Detecting Premature Bearing Failure.doc

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Detecting Premature Bearing Failure

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• Eugene Matzan Tags: bearing lubrication

Bearing manufacturers have long been aware of the relationship of heat to bearing life and

have designed formulas to accurately calculate safe operating temperatures. The results

show a temperature band in which both bearings and lubricants will operate at peak

performance with the least stress. Once outside the ideal temperature range, they will

degrade at an accelerated rate. So how do you interpret temperature readings, and how

should they affect your maintenance procedures? This article describes some temperature-

oriented methods for determining bearing health and life expectancy, both in the plant andin the field.

Figure 1. Heat Ranges of Bearings1

Figure 1 shows the thermal range of a typical rolling element bearing. Note that bearing

metal temperature is often higher (10 to 25 degrees Celsius) than the oil temperature in the

bearing within an oil circulation system. The green zone represents the sweet spot for

bearing and lubrication temperature; operating in the yellow zone reduces lubricant and

bearing life; and if your bearings are in the red zone, expect both the bearing and the

lubricant to be destroyed rapidly. There are different temperature bands for different

combinations of bearing and lubricant, but they will have the same general trend regarding

the best operating temperature and its effect on accelerated wear and failure. In most

standard lubricants, for every 15°C1 increase in temperature above 70°C, the lubricant life

is more than halved and there is a negative effect on bearing life. Any mineral oil operatingat a temperature above 80°C or 90°C will have a greatly diminished life. In no case should

bearing temperature ever exceed the maximum rating of either the bearing or the lubricant.

Monitoring Bearing Condition

Machine bearings are generally monitored through vibration analysis, oil analysis and/or

ultrasound techniques. Through these, it is possible to compare current data to historical

data and accurately assess the life of the bearings. Temperature increase due to increased

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friction is not even considered as a symptom of bearing failure in many bearing analysis

texts2 until Stage 3 bearing failure occurs.

If temperature is a reliable method of bearing life prediction, why is it ignored until after it's

too late? The monitoring of temperatures with thermography has been considered unreliable

because so many variables such as ambient temperature, speed, load and runtime all havea pronounced influence on bearing temperature. This article compares identical or near-

identical bearings on the same shaft which cancels the effects of these variables because

they are common to both bearings. The remaining temperature differences between the two

bearings on a common shaft with the same load, can only be the result of friction, an

indicator of bearing problems.

Perhaps subtle changes are hidden because there are so many variables that can potentially

contribute to bearing temperature. In addition to friction, other factors that can contribute

to temperature variation are load, speed, ambient environment temperature and runtime

duration. If these conditions could be predicted and accounted for accurately, then increases

in temperature would reliably indicate bearing problems.

In most cases vibration analysis and oil analysis are still the best ways to determine bearing

health. Unfortunately, it's not always possible or affordable to use these methods in hostile

production environments. Any environments where staff or technicians cannot easily access

the machine without taking it offline, or cannot access the machine due to hazardous

conditions or inconvenient locations make vibration or oil analysis expensive at best, or

even impossible. There are many industries and production environments where bearing

failure represents catastrophic loss, yet vibration analysis is not practical. Photographic film

and paper manufacturing, chemical processing and metalworking plants are a few examples

of industries that depend greatly on bearings, but where bearing accessibility can be a

major problem. Most manufacturers have at least some vital equipment in areas that are

not easily accessible.

Infrared Sensors

Outside of manufacturing, other industries are similarly affected. Wheel bearings on railroad

cars are a specific case in point: they are underneath trains, which are not hospitable places

for performing these tests while the cars are moving. Secondly, there is no practical method

of checking all such wheel bearings in a timely manner because of the sheer number of

them in use. Currently in the railroad industry, the only practical method for detecting

impending bearing failure is to use so-called hotbox detectors. These are infrared sensors

located along the train tracks that detect high temperatures in wheel bearings as the trainpasses. These are extremely limited and can detect bearings only in Stage 4 failure where

catastrophic failure (a wheel burn-off) is imminent. An alarm requires immediate emergency

action, disrupts train schedules, and is extremely costly. When these detectors miss bad

bearings or the alarm is not tended to immediately, the resulting wheel burn-off may lead to

a train derailment, widespread hazardous chemical spill, loss or severe damage of client

merchandise, or loss of human life. Because the consequences are so dire, every false

positive results in delays and inspections that can negatively affect the entire industry.



Studying Temperatures

If bearing temperature changes due to maintenance-related problems could be isolated

from all the other factors that contribute to bearing heat, a properly designed monitoring

device could detect bearing failure at the Stage 2 level. A newly patented technique is being

evaluated that could have significant benefit to industries that need to analyze bearing and

lubrication life in difficult-to-reach areas, such as under train cars. The heart of the patent isa technique that cancels all thermal variables except the increase in bearing temperature

due to wear or lubrication failure.

The procedure takes heat data from each bearing on a common shaft and compares the

data. Because the load, speed, ambient temperature, and run duration are common to all

the bearings common to the shaft, their effects on temperature are canceled. Any recorded

temperature variation is the result of unwanted maintenance- or repair-related conditions

such as over- or underlubrication, bearing damage, misalignment, or loose-foot condition. If

one bearing is more than 15°C greater than another on the same shaft, the bearing health

is in question and the root cause of the increased bearing temperature must be determined.

The bearing comparison is accomplished with electronic temperature sensors and

comparators powered by a self-contained power supply that recharges its battery through

the motion of the equipment.

The methodology involves the following:

• Temperature sensors are attached in close proximity to all the bearings on a

common shaft or axle.

• The sensors apply input to a sensing unit that is self-contained and has wireless

technology for communication with warning devices.

• The temperature data of each unit is analyzed and compared electronically.

• If any bearing temperature varies more that 15°C, an alarm is transmitted and an

LED indicator will light.

• The system is self-powered by a small power supply which is actuated by the

movement of the equipment.

• There is a maximum allowable temperature in case all bearings are out of normal

operating range.

This technique will never be as accurate as oil or vibration analysis, but in remote or

hazardous locations where these tools are not an option, it will provide an increased level of

condition monitoring that was not available in the past.

References

1. SKF bearing manual.



2. Entek IRD Volume I Vibration Analysis, p. 6-48.

Four Stages of Bearing Failure

Stage 1. Earliest detectable indication of bearing failure using vibration analysis. Signals

appear in the ultrasonic frequency bands around 250 KHz to 350 KHz. At this point, there is

approximately 10 to 20 percent remaining bearing life.

Stage 2. Bearing failure begins to "ring" at its natural frequency, (500 to 2,000 Hz) signal

appears at the first harmonic bearing frequency. Five to 10 percent remaining bearing life.

Stage 3. Bearing failure harmonics of the fundamental frequency are now apparent.

Defects in the inner and outer race are now apparent and visible on vibration analysis of the

noise signal. Temperature increase is now apparent. One to five percent of remaining

bearing life.

Stage 4. Bearing failure is indicated by high vibration. The fundamental and harmonics

begin to actually decrease, random ultrasonic noise greatly increases, temperaturesincrease quickly. Remaining life one hour to one percent.

Advice for Improved Oil Sampling

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• Noria Corporation

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"We have a 600-liter sump that supplies 150

liters per minute to eight turbine bearings from one reservoir. The oil flows from the

reservoir by a single pump and filter, then separates to the eight bearings. We take the oil

samples from the return lines before they join for the return to the reservoir. None of the

samples show much wear. On the last sampling when there was a sign of bearing failure,

the sample for that bearing showed only 4 ppm iron, 2 ppm tin, 1 ppm aluminum, 2 ppm

silicon, 2 ppm sodium, 2 ppm magnesium, and everything else 0. Viscosity was 66.7 on

Regal 68 at 1,000 hours (6,200 on the unit). Why would samples not show that there was a

problem?"

The answer to your question can likely be summed up in one word — dilution! Assuming, as

you state, that you are sampling on the return lines from each bearing, the reason for the

low wear metal levels is likely due to the comparatively high oil volume in the return lines.

In oil analysis, wear debris is measured in parts per million. When you state "2 ppm tin,"

what you are actually saying is "2 mg of tin for every kilogram of oil."

So the same amount of wear debris distributed in a large volume of oil, such as a circulating

turbine, will generate a much lower ppm than the same amount of wear in a small wet

sump system where the volume of oil is typically much smaller.

To minimize the effects, try to ensure the sample is taken as close to the bearings aspossible. In addition, ensure that the sampling method is precisely controlled with the same

method used every time, including flushing volumes. You might also need to tighten your

alarms considerably to the extent where "normal" really means 0 ppm of tin (and other key

elements), and any slight increase (even just 1 to 2 ppm) is considered "cautionary."

Other possible causes of the low wear metal limits could be a failure mechanism, which

really doesn't generate significant amounts of wear debris, or one that creates larger sized



particles (in excess of 5 microns), which do not show up in conventional elemental

spectroscopy techniques. However, given the nature of this application, dilution is the most

likely cause.

While most lubrication teams grasp the importance of good oil sampling, they are not

exactly sure how to address the specifics. The good news is that instituting a quality oilsampling program in a plant is generally a relatively inexpensive exercise with high, short-

term paybacks. If you haven’t instituted a world-class oil sampling program, now is a good

time to start. If a sampling program is in place, maybe now is the right time to review it for

compatibility with reliability goals. Don’t let a poor oil sampling program shoot your oil

analysis program from the sky.

Mapping Oil Pressure to MeasureBearing Wear

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• Gary Blevins, Wearcheck Africa Dan Burger, Wearcheck Africa Tags: bearing lubrication

One of the buzzwords used in regard to condition monitoring is oil pressure mapping. This

article explains oil pressure mapping, why this diagnostic technique was developed and how

it is used to measure engine bearing wear.

Testing for Bearing Wear

Traditionally, testing for abnormal wear or damage to the main or big end bearings was

carried out by measuring engine oil pressure at idle and maximum engine speeds. The

reasoning was that excessive bearing clearance would cause excessive oil leakage and a

resulting drop in oil pressure.

This test is no longer reliable as modern diesel engines are fitted with high-capacity oil

pumps, which are needed to deliver oil to the spray jets used to cool the pistons. As a

result, the pumps can cope with higher oil leakage rates, so there is little noticeable drop-off

in oil pressure. This is why oil pressure mapping is used.










Before discussing oil mapping in more detail, it’s helpful to take an in-depth look at

bearings, their importance in maintaining healthy equipment, and why oil pressure affects

bearing wear.

Bearings and Oil

A bearing is often an inexpensive part in a machine, but the failure of a bearing results in aconsiderable amount of consequential damage to other components. It is for this reason

that maintenance personnel are concerned about the health of bearings.

Oil analysis is an important tool used to assess the soundness of a bearing. Once a problem

is detected through oil analysis, it must be investigated to establish the cause and extent of

the problem.

The following are a few of the common causes of bearing faults:

• overloading or shock loading

• contamination of lubricating oil

• overheating of lubricating oil

• overheating of the bearing

• misalignment or incorrect assembly of the bearing

• insufficient pressure and/or volume of the lubricating oil

The secret to long bearing life, after installation and operational problems have been

corrected, is to ensure that the bearing is supplied with the correct grade of oil in sufficient

quantities, and that the oil is clean and runs at the correct temperature.

Plain bearings, in particular, are sensitive to oil volume and pressure. Insufficient pressure

will normally result in insufficient oil volume being delivered to the bearing. The decreased

oil volume causes the bearing to wear out faster, due to increased operating temperatures

and contact between the journal and bearing.

Antifriction (roller or ball-type) bearings can normally run on relatively small volumes of oil.

However, a drop-off in oil volume will cause wear on the cage due to the increased sliding

contact in this area. The wear then allows the rollers or balls to move out of position and

accelerate wear of the bearing races.

Oil Mapping

An oil pump, like most other pumps, produces a rapid increase in output as speed increases

until a critical point is reached, after which the output drops off again.

