Bel-Ray Specialty Lubricants: Tech Notes, Vol 3, Issue 5
What Is Oil?
Simply put, oil is a chemical compound that is in a liquid state at ambient temperatures and will not mix with water. Oils are derived from crude oil, also called petroleum, which is the product of ancient organic material that has been subjected to heat and pressure within the Earth’s crust.
The viscosity of crude oil can range from relatively fluid to as heavy as molasses. It is distilled by heating into light, intermediate and heavy fractions. The lighter fractions are converted into petrol and diesel. The heavier oils are refined to form clear, bright amber oils, some of which are used to blend engine oils. These are often referred to as API Group I and Group II base oils. Further refining of these oils, by a process called hydrocracking, will produce oils that are nearly colorless and have reduced volatility and improved oxidation resistance. These are referred to as API Group III base oils.
Years ago engines were filled with refined mineral oils called straight oils with nothing added. These early mineral oils deteriorated rapidly, leading to black sludge, corrosion and, before long, a worn-out motor. In the Fifties, lubricant manufacturers discovered how to improve the performance of motor oil by including additives with specific functions such as rust prevention, oxidation resistance, cleaning and anti-wear additives. The use of polymers or Viscosity Index Improvers allowed formulators to tackle the problem of cold starting by creating multi-grade oils. Polymers are long molecules that expand and contract as the oil is heated and cooled. Polymers effectively reduce the rate of viscosity change that the oil undergoes when heated and cooled.
Synthetic oils are man made fluids. Now-a-days, there’s a wide array of synthetic compounds, which are used in various quantities to give oil the desired performance and wear characteristics.
Chemical compounds can be blended to make molecules with desirable lubricating characteristics such as thermal and evaporation resistance. The two key synthetic base fluids in engine oils are PAOs (polyalphaolefins), which replace mineral oils, and esters. Where PAOs act like improved or superior mineral oil base fluids, esters also provide important functions such as improved additive solubility, detergency, lubricity or slipperiness and lubrication.
We all know that oil keeps metal parts moving by making them slippery, thus preventing metal components from making contact with each other. A plain bearing spinning at high speed floats on a film of oil so there is no metal-to metal contact. The high velocity drives oil between the two surfaces, and the oil film supports the load. At lower engine speeds, however, there is inevitably some contact between the bearing shells and crankpins. This is where oil must do its more sophisticated lubricating work. Special compounds in the oil react with metal at high pressure and temperature to provide a very thin protective film, which prevents scoring where metal surfaces come into contact. Finally, the esters used in Bel-Ray’s premium oils are attracted to metal by electrostatic forces and cling on even when surfaces are forced into contact.
Choosing the type of oil that will last longest is not as easy as choosing a synthetic product over a mineral product; the oil must be shear-stable. Bel-Ray offers a range of very high specification shear-stable motorcycle oils. The shear-stable part means the oil contains a high quality multi-grade polymer, which is more important than an unspecified synthetic claim. In fact, a shear-stable mineral oil is a better choice than a synthetic of dubious stability.
There are many oil additives on the market which claim to offer improved performance, but do they work? The simple answer is “no”!
Bel-Ray put vast amounts of money and research into obtaining optimum lubrication and if magical additives existed, then Bel-Ray would be using them already. Some additives actually contain substances, such as chlorine-based chemicals, that corrode engine internals, and additives containing PTFE do very little except clog the oil filter.
What Does Used Oil Analysis Really Tell Us?
Viscosity, acid number and water are parameters that generally indicate the condition of the oil and lend themselves well to setting minimum/maximum limits. These limits are set by the equipment manufacturer or operator, not by the oil company. However, it is best to analyze used-oil data over a period of time on samples taken at periodic intervals. This is called trend analysis, and is a useful approach for identifying problems early so that corrective action can be initiated before costly and catastrophic problems occur.
Wear metals are also part of the used oil analysis to indicate the changing condition of the various parts of the machine oil system. This includes oil pump, gears, bearings and other metallic parts that may rub and generate wear debris.
It is important to establish a practical interval to extract oil samples from the machine so good baseline data is recorded. This baseline data can then be used for comparison purposes if failures produce increased wear metals. The interval should be tailored to the particular testing program to provide timely data for analysis. The metals analysis is also referred to as SOAP (Spectrometric Oil Analysis Program). The chart lists major parameters and their limits.
|Viscosity (VIS)||+25% to -10%|
|Total Acid Number (TAN)||+2.0 mg KOH/g|
|Water Content (% H2O)||1000 PPM|
|Metals Analysis (SOAP)||+10.0 PPM and trend|
Viscosity and total acid number are analyzed to determine the condition of the oil. Upward movement of both these parameters is usually indicative of the oil being exposed to high temperature within the machine oil system, resulting in thermal or oxidative degradation of the oil. There may or may not be carbon deposition within certain areas of the machine oil system depending upon the source of the high temperature.
