When to Use Portable Oil Analysis Instrument？

What do a power plant, a hospital, a police station, and a remote mine have in common? They all have essential assets requiring uninterruptible power, commonly powered by an engine generator as primary or backup power. Engine generators, often termed “gensets,” combine an electrical generator and an engine. They supply electrical power where normal utility power is not readily available or is unstable. Gensets are used for temporary power demands and are often mounted on trailers or transportable skids.

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Unlike large facilities that typically have on-site central oil analysis labs, smaller, temporary, and backup generation has traditionally depended on preventive, time-based oil maintenance. However, now, portable, handheld oil analysis tools are widely available and can be used to extend oil drain intervals and reduce routine costs for these generation assets. These tools are getting a boost with the recently amended U.S. Environmental Protection Agency (EPA) National Emission Standards for Hazardous Air Pollutants (NESHAP) rules for emergency backup gensets. The new rules allow condition-based oil drain intervals, so asset owners can realize the benefits of oil analysis. This article outlines the challenges and solutions available to portable/emergency genset owners who have previously incurred the cost of time-based oil changes.

Routine Maintenance and Oil Condition

Some of the main operating costs of running and maintaining large engine generators are the material and labor costs associated with changing oil based on a fixed operating time interval. This routine is often recommended by the engine manufacturer and increasingly by local regulations aimed at curbing emissions. Oil changes are suggested based on operating hour or calendar-based intervals, regardless of whether the generator has been running at full load or is idle for most of the time. Until now, this task was nonnegotiable, especially if the genset was under warranty. The U.S. EPA actually mandates oil changes for stationary engines used for emergency backup power.

Here are some issues with scheduled oil changes that trouble engine owners:

■ Good oil gets changed unnecessarily. Not all generators run at the same load; therefore, it is likely that an oil change is unnecessary for some generators at the recommended change interval. This causes increased operating expense and waste, including material, labor, service engineer utilization, efficiency, as well as recycling cost. If an oil change interval can be extended for generators, the cost savings can be significant.

■ Scheduled oil changes will not solve an ongoing contamination problem. Engine damage due to contamination of the lubricant can continue, and usually increases in severity.

■ Catastrophic failures can still happen, and the cost of repair and downtime is not insignificant, even though it might be infrequent.

The Role of Oil Analysis

Forward-thinking genset owners and service providers have recognized these issues for some time, and they employ off-site or on-site oil analysis to determine the lubricant and equipment condition. In turn, they can determine if the oil can be extended or if the genset requires an overhaul.

The U.S. EPA has now acknowledged the benefits of condition-based oil changes founded on oil analysis results. The agency recently amended its regulations for stationary generators in emergency or backup mode to allow for extended changes if oil condition condemnation limits are not exceeded (Table 1).

Table 1. Time’s up! These are the new condemnation limits for in-service oil. Source: U.S. Environmental Protection Agency

The rule specifically states that condemned oil must be changed within two days of the engine owner receiving information that oil has exceeded any of the specified limits. If oil condition is examined at the time of scheduled service, a decision can immediately be made as to whether the oil needs to be changed or if minor repairs are needed. This approach reduces both operation and maintenance costs, and the engine runs longer.

A similar situation can occur in managing an automotive fleet. Time-based oil change has been proven to generate additional waste due to unnecessary oil changes. Though the cost savings are real and the marketplace is starting to support them, the question is why condition-based oil changes aren’t a popular practice.

One reason is that the investment in a dedicated laboratory is not always practical. In mining operations and large power generation plants, it is common to have central oil analysis labs located on-site to continuously monitor the oil and machine condition of equipment. Decisions about oil change and other maintenance activities are made based on the recommendation of experienced laboratory data analysts.

While this is a very good industrial practice, it is difficult to apply this practice in the case of engine generator fleets because of the large, upfront capital investment, as well as the need to hire laboratory technicians and data analysts. Even if a central laboratory is established, the distributed or temporary nature of the gensets prevents service engineers from making immediate decisions due to the delay in getting results from the central lab. This is the problem with relying on contract labs to perform such work.