To prevent erosion damage to the bearing from the excessively high oil pressures possible

with the high-capacity oil pumps fitted to modern diesel engines, a pressure-relief valve is



fitted to the engine oil pump. This vents excess oil back to the sump when the maximum

allowable pressure is reached.

Oil pressure mapping is simply a method of verifying that the oil pump pressure follows this

curve. When the shape of the curve changes, it indicates a fault with the oil pump or

excessive oil leakage in the engine, possibly due to bearing wear.

How to Map Oil Pressure

To map the oil pressure, you need an accurate oil pressure gauge which can accommodate

a range of pressures. Dashboard-mounted gauges are generally not accurate enough for

mapping purposes. An accurate tachometer is needed to measure engine speed while

performing the test. Graph paper to plot the resultant pressure curve is also useful.

Step 1

Make sure the engine has reached full operating temperature. Water temperature is not a

reliable indicator of oil temperature. The water temperature stabilizes quickly due to the

action of the thermostat, but the oil temperature lags behind during warm-up. If possible,

record the oil temperature when the pressure readings are taken.

The oil temperature is important because the oil thins rapidly as the oil temperature

increases, then thickens again when it cools down. The thickness of the oil (viscosity)

affects the pressures obtained and may give inaccurately high readings if measured at too

low of a temperature.

Step 2

Connect the oil pressure gauge to the main oil gallery before it enters the bearings; the oil

pressure sender unit is generally a good point. Connect a tachometer if required.

Oil pressure should then be measured at 10 or more speed intervals equally spaced

between idle and maximum engine speed. It is helpful to draw a straight line from the first

reading taken at idle to the last reading taken at maximum engine speed. All the

intermediate points on the curve should lie above this line.

If the pressure falls below the line or follows the line closely, there is likely a problem with

the oil pump or the pressure-relief valve, or excessive leakage is occurring within the engine

itself. Even if the oil pressure is close to normal at full speed, it may be too low at peak

torque where the bearings are subjected to maximum loading.

There are many different designs of engines and pumps, so when a problem is suspected, it

helps to have a reference graph against which to compare the results. It is, therefore,

advisable to map an engine shortly after it has been run in, and then use this baseline for

comparison with later graphs.



Any change or drop-off in the graphs should be investigated. First, check the pump and

pressure-relief valve. If no fault is found with the pump, the engine itself should be

inspected for excessive leakage.

Engines Fitted with Scavenge Pumps

Engines on some earthmoving equipment are designed for operating on slopes and arefitted with scavenge pumps. It is generally not possible to check the function of the

scavenge pump. It tends to wear out faster than the main pump due to oil aeration in the

scavenge pump when the engine is running level. An undetected scavenge pump failure will

soon result in bearing failure. Engines fitted with this type of pump must have the pump

stripped and checked for damage at planned intervals of at least every 10,000 hours of

operation.

When to Use Automatic Grease

Applicators••

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• Noria Corporation Tags: automatic lubrication, bearing lubrication, greases

If you regularly read this column, you have likely seen my articles on grease application and

selection. In the past, I have focused on manual grease application. For this issue, I decided

to offer opinions on the topic of automatic grease application - specifically, single-pointautomatic grease applicators.

There are two primary reasons to select automatic application: improved quality of

lubrication and/or reducing man-hour requirements for grease application. Like most other

lubrication methods, the successful use of single-point grease applicators requires some

knowledge of lubrication fundamentals; many common mistakes are made. In order to get

positive results from such devices, you must select the right type of applicator for a given

application, install the device correctly and determine the optimum application rate.

Comparing Methods

There are certainly advantages to automatic application when compared to manualapplication. Theoretically, it is preferable to apply small amounts of grease at short intervals

rather than large amounts of grease at long intervals.

With manual application, the trick is to apply as much grease as possible without causing

harm due to over-greasing, thereby maximizing the relubrication interval. While this is fine

for most grease-lubricated components, there are many applications that may benefit from

more frequent application or could be harmed by large application volumes. Of course, you

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could choose to simply lubricate these components very frequently, but the associated labor

cost would likely make the option of automatic lubricators attractive.

To accurately determine which lubricated components would be good candidates for

automatic applicators, you must understand the factors that cause a need for frequent

relubrication, such as excessive temperature, high speeds and contamination.

Figure 1. A Simple Comparison Between Manual and Automated Lubrication

Temperature is a perfect example. In high-temperature applications, such as those

commonly found in steel mills, some bearings may need to be lubricated every day or even

every few hours. While this is an extreme example, it's easy to see that it would require a

veritable army of technicians to perform manual relubrication on hundreds of bearings every

day, thus making automatic application the preferred method. Some high-speed

applications not only require frequent application, but they also may be damaged by the

addition of large volumes of grease, causing overheating or skidding of bearing elements. In

many cases, the largest contributing factor to grease reapplication requirements is

contamination. Any application can require very frequent application when contamination is

severe, regardless of other factors. These are just some of the primary factors to consider;

there may be others such as inaccessibility and limited manpower for lubrication activities.

Advantages of Single-Point

For systems with many lubrication points, such as the steel mill example, centralized

automatic systems are often ideal. But for many others, including systems with just a few

lube points or with long distances separating the lube points, single-point lubricators offer

many of the same benefits at a small fraction of the cost.

Consider an incline conveyor with bearings that require frequent lubrication due to

contamination ingression. In such an application, a centralized system would require

extensive plumbing to lubricate only a few points, making single-point applicators a great

fit. Grease-lubricated pump bearings, fan bearings and grease-lubricated packing seals are

all good examples where such devices would likely provide significant value.



Typical Issues with Single-Point

There are several issues to keep in mind when using single-point lubricators that may lead

to improper grease application. These issues include insufficient pressure to deliver the

grease, improper dispense rates and probably the biggest issue of all - a failure to properly

inspect the device for proper operation.

The issue of insufficient pressure isn't a problem with the applicator, but rather a problem

with selection. Depending on the delivery method, some of these devices only generate

approximately 50 to 75 psi. It is important to ensure that the system pressure will be

sufficient for a given application and installation method. This can be determined by first

manually applying grease to the component using a grease gun fitted with a pressure

gauge. This issue also should be considered when installing the unit. Take steps to minimize

the amount of back pressure on the device by using as few fittings as possible and keeping

the length of any tubing or piping to a minimum. Whatever the requirements are, you

should be able to select a device that provides ample pressure.

While there are factors that can affect dispensation rates, such as temperature and grease

consistency, the most common problem is simply selecting the wrong setting. Before

installing the unit, determine the appropriate application rate by using valid lubrication

engineering methods. Many problems can arise from over- or under-lubricating a

component, including overheating, excessive wear or simply wasting grease and making an

unnecessary mess.

Of course, the biggest pitfall is a failure to routinely inspect single-point lubricators for

proper function. Installing an automatic lubricator doesn't ensure that you will have a

properly lubricated component. They must be inspected just like anything else. In fact, a

proper inspection process should identify and allow for correction of the previously

mentioned issues. Determine the frequency of inspection based on the unit's application

rate and the component's sensitivity of over- or under-lubrication. A good idea for such

inspections is to record the installation date on the unit and make marks at each inspection

denoting the date and reservoir level. Based on the desired application rate and reservoir

size, you should be able to determine if the unit is operating normally. Inspect the

lubricated component as well to check for an indication that the grease application rate is

optimum. You may want to include condition monitoring such as acoustic energy

measurements or high-frequency vibration to monitor the condition of lubrication.



Education Before Selection

Most industrial facilities have at least some applications that may benefit from automatic

grease application; and for many of those, single-point lubricators may be the best option.

Those considering the addition of single-point lubricators to their lubrication program should

educate themselves on the different types of systems available, as well as the pros and cons

of each.

Centralized Grease Lubrication

Systems

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• Brad Jeffries, ExxonMobil Tags: automatic lubrication, greases, bearing lubrication

Centralized grease lubrication systems are widely used in industrial and heavy-duty mobile

equipment applications to lubricate multiple points on a machine. These systems range from

a simple single-port lubricator to complex dual-line, reversing units employing timers and

alarms to deliver grease reliably to hundreds of grease points.

The design parameters of centralized grease systems include the volume and frequency of

grease required at each point, the number of points requiring grease, operating conditions,

pump pressure, line diameter and distance to the grease points. When used and maintained

properly, centralized grease systems can help enhance technician productivity and simplify

equipment maintenance processes. The following is a comprehensive overview of















centralized grease systems and the benefits they offer, the various types, concerns to watch

out for and tips on how to maintain them properly.

Advantages of Centralized Grease Lubrication Systems

Centralized grease systems are designed principally to make the work environment safer for

maintenance personnel by simplifying the process of accessing remote grease points,especially in confined spaces, when equipment is in operation. However, the primary benefit

is derived from the continuous application of small amounts of grease resulting in improved

equipment life, due to the uniform supply of grease.

Hand application is typically performed infrequently and may result in uneven amounts of

grease being applied, which can lead to overgreasing resulting in damaged seals and

elevated bearing temperatures caused by grease churn.

It is important for maintenance professionals to realize that many centralized grease

systems have long lines, precise metering valves, fittings and numerous connections that

can malfunction due to vibration, air entrainment and other environmental impacts. Thus,

carefully monitoring and maintaining the systems on a consistent basis is critical.

Types of Centralized Grease Systems

Centralized grease lubrication systems are designed to lubricate the broadest range of

stationary and mobile equipment. As the lubrication application becomes more complex, the

design of the system also becomes more complex as additional features are added.

Most centralized grease systems fall into two categories. The first is a direct system in which

a pump is used to pressurize the grease and meter it out to the application point. The

second and more complex type is an indirect system in which a pump pressurizes the

grease. Valves built into the distribution line are then utilized to meter the grease into the

bearings.

Indirect systems are further broken down into two basic types, parallel and nonparallel. In

parallel systems, also known as nonprogressive, the system is pressurized and the metering

valves operate simultaneously. The disadvantage of a parallel system is that it can be

difficult to identify a failed (blocked) valve, as grease will continue to be dispensed through

the remaining valves. Pump pressure will not increase and there will be no outward sign of a

valve failure (Figure 2).



Figure 2. Single-line Parallel System

Courtesy of Lincoln Industrial

In nonparallel systems, also known as progressive, the metering valves are installed in-line.

After the system is brought up to pressure, the first valve operates. Grease then flows

through it to the next valve in line. In this setup, if one valve fails, the entire system fails

resulting in increased pressure at the pump and no grease consumption. No other obvious

problems can be used to quickly identify the exact point of failure (Figure 3).

Figure 3. Single-line Progressive System

Courtesy of Lincoln Industrial

Parallel and nonparallel systems can be further broken down into single- and dual-line

systems. Today, the most common type of centralized grease system is the indirect single-

line system, accounting for more than 50 percent of the market. For single-line machines,



injectors represent the key to quality performance. In single-line systems, injectors are

responsible for metering the correct amount of grease to the bearing or other surfaces

requiring grease lubrication. When advancing to a new cycle, one must always vent the

injectors.

The other type of system, the dual- or two-line system, uses two supply lines to providegrease to the injectors. A four-way valve is used to direct grease alternately to each of the

grease lines while relieving pressure on the other line. The second line provides a safety

margin but involves additional cost and complexity related to installation.

There are a number of ways to control both the single- and dual-line systems. The valves

can be operated manually, cycled by a timer or controlled by a counter that measures

grease flow.

Various strainers, filters, alarms and monitoring devices may also be included in the system.

These systems are set up in one, two or three stages, depending on the number of

lubrication points.

Besides injector valves, all centralized grease lubrication systems incorporate a reservoir of

grease, pump, controller, lines and metering blocks as shown in Figure 1.



Click Here to S

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Figure 1

Each part functions as follows:

• Reservoir: Provides a bulk quantity of grease that can be kept clean and readily

available to the system.

