1. Multiple Sample Ports: In complex types of equipment, such as rotating equipment like Motors, Gearboxes, compressors, having just one sapling port is inadequate to get a holistic picture of the condition of your components or the health of your oil. Typically, it is common to have one sampling point; what people call the “primary sampling point” on the return line of a hydraulic system. However, relying only on one sampling point doesn’t allow us to pinpoint exactly at what point oil is getting contaminated. For example, if we have a circulating system of the motor, gearbox and a compressor, it would be advisable to have a couple of sampling ports for each bearing on the motor, one port on the bearing of the gearbox to monitor the oil flowing through it, and one on the return line of a compressor. Running separate analysis on each of these samples would enable us to figure out exactly which component is faulty, or at what point does the iron/wear particle content of the oil shoot up.
2. Return Lines/Drain Lines: As much as possible, oil sampling ports should only be located downstream of wearing components, ie: ideally after it has gone through the entire system and flowing back to the tank through the return drain line. Oil collected at this point will have the most representative levels of contaminants.

Method of Oil Sampling

One of the common ways to collect oil samples is to have a drain plug from the bottom of the oil sump. Personally, I think this is not advisable for the following reasons:

• Sediments, Wear Particles and Contaminants often tend to settle at the bottom of the tank, and the oil that is collected in this way through a drain plug will have heavy concentrations of these contaminants, such oil samples are in no way truly representative of the oil flowing through the system. The drain plug sampling method should be avoided if at all possible.
• The draining plug method is also a slower, wasteful way of collecting the oil that often leads to unhygienic, unsafe surrounding areas with spillages and leakages. In addition, having a drain plug at the bottom of the oil sump defeats the purpose of collecting oil when from a point of system turbulence.

The most reliable way of collecting oil samples would be to have a fixed sampling valve installed at different collection points. Often, these valves come ready with the gearboxes and/or can be installed at the time of any routine plant shutdowns/when oil is drained out for oil changes, etc. This practice ensures you get good, consistent oil sampling every time, that is representative of the oil flowing through the system at operating conditions.

Summarizing:

1. It is important to have oil samples taken when your oil is flowing through peak turbulence during normal operating conditions
2. Oil Samples have to be collected when oil is flowing through bends and sharp edges to ensure no particulate fly-by occurs and we get a representative oil sample
3. Multiple oil sampling ports are critical to ensure root cause analysis for oil degradation can be apportioned to each component of rotating equipment (Motor, Gearbox, Compressor).
4. Oil Samples must be collected upstream of filters or separators so that oil collected is not devoid of the contaminants and particulate matter that are so easily lost once they go through filters and separators.
5. Oil Samples must be collected from return/drain lines before it reaches the sump tank.
6. Permanently fitted valves at critical sampling ports must be preferred over having wasteful drain plugs for the process of sample collection.