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.
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.
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.
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.
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 3722 provides a guideline for bottle cleanliness testing. The following cleanliness categories are frequently applied according to their contribution to the particle count:
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.
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 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 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.
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.
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.
The Condition Monitoring Pod is a multifaceted piece of equipment that lets an inspector perform multiple tasks from the same port. Described as a "multi-parameter inspection pod," the CMP is an oil sight glass and sampling port engineered into one piece of equipment. The CMP lets you readily view oil levels, color and clarity, aerating and foaming, corrosion, varnish and wear debris. Additionally, you can draw an oil sample from the built-in, vacuum pump-compatible sample port. The CMP includes a stainless-steel pilot tube that can be bent to the desired sampling location inside the machine.