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News from the Institute Branches – December 2018 

| South Wales Branch
Fascinating insight into oil analysis

Colin Macfarlance reports

The South Wales Branch met at the Village Hotel, Cardiff, and welcomed Mr Steve Greenfield, Chair of the BINDT Condition Monitoring Technical Committee, and Dr Dzmitry Korachkin, Laboratory Director/Manager at Swansea Tribology Services (Oil Analysis Services), for presentations on oil debris monitoring and oil quality.

Steve began his talk, titled: ‘Fundamentals of oil debris detection and reporting’, describing early failure detection (EFD) systems for lubrication systems, based on the inspection of ferromagnetic particles. He explained that metallic (ferromagnetic) particles within a lubricant are collected by a magnetic probe. The particles can be inspected immediately or later in a laboratory. It needs to be ascertained whether signs of normal wear or failure are present. It was noted that particle sizes of up to 100 µm are typical in the normal operation of large machines and helicopter transmissions. Particles bigger than 100 µm may be ‘failure relevant’. The condition of the system can be determined from the number, shape and size of particles that are trending. The ‘ideal’ EFD system was defined, along with the typical progression of a failure (bath tub curve).

Steve continued the presentation by describing the different magnetic plugs and levels of system sophistication, starting with the relatively simple magnetic plug (chip collector), where ferromagnetic particles are attracted by the probe’s magnet and captured on its surface. The plug needs to be removed and inspected for build-up of debris. A self-closing valve ensures that oil does not leak during the procedure. Then, Steve moved on to discuss an electric chip collector with a basic remote indication, where chips collected close an electrical circuit causing a warning light to come on. Further complexity was described with the electric chip detector with pulse network, which is similar to the above but is capable of displacing small particles, while larger particles of a critical size remain on the sensor. Amusingly, one producer of this type of sensor uses the trademarks ‘Zapper’ and ‘Smart Zapper’! Steve then described the state-of-the-art magnetic plugs with integrated induction coils, where a current pulse is generated when particles hit the sensor. All particles are counted and can be classified by size and mass as the pulse is proportional to the size and mass of the particle. A two-stage warning can be displayed (‘Service’ or ‘Early failure’). Examples of each type of detector were passed around the group and the pros and cons of each were highlighted.

Steve concluded by identifying the challenges ahead. Future generations of gas turbines will feature ceramic bearings, requiring new technologies for particle analysis such as optical, acoustic and carbon shaft seal wear sensors.

After some refreshments, Dr Dzmitry Korachkin commenced his presentation, titled: ‘Use of oil analysis to determine plant condition’. Opening with a compelling justification for effective condition monitoring, Dzmitry noted that continuous health monitoring can reduce maintenance costs and lost production resulting from plant failure, explaining that oil analysis can be used to identify which plant is failing and spot potentially critical faults at an early stage.

The presentation continued with the advantages and disadvantages of oil analysis compared to other monitoring techniques. Pros listed included: low initial/capital investment; the ability to detect issues before the fault develops; the ability to identify the location of wearing components; and the ability of this technique to work for low-speed systems (<5 r/min). Cons given were that the process is slower than some other methods and that there are ongoing costs.

The significant savings an effective oil analysis programme can make were highlighted with three examples: a large bus company (1000+ buses), Canadian Railways and the US Air Force. In each case, the savings realised were considerable against the potential costs of engine failure. The next section of the presentation covered the reasons for engine, gear and rolling element bearing failure. Following this, the role and requirements of a lubricant, why a lubricant fails to lubricate and methods of sampling were covered.

Dzmitry then moved on to the myriad of oil tests available, which included:
  • Appearance/colour
  • Viscosity
  • Acidity or total acid number (AN or TAN)
  • Total base number (TBN)
  • Water content
  • Elemental analysis 
  • Optical emission spectroscopy
  • Particle count – instrumental particle counters/patch test method
  • Particle quantifier index
  • Analytical ferrography
  • Oil oxidation and varnish
  • Rotating pressure vessel oxidation test (RPVOT)
  • Remaining useful life evaluation routine (RULER)
  • Membrane patch colourimetry.

Additional tests specific to particular applications were covered, including:
  • Fourier transform infrared spectroscopy (FTIR) for engine and turbine oils
  • Demulsification for steam turbine oils
  • Resistivity
  • Copper corrosion
  • Diesel- and biodiesel-specific tests
  • Scanning electron microscope (SEM) analysis of wear debris or failed parts.
The presentation concluded with an interesting question and answer session.

The South Wales Branch would like to express its gratitude to Mr Steve Greenfield and Dr Dzmitry Korachkin for two very interesting and enjoyable presentations.