Proper Oil Sampling: The First Step in Oil Analysis
For years companies have used oil analysis to determine the health and condition of their equipment. However, most companies are not getting the most out of their oil analysis program because they do not understand the importance of proper oil sampling.
Oil analysis is a highly effective method of determining the health of your equipment’s lubricant and discovering wear modes in your machine. With oil analysis you can: decide on when the oil needs to be changed, and prevent failures. However, most companies are not getting the most out of their oil analysis programs due to inconsistent oil samples.
The importance of taking a proper sample for oil analysis cannot be overlooked. A proper sample represents the true condition of the equipment, it is taken when the machine is running, and it is taken from the same spot in the active zone every time. A proper sample is then compared to the baseline sample and trended against past and future samples.
With oil sampling, there are two main objectives: safe sampling and reliable sampling.
Safety is the first objective. This means safety for both personnel sampling and the machine. Technicians need to understand the equipment and hazards. They should follow all safety procedures and use proper personal protective equipment while sampling. But even when following safety procedures, typical sampling methods can be dangerous. Oftentimes sampling from the drain has caused burns and opening up a system for sampling can expose the workers to dangerous hazards. With drain port sampling, it is also difficult to control the flow of oil out of the machine and too much oil loss can result in starvation. Furthermore, opening the equipment up to external particulate, moisture and water contamination can often defeat the purpose of getting a representative sample. It can even damage the equipment.
Drop tube sampling is another traditional method that is hazardous. It is extremely dangerous to insert a plastic sampling tube into the live zone while the equipment is running. Without extreme precision there is a strong likely hood of the plastic tube getting caught in the gears. Thus in order to get a safe oil sample the equipment must be turned off. Even when turning the equipment off the system is still being opened up to external contamination. Properly installed oil sampling valves can help keep your people and equipment safe. For starters, burns can be avoided as sampling valves allow oil to be directed safely and cleanly to the bottle. Additionally there are many remote access options available so that sampling can take place away from any and all of the equipment hazards (Figure 1). Sampling valves also allow you to sample from a closed system, preventing contamination from entering the system. Also, costly downtime can be avoided by sampling while the equipment is running.
While safe sampling is the first objective, getting a reliable sample is also important. Successful oil analysis is about accurate trending. Oil samples need to be taken the same way every time and from the same location every time. It is important that the trends in the oil analysis reports are because of changes in the oil and equipment and not because of who took the sample, or how and when the sample was taken.
Drain valve sampling and drop tube sampling do not produce representative samples. For starters, taking an oil drain sample can lead to the oil analysis results showing false positives. Since wear particles, contaminants and water settle at the bottom, the oil samples can show elevated amounts of wear metals or contamination. This can lead to unnecessary repairs, resulting in lost productivity and elevated maintenance costs to fix a problem that never existed in the first place. Additionally both sampling methods require machine shut off. The samples will not be representative of the equipment during operation. Additionally, shutting off the machine and waiting for the oil to cool down enough to safely take a sample allows for more wear particles settling in the drain. Thus the sample can show elevated amounts of wear particles.
Sampling valves are needed for obtaining consistent and reliable samples. They allow for oil to be taken directly from the active zone, safely, while the equipment is running. This means that oil samples can be taken at any time since shutdowns are no longer necessary. Technicians also no longer have to open the system, reducing the chance of moisture or contamination. Furthermore, sampling while the equipment is running ensures that the samples are a direct representation of the machine’s condition. The oil samples are reliable because they are coming from the same spot in the active zone every time. Each sample pulled will contain hot, information-rich oil that can be trended against previous samples to show the condition of your equipment.
Pressurized systems (such as engines, transmissions, compressors and hydraulics)
When installing a sampling valve on pressurized equipment, like hydraulics, look for a port that will provide the best representative oil sample. The ideal port will be located downstream of the components to be monitored (i.e. pumps, bearings) but before the filter (unless the filter is being monitored). Many times a simple pushbutton valve can be installed directly in a port on a pressurized system (Figure 2). However, if the port is not easily accessible many sampling valve manufacturers have remote access solutions to allow samples to be taken from a distance (Figure 1).
Low or Non-Pressurized Systems (Gearboxes)
Many times gearboxes only have a small number of ports to choose from. The drain port allows an ideal location to insert a sampling valve with an attached permanent sampling tube (Figure 3). The permanent metal tube should be bent and positioned close to gears to get the most representative oil. The sampling valve with tube will reach oil directly in the active zone and avoid getting sediment from the bottom of the gearbox, thus producing representative, and reliable oil samples. The breather port is also another option for sampling tube installation.
Get the Right Sampling Valve
Once a location and available port is determined, it is necessary to determine the oil viscosity range, pressure range (for pressurized systems), thread size and thread type of the port. Sometimes, this is available from the manufacturer. Often times, it is necessary to use a pressure gauge, micrometers, thread pitch gauge and a thread identification table.
Once the information is gathered, contact your oil sampling valve partner to get help in choosing the best valve, fittings and sampling accessories for your application.
Get the Right Procedure
After the valves are installed, take the time to create proper oil sampling and handling procedures. Use these procedures to help with training and minimizing data disturbances within the samples. Additionally, all involved in oil sampling should make sure that the fluid pathways are purged, the sampling bottles and tubes are clean, and the sample goes directly to the lab for analysis. Even these “little” factors can make a huge difference in the quality of your oil analysis results.
Oil analysis has a wealth of benefits for those who utilize it. A world-class oil analysis program starts with a good oil sample. The resulting data from a good oil sample will hold more useful information on the health of the machine. These results will give teams the information needed to maximize reliability and reduce unplanned downtime.
Preventive maintenance plans are no small feat. If you’re accustomed to reacting to unexpected breakdowns and critical emergency repairs, a preventive maintenance plan will force you to think months, even years ahead. This may take you out of your comfort zone, but it will instill peace of mind knowing that your critical assets are covered.
If you are considering to employ RCM analysis at your facility, it means you have recognized the need for a change in your maintenance strategies. Reliability-centered maintenance is an excellent way to keep your plant or machinery up and running by helping you choose the optimal maintenance strategy for all of your important assets.