A Guide to Oil Sampling Hardware - Machinery Lubrication

Using the right oil sampling hardware helps ensure you're getting an accurate sample every time. Below we'll talk about the oil sampling equipment you need to take an accurate oil sample.

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Quality Oil Sampling Hardware: Why It's Important

Coupled with the knowledge of how to take a proper oil sample, a lubrication specialist extracting a representative oil sample is only as good as his or her tools. Without these two things, you'll most likely wind up with a non-representative oil sample, which can have detrimental consequences down the road. Using the wrong or inadequate oil sampling hardware, taking oil samples from unsuitable locations, collecting samples incorrectly and even handling the samples improperly can all lead to an oil sample that doesn't represent the true condition of your equipment.

For example, taking an oil sample from the wrong location, such as a point downstream of a filter, won't show an accurate representation of the amount of wear debris or other contaminants in the oil, portraying the oil in the system as clean and eventually resulting in unexpected downtime. Conversely, using the proper oil sampling equipment by installing a correct oil sampling valve where needed (in this case, ahead of the filter) and extracting an oil sample there using the proper procedures will cost much less than any error resulting from incorrect sampling.

Proper oil sampling tools are also needed to prevent the sample and the system from being exposed to the ambient air, which contains airborne contaminants like water or particles. Sampling oil without opening the bottle can be done using the right oil sampling hardware. Having a correctly sized and properly cleaned bottle, a zip-lock sandwich bag, the right sampling port and valve, and a sampling device like a vacuum pump are all things you'll need to accomplish this.

Below we'll discuss the various pieces of oil sampling equipment you'll need to take a truly representative sample of the oil inside your machinery. These include oil sampling accessories like vacuum pumps, tubes and bottles; sampling ports, port adapters and gauge adapters; and sample valves for high- and low-pressure systems.

Oil Sampling Hardware: What You Need to Take an Accurate Oil Sample

While the procedure and method of oil sampling may vary depending on the type of application and machine you're sampling, oil sampling equipment can, in most cases, be applied universally.

Oil Sampling Accessories

• Sample extraction tube: A sample extraction tube takes oil from the valve or sump to the sample bottle. If it is used with a valve, it will have a probe or adapter fitting on the end. Typically, sample extraction tubing is made of low-density polyethylene, bought in bulk and cut to size as needed. Tubing comes in various sizes, most commonly 3/16, 1/4 and 5/16 inches. For more precise sampling or for sampling hard-to-reach machines, you can use microbore tubing. Microbore tubing refers to sample tubing in smaller diameters, typically around 2 millimeters.
• Vacuum pumps: Vacuum pumps are used to extract oil samples from pressurized systems not equipped with sampling valves. They are utilized in tandem with a flexible extraction tube to pull the fluid sample to the sample bottle. This tube can be fitted with sample port adapters if a sample valve is deployed. To set up the vacuum pump assembly, cut a piece of tubing long enough to reach halfway down into the vertical oil level height in the compartment of which you're sampling. If you are sampling from a valve, the tube must be long enough to reach the valve. On the other end, insert the tubing about 25 millimeters through the knurled knob on the vacuum pump. This is the pump location where you'll screw on the sample bottle below where you tighten the knurled knob to grip and seal the tube (do not overtighten).

  Make sure your vacuum pump accepts the size of your tubing. The bottle should be threaded tightly onto the pump to achieve a vacuum-tight seal. It's best practice to place each bottle in a zip-lock sandwich bag (see the previous link) in advance to restrict particle ingression from the ambient air and dirty hands during sampling. Once the pump is assembled, follow the proper method for drop-tube vacuum pump sampling or valve and tube-adapter sampling. It's important to note that you should change the tubing each time you draw an oil sample to prevent cross-contamination.

• Oil sample bottles: Choosing the correct oil sample bottle depends on the application and planned oil tests. Before selecting a sample bottle, you'll need to consider features like bottle size, cleanliness and material. Bottles are typically made of materials in three categories:
  • Opaque plastic: Opaque plastic like high-density polyethylene (HDPE) is one of the most common bottle materials on the market. You should try to avoid this material because it's difficult to visually inspect the sample due to its opaqueness (similar to a plastic milk jug). A less opaque polypropylene is also sold.
  • Polyethylene terephthalate (PET): This type of plastic is completely clear and compatible with most types of lubricating oil and hydraulic fluids, including synthetics. Other clear plastics are sometimes used including polyvinyl chloride (PVC).
  • Glass: Glass bottles are more expensive, heavier and come with the risk of breaking. Glass bottles can be cleaned and reused multiple times, and their cleanliness usually exceeds that of plastic bottles.

