Increasingly sophisticated machines and operations require more than legacy PM approaches.
By Ken Bannister, MEch Eng (UK), CMRP, MLE, Contributing Editor
The term “time-based maintenance” is well understood in industrial operations. The premise is simple. A regular maintenance/lubrication event is scheduled on the basis of a calendar anniversary, i.e., weekly, monthly, quarterly, yearly, or other interval, or on a machine’s run-time clock, i.e., 100, 250, 1,000 hr., or some other specified number of hours. Foundational to legacy preventive-maintenance (PM) programs, this type of event scheduling has served industry well for decades.
Plant equipment systems and processes, however, are becoming more complex and demanding by the day. In turn, they are requiring increasingly sophisticated maintenance approaches. Going forward, if they haven’t already done so, sites will need to adapt to an integrated, proactive-maintenance approach that maximizes machine availability and reliability. The economic justification is simple.
In a legacy time-based event, a forced machine downtime is usually scheduled to perform maintenance or lubrication, e.g., oil change. Older equipment designs usually dictate that a machine must be shut down and locked out to determine its status and conduct scheduled activities in a safe manner. This method obviously has an impact on an operation’s throughput capability.
Given today’s fast-paced operating environments, a forced two-hour downtime to change oil on a calendar schedule—whether it needs to be changed or not—is no longer acceptable. We still need to change oil, but we need to treat that oil as we would any asset and maintain it over an extended lifecycle. That means changing it only when conditions warrant change. This type of monitoring strategy reduces machine intervention and increases production throughput, as well as reduces costs related to the purchasing, handling, and disposal of lubricants at a site. It also fits perfectly in any corporate asset lifecycle or sustainability initiative.
Moving from a time-based to a condition-based lubrication program is an ideal change-management vehicle for transforming and improving an operation’s state of lubrication. Successful design and implementation of a condition-based lubrication program can manifest itself in different forms, depending on a plant’s industry sector and current state of lubrication. Several “conditional” strategies can help your site gear up for this move with little effort and expense.
Implementing conditional strategies
Two basic elements underpin a condition-based lubrication program. The first speaks to the integrated, proactive-maintenance approach through involvement of operators as the primary “eyes and ears” in performing daily machine condition checks. The second element assures consistency and accuracy in the execution of value-based condition checks and lubrication actions.
Some maintenance personnel might argue that the old PM job tasks stating “Fill reservoir as necessary” or “Lubricate as necessary” are perfect condition-based instructions. Not so fast: Those instructions, unfortunately, rely solely on maintainer experience. They will not deliver consistency and accuracy without controls that dictate how we assess a machine’s condition and take appropriate actions built into the “necessary” part of the work-task equation. That’s where implementation of the following conditional strategies pays off.
Strategy 1: Reservoir-fill condition
If a lubrication system is to deliver peak performance, it will require an engineered amount of lubricant. In re-circulating and total-loss systems alike, designated minimum and maximum fill amounts aren’t always clearly indicated on the reservoirs. In such cases, the first step is to ensure that a viewable sight gauge is in use, complete with hi-lo markers for manual checks.
For critical equipment, an advanced approach can utilize a programmable level control to electronically indicate the fill state to operators and maintenance personnel. Some equipment, of course, is designed with reservoirs inside the operating envelope that require machine shutdown to perform checks or fill up. These systems can be inexpensively redesigned with remote “quick-connect” fill-lines piped to the machine perimeter that will allow the reservoirs to be filled to correct levels while the machine runs. (For additional tips, see this article’s “Learn More” box at the bottom of this article.)
Strategy 2: Oil condition
When the term “condition-based” is used, oil analysis often comes to mind. The first stage in controlling the oil’s condition is to ensure the product is put in the reservoir at the correct service-level of cleanliness and that a contamination-control program is in place. This will require a number of things: an effective oil-receiving and -distribution strategy, operators and maintainers working together to keep the lubrication system clean, use of desiccant-style breathers, and remote, “quick connect” fill ports that can be hooked up to filter carts outside of a machine’s operating envelope. (For additional tips, see the “Learn More” box at the bottom of this article.)
The second stage is to monitor the oil’s condition for contamination, oxidation, and additive depletion through the use of oil analysis. Extracting oil samples for testing purposes is predominantly a manual process that can be conducted outside of a machine’s operating envelope through a remote-piped “live” re-circulating line or by using a remote-piped sight-level gauge with a built-in extraction port.
Based on a condition report, the machine’s oil can be cleaned by using a filter cart, with no downtime, or replaced at a conveniently scheduled time. An advanced alternative is to use an inline sensor to monitor and electronically indicate pre-set oil cleanliness and water-presence alarm levels. (For additional tips, see the “Learn More” box at the bottom of this article.)
Oil-temperature condition is important wherever ambient temperatures fluctuate and an oil might become too viscous to be pumped through a system. This situation can create a bearing-starvation effect. In environments where this could happen, a thermostat-controlled automotive block heater or battery blanket heater can be incorporated in the system to ensure lubricant usability and machine uptime.
Strategy 3: Machine condition
The ultimate lubrication-control is based on equipment running condition. Effectively lubricated machinery will require less power to operate and bearing life will be extended by as much as three times that of ineffectively lubricated machines. Correctly engineered and set up, automated, centralized lubrication-delivery systems ensure the right amount of lubricant is applied in the right place, at the right time. If your plant’s equipment is predominantly manually lubricated, investigate converting to automated systems that require less maintenance and return their investment in weeks or months. (For additional tips, see the “Learn More” box at the bottom of this article.)
Automated systems are highly adaptable to new IIoT (Industrial Internet of Things) protocols. The capability now exists to install bearing-heat sensors (that set temperature ranges of different bearings) for monitoring, amperage metering (needed because friction demands an increase in motive power that translates through amperage draw), and sensing of oil levels and cleanliness.
Condition signals can be sent to an automated system’s lubricator to turn on and off for a timed or actuation cycle, or to indicate an alarm state. These conditions can be monitored with software tools and used for computer-based automated decision making to reset a lubricator program based solely (and precisely) on condition needs of a machine within its ambient operating environment.
Condition-based lubrication respects and treats the oils that a site relies on as integrated assets in equipment and process uptime. The condition-based approach is an excellent first step for a site that wants to shift its focus from legacy PM approaches to integrated, proactive-maintenance strategies. Regardless of industry sector, this type of maintenance is what plants of today and tomorrow require to be competitive. MT
Condition-based lubrication and system design are among the topics covered in contributing editor Ken Bannister’s 2016 book, Practical Lubrication for Industrial Facilities–3rd edition (Fairmont Press, Lilburn, GA), co-written with Heinz Bloch. Contact Bannister at email@example.com, or 519-469-9173.