• Pump: Produces the flow of grease and builds up pressure in the line(s). Pump size

will vary depending on the distance between the pump and the farthest injector.

• Controller: Manages the pressure on the system by turning pressure supply valves

on and off on the basis of either time or cycle. It can also receive signals indicating

restricted or failed grease flow to the bearing.

Constant-level Oilers

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• Carolyn Boldt, Oil-Rite Corporation Tags: automatic lubrication, bearing lubrication

A constant-level oiler is used to maintain the fluid level in a piece of equipment that

naturally depletes fluid through use, wear, friction, misting or evaporation.

As oil is depleted in equipment, such as bearings, gearboxes, pillow blocks or pump

housings due to its natural operation and the generation of heat from friction, the level of

fluid changes. A constant-level oiler can be used to maintain optimum performance.

The operation is based on the liquid seal principle: as fluid is depleted in the equipment, the

liquid seal on the spout inside the constant-level oiler is broken. When this occurs, air enters

into the oil reservoir from the air vent. This releases the fluid from the reservoir and allows

it to flow into the equipment until the liquid seal reestablishes itself.

An automatic constant-level oiler can be used for antifriction, sleeve, roller, ball, tapered,

spherical or slinger bearings involving excessive backpressure. Applications include fans,

motors, blowers, gearboxes or other equipment where a constant level of fluid needs to be

maintained. Constant-level oilers are most useful in paper mills, cement plants, coal

handling mills or industries with similarly dirty environments, because the sumps are

opened less frequently.

Basic Design and Operation

In situations where pressure or a vacuum is generated in the sump, it is preferable to

provide a vent line back to the equipment housing above the oil level to equalize thepressure. By equalizing the pressure between the oiler and the equipment (Figure 1), the

level is more accurately maintained, creating a closed-loop system. In the event that there

is no place to pipe the air vent back to the equipment, a filtered vent plug at the reservoir

can be used to prevent environmental contaminants from entering the system. Figures 2

and 3 show the two fluid connection points, of which either point can be used for installation

or drain. One is located on the side of the housing while the other one is on the bottom.

These points will vary by design.











Figure 1. Style CS

The liquid level in the oil reservoir is visible through a clear reservoir available in acrylic or

glass and in various sizes. Maximum temperature rating is 160ºF for acrylic and 225ºF for

glass. The reservoir is mounted airtight on the base to prevent contaminants from entering.

The reservoir is easily refilled through the cap on top port which will automatically shut off

the flow while being refilled. Operation will resume when the cap is returned and secured. It

may be necessary to repeat the fill process until the fluid reaches the optimum level and no

longer drains from the reservoir when the cap is installed.

Constant level oilers may be installed remotely or directly to the reservoir. A liquid level line

is marked on the base of the constant-level oiler for ease in aligning to the proper oil level.



Figure 2. Style CS Adjustable

With certain equipment, high levels of oil can be carried to the upper portion of the housing

during operation. Upon shutdown, this oil surges back to the reservoir establishing a high oil

level. Should this amount of oil overtake the capacity of the reservoir, it will flow into the

vent line (Style CS) and dissipate or in the case of those piped to the sump through the

vent line, will run back to the housing.

A constant level oiler is installed with the oil level mark at the exact height at which the fluid

in the housing is to be maintained. It should be level with short, rigid connections to avoid

vibration. The air vent is sometimes equipped with a filter when vented to the atmosphere.

The air vent can also be connected back to the top of the gearbox or housing for a closed

circuit.

Constant level oilers have been known to operate for years or even decades without

maintenance. Degraded seals are the most likely cause of an operating problem. The oiler

can be tested by plugging the fluid outlets with pipe plugs, refilling the reservoir, tightening

the cap and observing for leakage. The oil should seek and stay at the oil level mark over

the course of several hours. If the seals are faulty, the oil will fill the viewing port and seep

out the vent hole. In the case of faulty seals, it is advisable to replace the entire unit.



Figure 3. Style C

Installation

Proper installation of the oiler will assure maximum long-term operation. Key issues that

must be addressed during installation include:

1. Verify that the oil level is clearly marked on the base of the oiler. Mount the oiler by

using side or bottom outlet at the desired level.

2. The correct oil level is the lowest level at which the bearing operates properly, which

should be at the middle of the element measured at the six o’clock position in the

race.

3. Lubricator must be level in all directions to function properly.

4. All connecting pipes should be short, rigid and close to the housing to avoid

vibration.

5. Assure that the housing is filled at initial installation. Fill the housing through the

oiler. Repeated filling may be necessary.

6. Verify that the filler cap is tightly fastened. Removing the filler cap will shut off oil

supply. Loose filler cap will cause leakage.

7. The sump should be fitted with sight glass to confirm oiler operation.

Troubleshooting

A variety of table-top tests may be conducted to identify and resolve issues in the



installation and maintenance of constant level oilers. A simple preventive maintenance

inspection can be conducted as follows:

1. Secure oiler so it is level in all directions.

2. Plug outlets with pipe plugs.

3. Remove fill cap and fill reservoir completely.

4. Quickly screw fill cap back on the reservoir. Note: Closing the fill cap allows the

check valve to open, thus allowing oil to fill the sight glass.

5. When the fill cap is tightened securely, the oil in the sight glass should seek a level

at or near the level mark shown in the casting.

6. Leave oiler to sit for several hours. If it continues to hold oil at the initial level, the

oiler is working properly. If oil appears to be filling the sight glass completely, and is

seeping out of the vent hole, the seals in the unit are bad and the seals should be

replaced.

Manual or Automatic Lubrication? Howto Decide

••

•

• Gustavo Sabogal, SKFTags: automatic lubrication

Lubrication is an essential part of machinery maintenance for nearly every production

facility. On average, lubricant purchases amount to only 3 percent of a maintenance budget,

but lubrication-related activities can influence an estimated 40 percent of total maintenance

costs.

In order to achieve optimum reliability and maximum benefits from a lubrication program,

several factors need to be taken into account. These factors are summarized by the well-

known five “R”s of lubrication:

• The right lubricant

• In the right quantity

• At the right time

• At the right point

• With the right method







The starting point of an effective lubrication program is the detailed mapping of all

lubrication points, including their working conditions, lubrication requirements and criticality.

This information is needed to select the most suitable lubricant and the quantity of lubricant

needed, as well as to calculate the adequate relubrication intervals. These are the first three

“R”s.

The fourth “R” refers to best practices, such as tagging and color-coding (or other

methodology) of both lubrication points and tools in order to avoid cross-contamination.

Maintenance Costs Influenced by Lubrication-Related Activities

Besides lubricant costs, half of acquired components require relubrication. Overtime labor is

mostly a result of machine failures typically caused by inadequate lubrication. In addition,

approximately 5 percent of labor costs can be attributed to lubrication activities.

The fifth “R” can be defined once the application conditions, asset criticality and

maintenance strategy are analyzed. This will help you make the decision on whether to

automate each lubrication point. In order to make that decision, the pros and cons of

automatic lubrication should also be understood and considered.

Once the five “R”s are defined, you can determine the best way to lubricate a component

with the resources available.

Criticality Analysis

A thorough criticality analysis of each asset will illustrate the impact of a failure in terms of:

• Overall production cost

• Overall maintenance cost

• Environmental impact

• Health and safety of personnel

The most critical assets are commonly the first targets of automatic lubrication.

Maintenance Strategy

The maturity level of a maintenance program (corrective, preventive, predictive, etc.) will

dictate the skill and knowledge level required of personnel involved in lubrication-related

activities.



As the maturity of maintenance and associated lubrication programs increases, so does the

complexity of tasks that lubrication technicians must be capable of completing. These

include activities such as:

• Lubricant analysis

•Continuous adjustment of lubrication routes (relubrication intervals and consolidationof lubricants)

• Contamination control and fluid reconditioning

• Inspection routes

Therefore, as more mature maintenance programs are adopted, the areas where skilled

maintenance technicians can add value to your operations need to be carefully considered.

For example, are they best utilized performing manual relubrication, which can easily be

automated, or by using their skills and knowledge to perform more analytical tasks,

lubricant analysis and making improvements to the lubrication program?

Benefits of Automated Lubrication

There are many advantages in using automatic lubrication systems. These include reduced

waste and risk of bearing failure, cleanliness, less labor, and improved environmental health

and safety.

Reduced Waste and Risk of Bearing Failure

Relubrication quantities are dictated by the physical space available in the bearing, while

relubrication intervals are dictated by the working conditions that determine the degradation

rate of the lubricant (speed, load, temperature, type of bearing, etc.).

A single-point automatic lubrication system can deliver the right amount of grease at the

right time to each lubrication point. This reduces both grease waste and the risk of bearing

failure.

For example, consider a bearing that needs to be relubricated with 2 grams of grease every

week. With a standard grease gun, this would mean that the bearing should receive about

1.3 “strokes.” However, manually delivering 0.3 strokes is difficult. In reality, two strokes

would likely be given. In other words, the bearing would receive 3 grams instead of 2 gramsof lubricant each time.



If we assume the technician is satisfied with two strokes (if he doesn’t see any grease

coming out of the seals), then after a year the bearing will receive 156 grams (52 weeks

times 3 grams per week) instead of 104 grams (52 weeks times 2 grams per week). Thismeans that up to 52 grams (50 percent) of grease will be wasted.

This example shows the benefit of accurately delivering the right quantity of lubricant (the

second “R”), but what about the frequency of lubrication (the third “R”)?

Extending relubrication intervals beyond the calculated limits will expose the lubricant to

excessive degradation and the bearing to lubricant starvation conditions. On the contrary,

shortened relubrication intervals with adjusted quantities would renew the lubricant’s

properties.

To illustrate this point, consider that on average, a human being requires about 2,000calories per day. Would you rather consume your weekly total of 14,000 calories once a

week or in nearly equal amounts over seven days?

Cleanliness



An automatic lubricator can supply

a continuous and accurate flow

of fresh and clean lubricant.

Lubricant contamination will also affect bearing life and increase the risk of failure. In

manual lubrication programs, avoiding grease contamination can be a challenge. Processes

must be clean to ensure no external contamination ingress to the grease, and eachlubrication point should have a cap on its grease fitting. In addition, the utmost clean

relubrication process for each point must be followed every time.

In the previous example, the technician will relubricate the given point 52 times a year. As a

result, the bearing will be exposed 52 times to external contamination as well as to over-

and under-lubrication. By comparison, a properly installed single-point automatic lubricator

can supply a continuous and accurate flow of fresh and clean lubricant, keeping the

application in proper condition while at the same time preventing contaminant ingress.

Labor Savings

The simple task of pushing a lever on a grease gun to provide manual lubrication can be

easily replaced by a machine. However, the real issue is whether you are getting the

maximum value from your skilled maintenance technicians. Such personnel can manage a

lubrication program through:

• Continuous improvement of the lubrication routes



• Implementation of a lubricant analysis program

• Implementation of a contamination control and oil reconditioning program

• Implementation of a leakage control program

Keep in mind that while deploying automatic lubrication systems can free personnel from

time-consuming basic activities to provide extra value, it cannot replace staff who can

deliver value at this level.

Environmental Health and Safety

Improper relubrication activities can have a significant impact on the environment. Consider

again the grease waste calculations in the previous example. Now try to estimate the impact

of this waste on the environment. Naturally, it depends on the disposal practices you

implement at your facilities, but in basic environmental terms, the less waste the better.

Next, consider points that are difficult or even hazardous to access and the potential impact

to your personnel. This is another area where automatic lubrication systems offer real

benefits.

Common Problems

Simply using automation doesn’t guarantee success. The technology must be considered an

instrument to achieve a goal. Basic decisions and activities must still be performed. The

following are typical mistakes that can jeopardize the potential benefits of deploying

automatic lubrication.

Lack of Inspections

Having an automatic lubrication device doesn’t mean that the system won’t require any

inspection. Regular inspection will help ensure the best results from an automated system.

