Pekka Vähäoja

Suitability of the Respirometric Bod Oxitop Method for Determining the Biodegradability of Oils in Ground Water using Forestry Hydraulic Oils as Model Compounds

Different forestry hydraulic oils were used as model compounds for evaluating the applicability of the respirometric BOD Oxitop method in following the progress of biodegradation of oils in ground water. It is obvious that the biodegradability values of substances depend on the measurement medium used. In this study the same ground water was used in all the ground water experiments. It was observed that the biodegradability of hydraulic oils is dependent on the oil type, being faster for bio oils than for mineral oils. The rate of biodegradation of used hydraulic oils was slower than that of corresponding new oils. All the experiments show that the respirometric BOD Oxitop method is a good and reasonable method for monitoring the biodegradability of oils in water, and the method is independent of the biology and composition of the measurement medium. No changes to the equipment are necessary if conditions are changed. Because the method needs only one sample for measurement, and monitoring of the pressure in the closed bottles is automatic, biodegradability is determined easily and quickly. The precision of the results studied was good. By contrast, traditional measurement of biodegradability using IR, for example, is time consuming, requiring several samples and a considerable amount of poisonous extraction solvent (CCl4). Nevertheless, studies describing the biodegradability of oils using the respirometric BOD Oxitop method have not been published previously.

Wear Metal Analysis of Oils

This article concentrates on reviewing the literature related with wear metal analysis of oils. An overview on the existence of metals in oils and typical wearing situations is discussed briefly. Different pre-treatment methods of oil samples before wear metal analysis are presented with application remarks. Common measurement techniques of wear metal analysis, both qualitative and quantitative, are handled and compared with each other.

Studies of biodegradability of certain oils in forest soil as determined by the respirometric BOD OxiTop method

The suitability of the respirometric BOD OxiTop method for biodegradation studies of different oils in soil was assessed. Different forestry chain oils and wood-preservative oils were used as model substances. Experiments were carried out on different types of Finnish forest soils. The results of these experiments are in good agreement with our earlier results of oil-biodegradation experiments in water. The BOD OxiTop method proved to be a highly suitable analysis method for biodegradation studies of oils in soil.

Studies on the Effects of Certain Soil Properties on the Biodegradation of Oils Determined by the Manometric Respirometric Method

The biodegradability of certain biofuels was studied in the case of forest soils using the manometric respirometric technique, which was proved to be very suitable for untreated, fertilized as well as pH adjusted soils. Experiments carried out in infertile sandy forest soil gave a BOD/ThOD value of 45.1% for a typical model substance, that is, sodium benzoate after a period of 30 days and mineral addition improved the BOD/ThOD value to a value of 76.2%. Rapeseed oil-based chain oil almost did not biodegrade at all in 30 days in nonprocessed soil, and when pH was adjusted to 8.0, the BOD/ThOD value increased slightly to a value of 7.4%. Mineral addition improved the BOD/ThOD value on average to 43.2% after 30 days. The combined mineral addition and pH adjustment together increased the BOD/ThOD value to 75.8% in 30 days. The observations were similar with a rapeseed oil-based lubricating oil: after 30 days, the BOD/ThOD value increased from 5.9% to an average value of 51.9%, when the pH and mineral concentrations of the soil were optimized. The mineral addition and pH adjustment also improved the precision of the measurements significantly.

On the Condition Monitoring of Worm Gears

There has been fairly little research into the condition monitoring of worm gears, although gears of this type have been attached to critical machines in various fields of industry and significant production losses may arise from their breakdowns. Literature has been published on the designing of worm gears but information is rarely provided on fault diagnostics concerning these gears, especially with regard to real-life industrial applications. Some research has been carried out with laboratory-scale test rigs. There is thus an evident need to develop the condition monitoring of worm gears as a basic form of research, but especially to meet the requirements of different fields of industry. This paper gathers together the general information and research reports available on worm gears. Experiences gained from the use of oil analysis and vibration analysis in diagnosing the condition of machines with worm gears are presented in the form of case studies carried in industry. Our experiences of industrial machines with worm gears cover machines employed in cable manufacturing and talc production. We have been monitoring pressers in a cable-manufacturing factory by means of vibration analysis and wear metal analysis of oils for several years now. Condition monitoring data for certain talc agglomerating machines in a talc factory have been gathered during the past few years by means of an oil analysis, and some vibration monitoring data have also been collected. Four similar machines were used here and compared with each other in order to point out similarities and dissimilarities in their behaviour. The aims of this study were to find suitable condition monitoring methods for different machine types all using worm gears and to choose the most sensitive features for routine use in the maintenance of such machines in future. Another aim was to find out if it is possible to propose any common recommendations for the condition monitoring of worm gears.