Another reason is that previous technologies for on-site oil analysis are insufficient to implement an effective condition-based oil change practice. The tools used to monitor oil condition need to meet the following requirements:

■ Easy to use. There’s no need to hire an experienced oil expert.

■ Portable. Maintenance engineers can carry it from one generator to another.

■ Fast. Engineers can use their on-site time more efficiently.

■ No waste stream and no recycling of hazardous material chemicals. This minimizes the cost of training to handle, store, transport, and recycle chemicals.

■ Comprehensive. The tool should capture the complete picture of oil condition with minimal chance of false alarms.

■ Repeatable and definitive. Decisions can be easily made.

■ Cost-effective. Return on investment is one or two years.

As you can see, this is not an easy list of requirements. There are many tools on the market that can partially meet them. The tools may be simple and easy to use, but not definitive, or they may be accurate, but expensive, difficult to use, or hard to deploy in the field.

Recently, Spectro Scientific introduced a comprehensive set of portable oil condition analyzers that provide a complete picture of in-service oil condition. Each tool is battery powered, small in a handheld form, and as accurate as laboratory instruments. These portable tools are even being used in some oil analysis labs.

Each tool uses a small oil sample—measured in drops—and does not generate any waste stream. No chemicals are needed to analyze the oil, so no hazardous materials or recycling are needed. Without sample preparation, it only takes a few minutes to analyze oil samples retrieved directly from engines. Results are shown on the analyzer’s display and contain alarms so users can make informed decisions immediately.

This set of tools all originated through a joint effort with the U.S. military aimed at developing a condition-based oil change program. The tools are used in the field to reduce costs and improve reliability. Now, maintenance professionals have the power to make decisions in the field, which makes condition-based oil changes both affordable and practical.

Portable Oil Condition Monitoring Combinations

The set of portable oil condition monitoring tools developed by Spectro Scientific includes an infrared (IR) spectrometer, a temperature-controlled kinematic viscometer, and a portable fuel dilution meter. This triple combination paints a complete picture of in-service oil condition, including oil degradation, coolant contamination, water contamination, fuel contamination, and viscosity. All three tools are battery powered and use less than 1 milliliter of oil combined. The in-service oil parameters for diesel, gasoline, biodiesel, propane, biogas, and natural gas engines that can be tested using the combination kits are: oxidation, nitration, sulfation, anti-wear additive, total base number, water, glycol contamination, soot, fuel dilution, and viscosity.

The FluidScan Q is a handheld IR spectrometer (Figure 1). It measures oil absorbance spectrum in the mid-IR range (2.5 mm–12 mm). Instead of using Fourier transform infrared spectroscopy technology, which was more widely used in oil analysis laboratories, diffraction grating-based optics with detectors is used for better portability and durability. Chemometric calibration is applied on the raw IR spectrum to obtain oil condition information, such as oxidation, nitration, sulfation, anti-wear additive, total base number, water, glycol contamination, and soot. The technology was recently granted an ASTM D standard method.

1. FluidScan Q. The handheld infrared spectrometer measures oil absorbance. Courtesy: Spectro Scientific

FluidScan is widely used in laboratories as a titration alternative, in fleet management for mining trucks, in marine vessels, in power generation plants, and in industrial plants for oil condition-based predictive maintenance. The patented flip top cell uses three drops of oil, takes one minute, and does not require any chemicals or solvents to clean. The tool also has an onboard database with asset information and preset alarm limits utilizing a traffic light system (Figure 2). As a result, maintenance engineers can make immediate decisions right after the measurement.