Inspection also will help to identify installation issues (damaged fittings, leaking or blocked

pipes, lubricators not dispensing at the right pace, etc.) and spot when it’s time to change

or refill lubricants.

Moreover, lubrication routes must be updated, and manual lubrication tasks must be

replaced with inspection tasks at an adequate interval. The frequency of inspection is lessthan that required for manual relubrication, but it still must be planned.

Improper Lubricant Selection

As a fundamental in any lubrication program, the lubricant selection must precede the

lubrication system selection. After all, the lubricant that goes into the application is what

lubricates, not the delivery system itself.



The lubricant and the automatic lubrication device must complement each other to ensure a

better overall performance. Needless to say, not all lubricants are suitable for all automatic

lubrication systems, and the impact of a lubrication system on the structure of the lubricant

depends on the technology of that given lubrication system.

Consequently, parameters like pumpability and oil separation must be taken into accountwhen an automatic lubrication system is to be installed. Furthermore, relubrication intervals

must be defined in a way that prevents the lubricant from being stationary inside the

lubrication ducts, especially when exposed to extreme temperatures that could promote

premature degradation. Failure to understand and act on these issues can affect the

performance and associated benefits of deploying an automatic lubrication system.

Investment Costs

Of course, deploying an automatic lubrication system requires some level of investment. To

maximize the return on that investment, the key is to choose the right solution based on

the requirements and criticality of the application. Typical solutions range from inexpensive

single-point automatic lubricators to very complex centralized systems with various options

for online monitoring. Determining which option is best for your application depends to a

great extent on your criticality analysis.

When to Use Automatic Lubrication

Automatic lubrication alone certainly is not the solution to all your lubrication issues. It must

be properly understood to boost its potential benefits. However, there are solutions

available in the market for virtually every application, so it is difficult to imagine that a

critical application is not worth equipping with an automatic lubrication device.

How Rolling Element Bearings Work

••

•

• Wes Cash, Noria Corporation Tags: bearing lubrication







Perhaps some of the most abundant components industry wide are bearings, more

specifically rolling element bearings. These bearings are found in everything from electricmotors to gearboxes and conveyor systems. Basically, if a shaft needs to spin, it can be

(and most of the time is) supported by a rolling element bearing. What some people fail to

realize is the actual makeup of these devices can be quite different based on the application.

Rolling element bearings are composed of two races separated by a group of rollers. The

shape of these rollers determines the load a particular bearing can hold as well as the

lubrication requirements.

The first type of roller we will discuss is one of the more common types - the ball bearing.

Ball bearings come in as many sizes, materials and finishes as can be imagined. This

provides incredible flexibility in their use. The balls in these bearings simply roll between the

two races, and it doesn’t matter which direction the elements are facing.

As their name suggests, cylindrical roller bearings are cylinders that are arranged between

the inner and outer races. These cylinders, which are shaped like soda cans, roll along their

sides in the tracks of the races. The elements can only roll along a single axis, unlike balls

which can roll in any direction.

http://www.machinerylubrication.com/Read/29038/rolling-element-bearings#bearings



Spherical roller bearings are very similar to cylindrical roller elements with one exception -

they are rounded around their midsection. Instead of being a perfect cylinder, spherical

roller bearings are rounded so the sides of the cylinder are no longer parallel to each other.

This gives them more surface area in contact with the race than a cylindrical element of the

same length.

Needle roller bearings are smaller in diameter than the previous examples, but they also

have more length. These elements are perfect cylinders but are stretched to the point that

they resemble needles. Although small in diameter, they make up for the surface area in

the length they span.

With tapered roller bearings, one end of their elements has a larger diameter than the

other. This gives them a slight conical structure and enables the elements to roll along a

diagonal plane. The angles created by these elements allow them to withstand both axial

and radial loading.

All of the above types of elements come in several different arrangements. Some bearings

have only a single row of elements, while others employ multiple rows. Cages are used in

certain bearings to separate the elements and keep their spacing constant. Seals are

another item that can be customized on bearings. All of these features make a difference in

the bearing’s functionality as well as its life expectancy.

Rolling elements undergo a lubrication regime known as elastohydrodynamic lubrication. In

this regime, the fluid film is usually less than one micron, and pressure up to 500,000

pounds per square inch isn’t uncommon. The oil momentarily turns into a solid and

elastically deforms the rolling element and the mating surface. Any contamination can

interfere with this process with devastating results. Particles present in the load zone cause



surface degradation of the mating surfaces and can lead to the generation of more wear

particles.

8 Factors Affecting Lubricant Selection

1. Bearing speed

2. Bearing size

3. Type of bearing

4. Load

5. Lowest and highest operating temperature

6. Ambient conditions (dust, dirt, moisture, etc.)

7. Convenience of application

8. Torque

Oils have a property known as the pressure-viscosity coefficient. This is a measure of how

well they can momentarily turn into a solid. Water does not have this property and thus can

lead to boundary conditions when it is present in rolling element bearings. It is important to

monitor water levels in the lube oil to keep this from occurring. In some cases, bearings can

lose 70 percent of their life because of water before the oil even gets cloudy.

58%

of lubrication professionals use ball bearings

at their plant, based on survey results from

machinerylubrication.com

There are two types of loads that bearings undergo: radial loads and thrust loads. Radial

loads are experienced as shear forces. These loads occur across the races of the bearing, as

opposed to thrust loads, which are forces that push into the face of a bearing. In other

words, the radial load of an electric motor would be found by any load pushing the shaft of

the motor up or down, while the thrust load would be any load pushing the shaft back into

the motor. The amount and type of loads your bearing is experiencing determine the type of

bearing you need, as well as the rolling elements within it.

Understanding the basics of how rolling element bearings work and their design can helpyou achieve added reliability at your plant. Determining the type of loads you wish the

bearing to handle as well as the ambient conditions will further assist you in the selection of

the proper bearing. The possibilities for bearings are endless, so you can guarantee there is

one that is perfectly suited for your application.



.

Machinery Lubrication (8/2012)

Developing an Effective Motor Bearing

Regreasing Strategy

••

•

• Noria Corporation Tags: bearing lubrication, electric motor lubrication

Our large manufacturing plant has a history of

never greasing electric motor bearings because management believes this practice does

more harm than good. The plant has a mix of motors, some of which have been in service

for 10 years, with others just a few months. Depending on motor manufacturer, speed and

horsepower, there is everything from sealed and shielded bearings to open bearings. How

should we go about developing a regreasing strategy for these motors?

First, you will want to establish a way of tracking each motor as an asset. Develop a

preventive maintenance (PM) program in your computerized maintenance management

system (CMMS) to track these motors.

Next, it is time to play detective and find as much information on each motor as possible,

including the date of installation, horsepower (hp), revolutions per minute, bearing type,

type of duty, volts, frame size, warranty, etc., as well as the last vendor to repair the motor

and the type of grease and bearing used. Start with your most critical motors and new

replacements.

http://www.machinerylubrication.com/Magazine/Issue/Machinery%20Lubrication/8/2012




http://www.machinerylubrication.com/Meta/Tags/electric%20motor%20lubrication







Now separate the sealed, shielded bearings into one group and the open bearings into

another group. Perform vibration analysis on the sealed and shielded motor bearings. Trend

the vibration until replacement. On motors of 15 hp or less, stay with the sealed bearings.

You may wish to replace the motors and not repair them. Use your own formula for

replacement vs. rebuild. On larger motors when vibration shows bearing near failure,

consider rebuilding the motor with open bearings and bring them into the grease program.

It is best to develop your PM frequency based on runtime (for example, 6,500 hours). Some

organizations prefer to relubricate the bearings with the motor running at operating

temperature whenever possible.

For open motor bearings:

1. Clean the top grease fitting and remove the bottom grease-relief valve.

2. With a manual grease gun, pump and listen to the bearing using an acoustic grease gun

adaptor, following the manufacturer’s directions.

3. Watch for grease coming out of the bottom port. If you pump excessive grease into the

motor and none comes out of the bottom port, stop and check for hardened grease in the

bottom passage.

4. Allow the motor to run for 1 hour to expel any excess grease before installing the bottom

grease-relief valves.

5. Clean any excess grease from the exterior of the motor.

6. You must determine if the original grease is compatible with the new grease. On new

motors, you will need to contact the manufacturer.

When sending out a motor for repair, evaluate the bearings and assess how well your

program is working. Start with your more critical motors or your most frequent failures.

Also, perform vibration analysis on critical motors. This all depends on whether you can run

to failure and how much downtime your plant can endure.

For bearings 2 years or older that have supply tubes where the grease fitting attaches to a

pipe or tube, that tube needs to be removed and swabbed out. Grease could have become

caked in these supply tubes over time. Be sure to fill the supply tube with grease after

cleaning.

3 Suggestions for Removing Wear Debris



••

•

• Noria Corporation Tags: contamination control, bearing lubrication

"We are experiencing sleeve bearing failures on a piece

of equipment. The main cause of failure is bearing wear due to mechanical misapplication of

the equipment. We are not in a position to change the bearing type yet because we have to

meet current production demands. Would a simple magnetic plug help to remove 'free'

particles of entrained bearing material and slow down the rate of wear until we can correct

the root cause?”

Unfortunately, magnetic plugs trap only large ferromagnetic wear debris (typically larger

than 100 microns). Non-ferrous particles associated with babbitt used in sleeve bearings

would not be removed, nor would ferrous particles (shaft metal, for instance) smaller than

100 microns.

Therefore, wear metal is unlikely to be trapped by a magnetic plug. Instead, try the

following:

- Fitting a couple of quick connects to the bearing housing (top and bottom) would allow a

small portable filtering unit to clean up the oil very rapidly. On the assumption that you

would need to turn over the volume seven times, a 5-liter-per-minute pump would take less

than 10 minutes to clean up the oil to a very clean level. In conjunction with the new

breather unit, this would minimize the main cause of wear.

- Upgrade the breather/vent units if these are fitted. Bear in mind that a 10-micron particle

entering through a vent plug is like a snooker/pool ball rolling through a doorway — there islittle chance of stopping it. A good breather will help ensure that no additional

contamination is entering.

- If the machine is being stressed, oil temperatures are probably higher. The OEM-specified

oil may be too thin at the higher temperatures. Consider a change of lubricant viscosity

specification, perhaps even to a multi-grade or synthetic.

http://www.machinerylubrication.com/Meta/Tags/contamination%20control







How to Interpret Oil Analysis Data

••

•

• Noria Corporation Tags: oil analysis, hydraulics, particle counting, contamination control, lubricant sampling

"On a recent hydraulic oil sample analysis, the

iron count was high, about 30, yet the particle count was fairly clean at 17/14. I would

expect the iron count to be low if the system was clean. Can you offer any insight into what

we are seeing?"

In a mission-critical hydraulic system, an X/17/14 cleanliness level may not be all thatdesirable. When looking at a scale for average hydraulic system cleanliness, a level such as

this is borderline between clean and dirty. Generally, a cleanliness level of 16/14/11 or

better would be recommended for this type of application.

You mention a cleanliness level of 17/14. This provides the cleanliness at the greater than 6

micron and greater than 14 micron levels (assuming ISO 11171 calibration). If the

spectrometer is showing 30 ppm of iron, we know this is measuring particles less than 5

microns due to the inherent limitation of this test. Do you have a cleanliness level for the

greater than 4 micron level?

You would also expect the iron count to be low if the system is clean ... provided there areno mechanical conditions that would create iron debris as a leading indicator.