These two parameters are measured and monitored as indicators of high temperature problem areas within the machine. It should be noted that carbon can form on internal parts of the oil system where a “hot spot” exists and not manifest significant change in these two parameters. The limits used by most machine builders are shown in the preceding chart. However, it is advised that movement toward those limits during a consistent monitoring program may indicate that a problem is developing in the machine oil system before it exceeds one of the noted limits.
Water in the oil is monitored as a potential contaminant. Water can enter the machine oil system both as an accidental contaminate or through condensation. The main concern is the potential for corrosion due to acid formation.
Analysis of metals is accomplished primarily as a tool to help monitor the condition of the engines, bearings, hydraulics, gears and other machine parts. Typically, people use 10 PPM as a gross limit for all metals (except phosphorous) monitored in engine oils. This is based on the general observation over the past 20 years that most engines operating satisfactorily produce wear metal levels close to zero. Most engines that have a wear metal result greater than 10 PPM usually have a wear anomaly.
Having said that, the use of an absolute limit in wear metals is not nearly as significant and useful for analyzing problems in the engine oil system as the trending upward or downward of a given wear metal, or a group of wear metals. Trending is important in identifying wear or damage of bearings and gears. These results can be combined with oil filter inspection, vibration results and/or chip detector inspection. The metals monitoring helps to identify slow progressing damage to gears, bearings and spinning bearing races when the wear particles are in the 1-5 micron size.
In analyzing the wear metals results, it is important to have a knowledge of the metals used in the engine under construction. The values of the wear metals should be plotted on a graph against engine operating hours. The most common wear metal to show movement is iron because most bearings have a high percentage.
Depending on the bearing metal composition, if a bearing fails, many times the iron level will increase accompanied by another metal such as chromium (which may be the second highest compositional metal in the bearing). Upward movement of iron and titanium and chrome may indicate a spinning bearing outer race if the engine case is titanium. Catastrophic failures of mechanical parts in the oil system usually generate large metal particles which are not easily analyzed by spectrometric oil analysis, but can be analyzed by other means such as ferrography and debris analysis from magnetic chip detectors.
Silicon may indicate either dirt contamination in the oil sample or ingestion of dirt/dust in the machine inlet system. Another source can come from excessive use of silicone-containing sealants to seal certain parts of the engine/gearbox. High levels of this type of silicone can result in oil foaming and possible loss of lubricating qualities and heat transfer capabilities.
Inspection of the machine oil filter will many times provide the answer to silicate (dirt) or silicone. A foam test on the used oil may be needed if silicone contamination is suspected. The graph below is a typical trend plot of wear metals indicating possible abnormal bearing wear.
For more information about your used oil analysis, please contact your Bel-Ray Representative or the Bel-Ray Technical Services Department.
Anti-Leak Gear Lubricant; A Practical Solution
Due to the increase in mining materials demand, maintenance of equipment is often postponed to keep the process flowing and the materials delivered. New equipment, to replace equipment that is critical to the process, can be justified but cannot be installed due to the excessive demand of the mining operation. You have to keep the equipment going until you get a window to change or repair it.
To achieve the uptime required of the equipment, special anti-leak lubricant may be necessary.
In the case of the enclosed gear cases with leaking seals, the gear lubricant needs to provide the correct viscosity, Extreme Pressure, anti-wear, anti-rust, anti-corrosion, antioxidation, low coefficient of friction properties and must have the ability to control leakage from the gear case.
Safety is always a concern; leaking gear cases pose a safety hazard that needs to be addressed.
Best practice is to lock out the equipment in question, make a detailed inspection of the equipment and identify the source of the problem. If seals are the problem, repair the seals and leave the area free of lubricant to prevent an accident from happening. However, a total stoppage of the equipment can have a high impact in the cost of production.
Bel-Ray has found a solution for most of the lubricant leaking problems encountered with enclosed gear cases. Bel-Ray’s Semi-Fluid Grease offers superior leak suppressing capabilities provided by a unique gelling system. When the gears start rotating, Bel-Ray’s Semi-Fluid Grease becomes a fluid in the contact area with the gears, and forms a semi-solid or gel when the gears are at rest. Bel-Ray’s Semi-Fluid Grease seals the lubricant in while sealing contamination out.
The Semi-Fluid Grease gelling property is called thixotropic behavior, indicating a lubricant that has a cycle from gel to fluid to gel.
Bel-Ray’s Semi-Fluid Grease contains molybdenum disulfide or moly, graphite lubricating solids and Extreme Pressure additives to provide high load carrying capacity to extend equipment life.
Bel-Ray’s Semi-Fluid Grease is a solution to gear case leakage that is caused by faulty seals.
Bel-Ray understands the needs of customers and provides lubricants incorporating the latest technology with superior protection for customers’ equipment. Bel-Ray Total Performance Lubricants protect equipment exposed to severe requirements, extending the useful life of the equipment while protecting the investment of the client.