Degradation of Industrial Lubricants – Technology Demonstration Demonstration
Preamble
The lubricant in rotating equipment is a key component of the machine as a whole, and it needs to be taken good care of - as much as all of the machines’ solid parts. From its first hour of operation to its last, all efforts need to be made to keep the lubricant free of contamination. Degradation Degradation of the oil is naturally unavoidable, unavoidable, but it does not not have to result in mechanical consequences. Only if left unattended, it will cause problems.
One possible outcome of lubricant degradation is deposits - which can affect coolers, gears, bearings, piping, reservoirs, valves, servos, actuators, and other systems parts. All of these possibilities present high high risk to the system and its efficiency. It causes downtime and the need for changing of parts. parts. Yet, in many case interruptions interruptions to production are not properly properly researched or linked back to the lubricant. On bearings and gears, failure is often blamed on wear and/or metal fatigue.
Deposits are often referred referred to as varnish varnish or lacker.
Their exact cause, chemical
composition, colour, and location can vary hugely, but the commonality is that they are the consequences of oil degradation. degradation.
Around the world OEMs and customers are recognising an increase in varnish due to the use of highly refined lubricants with complex, complex, multi-component multi-component antioxidant content. content. This calls for renewed focus on condition monitoring, trending, and management of lubricants as an integral part of your rotating equipment.
Proposed Technology Demonstration
Higrotek (Pty) Ltd, as the Southern African agent for Fluitec International, seeks to perform a technology demonstration on a heavily varnished rotating compressor in the South African
mining industry. The demonstration forms forms part of the launch of a new application of Fluitec’s ground-breaking Electrophysical Separation (ESP) technology for the in-service removal of lubricant varnish, and is planned to take place during the 3 rd quarter of 2013.
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For the demonstration, we are looking for a rotating compressor which is currently in service and either has been confirmed to have high levels of varnish or is suspected due to operational difficulties that relate relate to oil degradation. Once a worthy case has been identified, identified, Higrotek will arrange for the necessary tests to be performed to confirm oil degradation and varnish potential, before making a choice on the demonstration site.
Should you have such a compressor and are willing to make it available to Higrotek for the mentioned demonstration, you can notify Pieter Brand on
[email protected] or call on 082 457 6547 for more information. information. The mentioned demonstration demonstration shall be free of charge and with the full benefits benefits accruing to your company. Your company will be involved involved in the demonstration and will throughout receive feedback and valuable information on the cleaning process.
MORE ON DEGRADATION
Condition Monitoring Lubricating oil is one of the most important but often neglected “components” “components” of any machine - protecting vital parts, and the machine as a whole. Uptime and reliability are essential indicators for industrial plant, and it is absolutely essential to monitor and trend the condition of the oil on a regular basis to sustain high performance.
This field is undergoing great improvements, driven by new solutions & technologies from manufactures (OEMs) such as Siemens & GE, world industry bodies such as ASTM & DIN, leading lubricants companies like Shell, Chevron, ExxonMobil & Fuchs, and by some of the world’s leading operators of critical equipment. The aim of these improvements is to predict oil degradation before it happens, be in a position to predict mechanical consequences and act in time to t o prevent damage.
Turbine oil degradation Turbine oils are subjected to several different types of stresses as they are used, depending upon the type of system and operating environment that they are employed in. The most common modes of degradation are: 2
Oxidation: Oxygen reacts with the base oil and additives, degrading the oil. The most reactive of the additives are antioxidants, which which protect the base oil.
Once the antioxidants are
depleted, the base oil starts to degrade fast. Thermal degradation: degradation: Thermal degradation is a high temperature process that occurs in the absence of oxygen. This includes the phenomena of micro-dieseling or spark discharge. Degradation from foreign contaminants: contaminants: This may include incompatible lubricant formulations or other fluids improperly added to the fluid during maintenance activities. Foreign contaminants such as moisture and debris can accelerate acc elerate degradation.
What is varnish? In many cases, the degradation of turbine oils creates organic, oil-insoluble, polar contaminants, better known as varnish. The origin of these deposits may be from depleted antioxidant-additives or degraded base oils. These soft contaminants are responsible for settling out of the oil and forming deposits in the system, especially on white metal surfaces (bearings) and gear teeth.
Soft contaminants can create varnish and (burned) deposits at the highest temperatures and load zones of the bearings, as well as in the more stagnant areas of the equipment – resulting in sticky valves and hydraulics, bearing failure, poor cooling c ooling and premature damage to components. These contaminants contaminants form particles that are sub-micron sub-micron in size and can be unaffected by conventional filter technologies.
Varnish on gears
Varnish on pinion bearing
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Detecting and removing varnish–forming contaminants The earliest sign of oil degradation is detected with voltammetry or individual antioxidant count, since antioxidants are the most reactive additives in turbine oils and are the first to deplete. For predicting varnish varnish formation, the best best method is Membrane Membrane Patch Colorimetry (ASTM D-7843) which measures the colour of the sub-micron oil degradation products.
As mentioned earlier, these varnish forming contaminants are sub-micron in size and cannot easily be removed by conventional filtration processes. processes. To make things things worse, many of of these degradation degradat ion products become soluble solubl e between 40–55 °C, causing the contaminants contam inants either to be “in suspension” or “in solution”, depending on the temperature of the fluid.
Removing suspended contaminants is possible through technologies that are based on electrostatic forces or depth media filters, whose polar nature can adsorb some degradation products. That means the removal efficiency of these technologies is strongly influenced by the physical condition of the contaminants, which often results in the removal of the solid particles only. Partial removal of contaminants contaminants however however gives very little to no assurance of reliability and avoidance of mechanical consequen c onsequences. ces.
More recently the Electrophysical Separation Process (ESP) has been developed, which uses a resin-based technology that has the capability of removing contaminants whether in suspension or in solution. This process is now recommended by most OEMs and has seen several success stories in large and small steam and gas turbines, as well as industrial compressors. In all cases, the varnish-forming varnish-forming contaminants appeared appeared to be removed from the fluid in a few weeks, whilst the “continuously cleaned oil” successfully removed most varnish deposits on gears and bearings within a month or two.
The benefit of clean oil Very often damage to bearings is described as purely mechanical, and the initial chemical cause due to oil degradation is never identified. Worldwide experience however demonstrates that oil degradation is causing unacceptable (and avoidable) costs in most industrial sites – yet, often it remains unidentified and unattended.
A good Condition Monitoring Program that involves the latest technologies and swift action to abnormalities will not only save your company hundreds of thousands of Rands in restoration and downtime, but it will also maximise the life of your lubricants and equipment, savings you millions over time and contribute to your company’s environmental footprint. ___________________ _______________________ ____ 4
