Oil analysis on oil reservoirs, such as a paper machine, provides much more value than most maintenance managers realize.

Regular reservoir oil sampling can provide the following:

• Reactive information, such as a spike in wear metals identifying a failed bearing or another component.
• Predictive information, such as a slight increase in wear metals indicating early stages of an impending failure.
• Or, most valuable of all, it can provide proactive information. Oil analysis can tell you when your additives are getting depleted, contamination levels are getting to a point where additional filtering may be needed, moisture levels are to the point where corrective measures are required to prevent damage, and with enough data, may even tell you if your equipment is operating outside of its intended design (too hot, too slow, cavitation).

It’s all about using facts and data to help us make better maintenance decisions and get the most out of our investments. Improving the life expectancy of equipment, extending the life of oil life, and reducing unplanned downtime (which also improves safety) are just a few reasons the value of oil analysis far outweighs the cost.

So, would continuously monitoring the oil add more value if oil analysis provides that much value? We recently decided to add a continuous oil monitoring system to the main lube on our paper machine lubricating system.

We then took that information and sent it to our historian to be trended 24/7. We are trending the oil temperature, the moisture level, and the ISO 4/6/14 particle counts.

When we started this project, we did not realize how fast it would pay for itself! Shortly after getting the system online (but before trending), the maintenance manager notified us that the paper machine dryer head had developed a steam leak.

We watched the oil condition and saw no change. A few days later, the moisture levels began to climb rapidly. Thanks to the monitoring system, we reacted to this issue by periodically draining some oil and hooking up a vacuum dehydrator.

Within 24 hours, we reduced the moisture to an acceptable level and returned to normal within 72 hours. No doubt, this quick response minimized the amount of damage the water in our system caused.

Nicholas Knott, a colleague at another paper mill, had the same experience while trending moisture levels in his paper machine. He also caught it quickly and believes this technology prevented many bearing failures. Below is the trend showing how quickly the moisture reaches unacceptable levels and how fast his team could resolve it.

The lesson from these unfortunate situations is that if we were not doing continuous monitoring, how much damage would’ve occurred? We will never know, but we know that steam leaks on a dryer head were common in the past, and oil analysis was rare.

We also know that we had to replace many bearings in the past, which is rare now. Using continuous oil monitoring systems may only be necessary for some situations. Still, in a challenging application like a paper machine, it adds way more value than it costs.

Soon we expect to have enough data to understand if situations like start-ups, shutdowns, wash-ups, and machine speeds have impacted our oil quality.

Many of us use kidney loop filtration to clean our oil and extend the life of our equipment.  Don’t overlook small gearbox oil filtration! Neglecting to filter small reservoirs may keep you from reaching your machine reliability goals.

Whether to use kidney loop filtration should be based on criticality, maintenance history, and difficulty achieving target cleanliness. The reservoir size can undoubtedly create challenges but has little to do with whether to install kidney loop filtration.

Factors to consider:

• Equipment criticality:  If the equipment being considered is vital to your process, then keeping the oil clean is necessary.  To determine equipment criticality, consider factors like cost of downtime, impact on safety, impact on the environment, spare availability, and the impact on production.

• MTBF: Mean time between failure can also help you prioritize the equipment needing oil filtration improvement.

• Current contamination issues: All oil reservoirs of critical equipment should have cleanliness targets, but the difficulty in maintaining oil cleanliness can vary drastically.  If you have trouble maintaining the cleanliness target and all contamination ingress steps have been completed, offline filtration may be the solution.

• Accessibility to the equipment: Some equipment is difficult to access.  If an offline filtration system is designed correctly, it can provide safer and easier access to the oil for sampling and filtering.

• No amount of filtration can or should replace due diligence in controlling contamination ingress.

Once you decide to proceed with kidney loop filtration, the real work begins. 

• Choose a location for the small gearbox filtration equipment that is out of the way yet provides access for oil sampling, filter changes, and pressure monitoring. Choose a location that prevents damage from occurring to the filtering system.  Be sure to build a robust system and monitor it frequently.  A failed component on kidney loop filtration can quickly pump your oil to the floor instead of returning it to the reservoir.

• Choose the correct filter media and beta rating for the situation. To do this, you must compare current cleanliness levels to the target.  You will also need to consider the type of contamination you are attempting to filter, such as water. 

• Choose the correct flow rate. For small reservoirs, I prefer to err on the low side.  Low flow rates make managing the reservoir level easier and can provide better filtration. 

• Consider what will happen to the oil levels of the reservoir if the filtration unit fails or loses power. We prefer to mount the filtration below the oil reservoir.  Then recheck the oil reservoir after the filter unit is full of oil.  Then we unplug the unit to test that the oil levels stay satisfactory.  If the filtration unit is mounted above the reservoir, loss of power to the filtration unit could result in an overfull gearbox or reservoir.

The payback can be impressive if your equipment choices and the installation are made correctly.  Below is an example of a Warren Thick Stock Pump with two bearing reservoirs. The smaller of the two only has a capacity of about 2.5 quarts.  

For this application, I chose the CC Jensen 15/12 filtration unit with a flow rate of .088 GPM (Yes, 5.3 gallons per hour!).  We also made several changes to the system to lessen the moisture ingress that was occurring during upset conditions. Our efforts lowered the oil particle count from ISO 25/22/15 with very high moisture levels to 16/14/11 with Karl Fisher moisture levels under 100 ppm.

 These improvements have more than doubled the MTBF.  This reduction in maintenance/production costs translates to an estimated $80,000 per year in savings.

Kidney loop filtration on small gearboxes and reservoirs can provide the same benefits and life extension on larger systems. Remember to reduce contaminant ingression as much as possible, build a robust system, and size the flow rate accordingly.