2. Danger! Results are flagged using a color-coded system that alerts users to out-of-specification conditions. Courtesy: Spectro Scientific

The Q portable kinematic viscometer (Figure 3) is a battery-powered tool that measures oil viscosity at a controlled temperature (40C). It can extrapolate viscosity at 100C based on a preset viscosity index of a given oil. The patented split cell (Figure 4) uses only two drops of oil—60 microliters (µL)—takes a couple of minutes to test, and does not require any chemicals or solvents to clean. The result is accurate within 3%—enough to make informed maintenance decisions. It is a good companion to the FluidScan Q and is widely used in marine vessel and mining truck settings.

3. Q kinematic viscometer. This portable tool quickly and accurately measures oil viscosity. Courtesy: Spectro Scientific 4. The split cell opens for easy cleaning. No chemicals or solvents are needed to prepare the cell for its next use. Courtesy: Spectro Scientific

The Q portable fuel dilution meter (FDM, Figure 5) is a new member of the oil condition family. Its predecessor was the FDM Q600, a stationary analyzer used in analytical labs and on-site labs to screen for fuel dilution in engine oil. It was jointly developed with the U.S. Navy and is widely used in mining, railway, and marine environments.

5. Q fuel dilution meter. The analyzer measures the concentration of fuel vapor in the headspace of a sample to determine contamination levels in oil. Courtesy: Spectro Scientific

The measurement is based on a calibrated response of a surface acoustic wave (SAW) sensor to a fuel vapor aromatic in the sample bottle headspace, which is proportional to the fuel content in the engine oil sample. The new FDM inherited the SAW sensing technique, but it is smaller and battery operated. The patent-pending sampling system makes it easier to use in the field and requires only 500µL of used oil.

The three tools complement each other and present a complete set of oil condition information. Each one is:

■ Small, light, portable, and battery operated

■ Efficient, using small volumes of oil (<1 milliliter combined)

■ Easy to clean, requiring no chemicals or solvent

■ Fast (1 to 2 minutes each)

■ Accurate (correlates to laboratory results)

■ Easy to use

This set of characteristics is what makes the maintenance professional’s life easier. Using these tools, it is possible to perform oil analysis at the generator and make immediate and accurate decisions with confidence. Engine generator fleet managers can implement a condition-based oil change practice, lowering operating expenses and reducing maintenance costs.

A hospital, a police station, a treatment plant, and a remote mine all have assets demanding uninterruptible power, commonly powered by an engine generator as primary or back up power. Engine generators, or also known as “gen sets,” are a combination of an electrical generator and an engine. They provide electrical power to areas where normal utility power is unstable or is not readily available.

Engine generators are used for temporary power demands and are often mounted on transportable skids or trailers. Portable, handheld oil analysis tools are now commonly available and can be employed to extend oil drain intervals and lower routine costs.

The recently amended US EPA NESHAP rules for emergency backup gen sets provide further boost to these tools, allowing condition-based oil drain intervals, so asset owners can realize the advantages of oil analysis. This article discusses the challenges and solutions available to portable/emergency gen set owners who have incurred the cost of time based oil changes.

Figure 1. Typical Generator engine enclosure located adjacent to a customer site (Ref: Jenbacher)

Why Change Oil?

It is important to change engine oil before it can no longer adequately perform its intended functions within an engine. Oil in Rotating Internal Combustion Engines (RICE) becomes increasingly contaminated, and the contamination rate can differ based on duty cycle, load factor, environment, age, and fuel types.

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Additives deplete to the point that the combination of oil and additives can no longer provide satisfactory protection to the engine. The type of contaminant in the oil needs to be known as this data provides symptoms of the engine condition and enables a direct remedy to rectify the problem.

Top Oil Contaminants

During normal engine operation, a wide variety of contaminants are introduced into the lubricating oil. The following are the most common types of contaminants:

Combustion By-Products

These are exhaust gases (blowby gases) that leak past the piston rings, turbocharger seals, and valve guides into the crankcase. These gases consist of particles of carbon, acids, water, varnish, partially burned fuels, and lacquers. The oil is contaminated by all of these particles.

