LWF - LWB Calibration


Defining Calibration

To correlate the readings of an instrument with those of a standard in order to check the instrument's accuracy. 

With regards to a screw feeder, loss in weight, or a loss in weight batcher, this means that you can trust the massflow reading that the controller is displaying. Without calibrating and verifying this process variable, there is no way to know if it's accurate. Gravimetric feeders are expensive. You need to know how to quantify their performance.   Leming Process Services LLC can calibrate any controller type, KCM, SCM, KSM, K10s.  


Coperion K-Tron ®  has developed their own program to automatically test, calibrate, and certify their load cells. K-Sampler® is used to check each scale with static weights before it leaves the factory. 

Typically, the customer will supply the calibrated weights. This guarantees their certifications match your quality standard. 

The program automatically conducts a friction test to check for scale interference, a linearity test (by stacking equal weights consecutively on the feeder), and a creep test to make sure the scale is operating within the original specifications from the factory. 

K-Sampler can also function with a secondary scale. This scale weighs and records the product coming from another feeder. The feeder being tested is started in normal operation while its output is diverted directly to the K-Sampler Scale. The program runs for a period of time and can analyze the consistency of the samples to verify performance of the feeder. 

K-Sampler report Example

Static Weights

Because of the day to day need to verify your scales before starting production, it's prudent to purchase your own weights to keep in house. A first step of troubleshooting a massflow issue for a LWF gravimetric feeder is to place a known weight on it. Did the net weight increase accurately? Did the net weight return to the starting weight after you removed the weight? If not, you may have a problem with your scale. typically, there should be less then 0.1% error during this test. 

Leming Process Services LLC can supply weights or use your in house weights to calibrate LWF feeders. We can also recommend and or supply the ideal weight sets to fully test your feeder scales. 

Catch Samples

Although prone to human error, physically catching and weighing the product coming from the feeder while it's running in continuous mode often provides a clear picture of how the feeder is performing. This requires room around the feeder to safely catch material fed from the feeder and the ability to avoid a huge mess. Since the feeder discharge is open to the air during a catch sample, the dust hazard needs to be realized and remedied. 

The best practice is to use a K-Sampler to handle the testing of catch samples. 

Span Adjustment

The span is one of the most important parameters on a Coperion K-Tron Feeder. At 1.000 by default, it offers a way to calibrate the scale. For example, if you placed 200 lbs on a scale, and the controller weight only changed to 195 lbs, you would adjust the span so the display showed 200 lbs. 

The span does not correct for scale friction problems or poor feeding materials or other mechanical noise or vibration. It cannot improve precision. It can only improve accuracy.

Best Practice

To have the best performance from your Coperion K-Tron Feeders you should do the following:

  1. Have an annual calibration by Leming Process Services LLC
  2. Use the factory silicone bellows at the feeder inlets and outlets to minimize feeder vibration from the environment. 
  3. Use flexible cable to the motor, avoid conduit or sealtite. 
  4. Keep dust filters clean or use another method of dust collection. 
  5. Keep a weight nearby the feeder so the operators can check the scale before production. 
  6. Educate operators and maintenance in proper operation and handling of the feeders. 


KSampler-sample (pdf)