Further analysis of debris in oil
Off-line analysis is an extra service provided by Techenomics that allows for additional checks to be made on the same fluid sample. It provides further detailed examination of the debris found during regular oil and fluid analysis, thereby allowing equipment operators to make more informed decisions about maintenance programs.
The PQ90 or PQM figures on oil analysis reports provided by Techenomics indicate the off-line analysis results. These figures are also available on reports provided through on-line devices.
Techenomics CEO Chris Adsett says the off-line analysis adds to Techenomics’ innovative Total Fluid Management Solutions which aim to effectively predict maintenance issues in engines or mechanical components before they lead to breakdown or failure, thus resulting in loss of production. He says three primary off-line methods are used – patch analysis, Ferrograph and particle concentration.
Patch analysis is one of the most effective methods of off-line analysis. A quantity of liquid is passed through a filter membrane and debris that is trapped on the membrane is then examined.
There are a number of ways of examining the debris, depending on the level of detail required. These include gravimetric analysis, shade analysis, standard comparisons, particle counts, visual observation and a scanning electron microscope.
A Ferrograph is extremely valuable in determining the presence of ferrous and paramagnetic materials but also reveals other particles. A Ferrogram includes ferrous and non-ferrous particles.
Debris is placed on a slide and when that slide is heated, different colours indicate different materials depending on the temperature.
For instance, at 330 degrees C speckled blue and orange colours indicate the presence of oxidised lead and/or tin, blue indicates carbon or low alloy steels, tan indicates cadmium and straw or bronze indicates medium alloy steels.
At 400 degrees light grey indicates carbon or low alloy steels, light tan indicates titanium, tan or straw with some deep purple indicates molybdenum, deep bronze with some speckled blue indicates medium alloy steels and some yellowing indicates stainless steels.
A particle concentration test can be measured optically but Chris Adsett says more accurate results are obtained when other tests are used, particularly when metallic particles are involved. “The optical test will provide a measure of the total metallic debris present but greater information is obtained by measuring the changes as particles fall after being thoroughly shaken in the bottle.
“One such application is the PQ 90 MIDAS which uses an inductive coil to detect ferrous particles. The sample is analysed as a total quantity in which a small sample is placed in the instrument and a ferrous index displayed,” he says.