesive.
Exclusive Powder Feeder Technology
Patented U-trough feed chamber with independently driven agitator assures precise, reliable delivery of material to
the feed screw. Eliminates material build-up, controls material aeration and delivers a steady constant flow of material.
Optional (patented) compound flight feed screw can be used with most materials to downwardly extend the operating
range of the feeder by a factor of 10 (typically).
Fast and easy to clean
The PF-18L-S is designed for fast, easy and thorough clean out. Feeder completely disassembles in less than one
minute. High quality, rugged, stainless steel construction assures years of reliable, trouble free operation even in the
most severe industrial environments.
Specialized scale design assures reliable, accurate metering.
The heart of any gravimetric feeder is its scale system. The PF-18L-S incorporates a unique flexure suspension scale
designed exclusively for use on Loss-In-Weight Feeders:
- High efficiency dead load counterbalancing
- Non-tilting platform design
- Tolerant of shocks and overloads
- Mechanical force summing to a single load sensor
- Full range sensor utilization = maximum resolution
- Low mechanical resonance frequency
- Easily adapted to future re-rates
Conventional platform scales are NOT well suited for this service. Single point platforms are unsuitable for supporting
machinery having this degree of vertical height and elevated mass. They are very vulnerable to side loading and
other tilting disturbances. Multiple load cell platforms are unsuitable for low loading applications where forces
no greater than that of an operator standing on one corner of the platform can cause damage. Finally, both types of
platform scales resonate at frequencies much nearer the disturbing frequencies of other processing machinery driven
by motors or vibratory drives. While electronic or software filtering may smooth out signal levels, they offer no
protection to the load cells.
Exclusive trough design defeats flooding by dissipating kinetic
energy of material stream at initial fill
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