Filtered oil can be analyzed for the purpose of verifying its cleanliness level. Oil analysis can be broken into three categories for sampling a machine. The first is offline sampling, which consists of pulling a sample from a minimess, drop tube or drain valve. This analysis may be done in-house or sent to a laboratory. While the user will receive good data if the analysis is performed correctly, there are drawbacks if time-sensitive data is required. The lapse in time from when the sample is drawn to when it is analyzed or forwarded to the lab may be hours or weeks, which means machine damage could occur before the results are known or interpreted. To minimize this risk, always ship the sample to the lab within 24 hours.
Another way to draw an oil sample from a machine is through online sampling. With this method, the sample is analyzed from a location that is not in the direct line of the oil flow path. Oil still flows through the line, just at a lesser rate. The user normally avoids many of the costs of having to tap into the direct flow of the line by utilizing existing fittings to make a loop. These systems have little impact on the oil flow. Not only can direct results be obtained, but this type of sampling also removes the influence of external contamination sources. There are many positives to this type of system, but one disadvantage is the misrepresentation of the sample size versus the full oil flow of the equipment piping.
The third technique is called inline sampling. Here, a sensor is placed in the direct path of flowing oil. Whether positioned after a pump or in a return line back to the reservoir, the sensor will always receive the same data that is making contact inside the machine surfaces. While not always feasible, this approach will provide the best results.
Both online and inline sampling fall into the category of real-time oil analysis. Your car's oil pressure gauge is an example of a sensor that offers real-time results. These types of sensors show what's happening at this instant inside your machine. Unlike offline sampling, which requires individuals to pull a sample, ship the sample, and wait on laboratory analysis and interpretation of the sample, real-time sensors can indicate problems without a time delay.