  Speak with the lab to ensure you're using the correct bottle size for your sample. Bottle size is based on the type of fluid and the types of tests the lab will run. Most standard oil tests require the sample to be taken in a 100- or 120-milliliter bottle. Sometimes the test requires a 200-milliliter or larger bottle.

  
  

  Finally, you'll want to confirm that your bottle meets ISO cleanliness standards to ensure the bottle doesn't add a reportable amount of contamination to the sample. Again, cleanliness depends on the type of test to be conducted and the objectives. Generally, the sample bottle should have a specific cleanliness level of two ISO codes cleaner than the target cleanliness objective. ISO provides a guideline for bottle cleanliness testing. The following cleanliness categories are frequently applied according to their contribution to the particle count:

  
  
  • A clean bottle requires fewer than 100 particles greater than 10 microns per milliliter of bottle volume.
  • A superclean bottle requires fewer than 10 particles greater than 10 microns per milliliter of bottle volume.
  • An ultraclean bottle requires fewer than one particle greater than 10 microns per milliliter of bottle volume.

  It's important to flush all sampling hardware (hoses, tube, valves, etc.) to get a truly representative sample. Flush five to 10 times the dead space volume before you collect your sample. Flushed oil can be collected into a purge bottle and returned to the system.

Sampling Ports

Two of the most critical aspects of the sampling process is where and how oil samples are collected. However, ports (and valves) aren't always where you need them to be. In fact, 71 percent of people reported to Machinery Lubrication magazine that they had to modify their equipment to enable oil sample ports and valves to be accurately located in order to obtain an accurate sample.

Installing multiple ports in strategic locations can isolate components to help troubleshoot the source of problems after abnormal conditions are found. Primary sample ports should be positioned where routine samples are taken to get the best overall assessment of fluid and machine condition. They are used for monitoring oil contamination, wear debris, and the chemical and physical properties of the oil. Primary sampling port locations vary, but for circulating systems they should be located on the return line before the fluid enters the sump or reservoir.

Secondary sampling ports can be placed strategically on a system to isolate components. This helps you localize the root cause of contamination by looking at individual components. An oil sample from the secondary port location should only be taken when the sample from the primary port detects an abnormal reading and you need to investigate the root cause further.

A good sample port is designed to draw samples from the most representative areas on the equipment and under normal operating conditions. This is done by using gauge adapters, port adapters and sample ports with pilot tubes (in the case of sumps and tanks). Below are examples of sample valves positioned at various locations on circulating and non-circulating systems.

Sometimes a machine's design or operating environment requires you to install a remote oil sampling port using line extensions. These may be necessary to effectively take samples for condition monitoring during runtime conditions. Many machines can't be easily accessed during normal operating conditions, but yet they may be the most critically important to sample. Cooling towers are a good example. They are critical and also difficult to conduct routine condition monitoring. Modifying cooling towers with remote sampling ports helps ensure they are properly maintained.

Sample Valves

Sample valves are installed into ports located on sumps and oil circulating lines for clean and efficient oil sampling. This achieves a controlled, fixed sampling location. Sample valves can help prevent leakage and accidental sample contamination. They also don't interfere with the machine's normal operation. As such, samples can be taking during normal operating conditions, which improves the quality of the sample.

Depending on your system, you might need to use multiple pieces of oil sampling hardware with the appropriate valve. For example, high-pressure hydraulic systems require a pressure-reducing valve, sample port adapter and hoses. A low-pressure system may demand a vacuum pump with a valve adapter to draw an oil sample. There are several valve options to consider:

• Portable high-pressure valves: High-pressure systems are difficult to sample during operation for safety reasons. Pressure must be reduced with either a portable pressure reducer (attached to the main sampling valve) or with stainless-steel helical tubing to lower the pressure. Be sure to get expert advice on the proper oil sampling hardware and procedure.
• Minimess valves: many consider the minimess or probe valve considered the best valve for taking a consistently accurate sample. Minimess valves should be installed on an elbow if possible for lines with high fluid velocity. To draw a sample, attach the probe fitted to the tube protruding from the sample bottle to the valve to let the oil flow into the bottle. Probe adapters can also be used. The probe unseats the mechanical check (spring-loaded ball) located inside the valve. As the probe is engaged, it pushes the check in the valve off its seat, allowing fluid to flow through. The vented bottle cap forces out air or exhaust. Minimess valves can be used on low-pressure systems. Low-pressure systems require a soft valve seat to avoid leakage.
  
