B-R controls has released Anton Paar SPR monitor for continuous monitoring of oil content in rolling, cutting oil and emulsions.
Rolling oil is used in hot and cold rolling of ferrous and non-ferrous metals to facilitate feed of the metal between the work rolls, improve the plastic deformation of the metal, conduct heat from the metal, and extend the life of the work rolls.
Oil content of the rolling oil emulsions typically ranges from 1.5 to 3% (other ranges 0.4 to 1%, and 7 to 15%) and has to be kept within tight limits (+/-0.1% to 1%, depending on range).
In addition to mineral or synthetic oils, the fluids contain emulsifiers. Oil concentrations above target result in increased costs for purchasing and for removal of excess oil.
Even carbonisation of the surface may occur, resulting in reject product. Oil concentrations below target cause poor surface quality, damaged surface and eventually also reject product.
The oil content directly relates to the sound velocity of the fluid. A change of 1% oil content brings about an increase of approx. 2 m/s. The measurement is done with a sound velocity sensor SPR 4115, connected to the process control unit mPDS 2000.
The concentration directly correlates with the sound velocity; concentration and temperature are continuously displayed on the screen of the process control unit.
Up to 255 different characteristics of oil emulsions can be stored in the processor of the control unit, each with its own target concentration and limit range.
To interface with control / monitoring systems the mPDS2000 provides 4-20 mA output signals, alarm relays and serial communications.
A pressure measurement and compensation should be performed in case of large pressure fluctuations, as the sound velocity of the emulsions is influenced by pressure (compressibility of oil). Typical values for pressure influence: 0.15 m/s per bar.
Additional sources of uncertainty: formation of coating on the sensor abraded particles in the emulsion entry of other oils. The A version of the SPR sensor (robust DIN 11851 thread connection) is easily removed from the line for quick cleaning.
Depending on the oil type, cleaning of the sensor may be required once or twice a day to avoid drifting results. Simple wiping with a soft cloth will remove any coating.