Sulfur oxides (SOx) are commonly gases with sulfurous fuels (diesel, heavy fuel oil, and liquid fuel distillates). Nitrous oxides (NOx) are more common gases with natural gas (LNG, CNG, propane) fueled engines. Hydrocarbon oxidation (HCOx) can be found in varying amounts.

Acids, Varnish, and Sludge

When the lubricating oil is exposed to hot engine components, or when hot oil is exposed to entrapped air, contaminants such as acids, sludge, and varnish are created due to oxidation and decomposition.

Fuel

These contaminants are usually associated with engine malfunction. However, excessive engine idling or stop-and-go operation can also cause fuel dilution. Viscosity loss is the result of fuel dilution of the oil, causing severe wear and potential seizure if left unchecked. Fuel pump failure, clogged air filters, and faulty injectors are common sources for fuel dilution, although in some cases, fuel lines can rupture and contaminate the oil.

Water

Water vapor is introduced into the oil as a byproduct of combustion. Low load engines and backup generators do not let the oil get hot enough to boil off the water rapidly. Water in combination with blowby gases generate acids, which degrade the oil and corrode the engine surfaces. Ingressed water sourced from the environment or broken cooling lines will lead to rapid oil degradation and in some cases cause severe wear and engine failure.

Coolant

Glycol-based engine coolants are widely used. Head gasket seal rupture, improper cooling line fittings, or cooling system corrosion can all cause coolant mixing with the oil. Glycol is particularly corrosive to non-ferrous bearing surfaces. Excessive coolant results in the telltale sheen or mayonnaise oil emulsion, causing engine seizure.

Soot

Soot is formed by retarded injection timing and burning fuel mixing with oil on the cylinder liner(s). Excessive soot leads to abnormal valve and injector train wear and overloads the emissions control systems, resulting in air quality fines.

Oil analysis, a method designed to assess the engine health through fluid analysis, can monitor all of these contaminants.

Routine Maintenance and Oil Condition

Some of the main operating costs of running and maintaining large engine generators are the material and labor costs associated with changing oil based on a fixed operating time interval. This process is usually recommended by engine manufacturers and increasingly by local regulations aimed at curbing emissions (EPA NESHAP rules).

Oil changes are recommended based on operating hours or calendar based intervals, irrespective of whether the generator has operated at full load or is idle for most of the time. Until now, this task was non-negotiable, especially if the gen set was under warranty. In fact, the US EPA mandates oil changes for stationary engines used for emergency backup power.

There are problems with scheduled oil changes that trouble engine owners:

• Good oil is changed unnecessarily. Not all generators are operated at the same load amount, so it is perhaps unnecessary to change oil for particular generators at the recommended change interval. This leads to increased operating cost and waste, including material, labor, service engineer utilization efficiency as well as recycling cost. A significant cost saving can be achieved if it is possible to extend an oil change interval for even a fraction of the generators
• An ongoing contamination problem cannot be resolved by scheduled oil changes. Engine damage caused by contamination of the lubricant can continue, usually increasing in severity.
• Catastrophic failures can still occur and the cost of repair and downtime is not insignificant, even though it may be infrequent

The Role of Oil Analysis

Forward thinking gen set owners and service providers have been aware of these problems for some time, and use onsite or offsite oil analysis to identify the condition of lubricants and equipment. Using this information, they can determine whether the oil can be extended or if it needs an overhaul.

The US EPA acknowledged the benefits of condition-based changes due to oil analysis. Recently, the agency amended its regulations for stationary generators in backup or emergency mode to enable extended changes if oil condition condemnation limits are not exceeded (Figure 2).

Figure 2. Oil is contaminated by a number of contaminants from the combustion chamber (Ref: MIT)

The rule is specific that condemned oil must be changed within two days of the engine owner receiving this information. If oil condition is analyzed at the time of scheduled service, a decision can be taken immediately as to whether the oil needs to be changed or if minor repairs are required.

