- Buyer's Guide
Ready, aim, fire! Or is it ready, fire, aim? Unfortunately, the latter is more prevalent in the deployment of lubricant analysis programs. Strategy is often viewed by technologists as just a bunch of lofty objectives, or trendy catchphrases of the day that aren’t really applicable to real life. However, strategy determines the direction in which a group travels. It may sound trite, but the goal of management is to ensure that things are done correctly. Without proper leadership and strategy, investments in lubricant analysis might be wasted. With effective strategy, lubricant analysis yields significant benefits. Key elements of strategy discussed here include alignment to organizational objectives, reliability-centered maintenance (RCM), condition-based maintenance (CBM) and finally, a strategically designed lubricant analysis program.
Alignment to Organizational Objectives
It is impossible to devise an effective lubricant analysis program without a clear understanding of the equipment maintenance and reliability framework in which the program must serve, and a clear understanding of how the program will add value to the organization. That means that the lubricant analysis professional needs to understand these relationships before embarking upon a new lubricant analysis program, or to expand an existing program. Activities must be sustainable, and they must deliver value that is consistent with the mission of the organization. Strategic misalignment creates friction and destroys value in much the same way as shaft misalignment. To be effective, the mission of the lubricant analysis program must align with the mission of the maintenance and reliability effort, which in turn must align with the mission of the plant, which must align with the mission of the corporation, which must align with the needs of the corporation’s owners and stakeholders (Figure 1). Failure to achieve strategic alignment ultimately leads to program failure.
Figure 1. Ensure the Lubricant Program
A lubricant analysis program that fails to align with the organization’s mission and fulfill the expectations of stakeholders can’t produce a paradigm shift, or a change in business-as-usual. It is only when the old business-as-usual is replaced with a new business-as-usual that the paradigm actually shifts and the new program is entrenched and capable of sustained existence until the next new business-as-usual comes along. Basing equipment maintenance and lubrication decisions on lubricant analysis requires a significant behavioral change in most plants. Companies have been conducting business in a particular way for a long time in many cases. Long-standing traditions produce a business-as-usual inertial force that the new program must overcome. Not only must the new program be forceful enough to stop existing practices, but it must also have sufficient strength take hold as the new practice, or the new business-as-usual. Several factors influence the likelihood of success, but no program can thrive unless it builds value for the organization, which means that it must be aligned with the organization’s goals. Lubricant analysis professionals must gain a clear understanding of this relationship, which begins with a thorough understanding of maintenance strategy.
Make no mistake - reliability-centered maintenance (RCM) is not merely a program of the day. The adoption of reliability engineering principles and techniques in industrial plants, mines and fleets is fundamentally changing the manner in which assets are designed, purchased, installed and maintained. A few short years ago, employees were a part of the maintenance team. Now, they are a part of the maintenance and reliability team. RCM is being adopted rapidly in various industries and across the globe. If RCM is not being implemented at your plant or at your mine, just give it some time.
In its simplest terms, RCM is a resource allocation tool. It is not a magic formula. Quite the contrary, when done correctly RCM is hard work - but it is the kind of hard work that produces permanent and sustainable change. Done incorrectly, or if the implementation is completed so the organization can hang a plaque on the wall proclaiming “we’ve performed RCM,” it is of little value at all.
RCM provides equipment managers with a framework with which to select the maintenance strategy that best fits the needs of the situation. RCM begins with an assessment of an asset’s mission criticality (Figure 2).
Failure in a mission-critical equipment results in an unacceptable risk of a personal injury (associated with the failure itself, or the subsequent restoration of the asset), an environment-impacting consequence or a profit-impacting loss of production. If a system or subsystem is not deemed mission-critical, its frequency of failure is evaluated relative to the cost of repair. If the cost of failure is low, the asset is designated as run-to-failure. In other words, if the cost to avoid a failure exceeds the cost to live with it, no intervention is required.
The failure histories are analyzed extensively for machines deemed mission-critical or expensive to repair by reliability engineers so that they can understand the nature and severity of common failure modes and mechanisms. If the current reliability of the asset is deemed acceptable, maintenance tactics are implemented to assure it. Depending upon the nature of failures and the dominant modes of those failures, these tactics might be calendar-based (preventive) or condition-based (predictive) tasks.
