Mods Enhance Lube Practices
EP Editorial Staff | October 13, 2020
Modify your assets to make it easier to execute your precision lubrication program.
By Mark Barnes, PhD CMRP, Des-Case Corp.
For asset-intensive industries, precision lubrication is a fundamental cornerstone of a well-engineered maintenance program. While not complex, precision lubrication requires meticulous execution of simple time- and condition-based maintenance tasks. Basic tasks, such as greasing bearings, checking oil levels, changing oil, and/or applying filtration, all need to be part of daily or weekly PM rounds. Failure to do so can result in poor reliability, leading to higher maintenance costs and unscheduled downtime.
Precision lubrication requires following the 5Rs of lubrication:
• Right oil or grease
• Right place
• Right amount
• Right time
• Right cleanliness (clean and dry).
Strict adherence to preventive (time-based) tasks, such as re-greasing, and condition-based tasks, such as large-volume oil changes, are required so that activities are performed at the right interval and/or condition.
What happens when machine accessibility precludes performing these tasks? When maintenance personnel do not have access to equipment, maintenance schedules tend to default to production schedules which may not necessarily conform to precision-lubrication best practices.
Take, for example, the simple act of checking the oil level in a production-critical, splash-lubricated gearbox that operates continuously. Precision lubrication best practice may suggest the need to check the level daily or even once a shift. If the gearbox has nothing more than a dipstick or level plug, it is all but impossible to properly check the level, short of shutting the gearbox down and waiting for the oil to drain back to the sump.
Of course, it’s tempting to argue that production schedules should be modified to permit time-based maintenance tasks. We all know that the chances of production shutting down just to permit a gearbox level check fall somewhere between slim and none.
Instead, we need to look at all time-based maintenance tasks—including lubrication—and ask a fundamental question: Can I modify the task or asset to change a downtime task to a runtime task? While not always possible, having the ability to conduct routine time-based maintenance during normal operation offers several advantages. Not only does it permit the task to be performed at the right frequency, it also reduces the amount of work that needs to be done during scheduled outages when maintenance resources are at a premium.
The problem with doing many lubrication tasks during normal operation lies with how our assets are configured. While the top two or three most critical assets in the plant are often equipped with every bell and whistle needed to promote proper maintenance, it’s the critical assets that fall just below level-one status that suffer.
Most at fault are wet-sump applications such as splash-lubricated gearboxes and pumps and smaller hydraulic-powered units in which, in the interest of keeping the purchasing price low, many OEMs overlook the need for simple features such as visual (runtime) level gauges or oil-sample ports.
Modify for precision lubrication
The modifications that need to be made to assets depend on the type of asset and the maintenance tasks that need to be performed. For lubrication, here are some basic modifications:
Grease-line extension: With few exceptions, re-greasing bearings should be done while equipment is operating. While this is straightforward if the bearing housing or grease fitting is readily accessible, sometimes guards or bearing locations make runtime re-greasing impossible. Where bearings cannot be accessed during normal operation, thought should be given to extending grease lines to a safe, readily accessible area or using an automatic lubricator to apply grease to the bearings.
When you extend grease lines, consider consistency and its impact on the ability to pump grease at all in-service temperatures. With auto-lube devices, pay attention to grease selection. Also, add a PM to inspect and service the automatic lubricator to avoid a set-it-and-forget-it mindset.
Oil-level indicators: Maintaining the correct oil level is a basic, but important, consideration, particularly for small, wet-sump applications such as gearboxes and pumps where a 1/4- to 1/2-in. difference in oil level can determine success or failure.
In wet-sump applications, oil is distributed by splash, slingers, or flingers, meaning that the oil level, during operation, may not necessarily be the same as when the asset is idle. For smaller process pumps, equipped with either a flat-faced bullseye or level plug, adding a 3-D bullseye can help better determine the oil level while the pump is operating.
For splash-lubricated gearboxes, the oil level when the machine is shut down will be different from the level when the gearbox is operating. Common gearbox level-check devices, such as level plugs and dipsticks, are designed to check the level when the gearbox is shut down, making level checks inaccurate during operation. In some cases, the tendency is to fill the gearbox to the level plug or dipstick mark while the asset is operating, meaning that as soon as the gearbox shuts down, the oil level rises above the shaft seal, resulting in oil leakage.
For gearboxes or other wet-sump applications with a varying oil level, best practice is to install an external level gauge with two marks; one indicating normal operating oil level and the second indicating the normal level when shut down.
Oil-sample valves: Drawing oil samples from critical assets is an important aspect of any condition-monitoring program. Unfortunately, many assets do not have proper oil-sampling valves. In the absence of a valve installed in the right location, the only options are to use either a vacuum sampling gun and drop tube inserted through the fill port or to crack a drain valve to fill a sample bottle. Neither of these approaches is ideal. Installing an oil-sample valve in a location that is representative of oil and machine operating conditions should be a prerequisite before starting any oil-analysis program.
Hardware for contamination control: Contamination is the leading cause of component failure. Contaminants enter oil-lubricated assets externally through shaft seals, active breathing, or the addition of unfiltered new oil. Internal contamination results from active machine wear and/or oil degradation. Either way, best-practice contamination control calls for adding desiccant breathers on the vent port and quick-connects on drain and fill ports to permit the addition of new oil using a portable filtration system or to facilitate periodic offline filtration.
Put it All Together
Since most OEMs do not provide adequate provisions for runtime level checks, oil sampling, or offline filtration, most equipment modifications need to be done after the equipment is installed. This can prove challenging since some assets, particularly smaller sumps and reservoirs, may only have a single drain/fill port. Without significant re-engineering, adding each modification can become complicated and expensive. With a bit of ingenuity and off-the-shelf manifolds, a single drain or fill port can be used for multiple adaptations.
Precision lubrication doesn’t have to be complex. Even the most basic task can be easily executed by making simple modifications. Ask, “How can I improve asset configurations? Are there additions or modifications that will make lubrication a simple runtime task?” EP
Mark Barnes, CMRP, is Senior Vice President at Des-Case Corp., Goodlettsville, TN (descase.com). He has 21 years of experience in lubrication management, oil analysis, and contamination control.