  

  Portable minimess valves can be installed onto the female end of a standard quick-connect coupling. The male end is permanently fixed to the pressure line at the proper sampling location. Just like a regular minimess valve, as the female end is threaded onto the male end, the check inside the valve is depressed, allowing fluid to flow. Portable minimess valves can be utilized on both low- and high-pressure lines as long as a pressure-reduction valve or a helical coil is used.

• Ball valves: Like minimess valves, ball valves should be installed on an elbow on low-pressure systems. Ball valves let you start, stop, adjust and direct flow or prevent backflow. Make sure the ball valve is flushed before taking the sample.

Other sampling valves are sold for specialized applications and needs. These include the valves shown and discussed below. Advantages to many of these models include a tethered dust cap to prevent contamination and oil leakage after sampling, the ability to also bleed air, and minimal dead volume. Common disadvantages include having only one or two sealing features, the inability to be used as a diagnostic port for periodically installing sensors and transducers, and the risk of damage to the "soft-seat" design in high-pressure conditions.

• Stauff sampling valve: Stauff sampling valves come in five models with maximum operating pressure ranging from 5,800 to 9,000 psi. The valve design provides you with three sealing techniques to protect against oil leakage: a dust cap oil ring seal, an internal valve core hard-seat seal and a dust cap internal probe seal.
• Circle-seat control valve: The P-500 series sample-and-bleed valve has an operating pressure of 0 to 3,000 psi. To draw a sample, turn the valve head one-quarter of a circle to allow the oil to flow into an open bottle.
• Fluid line sampling valve: Wear check oil sampling valves on fluid lines have an operating pressure of 0 to 600 psi and allow for a sample to be drawn into an open bottle by depressing the valve button.
• Parker aerospace sampling valve: With a rated operating pressure range of 30 to 5,000 psi, these valves provide good sealing at low to medium pressure. A sample can be drawn using a hand-held probe device connected to a tube inserted into the mouth of an open bottle. The tube can also be attached to a port on a bottlecap or connected to a vacuum sample pump.
• Taylor sampling valve: Taylor valves are available in brass (with an operating pressure up to 2,000 psi) and stainless steel (with an operating pressure up to 5,000 psi). Soft-seat technology makes these valves good for sealing at low to medium pressure.
• Eaton sampling valve: The Eaton FD 150 oil sampling valve should be installed in low-pressure dynamic fluid lines and return lines. Operating pressure for the Eaton FD 150 is 0 to 300 psi. It should be noted that this model is not intended for aerospace applications.
• Checkfluid sampling valves: These valves come in three models: KP Series Pushbutton, KST Series and LT Series (drain port sampling device). The KP series has a sampling pressure range of 5 to 750 psi and the KST has a sampling range of 5 to 4,000 psi; both with maximum operating pressures of 6,000 psi. The LT series has a sampling range of 0 to 125 psi with a maximum operating pressure of 1,000 psi.
• Caterpillar sampling valve: The S.O.S. oil sampling kit is approved for use by Caterpillar and is standard on its products. The valve uses soft-seat technology to enable good sealing at low to medium pressure and allows for sampling in nearly any orientation.

Improvements to Oil Sampling Hardware

Over the years, technology and ingenuity have improved upon the designs and availability of oil sampling hardware to make sampling easier to obtain and more representative of system and fluid conditions. Two of the most notable pieces of oil sampling equipment that have been recently introduced are the Ultra Clean Vacuum Device (UCVD) and Luneta's Condition Monitoring Pod (CMP).

The UCVD is an advanced sampling bottle designed to hold a pre-established, pre-distribution vacuum, making it "ultraclean" by being free of almost all moisture and contaminants. It works by attaching the bottle's nozzle to a sampling tube, inserting the other end of the tube into the sampling valve and turning the nozzle to release the vacuum, which draws oil into the bottle. This method actually eliminates the need for a traditional hand-pump vacuum pump and can be used on any lubricating system, including pressurized systems.

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.

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).

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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.

Contact us to discuss your requirements of Portable Oil Analysis Kit. Our experienced sales team can help you identify the options that best suit your needs.