Industrial oil: composition of used oil

Successful purification of industrial oil requires knowledge of its composition.  In practical terms, samples of industrial oil in use allows the equipment operator to determine its quality and the need to purify it or not.

Knowing the oil’s content level of each contaminant, one can select the most efficient methods of oil regeneration.  Let’s first consider the general composition of used industrial oil and then the possible methods of removal of the various contaminants.

Used industrial oil is chemically similar to motor oil.  The approximate composition of oil after being used in lubricating systems of machinery is as follows:

  • oil – 78%;
  • degradation products – 8%;
  • water/moisture – 4%;
  • particulate matter – 3%;
  • additives – 1%; and
  • fuel – up to 6%.

The main chracteristics also change especially in comparison with fresh oil specifications: Viscosity at 50ºС/122ºF – 23-43 mm2/second, acid number – 0.07-0.37 mg KOH/g, ash content – 0.019-1.288%.

A common property of used industrial oil is poor water solubility (below 5%), fire hazard (flashpoint in the range of 135-214ºС), and chemical inactivity in storage.

Used industrial oil is stored temporarily in special closed vessels.  Physical purification methods are used to remove particulate matter, microscopic water droplets and some coke and tar from the oil.  Volatile substances are removed by an evaporation method.

Oil can be treated by the application of centrifugal, gravity or other forces such as electric, magnetic, and vibration forces.  Physical methods of treatment also include heat and weight exchange processes to remove oxidation products, water, volatile fractions and hydrocarbons.

The simplest method of treatment is settling.  This occurs through the natural settling of particulate matter under the force of gravity.  The amount and kind of contamination of the oil defines the actual role of settling.  It may be a separate process or preparation for filtration or centrifugal purification.  The main disadvantage of settling is the duration of particle separation from the oil and the ability to only remove the largest particles from 50 to 100 microns.

Filtration is the removal of solid particles and tar from the oil by passing the oil through special porous or mesh filters.  The most commonly used filter media are plastic and metal meshes, fabric, felt, paper and ceramics.  There are also systems with two stages of filtration where coarse filters are followed by fine filters of the corresponding type.

Centrifugal purification of industrial oil is considered the most efficient and high performance method for removal of water and solid particles. The fractions separate under the influence of centrifugal force.

Combined physical and chemical methods of industrial oil reclamation are adsorption, coagulation and selective purification.  One kind of adsorption purification is ion exchange purification.

Obviously, the chemical composition of used industrial oil can be very different, with numerous contaminants in varying quantities.  It is therefore, impossible to practically remove all contaminants equally well by using just one method.  It is recommended to use a combination of several methods for purification.

GlobeCore produces mobile oil purification units in its CMM-5CM line.  These units are designed for removal of water and solid particles from oil with viscosity of no more than 70 cSt at 50ºС/122ºF. The GlobeCore СММ-5CM offers complete sorbent purification of oil with subsequent reactivation of the sorbent in the unit.

Using the CMM-5CM unit for regeneration of industrial oil significantly extends the service life of the oil and the industrial equipment. These units are easy to transport and simple to operate and service.

обновлено: June 24, 2016 автором: dannik