It is possible for a system to be "clean" of environmental and external contamination and

still show wear. In fact, this is what we'd prefer to see. Then we can focus our attention on

repairing the mechanical problem right away rather than dealing with external

contamination control just to find a mechanical problem shortly thereafter.



http://www.machinerylubrication.com/Meta/Tags/hydraulics



http://www.machinerylubrication.com/Meta/Tags/particle%20counting












To help judge the true severity of the iron, it's important to know where you are sampling

from. If you are pulling the sample from the drain port of the hydraulic reservoir, you can

expect to see a higher concentration of debris, as build-up and settling are likely to occur. If

the sample point is located in the middle of the reservoir but away from the return line, you

can assume some type of dilution effect, which would suggest a higher concentration of

wear is likely.

The best place to pull a sample from a hydraulic system is from the return line prior to

passing through a return filter if equipped. From here, it would be ideal if there were

secondary sample points after major components within the hydraulic system. This would

allow you to pinpoint the source of the debris with a high degree of confidence. In the

absence of secondary sample ports, you must rely simply on the knowledge of the hydraulic

components within this specific system.

Additional testing will also be required on your sample to help identify the mode of wear

that is taking place. Because iron is what is being seen, analytical ferrography would be the

test of choice. This will also help to identify the source of the wear. You may want to add

ferrous density testing to future samples from this system to help monitor larger particles of

iron debris. Check with your lab to see what it offers for ferrous density.

In general, iron in a hydraulic system is likely coming from the pump or cylinders. The

precise source and cause must be identified. Some initial ideas to consider include making

sure the fluid properties are consistent with system manufacturer recommendations and

that they are still within the appropriate tolerances for that fluid. If the system is set up with

appropriate and functional contamination control measures and there is a change in fluid

properties, abnormal wear can quickly and easily occur.

Know the Proper Base Number of Your Oil

••

•

• Noria Corporation Tags: motor oils, oil analysis

http://www.machinerylubrication.com/Meta/Tags/motor%20oils







"What base number should oil have?"

The base number (BN) is a property that is more associated with engine oils rather than

industrial oils. It can be defined as the oil’s ability to neutralize acids that are produced

during use. The higher the base number in the engine oil, the more acid it will be able to

neutralize during use.

New engine oils usually have a range of 5 to 15 BN. As oil is used in service, it becomes

contaminated with acids, causing the base number to drop over time. By using oil analysis

for your engine oil, you will be able to track the BN of your oil and determine how much life

is remaining. Once the base number drops below 3, this is considered too low and should

trigger an oil change for your engine.

The most common reasons for a drop in the base number are related to low-quality fuel and

oil oxidation. During combustion, a low-quality fuel with high sulfur content can produce

sulfuric acid, which attacks the oil and causes a drop in the base number. Oil oxidation as a

result of the engine overheating or an attempt to extend the oil drain interval is another

reason you may see a drop in the BN.

The acid number (AN) is a property that is generally more associated with industrial oils

than engine oils. It is the amount of acid and acid-like substances in the oil. As mentioned

previously, oil oxidation is one of the main producers of acid.

As oil is used in service, acidic components are generated and build up in the lubricant, with

the end result being an increase in the acid number. A high acid number represents the

potential for corrosion, rust and oxidation. It can also be a signal to perform an oil change.

Again, by using oil analysis, you will be able to track the AN of your oil and schedule oilchanges.

You also will need to set a critical limit for when the acid number reaches a certain number

in order to schedule an oil change. This critical limit will be dependent on the type of oil

being used. Typically, for R&O or light-duty oils, a maximum acid number limit of 2 is

appropriate. For anti-wear and extreme pressure (EP) oils, an AN limit of 4 is a good

starting point.



Possible Reasons for Low Oil Pressure

••

•

• Noria Corporation Tags: viscosity, motor oils

"Last winter at our small construction company

in Minneapolis, we attempted to start the engine of a dozer that had been sitting outside for

several days. Since last running the engine, outside temperatures had slowly dropped to

around minus 13 degrees F (minus 25 degrees C). The dozer's motor oil viscosity is SAE 10W-30. The engine cranked slowly but still started. However, the oil pressure was very low

and stayed low. What might have caused this? What risks or damage to the engine can

result?"

The high viscosity of the engine oil did not allow oil pressure to build quickly and may also

have caused the system to go into bypass, thus the low oil pressure. Severe damage can

result to the engine from lack of lubrication, including seizure of main and connecting rod

bearings, piston scuffing/seizure, etc.

One solution to the problem would be better storage of the machine exposed to these

severe low temperatures. Covering the engine with insulating material or raising the entiremachine temperature with space heaters within a tent-type cover before attempting to start

the engine might be an option.

If starting in such low temperatures is expected, using a lower viscosity oil like an SAE 5W-

30 may help. The oil should be replaced before the winter season, not at the time the cold-

starting is attempted.

http://www.machinerylubrication.com/Meta/Tags/viscosity







Cold-starting should not be attempted unless the oil will "flow" off the engine dipstick. This

is a quick, simple visual test. You also need to determine if the in-service lubricant has the

ability to provide proper cold-start performance at this starting temperature.

Lube oil tests that show the viscosity at 40 degrees C and 100 degrees C would indicate that

oil has degraded from new. Soot loading would be high. Oxidation and sulfur would alsoread high.

In this unit (diesel engine), soot loading would be the primary factor for the increase in

viscosity. Soot loading also increases the oxidation rate of the oil, which in turn increases

the viscosity.

Sulfur in the oil (from fuel) could also be high, either from extended oil change intervals or

from the engine running too cold (cooling system problem or short operating cycles).

Condensation (and the rise in acid formation) would also be a factor in a cold-running

engine. All of these combined factors would lead to a severely degraded oil with highviscosity in a short period of time.

Measuring Viscosity with OnsiteViscometers

••

•

• Noria Corporation Tags: viscosity, oil analysis








“We are using an onsite viscometer to measure

viscosity at 40 degrees C. At the same time, our lube supplier is testing samples from the

same system regularly. However, our viscosity numbers are often up to 10 percent different

from the lube suppliers. What are we doing wrong?”

Because the viscosity of an oil is probably its single most important property, it makes

sense to measure viscosity frequently, using onsite test equipment. However, like all onsite

equipment, it’s important to understand how these instruments work and their relative

strengths and weaknesses.

When it comes to viscosity, there are two determinable parameters — absolute and

kinematic viscosity. Kinematic viscosity measures the resistance of an oil to flow and shear

under gravity, such as oil flowing through a funnel. Absolute viscosity, on the other hand,determines an oil’s internal resistance to flow and shear. To visualize absolute viscosity,

imagine the force needed to stir an oil using a metal rod.

The viscosity reported by your lube supplier and oil analysis lab is likely the kinematic

viscosity. There are two main reasons why your onsite measurements may not correlate

directly with the lab data.

First, most onsite test equipment actually measures absolute viscosity, but calculates the

kinematic viscosity by dividing absolute viscosity by density. Because the onsite viscometers

don’t actually measure density but rather estimate it from the oil’s spec sheets, an error can

occur when translating absolute viscosity into kinematic viscosity. The measure of theabsolute viscosity is correct, but because the density of the oil is only estimated, the

conversion to kinematic viscosity can become overstated. Contamination and oxidation,

among other things, can cause a rise in the density of used oil.

Second, if your onsite instrument does not heat the oil to 40 degrees C, and most do not,

you are likely determining the oil’s viscosity at the temperature of the onsite lab (typically in

the 20 to 25 degrees C range), and extrapolating, again using a software algorithm to



determine the viscosity at 40 degrees C. This extrapolation can also introduce errors into

the reported measurement due to changes in viscosity index of the used oil.

Despite these limitations (which actually are not negatives), used properly, onsite

viscometers make very valuable additions to any onsite test program. As a general rule,

always baseline your new oils using your own onsite viscometer to determinenonconforming used oil viscosities quickly and simply.

The Importance of an Oil's Viscosity

••

•

• Noria Corporation Tags: viscosity

Viscosity affects heat generation in bearings,

cylinders and gear sets related to an oil's internal friction. It governs the sealing effect of

oils and the rate of oil consumption, as well as determines the ease with which machines

may be started or operated under varying temperature conditions, particularly in cold

climates.

Viscosity is a measure of an oil's resistance to flow. It decreases (thins) with increasing

temperature and increases (or thickens) with decreased temperature. These conditions

explain why an oil will flow much more easily in summer at a temperature of 25 degrees C

(78 degrees F), than it will flow in winter at minus 25 degrees C (minus 13 degrees F).





An oil's viscosity is measured most commonly by kinematic viscosity and reported in a unit

called the centistoke (cSt). Kinematic viscosity is measured in the time it takes for a specific

volume of oil to flow through a special device called a capillary tube.

Not all oils respond in the same way to a given change in temperature. Many oils contain an

ability to resist changes in viscosity due to a change in temperature. This property isreferred to as the oil's viscosity index or VI. The higher the VI of an oil, the less its viscosity

is altered by temperature changes.

The benefits of oils with a higher VI are:

1. A general increase in viscosity at higher temperatures, which results in lower oil

consumption and less wear.

2. A reduced viscosity at lower temperatures, which will improve starting and lower fuel

consumption.

Another factor in the measurement of viscosity is the ability of an oil to resist shearing orthe "tearing away of one plane of lubricant from another" during the hydrodynamic

lubrication function.

However, under certain conditions, such as shock loads, continuous heavy loading,

extremely high temperatures and/or critically low (thin) viscosity, lubricants may not remain

in their normal hydrodynamic film state.

A condition begins where there is intermittent contact between the wear surfaces. This

intermittent contact is called boundary lubrication, and damage starts to occur. If the

conditions noted above are not corrected immediately and boundary lubrication continues, a

failure due to the lack of an oil film can occur within hours.

Kinematic viscosity, viscosity index and shear stress/shear rate are all factors that should be

taken into account by a lubricant manufacturer when blending lubricating oils, but what

does all this mean to the end user? It means that the viscosity of an oil is the first and most

important consideration when selecting an oil for a specific application.

Remember, for the most effective lubrication, the viscosity must conform to the speed, load

and temperature conditions of the lubricated parts.

Scheduling Engine Oil Changes

••

•

• Noria Corporation Tags: oil changes, viscosity, fuel dilution

http://www.machinerylubrication.com/Meta/Tags/oil%20changes




http://www.machinerylubrication.com/Meta/Tags/fuel%20dilution



http://www.machinerylubrication.com/Meta/Tags/fuel%20dilution



“My laboratory provides feedback on kinematic

viscosity at 100 degrees C for our engine lubes. At what level of viscosity change should we

drain the engine oil?”

Because viscosity changes can be an indication of a number of problems, whether the

change is an increase or decrease (or both, therefore negating any perceivable change),

monitoring viscosity alone as an indicator of an oil change is insufficient, especially on

engines.

Engines can suffer fuel dilution, which results in a decrease in viscosity, as well as glycol or

soot loading, which leads to an increase in viscosity. Changing the oil will not cure the root

cause of these problems. In addition, if a multi-grade engine oil is used, then a decrease in

viscosity is possible because the viscosity index improvers shear in service. Further

inspection or a more detailed confirmation analysis will be necessary to determine the cause

if the viscosity has changed before the end of the anticipated service life.

However, on engines, setting both upper and lower caution and critical limits will be an alert

to oil life and contamination issues. The recommended lower limits are -5 percent and -10

percent, while the upper limits are +10 percent and +20 percent. These kinematic values

are based on changes in centistokes at 100 degrees C.

Tips for Reducing Wrong Oil Mistakes

••

•

• Noria Corporation Tags: oil analysis, lubricant storage and handling, oil changes



http://www.machinerylubrication.com/Meta/Tags/lubricant%20storage%20and%20handling









"Is there any way to tell if an improper lubricant is

being used without performing an oil analysis or without a part or system failure? We

currently have an oil analysis program in place, but I still find that wrong oils and fluids are

being used from time to time in between the oil analysis."

The most effective way to determine if wrong oil has been used is by oil analysis, by looking

at either a change in viscosity and/or a change in additive concentration, etc. Unless there

is a significant difference in oil type (viscosity, base oil type, additives, etc.) or any dye thatmay be used in the oil or grease, it is unlikely that a sensory inspection is sufficient.

