Turbines are critical pieces of equipment for power plants and related industries. Varnish
formation is the first root cause for down time and loss of reliability in turbines. The
lubricant’s oxidation condition can be effectively monitored through RULER (Remaining
Useful Life Evaluation Routine), MPC (Membrane Patch Colorimetry) and RPVOT (Rotating
Pressure Vessel Oxidation Test) tests. Besides the nominal ASTM (American Society for
Testing and Materials) value for these tests, significant information can be gathered from
digging into these tests and integrating their outcomes. One major application for this
integration is the estimation of the lubricant refreshment for lean operation. Through lab
tests, this can be accurately estimated, by planning ahead of the upcoming maintenance
intervention. This method will be shown, together with case studies.
In many ways, the properties of acids and bases are embodied by the classic cartoon strip, “Spy vs. Spy”, which was fi rst published in Mad Magazine in 1961. This Technical Bulletin will help you understand what acids and bases are all about, why they need to be assessed, methods of assessment and what these parameters have to do with industrial and mobile equipment. If the amount of acid or base present in your oil is unfavourable, then the oil – or more critically, the machine – can be damaged. It is thus essential to understand these terms with reference to oil analysis in order to get the best life from your assets by reducing downtime and minimising costly repairs.
Oils have a finite lifetime - they will eventually degrade and/or become contaminated and will need to be changed. Lubricants consist of a base stock that can either be mineral or synthetic. In the case of synthetic base stocks, these are a family of compounds that are manufactured in a laboratory to have precisely the properties that the chemists and engineers want. Mineral base stocks are derived from crude oil that comes out of the ground and is refi ned to produce a base stock that can do the desired job. Synthetic bases are superior to mineral ones but are much more expensive.
Lubricants do not last forever - a statement well understood by lubricant users all over the world. They are susceptible to the ageing process like most things on earth. An example of the aging process that is witnessed by everyone is the human skin. It ages with time and degrades by a process known as oxidation. Lubricants are no exception. Oxidation is currently being accepted as the major cause of lubricant ageing/degradation.
Earlier this year we published a Technical Bulletin on the ups and downs of viscosity. This was an important topic to cover as the viscosity of an oil is its most fundamentally important property. Both physical and chemical degradation can cause a change in the viscosity of an oil and, in terms of an increase in viscosity, poor combustion and sludging have been covered extensively in a number of Technical Bulletins. This Technical Bulletin will deal with high temperature operation and the effect it has on the rate of oxidation and, in turn, the degradation of lubricating oils and consequent increase in their viscosity.
It is well known that regular oil analysis is extremely useful in monitoring the condition of engines, drivetrains, hydraulics, turbines and many other types of oil lubricated equipment. The same can be said for transformer oils which are used to insulate many transformers and other electrical distribution equipment. The analysis of transformer oils not only provides information about the oil, but also enables the detection of other potential problems, including contact arcing, ageing insulating paper and other latent faults and is an indispensable part of a cost efficient electrical maintenance programme.
What is infrared? This thing that allows us to "see" in the dark, helps secure our homes, allows those couch potatoes amongst us to change the channel on the TV without leaving our seats and, in our case, monitor oil degradation. To answer this we need to take a look at the electromagnetic spectrum. To many, the electromagnetic spectrum is a formidable subject, yet to the analytical chemist it is a tool so useful it is without comparison. The electromagnetic spectrum is made up of electromagnetic waves. These are waves of energy that have both an electrical and magnetic component. These waves all travel at the same velocity - the speed of light (approximately 299 792 km per second) but their properties are determined by their frequency and wavelength.
The use of infrared spectroscopy for routine monitoring of oil-lubricated components, breakdown products and contaminants has not been widely used in the past, although infrared studies of lubrication oils themselves have been performed for a number of years. The reason for this is that older dispersive infrared spectrometers would take several minutes to generate a spectrum of the used oil and then considerable additional time would be needed to reduce and interpret spectral data.
Degradation of oils in service is an inherent part of their use. The rate at which oils degrade is dependent on several factors including the chemistry of the oil basestock, the type and amount of various inhibitors, and additives present in the oil, and the operating conditions of the oil over its service life. The main factors that attribute to the extended life of an oil in service are its thermal and oxidative stability. Thermal stability represents the oils ability to resist chemical change with increasing temperature in the absence of oxygen. Oxidation stability is the oils ability to resist chemical change, typically with increasing temperature, in the presence of oxygen.