Are Your Lubrication Practices Disaster Proof?
EP Editorial Staff | May 14, 2020
When outside forces affect normal manufacturing processes, adapt your lubrication systems.
By Mark Barnes, PhD CMRP, Des-Case Corp.
Machine reliability is closely tied to consistency—consistency in operation, consistency in function, and consistency in (proper) maintenance. As W. Edwards Deming put it, “uncontrolled variation is the enemy of quality.” Under normal circumstances, consistency can be readily achieved through standardized processes, documentation (procedures), and training. However, what happens when we are forced to change our “normal?” How can we react to ensure that the “uncontrolled variation” that is thrown at us does not affect our ability to operate and maintain our assets at a high level?
Production Change Causes
Changes to production schedules are caused by several factors. Seasonable variability in some industries, such as fresh-food processing, naturally leads to peaks and troughs in production and, hence, maintenance. Likewise, natural business cycles, driven by economic conditions, have a significant impact on resource industries such as mining or oil and gas, which consistently seem to be operating in either feast-or-famine mode. For people in those industries, this is nothing new and they plan accordingly.
However, what happens when economic turmoil or natural disasters that no one could have foretold affect our production and maintenance schedules? How can we ensure that our equipment is protected?
Not Every Plant Shuts Down
For some industries, such as food and beverage, pharmaceuticals, consumer products, pulp and paper, and building products, natural disasters drive increased, not decreased production. While operating equipment to meet peak demands, maintenance intervals may be deferred to a later date, production line speeds may be increased, and a shift in the grade or type of products being manufactured may change. Layer that on top of a possible reduction in available labor and there is recipe for a “natural disaster” for our critical production assets.
When it comes to lubrication, there are things that can be done to mitigate the potential negative impact of a change in maintenance schedules. The first thing to do is to take a critical look at what work needs to be done. During disruptive times, lubrication is often the first thing that is deferred. However, while missing an oil sample for a month or two may not induce a failure, not greasing a critical high-speed fan or motor for six to eight weeks may be devastating.
Focus on high-speed assets; the time between a problem becoming apparent (point P on the P-F curve) and functional failure (point F) is much shorter for high-speed assets.
Oil flow rates should also be checked. For circulating lubrication systems, such as those found on paper machines, oil flow is matched to operating speed. As speeds increase, it may be necessary to adjust oil flow rates to match. This is particularly important where high temperatures are present, such as dryer cans.
Also, take a look at oil changes. Assuming you have been taking routine oil samples, let oil analysis guide oil-change decisions rather than relying on time-based oil changes. However, what happens if an oil change becomes necessary, but production won’t (can’t) release equipment to maintenance? While typically not recommended, oil changes can be done “on-the-fly” using a process referred to as sweetening. By draining 10% or less of the oil in the sump or reservoir at any given time and replacing it with fresh oil, it may be possible to limp along for several months without a complete oil change. While this is relatively straightforward in systems with large oil volumes, extreme caution is required for smaller wet-sump systems, such as gearboxes and pumps, to prevent lubricant starvation.
Where oil changes are not possible or where an active wear problem is occurring, consider using an offline filtration system. While the filtration system will not necessarily fix the underlying root cause of the problem, it may have the effect of “flattening” the P-F curve, extending the time between point P (when the issue becomes apparent) and the point of functional failure (point F).
Protect idle equipment
For many industries, economic downturns or natural disasters mean that some equipment will inevitably be idled for a period of time. Taking the time to protect equipment that is being shut down means that once economic conditions improve, equipment will be ready for action. Just like making sure critical bearings still get greased during busy times, ensuring that bearings aren’t over-greased during idle periods is just as important.
PM schedules should be adjusted to ensure that we are not blindly adding grease because “our CMMS system says so.” For bearings that are lubricated automatically, make sure that the lubrication system is turned off when equipment is not running. While larger series and parallel multipoint systems are often tied to our PLC system, meaning they shut down when the machine is not running, some smaller systems, such as single-point lubricators on gravity-feed oilers, may need to be manually turned off.
For idled equipment, the critical time is when the oil and machine cool down. As the oil temperature drops, the air inside the oil sump or reservoir will also cool and contract. In doing so, make-up air will be pulled in from the outside. If the make-up air is dirty or moist, the contaminants may cause failures to occur at a later date. For idled equipment, water is more of an insidious contaminant than particles. As the air cools, water vapor in the headspace will condense, causing free and emulsified water to form in the oil. In turn, this can cause rust, corrosion, and other failure modes.
The best way to protect against moisture ingression is to install a desiccant breather on all oil sumps and reservoirs. Not only does a breather remove moisture when make-up air enters the machine, it will also actively dehumidify the headspace when the machine is shut down, much like a sachet of silica gel that is often included to protect high-end consumer products, such as electronics, from moisture. For gearboxes, it may also make sense to use vapor-phase corrosion inhibitors that can be added to the gear oil to provide headspace corrosion protection. Always consult with the lubricant manufacturer prior to using corrosion inhibitors to insure compatibility with the lubricant.
Re-starting idle assets?
Downturns caused by economic conditions or natural disasters do not last forever. Inevitably, conditions will improve and production will be back in full swing. While some start-up activities are simply the reverse of shutdown procedures—reinstate deferred PMs, turn auto-lubricators back on—significant care must be exercised with some equipment.
For circulating lubrication systems and hydraulics, we need to look at deposits that may have formed when the machine was shut down and the oil temperature was lower. Byproducts of oil degradation, such as sludge and varnish, may come out of solution at lower oil temperatures and can cause restricted oil flow, valve stiction, and other operational challenges when equipment comes back online.
Taking a baseline oil sample as a “health-check” to measure oil cleanliness (water and particle count), varnish potential (MPC test), and additive health (RulerTM test), is a good idea prior to starting the machine. If excessive contamination or deposit formation is found, these contaminants should be removed through appropriate offline filtration prior to and during start-up.
Machines thrive on consistency. Sometimes life throws us a curve ball and, while our natural inclination may be to hunker down, perhaps we should follow Sir Winston Churchill’s advice and “never let a good crisis go to waste.” Let’s take the opportunity to look at how we protect our assets, whether we are shut down, producing at unprecedented levels, or just about to turn things back on. EP
Mark Barnes, CMRP, is Senior Vice President at Des-Case Corp., Goodlettsville, TN (descase.com). He has 21 years of experience in the fields of lubrication management, oil analysis, and contamination control and has published more than 150 technical articles and white papers.