However, your problem probably has little to do with oil analysis but is more of a procedural

issue. The bottom line is that you need to make those who are empowered with

adding/changing oil understand why adding the wrong oil is bad.

The first stage is understanding through education, whether it be formal training or simply

internal training sessions. Secondly, you need to make the process of adding oil as foolproof

as possible. The best way to achieve this is to practice lube tagging. In this approach, new

oils are tagged with a designated color and shape. For example, ISO VG 220 gear oil is

given a red circle, AW 46 hydraulic fluid a green square, etc.

The next step is to similarly label dedicated oil transfer equipment such as oil top-off

containers, funnels, filter carts, etc.

Finally, label the gearboxes, etc., with the same red circle, green square, etc. The strategy

is simple: Red-circle oil gets added to red-circle components using red-circle hardware. This

can be applied to all components and hardware, including greases, grease guns, etc.

A good example of lube tagging occurred at the General Motors Linden Assembly Plant in

New Jersey. Management addressed the need to coordinate the equipment requirements

with the labeling of lubricant storage and delivery containers. It created a coding system

that used words, images and colors to define the specific product for each application. Once

identified, the products were then matched with the correct storage and transfer container.

The result was a visual system that clearly communicated which lubricant the machine

required and which container held that particular lubricant. The technician or mechanic

needed no special knowledge to use the simple matching system.



New Method for Evaluating LubricantDispersancy

••

•

• Gerard Abellaneda, PSA Peugeot Citroen Didier Pigeon, AD Systems Tags: oil analysis

One of the primary functions of a lubricant is to preserve the cleanliness of a combustion

engine’s mechanical parts. The cleanliness of these parts is facilitated by the introduction of

detergency and dispersancy additives to the engine oil. This last property, dispersancy, is

the property that allows the oil to suspend and carry away pollutants of diverse sources,

such as soot from combustion, metallic particles from wear, corrosion of mechanical parts

and insoluble products resulting from the aging of the oil, etc.

With the arrival of new fuels (e.g., biodiesel, ethanol blends, etc.), the existing or traditional

lubricants present an important variability in terms of durability and resistance to pollutants.

Studies show that the dispersancy capacity of certain types of lubricants is significantly

degraded by the presence of specific pollutants, in particular fatty-acid methyl esters of

biofuels, which have a significant impact.

Figure 1. Dispersancy tester instrument

It is therefore important to quantify the degradation of the oil in service (engines or

transmission oils) and to monitor the evolution of the oil’s dispersancy properties during use

to be able to determine steps and intervals for maintenance. Additionally, for the

development of new lubricants, it is necessary to define a criterion of acceptance of the oil

by its dispersancy capacity.









Existing Methods for Analyzing LubricantDispersancy

To date, no rigorous analytical method makes possible the measurement of the dispersancy

capacity of the lubricant. The blotter spot method could provide an answer to this need, butthe only method practiced to date is based on a visual evaluation. This subjective visual

interpretation is not rigorous and consequently limits the information that could be provided

by the method.

Engine Test

The objective of the engine test (DV4TD – CEC-L-93-04) is to evaluate the effect of

combustion soot on engine oil viscosity increase and piston cleanliness. This procedure

simulates high-speed highway service in a diesel-powered passenger car. The procedure

fixture is an engine dynamometer procedure stand with a Peugeot DV4TD/L4 four-cylinder,in-line, common rail diesel engine installed. Pistons and rings are future rated for lacquer

deposits and ring sticking. Kinematic viscosity at 100 degrees C, soot content and iron

content in the used oil are evaluated at 24-hour intervals during the procedure. The final oil

drain is used in conjunction with the intermediate samples to interpolate the absolute

viscosity increase at 6 percent soot.

This approach has the merit of exactly reproducing the behavior of the lubricant under

definite conditions of the test. However, the evaluation methods on the engine are very long

and expensive. In addition, the precision of this test is not at the level of a laboratory

method.

Blotter Test Method

Several versions of this old method exist in industry. Many studies show the value of this

method as being rich in practical information on in-service lubricants, but it remains mainly

manual and homemade. The interpretation of the blotter spot continues to be subjective

and not formalized by a universally recognized method.

To conduct the test, a small quantity of a homogenized sample is heated to 240 degrees C

(464 degrees F) for 5 minutes. The purpose of this short period of intense heating is to

stress any oil that is close to thermal or oxidative failure so that the blotter spot shows apositive response. Any oil that is still in good shape will not be affected by such a short

heating period, which will be reflected in the dispersion pattern of the blotter spot.



Figure 2. Lubricants at different levels of wear

Once the sample cools, an approximately 25-microliter aliquot is dropped onto

chromatography paper (or filter paper) and allowed to spread or wick for 1 hour in an oven

set at 80 degrees C (176 degrees F). The filter paper is then placed under a light source in

order to locate the various rings. The calculation of a dispersancy index is provided by the

measurement of the different sizes of the diffusion rings of the oil and the pollutants.

The current blotter test method by visual quotation remains subjective and not based on

mathematical models. Although the blotter test offers limited value measuring soot

concentration, it provides an excellent assessment of the lubricant’s dispersancy

performance. An oil that is properly dispersing soot and other insolubles produces an evenly

graduated blotter. A blotter indicating a high soot load but even graduation suggests that

the oil is still fit for service but should be watched closely for degradation.

When dispersancy begins to fail, the insolubles start to form a dense ring on the exterior of

the absorbing oil drop, as seen in spot 7 of Figure 2. Spot 9 indicates the characteristic

dense black dot and shape periphery that forms when the oil completely loses dispersancy

performance. From a maintenance perspective, when the ring begins to form around the

exterior of the oil blotter, it is time to look at scheduling an oil change.

Figure 3. Oil spot preparation

Certain laboratories have established their own quotation method of the spot by a

measurement of the diameter of certain halos (or rings) and calculations of diameter ratios.

Because these methods are not published, it is almost impossible to compare the results



obtained between various laboratories. Moreover, with the introduction of new oils and fuels

(e.g., biodiesel, ethanol, etc.), the appearance of multiple rings caused by various pollutants

(carbon particles, etc.) is noted. For these reasons, the visual/manual interpretation of the

various rings is very complicated and not easily exploitable.

There exists an automated apparatus that facilitates the interpretation of the spot andeliminates the subjective aspect from the manual method. This instrument is equipped with

a monochromic charge coupled device (CCD) camera and does not use the information color

of the spot or differentiate each ring of the spot. The apparatus compares the diameter of

the spot with a theoretical diameter and analyzes the opacity homogeneity of the spot. Of

these two parameters, the device calculates a dispersancy index that varies from 0 to 100

(with 100 being the ideal dispersancy).

A New Approach

The goal of this new approach was not to reinvent the blotter test. A computer is used withdedicated software that was specifically developed for recognition and analysis of color

images. With the digital imaging analysis of the spot, in particular its opacity and its

spreading out by means of a dedicated algorithm and the choice of perfectly adapted filter

paper, it becomes possible to evaluate in an objective and quantified way the residual power

of a lubricant to disperse insoluble matter.

The general principle of the method for the preparation of the spot remains virtually

unchanged. It consists of depositing a volume of 15 microliters of oil on a specific filter

paper and analyzing the rings of the spot, which are representative of the dispersion of the

pollutants. The sample volume was decreased from 20 microliters to 15 microliters to limit

the size of the spot and to make it compatible with the image-analysis system, as well as tobe able to analyze all types of lubricants.

The deposit of the oil on the filter paper is carried out at room temperature or in certain

cases at 200 degrees C in order to free itself from the viscosity of the sample. The filter

paper is then placed in a drying oven at 100 degrees C for 24 hours.

The instrument used for this new approach features a light source positioned above the

measurement table (direct light) and a color CCD camera equipped with a high resolution. It

also has dedicated software that is capable of monitoring both the light source and the

camera. The software memorizes the numeric color picture of the spot.

This instrument makes it possible to take a digital color picture of the spot as the human

eye sees it but with higher resolution. The image is memorized for the treatment and added

to the test report, which enables you to visually check the results reported by the software.

The use of a color camera allows you to identify the various rings by obtaining chromatic

information on the spot.



In order to analyze the spot under the same conditions of lighting for optimized

reproducibility, the calibration of the device is carried out on a white sheet of filter paper.

The software reports the following data:

•The color image of the spot as the human eye perceives it.

• The digital model in levels of gray associated with an opacity of the delimited ring by

its real form.

• The number of rings present in the spot, with ring 1 being the last external ring.

• The diameter of each ring.

• The surface of each ring.

• The average opacity of each ring.

The software was designed to be able to analyze a series of spots coming from the same oilat various stages of degradation. This possibility was created in order to carry out a follow-

up of each value measured during artificial life tests and also during the engine follow-up.

The new approach makes it possible to obtain results of dispersancy analysis in a numeric

format. With this technique, the detection of the rings is much more precise and repeatable.

Case Study #1: Thermal Qualification of an

Engine Oil

Before testing the new method on lubricants contaminated by biofuel, two lubricants

considered internal references were tested.

• RH 2010 engine oil was qualified as a high-level reference.

• RL 2010 engine oil was qualified as a low-level reference (judged as “borderline”).

For the evaluation of the thermal behavior of engine oil, new and pure engine oil was

stressed with an accelerated aging, including a thermal stress (170 degrees C) in the

presence of oxygen and an oxidation proprietary catalyst. After 72, 96, 120 and 144 hours,

samples were taken. Each sample was then analyzed with the new method and instrument

described previously.

A spreading out of the high-level reference oil RH2010 in comparison to the borderline oil

RL2010 was observed. In addition, it was noticed that opacities of the central rings were

much darker. These tests carried out with the new blotter test method confirmed the

respective quality level of the two engine oils. In this particular case, their capacity to

disperse insoluble oxidation matter was verified.



Case Study #2: Thermal Qualification of anEngine Oil in the Presence of Biofuel

The same two qualified engine oils, the high-level reference and the borderline reference,

were stressed with the aging method, but diesel B10 was added starting from 72 hours of the test. Then, the contamination level of diesel B10 was maintained to 10 percent during

the remainder of the test.

A reduction in spreading out and a more important opacity in the presence of biofuel

GOPSA10LUB for the high-level reference oil was observed. The RH2010 oil approached the

rupture limit at the end of the 144 hours, but the total result according to the criteria

remained satisfactory, although the bad dispersancy in the presence of biofuel was

highlighted.

With this engine oil evaluated as borderline, a reduction in spreading out in the presence of

biofuel GOPSA10 was observed. This result becomes critical with respect to the acceptable

requirements that are based over the duration of 120 hours.

Conclusion

Although a relevant mathematical model must still be developed, this new method will make

it possible to determine the dispersancy of an oil by its capacity to disperse insoluble

matter. It also is able to precisely evaluate the resistance of a new oil to disperse insoluble

matter when submitted to an oxidation test and/or thermal behavior test. In addition, it can

determine the impact of pollutants such as biofuel on the dispersancy capacity of oils thanks

to the precise measurement of each ring.

The process and the instrument of the new method are usable in the laboratory and on

engine benches or rolling vehicles for any mechanical parts lubricated with oil, such as a

marine engine or a wind turbine, and for many types of oils, including industrial oils, cutting

oils, etc. Specific calculation criteria for oils resulting from rolling bench or in-service

vehicles can also be defined.

By analyzing the measured parameters in each ring, it should be possible to determine the

types of pollutants present in the oil and their implication on dispersancy. Thus, it becomes

possible to have an indication on the cleanliness of the bodies and to quantify in a precise

way the pollutants in oil (soot resulting from the combustion of the fuel, metal particles due

to the wear and corrosion of the bodies, products resulting from the aging of oil, etc.).