It not only lowers the operation and maintenance costs, but also makes the engine run longer. A similar scenario can occur in managing an automotive fleet. Time-based oil change has been proven to produce waste because of unnecessary oil changes.

Although the cost savings are real and the market is starting to support them, why condition-based oil changes have not yet become a popular practice is an intriguing question. Two good reasons are as follows:

1. Investment in a dedicated laboratory is not always practical. Large power generation plants and mining operations often have central oil analysis labs located onsite for continuous monitoring of the machine and oil condition of an equipment population. Based on the recommendation of experienced laboratory data analysts, decisions about oil change and other maintenance activities are taken. Although this is the best industrial practice, applying this practice is difficult in the case of engine generator fleets due to the large, upfront capital investment and the requirement of hiring laboratory technicians and data analysts. Even after establishing a central laboratory, the distributed or temporary nature of the gen sets prevents service engineers from taking immediate decisions because of the delay in receiving results from the central lab. This is the issue with relying on contract laboratories to execute this task.

2. Previous onsite oil analysis technologies are insufficient. The tools used for oil condition monitoring have to satisfy the following requirements in order to implement an effective condition based oil change practice:

• Portable – Maintenance engineers can carry it from one generator to another
• Easy to use – No need to hire an experienced oil expert
• Cost effective – Return on investment in one or two years
• Fast – Allows engineers to use their time on site more efficiently
• Comprehensive – Provides the complete picture of oil condition with minimal chance of false alarms
• Repeatable and definitive – decisions can be easily made
• No waste stream and no recycling of hazmat chemicals – lowers the cost of training on handling, storage, transportation, and recycling of chemicals

This is not an easy list of requirements as most of the commercially available tools can partially fulfill these requirements. The tools may be simple and user-friendly but not definitive, or they may be expensive and accurate but not user-friendly or easy to deploy in the field.

Spectro Scientific has recently launched a comprehensive set of portable oil condition analyzers that provide a complete picture of in-service oil condition. The battery-powered tools are compact in a handheld form, and as accurate as laboratory instruments. These portable tools are currently even used at oil analysis laboratories.

Each instrument uses a small oil sample volume, measured in drops, and does not generate any waste stream. Chemicals are not needed for oil analysis, eliminating the need for hazmat materials or recycling. Without sample preparation, oil samples retrieved directly from engines can be analyzed within a few minutes.

Results can be read on the analyzer’s display and contain alarms to alert users to make informed decisions immediately. The set of tools all originate from joint development with the US Military for condition-based oil changes. These tools are used in the field to improve reliability and lower costs.

Maintenance personnel now have the power of decision making in the field and are transforming the industry. As a result, condition-based oil changes now become both affordable and practical.

Spectro Scientific Portable Oil Condition Combinations

The set of portable oil condition monitoring tools from Spectro Scientific include a temperature-controlled kinematic viscometer, a portable fuel dilution meter, and an infrared spectrometer (FluidScan). This triple combination provides a complete picture of in-service oil condition, including coolant contamination, oil degradation, fuel contamination, water contamination, and viscosity.

All three instruments are battery powered and use less than 1 ml of oil collectively. Table 1 lists in-service oil parameters that can be determined using these combination kits.

Table 1. US EPA NESHAP ZZZZ rule Amendment (Oct ) Condemnation limits for in-service oil

PARAMETER CONDEMNING LIMITS Total Base Number
(CI RICE only) <30% of the TBN of the oil when new Total Acid Number
(SI RICE only) Increases by more than 3.0 mg of potassium hydroxide per gram from TAN of the oil when new Viscosity Changed by more than 20% from the viscosity of the oil when new % Water Content by Volume >0.5

Table 2. Critical engine oil parameters

GENERATOR ENGINE TYPE LUBRICANT PARAMETERS Diesel, Gasoline, Bio-diesel, Propane, Bio-gas, Natural Gas Oxidation, Nitration, Sulfation, Anti-wear additive, TBN, Water, Glycol contamination, Soot, Fuel dilution, Viscosity

FluidScan®

FluidScan (Q) handheld infrared spectrometer[1,2] measures oil absorbance spectrum in the mid IR range (2.5 mm - 12 mm). For better portability and durability, diffraction grating-based optics with detectors was used in place of FTIR technology, a commonly used method in oil analysis laboratories.

