PF-18L-S Loss-In-Weight Screw Feeder

THAYER Model No.
Approximate Feed Rate Range (ft³ hr)
0.14 – 200
Scale Capacity (pounds)
10 – 500
Scale Suspension Type
Weigh Hopper Liquid Capacity (ft³)
2.25 – 9.75
Available Screws Diameter (in)
1.0 – 4.0
Load Cell Type
Strain Gauge / LVDT
Typical Materials Handled


PF-18L-S Loss-In-Weight Screw Feeder

Thayer Scale Loss-In-Weight Feeders are designed to provide precision class accuracy and repeatability even in the harshest of industrial environments. They range in capacity from grams per minute to tons per hour.

These are the most versatile feeders in the industry. At the heart of each Loss-In-Weight Feeder is a THAYER scale that has been designed exclusively for the stringent requirements of Loss-In-Weight feeding.

Thayer Scale offers a powerful set of proprietary add-on accessories that are designed to defeat the problematic flow issues encountered by industry such as bridging, flushing, adhesion and cohesion. Comprehensive process solutions that can only come from a company with over sixty years of experience.

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

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.

Weight Measurement System

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 = maximized resolution
  • Low mechanical resonance frequency

Flexure plate system eliminates all wearing parts, such as bearings, pivots and knife edges and is not susceptible to vibration. Flexure suspension system transfers all loading forces to a single load transducer, which accurately measures load regardless of load position. Most platform scales are not designed to be immune to side loading and/or tortional loading caused by the plant environment and by the movement of the feed screw, agitator, etc. These factors can cause poor accuracy and poor calibration stability. Thayer’s flexure system cancels all horizontal force vectors and also allows heavy tare loads (weight of feeder and hopper) to be completely mass counterbalanced , permitting load cell sizing based on net rather than gross weight.

  • Accurately measures load regardless of load position
  • Immune to support structure deflections and process vibrations
  • Inherently self aligning to gravity
  • Nulls out heavy tare loads
  • 1,000% over load capacity
  • Scale may be suspended from above or supported below
  • Immune to shock or impact loads
  • Easily accessible load cell can be accessed without removing the feeder

Two Types Load Cells to Choose From

The LVDT Load Cell was specifically developed as the ideal adjunct to THAYER’S ‘reverse-action’ Force Measurement Suspension System. It is essentially a precision and extremely durable “tensionstyle” force transducer that is manufactured in a fine series of force ranges to produce scale capacities from 10 to 500 lbs depending on the application. The LVDT is the ideal load cell for ” light loading” applications where mechanical tare loads represent as much as 10 to 40 times the net material load and provides unparalleled overload protection at 1000% of rated output.

THAYER Strain Gauge Load Cell
The Strain Gauge Load Cell is available in force ranges from 25 to 500 lbs with an overload protection of 300% of rated output.