AMEPA chronology - Online Oil Film Measurement
Service - Online Oil Film Measurement
Field of application - Online Oil Film Measurement
Distribution partner - Online Oil Film Measurement
References - Online Oil Film Measurement
Health and safety system - Online Oil Film Measurement
CFM - Coal Flow Measurement
ESD - Electromagnetic Slag Detection
OFIS - Oil Film Thickness Measurement
OFM - Online Oil Film Measurement
RSD - Residual Steel Detection
SRM - Surface Roughness Measurement
TSD - Thermographic Slag Detection
MFM - Mould Flow Measurement
SFM - Ladle Purging Monitor
Slagmeter - Slag Thickness Measuring
Wavisurf - Online Waviness Measurement

Improper oil film layer distribution or even dry stripes on a metal strip creates problems in the forming process. Therefore an online measuring system is needed for the supervision. The AMEPA OFM system is the first system enabling online oil film measurement and automatic classification of the strip.

Technical data


Current tools to measure oil film thickness on a steel strip are limited to an offline analysis in a laboratory or to hand-held devices. Offline measurements cannot provide adequate information, thus any oiling problems are detected too late in the production process causing loss of both time and money. The Oil Film Measurement System OFM solves this process-measurement need. It fulfils operational requirements by providing an online tool for accurate measurements and offers a continuous documentation of quality. The OFM System provides:

  • A graphical display of the oil layer on the entire coil
  • Objective measurement, even with pre-oiled coils
  • Real-time detection of: – dry straps – non-uniform distribution – out-of-tolerance conditions
  • Adjustable automatic coil classification
  • Complete documentation


The OFM technology takes advantage of Lambert Beer‘s light absorption law. It states that the thickness of an oil film is directly proportional to the extinction of light (image 1). As the oil strip surface is illuminated, part of the light is reflected by the metal. On its path, the light penetrates the oil film twice and specific wavelengths are partially absorbed by the oil.

In practice, special lamps are used as light sources. Only a small number of characteristic wavelengths in the mid infrared range (MIR) of the electromagnetic spectrum are examined by the detector (image 2). AMEPA‘s OFM System has the following features:

  • Direct measurement of oil film thickness
  • High safety sensor-to-strip distance
  • Immunity to strip vibration
  • No calibration necessary for common oil types
  • Dynamic compensation of age-related light power variations
  • High scanning rate


Image 1: Measurement principle

Image 2: Comparison of different oil spectrums

Image 3: Example of installation

Technical data

  • Measuring range 0,1 – 5,0 g/m²
  • Measuring resolution 0,01 g/m²
  • Sensor-to-strip-distance 120 mm
  • Allowed strip vibration +- 10 mm
  • Scan rate 12,5 Hz
  • Customer Interface Profibus, Profinet
  • Sensor dimensions 370 X 257 X 88 mm
  • Sensor weight 8 kg


  • Bilstein, W.; Enderle, W.; Moreas, G.; Oppermann, D.; Routschek,T.; Van De Velde, T.: „ Two Systems for On-Line Oilfilm and Surface Roughness Measurement for Strip Steel Production”, Steel Rolling Conference, 19-21 Juni 2006, Paris, France. Download