Particles: Friend or Foe?Understanding the Value of Particles in

Oil Analysis••

•

• Mariaan Avis, Eskom Enterprises Tags: particle counting, oil analysis

In the field of tribology, the word “particles” means different things to different people. The

following case studies illustrate how differently the mechanical engineer, tribologist,

sampler, analyst and diagnostician interpret the presence of particles.

The Mechanical Engineer and Tribologist

To the mechanical engineer and tribologist, the presence of particles is an indication that

contaminants have entered the system or that certain components are wearing abnormally.

Particles that are smaller than the minimum clearances could result in abrasive wear, which

in turn causes premature aging or failure. Large particles could result in blockages of oil

channels, which could lead to oil starvation. Thus, both conditions spell trouble to these role

players.










This illustration shows how particles cause damage

to parts in contact. (Ref. Triple-R Oil Cleaner)

The Sampler

The main concern of the sampler is to produce a homogenous sample that is representative

of the bulk volume of oil in the system. The presence of particles complicates the task of the

sampler, as particles tend to settle at the bottom of the tank/sump.

Prior to sampling, oil should be hot and well agitated to ensure that the sample includes

particles that have settled. For routine oil analysis, the container must not be filled morethan 80 percent to enable the laboratory to agitate the sample prior to analysis.

Improper sample handling includes overfilling containers, decanting samples that were

originally filled to the top and sampling when the oil has not been circulated sufficiently prior

to sampling. Overfilling a container leads to insufficient agitation. Shaking the container

prior to decanting will result in large particles remaining at the bottom of the container.

There’s also the possibility that the less contaminated portion is decanted, causing the

laboratory result to be higher than usual.



The Analyst

Once the samples reach the laboratory, the presence of particles directs the tasks and

methods that the chemical analyst will use to analyze the samples. The method of sample

preparation, the analytical techniques and instrumentation required to ensure that the

results are representative of the condition existing in the application all depend on the type,

size, properties and distribution of the particles present in the samples.

Various analytical techniques, including inductively coupled plasma (ICP) spectrometers, theflow cell of Fourier transform infrared (FTIR) spectrometers and some particle counters, rely

on peristaltic pumps and transport systems (tubing) to introduce samples to the various

instruments. When large particles are present in samples, the possibility exists that the

tubing could become blocked.



68%of machinerylubrication.com visitors view the

presence of particles as a valuable indicator in

an oil analysis sample

Analysts also must be aware of the tendency of particles to settle at the bottom of the

container. Prior to each analysis, samples should be agitated sufficiently to ensure a

homogenous state. Lowering of the fluid’s viscosity either due to fuel dilution in the engine

or dilution due to analytical requirements (e.g., ICP) aggravates the tendency of particles to

settle. With ICP analysis, the samples must be diluted to assist with the transportation

process. Due to dilution, suspended particles are more prone to settle out on the bottom of

the test tube and will not be available for analysis. However, no dilution is required with

rotating disk electrode (RDE) analysis.

The Diagnostician

Particles can be of value to a diagnostician who studies the shape and nature of particlesfound in a sample. A scanning electron microscope (SEM) can assist in investigating the root

cause of mechanical failure by allowing the diagnostician to pay special attention to

evidence such as scratch marks on particles and methods of particle formation.

Fine filtration is a proactive process aimed at removing contamination and wear particles

from the system. If this process is not executed with special care, knowledge and sensitivity

to the value that particles add for the diagnostician in root-cause analysis, crucial evidence

can be lost.

Case Study #1: RDE vs. ICP SpectrometryIn 2002 the Eskom laboratory changed from ICP to RDE spectrometry to perform wear

metal analysis on used oils. To obtain a new baseline, it was essential to perform both

spectrometric methods as well as the ferrous particle quantifier (PQ) on all samples received

for a three-month period.

When the spectrometric results were plotted against the PQ values, it was determined that

the higher the PQ value was for a sample, the greater the difference between the ICP and

RDE results. For a PQ value of 15 milligrams of iron per liter (mg/l Fe), the expected

difference between the two techniques was about 0 to 5 ppm. However, above a PQ value of

approximately 75 mg/l Fe, the relation seemed to become non-linear, where the differences

between ICP and RDE results were from 50 to more than 500 ppm.



This graph charts the relationship between RDE and ICP relative to PQ

as determined on samples of different sources.

One sample with a PQ value of 1,712 mg/l Fe had an iron value of 699 ppm with ICP. The

result on the RDE for this same sample was found to be in the region of 3,000 ppm. The

difference in results obtained by the two spectrometric methods was as high as 2,300 ppm.

When the wear trends of the unit with the PQ value of 1,712 mg/l Fe were examined, the

ICP results gave the impression that the problem was either resolved or stabilized.

However, when the RDE results became available, it was evident that there was an increase

in wear. The final report recommended the unit be shut down for emergency maintenance.

Due to the lower particle size limitation of the ICP, a plateau was reached much sooner than

with the RDE. Applications most affected by the ICP’s lower size limitation were those that

did not have internal oil filtration systems such as gearboxes and certain compressors.

Geometry of the particles being analyzed by the RDE also affected the results. For example,

if thin flakes of metal were present in the sample, flakes that had flattened out on the RDE

gave a different reading than particles that had not flattened out. Thus, the results on the

RDE varied due to the particle size as well as the geometry of the particles.

Case Study #2: Severe Scratching in aLocomotive Engine

The engine of a particular locomotive was replaced with a newly refurbished engine. When

the engine was installed, the maintenance team had difficulty eliminating abnormal

vibration in the engine. Eventually, it was determined that a bent flywheel caused the

vibration.



As soon as the vibration problem was eliminated, scratching noises were audible. Everything

was checked, yet the source of this noise could not be traced. The maintenance engineer

decided to involve the laboratory that performed the oil monitoring program in the

investigation.

Since the engine was recently refurbished and the original source was unknown, thelaboratory had no history on which to base the diagnosis. To obtain more knowledge about

the solid content of the oil sample, the lab employed specialized methods, such as the

electron diffraction X-ray (EDX) scan technique using the SEM.

To find out if the noise was due to insufficient lubrication, the laboratory determined the

oil’s viscosity. This was to establish if metal-to-metal contact had occurred as a result of the

oil being too thin. A new oil sample of the specified lubricant was submitted for comparison

with the oil sample taken from the engine.

A PQ analysis was then conducted to determine the magnetic property of the oil, followed

by spectrometric elemental analysis using RDE spectrometry. An EDX scan using the SEM

was performed on particles caught after the sample was filtered through a 0.8-micron-filter

membrane and rinsed with pentane to remove oil residue.

The results revealed that the viscosity was acceptable when compared to that of the

reference sample, while the PQ values were very high (more than 1,000 mg/l Fe). The RDE

spectrometric analysis indicated an increase in copper, iron and zinc when compared to that

of the reference sample.

The EDX scan using the SEM found the following components on the filter:

• High occurrence of white metal bearing material

• Metal frets

• Iron, lead and copper shavings with scratch marks

• Metallic iron shaving with lead bound to it

• Zinc particles not in combination with copper

• Mineral/rock/soil containing calcium phosphate

• and calcium silicate

• Silicon and aluminum silicate

• A piece of silicone

Ionization Energy and Spectrometric Analysis



The available ionization energy to energize large particles reaches a plateau, which is one of

the reasons different spectrometric methods have limitations concerning particle size (3

microns maximum for ICP and 8 to 10 microns maximum for an RDE spectrometer).

Spectrometers, as they are applied today, are blind to large particles. Traditional methods

of determining large particles (larger than 10 microns) are acid digestion (expensive andhazardous), microwave digestion (expensive and time consuming) and direct ferrography

(does not include non-ferrous metals).

Rotrode filter spectroscopy (RFS) was developed to provide an improved spectroscopic

method for analysis of used oils for condition monitoring/predictive maintenance without the

particle size or metal-type limitations of previous combined spectrochemical and direct

ferrographic techniques.

Particles as Enemies

Special evidence, such as the scratch marks on the metal frets, suggested that uneven

objects (particles) were responsible for abnormal wear of the liner and/or the crankshaft.

The piece of silicone found indicated overuse of a silicone-containing substance like a

sealant, which possibly was squeezed out between parts, cured and ripped off by the hot

flowing oil. These silicone pieces could have blocked oil passages, resulting in a damaging

situation of oil starvation.

Particles including silicon (quartz) and sand (aluminum silicate) as well as other debris

discovered in the oil sample were responsible for the abnormally high wear. Since abrasive

wear was the main cause of premature aging and resulted in severe damage to the parts in

contact with these objects, the maintenance engineer wanted the reason for the initialingress of those particles into the system to be investigated.

For the sampler, it was essential to ensure that as much evidence as possible was captured

in the drawn sample. In this case, where the ultimate failure would have been catastrophic,

the task could have been quite difficult, since all particles had settled to the bottom as the

oil cooled. Thus, a typical sample drawn in the normal fashion may not have allowed all the

evidence to be captured.

Particles as Friends

By unlocking the treasure of evidence that was captured in the particles found in the oil, the

diagnostician obtained information about the formation of such particles. The presence of

metal shavings indicated possible misalignment. Lack of lubrication also was detected,

which possibly was due to blocked oil channels resulting from the presence of foreign

particles. The metallic iron shaving with lead bound to it suggested welding due to oil

starvation (metal-to-metal contact).



The discovery of a particle with scratch marks led to an investigation of objects that could

have been responsible for the damage. One possible culprit was detected in a particle

consisting of calcium phosphate and calcium silicate. This specific mineral (possibly apatite)

together with particles containing quartz and sand led to the conclusion that the engine

originated from a locomotive that was involved in an accident with subsequent derailment

where soil was introduced to the engine. Evidently, the soil was not removed successfullywhen the engine was refurbished.

An iron shaving with scratch marks (top) and soil (above) were found in the oil sample.

Case Study #3: Wrist Pin Bearing Failure on aDiesel Locomotive

Prior to a wrist pin bearing failure, oil samples from a diesel locomotive were sent to two

different laboratories for routine oil analysis. The first laboratory issued wear alerts on

possible wrist pin bearing wear four weeks prior to the failure, while the second laboratory

indicated no abnormal wear was taking place. A resample was taken, and again the second

lab did not find any abnormal wear, while the first lab issued another wear alert.



The fleet owner decided to stop the locomotive to find out whether the alerts issued by the

first laboratory were justified. It was discovered that the wrist pin bearing had failed with

damage to four power packs. An investigation was launched to determine the root cause

that resulted in the different diagnoses from the two laboratories.

Routine oil monitoring tests were performed, including spectrometric analysis using RDEspectrometry and PQ. An EDX analysis using the SEM on the filter debris was conducted

after the sample was filtered through a 0.8-micron-filter membrane and rinsed with pentane

to remove oil residue. The results of the RDE spectrometric analysis revealed an increase in

silver, copper and iron, while the SEM analysis confirmed the presence of particles larger

than 10 microns.

Since both laboratories performed similar analysis on a routine basis, the investigation

focused on the differences in the techniques used by the two labs. The only major difference

found was that the laboratories employed different spectrometric techniques to determine

the wear metal content of the samples, namely ICP and RDE spectrometry.



These images of a locomotive engine

reveal wrist pin bearing failure.

The primary variation between the two techniques is the way the sample is introduced to

the system. For ICP analysis, the sample is diluted prior to introduction to the instrument.

Therefore, it’s possible that the particles settled prior to analysis. The ICP also uses a

peristaltic pump and transport system, which is subject to blockages.

In addition, the size limitation of the ICP is 1 to 3 microns, while the range of the RDE is 8

to 10 microns. The SEM analysis confirmed the presence of particles larger than 5 microns,

so it seems the failure progressed beyond the point where the ICP could detect the wear

particles but remained within the range of the RDE.

Case Study #4: Scored Liner and Piston Wearon a Diesel Locomotive

As part of an oil analysis program, the crankcase oil of a locomotive was monitored on a

monthly basis. However, no samples were received for the period between January and the

end of June. The engine failed at the end of September.

