Technical - Oil Sampling

The single most important activity with regard to oil analysis is the practice of obtaining an oil sample. An oil sample that is not representative of oil obtained from the sample port location, will give false and misleading information to oil analysts as well as to those charged with implementing recommendations from the oil analysis results. In order to determine if representative samples are being collected from the sample ports the following must be reviewed:

• Equipment sampling location (including primary and secondary sample points)
• Sampling ports are properly located to isolate area of concern
• Sampling location should be reviewed to help determine quality of data
• Sampling valves are correctly selected and installed
• Sample containers are properly selected and stored
• Sampling hardware meets cleanliness and safety requirements
• Correct, machine-specific sampling procedures are employed
• Sample bottle labels and documentation are properly completed
• All samples are obtained by trained and qualified technicians

Troubleshooting or identifying equipment problems using oil analysis is greatly assisted by the installation of several sampling ports in various locations to isolate individual components. These points should allow for trouble-free, repetitive and representative sampling of the health of the equipment and the health of the lubricant. Isolating using multiple sample ports, gives an analytical edge for both discovering potential component failure and analyzing the root cause. The location of the sampling port should allow the equipment to be tested under its typical operating condition while being non-obtrusive and maintaining a safe sampling method for the technician.

Sample ports are classified into two categories, primary and secondary.

Primary Sampling Ports
If the intent of your lube oil program is only to monitor the health of the lubricant, a primary sample is all you will need for routine oil sampling. It is very easy and inexpensive to draw a sample from these locations. The oil from these sample locations are usually used for monitoring oil contamination, wear debris and the chemical and physical properties of the oil. Primary sampling locations vary from system to system, but are typically located on a single return line prior to entering the sump or reservoir. Often in lubricated pieces of equipment, a primary sample is the only type that can be installed. For example a bearing housing or small gearbox will only have one primary sample port.

Secondary Sampling Ports
Secondary sampling ports can be placed anywhere on the system to isolate upstream components. This is where contamination and wear debris contributed by individual components will be found. Secondary sample ports provide other information, such as post-filter condition, condition after and supply pump, and condition of the tank bottom, and condition of a component part. These secondary points are used for the purpose of follow-up samples. They are performed on an infrequent basis to better define the condition of the system's lubricant after initial indications are provided by the primary sample point.