Chemometric calibration was applied on the raw IR spectrum to get oil condition information such as oxidation, sulfation, nitration, anti-wear additive, water, total base number, glycol contamination, and soot. [3,4] The technique was recently granted an ASTM D standard method.

FluidScan is widely used in labs as a titration alternative, in marine vessels, in fleet management for mining trucks, in industrial plants, and in power generation plants for oil condition-based predictive maintenance. The patented flip top cell uses three drops of oil, requires one minute and does not need any chemicals solvents or chemicals for cleaning.

The instrument also has an onboard database with asset information and preset alarm limits utilizing a traffic light system, enabling maintenance engineers to make decisions immediately right after the measurement.

Portable Kinematic Viscometer

The battery powered Q portable kinematic viscometer measures oil viscosity at a controlled temperature (40 °C).[5] Based on a preset viscosity index of a given oil, the tool can extrapolate viscosity at 100 °C. The patented split cell requires only two drops of oil oil (60 µL), completes the test in a couple of minutes, and does not need any solvents or chemicals for cleaning.

The result is 3% accuracy, which is enough to make informed maintenance decisions. It complements FluidScan well and is commonly used in marine vessel and mining truck settings.

Fuel Dilution Meter

The portable Fuel Dilution Meter (Q) is the new member of the oil condition family. The Fuel Dilution Meter (Q600) was the predecessor, a stationary analyzer used in analytical laboratories and onsite laboratories to screen for fuel dilution in engine oil. It was jointly developed with the US Navy and is commonly used in railway, mining, and marine environments.

The measurements are based on a calibrated response of a Surface Acoustic Wave (SAW) sensor to a fuel vapor aromatic in the sample bottle headspace, which varies in proportion to the fuel content in the engine oil sample. The new fuel dilution meter inherited the SAW sensing technique but is compact, battery operated, and the patent-pending sampling system makes it user-friendly in the field and uses only 500 µL of used oil.

The three instruments complement each other and provide a complete set of oil condition information. They all feature the same set of characters, including

• Small, light, portable and battery operated
• Fast (one to two minutes each)
• Use small volumes of oil (<1 mL combined)
• Accurate (correlates to laboratory results)
• No need for chemicals or solvent to clean (requirement for onsite analysis)
• Easy to use (no need for an oil expert)

This set of features makes maintenance professional's life easier. Now, oil analysis can be performed at the generator and immediate and accurate decisions can be made with confidence.

Conclusion

Advances in oil analysis techniques make portable and accurate oil condition monitoring instruments available to maintenance professionals. Companies managing of a fleet of engine generators can now easily implement a condition-based oil change practice. As a result, operating expenses can be lowered by minimizing unnecessary oil change waste and maintenance costs, improving the reliability of the machine and eliminating catastrophic failures. These cost benefits can be achieved with the Spectro Scientific portable fluid condition monitoring combination solution.

References:

1. Under the Hood – Meeting the Design Challenge of the FluidScan® Handheld Infrared Oil Analyzer – Spectro Scientific white paper
2. Overview of FluidScan® Handheld Infrared Oil Analyzer – Spectro Scientific white paper
3. Using Infrared Spectroscopy for the Determination of TAN and TBN in Machinery Lubrication Oils – Spectro Scientific white paper
4. Measuring Water with the FluidScan® Fluid Condition Monitor
5. EPA NESHAP Quad Z Requirements
6. P. Henning, SpectroVisc Q Series Viscometer – a Portable Oil Analysis Solution for Field Based Users

This information has been sourced, reviewed and adapted from materials provided by AMETEK Spectro Scientific.

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