The reason for concern was that all laboratory reports returned with no indication of an

increase in wear metal content. An investigation was initiated to explain why the laboratory

tests failed to detect any increase in wear when it was evident that abnormal wear was

taking place from the mechanical failure that occurred.



Since no abnormalities were found except for fuel dilution over a prolonged period, the

investigation focused on sampling intervals and techniques that could have affected the

results.

Routine oil monitoring tests, including spectrometric analysis using RDE spectrometry, were

performed, as well as EDX analysis using the SEM on the filter debris after the sample wasfiltered through a 0.8-micron-filter membrane and rinsed with pentane to remove oil

residue.

The results showed severe fuel dilution. The RDE spectrometry indicated no increase in

metal content since the previous sample was analyzed. The EDX analysis revealed that

isolated large particles (larger than 20 microns) of heavy metals and other inorganic oxides

were present on the filter. Many of the larger particles were iron or iron oxides. The small

particles consisted mainly of calcium sulphate.



These photos of a locomotive engine indicate a severely scored liner and piston wear.

Lowering of the fluid’s viscosity, which may have resulted from fuel dilution in the engine,

aggravated the tendency of particles to settle. Therefore, it is possible that suspended

particles had settled to the bottom of the sump and were not included in the sample.

In the earlier stages of failure, smaller particles were produced (likely during the period

when no samples were submitted). As the failure progressed, the size of the particles

increased. Since particles larger than 10 microns were found, it is possible that the failure

progressed beyond the point where the RDE could detect the wear particles. Thus, severefuel dilution over a prolonged period of time combined with not submitting oil samples at

the initial stages of failure resulted in the inability to detect the failure through a routine oil

analysis program.



A particle larger than 20 microns

was found in the oil sample.

In conclusion, it is apparent that removal of particles from a system prior to sampling by

means of indiscriminate filtration, improper sample handling and settling of particles can

result in the loss of important evidence that could lead to the early detection of possible

failures or assist in root-cause analysis.

Remember, the purpose of oil analysis is to avoid failure before it happens. Sensitivity with

regards to particle sizes and size limitations of analytical techniques relative to sampling

intervals is vital to reach this ultimate goal. In the end, the success of an oil analysis

program to detect possible failure modes relies on the ability of the mechanical engineer,

tribologist, sampler, analyst and diagnostician to treat and react to the presence of particles

in the appropriate manner.

Machinery Lubrication (6/2012)

How Important is the ISO CleanlinessCode in Oil Analysis?

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Matt Spurlock, Noria Corporation Tags: oil analysis, particle counting

The International Organization for Standardization (ISO) has developed a cleanliness code

that is the primary piece of data reviewed on most industrial oil analysis reports. The value

of this code can help determine the overall cleanliness of the monitored system. Often

times, an end user will establish a target value to achieve, thus offering a level of

confidence so long as the used oil sample meets this established target.














The trend in the oil analysis world is to give too much credit to the value of the ISO

cleanliness code. Some laboratories have even begun to only report the ISO code. There is

also a heavy reliance on this value by end-user analysts.

The ISO code is a fantastic tool to use for setting target alarms and establishing a goal to

achieve and maintain as it relates to system cleanliness. It is also the perfect value to usefor key performance indicator (KPI) tracking, charting and posting. However, the ISO code

should play only a secondary role when it comes to evaluating used oil sample data.

73%of machinerylubrication.com visitors have

used the ISO cleanliness code to set target

alarms for system cleanliness levels

How the ISO Cleanliness Code is Determined

Most oil analysis samples that receive particle counting are getting what is known asautomatic particle counting (APC). The current calibration standard for APC is ISO 11171.

When sending a sample through an APC, particles are counted either through laser or pore

blockage methods. Although different laboratories may report different particle count micron

levels, an example of the various reported micron levels includes those greater than 4, 6,

10, 14, 21, 38, 70 and 100 microns.



ISO 4406:99 is the reporting standard for fluid cleanliness. According to this standard, a

code number is assigned to particle count values derived at three different micron levels:

greater than 4 microns, greater than 6 microns and greater than 14 microns. The ISO code

is assigned based upon Table 1. This can be seen in the example on the left.

However, without seeing the raw data, the only thing the ISO code can positively identify iswhether a sample has achieved the desired target value. The ISO code does nothing to help

determine any type of real trend information unless the value of the raw data at the given

micron levels changes enough to raise or lower the ISO code.

What the ISO Code Can Tell You

It’s easy to look at the ISO table and notice a pattern. At each row, the upper limit for each

code is approximately double that of the lower limit for the same code. Likewise, the upper

and lower limits are double that of the upper and lower limits of the next lower code. This isknown as a Renard’s series table.

The unit of measure for particle count data is “particles per milliliter of sample.” The particle

counters used in laboratories incorporate much more than a milliliter of sample. During the

testing process, approximately 100 milliliters of sample are taken into the instrument. The

numbers of particles are counted based on this value. The total number of particles is then

compared to the number of times that 2 will go into that total count exponentially.



Staying Clean

Why is cleanliness so important? The answer is simple: competition. In such a globally

competitive market where products can potentially be manufactured and shipped from

overseas at a lower cost than can be manufactured from here at home, maintaining a

precise level of reliability and uptime is necessary to keep costs at a manageable level.

Contaminant-free lubricants and components will extend the lifetime of both, and in turn

increase the overall reliability of the equipment.

Using the previous example (20/17/13), this means that at the greater than 4 micron level,

the number of particles measured was at the most 2^20 and above 2^19. Since particle

count data is reported in particles per mL of sample, the raw data must be divided by 100.

While the general rule of thumb is that for every increase in the ISO cleanliness code, the

number of particles has doubled, this certainly is not the case in every situation. Because

the number of allowable particles actually doubles within each code number, it is possiblefor the number of particles to increase by a factor of 4 and only increase a single ISO code.

This becomes a significant problem when you have a target cleanliness level of 19/17/14,

your previous sample was 18/16/13, and your most current sample is 19/17/14. For all

reporting purposes, you have achieved and maintained the target cleanliness level of

19/17/14. This suggests that your component should be in a “normal” status. Given the

information presented previously, it is easy to see how you could have two to four times the

amount of particle ingress and only increase by a single ISO code or have no increase at all.

The ISO cleanliness code should be used as a target. It is a value that is easily tracked for

KPI reporting and a value that most people can easily understand. However, using the ISOcleanliness code for true machine condition support is limited in its effectiveness. The raw

data from particle count testing allows the end user to confirm data from other tests such as

elemental analysis and ferrous index. The ISO cleanliness code does not allow this cross-

confirmation to occur. Reviewing the raw data of the particle counter at all reported levels is

absolutely vital in performing quality data analysis on oil sample data.



Question:

What is the name of the additive that is primarily designed to control rust?

Answer:

Rust inhibitor

Six Steps For More Effective OilAnalysis

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Aaron Black Tags: oil analysis, lubricant sampling

Whether you currently have an oil analysis program in place, or are putting one together, it

is imperative to ensure that equipment is properly sampled to meet the goals of a specific

maintenance program.

To provide the program with the proper foundation, six basic questions must be asked:

• What do you want to get from your oil analysis program?

• What units need to be sampled?











• Where does the sample need to be taken on the equipment?

• How are the samples going to be procured?

• How often do samples need to be taken?

• What tests are needed?

Some of these steps can be performed simultaneously, while others must be done in

sequence.

Step 1: The Functions of an Oil Analysis Program

This first step is critical. It provides the direction for nearly all future decisions regarding the

oil analysis program. Can failures be caught early? Are there lube-mixing problems that

need to be prevented or caught before resulting issues occur? Or does the lubricant health

simply need to be monitored to provide accurate lube change intervals? The reasons for

performing lubricant analysis can vary, but overall, the choice can have the most effect on

what can be accomplished with an oil analysis program.

Step 2: Sampled Units

The next problem to tackle is deciding which units to sample. Individual units do not need to

be determined immediately, but for other steps later in the process, it will be necessary to

decide what unit types to sample. Gearboxes only? Super-critical units? Everything? This

step can be one of the most challenging, but when all of the fundamentals are combined, it

is relatively simple due to the limiting factors some steps provide.

The most likely solution is to make a list of everything the user might want to sample and

then prioritize them into groups (definitely want to sample, would like to sample, must be

sampled). Therefore, if the cost is too prohibitive, the units can be pared down to sampling

either less often or not at all.

Step 3: Sampling Location

While this step can be performed in any order, it is useful in helping place limits on the

scope of the sampling project. Sample location is sometimes cut-and-dried regarding where

the sample can be pulled from on the equipment.

The pros and cons of each sampling option must be weighed against many variables

including questions such as "What does the budget allow with the number of units that need

to be sampled?" and "Which sampling method will allow me to monitor what I need to reachthe goal of this project?" In some instances, drop tube sampling is appropriate. Other

instances require a sample point to be installed to obtain accurate and useful data.

Selecting the proper location on equipment may not be as easy as it seems. If the wrong

type of sampling is performed or the sample port is placed in an inactive zone, a unit may

end up failing while the data analysis continues to show positive results.



Safety can also be an issue. Is the unit a high-pressure hydraulic? Be sure to check that if a

sample port is being installed, the pressure rating is within the proper range.

Step 4: Procuring the Sample

If the drop tube sampling method is chosen and only diesel engines are used, this choice is

an easy one. Buy a vacuum gun and get to work. If, however, there are challenges withensuring the proper location has been chosen for taking samples, this can be a significant

problem. There are many reasons why particular units cannot be sampled at any point in

time.

There is always going to be a unit that just doesn't have a feasible solution, but there are

typically solutions for problems if one is willing to dig in and search. Make sure that when

the equipment and sampling method have been selected, the ability to pull the sample

exists as well.

If you encounter a problem while searching for a way to retrieve samples from a piece of

equipment, the equipment vendor may be able to provide a solution. If there is no

equipment vendor available, look up a sampling equipment vendor on the Internet (or just

continue looking through this magazine - there are usually several). If the first vendor

cannot find a solution to the problem, try another one.

Step 5: How Often is a Sample Needed?

Sampling frequency can be dictated by two factors: what the user is trying to find and how

fast it needs to be found. Cost can also be factored in because monthly sampling is not

always an option. However, if cost for having the analysis completed becomes a major

issue, the scope of the sampling project may have to be changed to effectively limit

sampling to a financially manageable situation that doesn't involve randomly removing units

from the sampling plan.

When determining the frequency of sampling, issues such as the likelihood of failure and

equipment history should be addressed while deciding which interval to set up the

equipment.

The more frequently sampling takes place, the more effective one will be at discovering

problems before a failure occurs. Most oil analysis users have heard stories involving a

failure that went from inception to disaster in a matter of days. While this is the exception

rather than the rule, keep in mind that failures can happen quickly, and it is necessary to

limit exposure to that magnitude of failure on units that will cripple operations if they godown.

A functional equipment history may be the difference between a good call and a complete

miss with the analysis. A unit sampled yearly to monitor oil will not provide the analyst with

much equipment history. Quarterly sampling may be the beginning of a stable and

trendable equipment history, and with monthly sampling, there is a 90 percent range of

problem detection before failure.



Step 6: Tests

Which tests are needed is strictly determined by what one wants to find with the testing.

Viscosity and acid number tests may be useful if it is just to monitor lubricant health. To

monitor equipment health, metals and ferrous density testing may be the route to take.

Most oil analysis users look for a combination of equipment health, lubricant health and

lubricant cleanliness.

Many oil analysis providers offer discounted packages for oil analysis geared toward general

equipment types, so be sure to ask for any packaged tests that receive a discount to meet

specific needs.

In conclusion, if all of these fundamental questions are brought to the table when traveling

down the path of lubrication excellence, and the answers have proved appropriate, then an

effective program which has a solid foundation and a rewarding outcome should be in place.

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