In some cases, maintenance alone is not sufficient to achieve reliability requirements. In some of these instances, a redesign is required to eliminate an existing design flaw or to enable the equipment to deal with unforeseen operational challenges. Sporadically, machines are procured and placed into service in applications for which they were not intended, which can lead to poor reliability. In these instances, the redesign targets the limitation in the equipment relative to the application. Often, the redesign or modification targets a dominant failure mode that has surfaced due to the misapplication of the machine. In other cases, the machine is pushed to or beyond its design limits due to incorrect specification or rerating of the production system. The redesign is intended to offset the abnormal forces that produce a high failure rate.
Occasionally, redundancy is employed to increase overall system reliability. However, a redundant system is the surest way to increase reliability, but it is an expensive strategy that can be a perilous path. Redundancy is generally classified into one of two categories, backup systems and shared load systems. A backup system sits idle except in the event of a primary system failure. Backup systems can be brought online manually, or by a relay-driven automatic switching mechanism. Sometimes backup systems aren’t operational when required because of maintenance neglect, static system degradation (rust, corrosion, fretting) or failure of a switching mechanism. A simple shared load system is comprised of two systems, each of which is capable of providing full production, operating in unison at a reduced load. Because the two systems operate at a reduced load, the rate of failure is decreased. In the event that one should fail, the other unit carries the load until its partner is restored. Only in the unlikely event that both systems fail would production be affected. Another type of shared load system is called an “R out of N” system. In this design, for example, the plant may have six units operating, while only four are required. Production would be affected only if more than two of six units reached a failed state.
RCM is an indispensable tool to the plant, mill or mine for driving maintenance strategy and resource allocation decisions. The process results in the practical selection of appropriate strategies that balance investment in reliability relative to the organization’s mission objectives.
Maintenance Strategies and Condition-Based Maintenance
Preventive, or calendar-based maintenance rebuild or replacement of an asset, has generally proven to be an unsuccessful strategy for maintaining equipment because of the random nature of failures. In other words, failures tend to occur on their own time, not according to the plant’s schedule. As a result, machines are often rebuilt or replaced in the prime of their life. Also, some machines are likely to fail prior to the scheduled rebuild or replacement. Likewise, intrusive maintenance, like a rebuild or replacement of an asset, often introduces new failure modes that didn’t previously exist, producing the phenomenon called premature or infant mortality. If the dominant failure mode has a clearly defined mean-time-between-failure (MTBF) and a small standard deviation, it might be a candidate for preventive, or schedule-based maintenance if the dominant failure mode can’t be brought under control or eliminated through modification.
Because of the random nature of most critical mechanical machines, organizations tend to opt for condition-based maintenance (CBM) for their critical and important machines. As the name implies, maintenance is performed on-condition under a CBM program. Generally, CBM falls into one of two categories, predictive maintenance and proactive maintenance (Figure 3).
Another variation, called protective maintenance, utilizes sensors designed to provide operators with a last-chance warning of impending machine failure. These sensors are occasionally tied to a relay-based shutdown system.
Predictive maintenance employs various sensors, technologies and inspections that detect abnormalities in the condition of the equipment in the early stages of failure. Vibration analysis, thermography, motor current analysis and lubricant analysis are among the techniques that can detect the signals of incipient failure, which are often faint and undetectable by unaided human senses. These technologies not only detect the presence of an early stage failure, but they are also quite useful in diagnosing the problem to determine its root cause and to estimate its severity.
If the reliability of the equipment is deemed unacceptable, or if management wishes to reduce maintenance costs or further reduce the risk of failure, proactive maintenance techniques are employed. Proactive maintenance targets the root causes of machine failure for control. Rather than routinely monitoring the equipment to detect an in-progress failure, proactive maintenance-based condition-monitoring activities measure the degree to which failure root cause conditions, like misalignment, imbalance, lubricant contamination, lubricant health, etc., are under control. When a failure root cause parameter falls outside of acceptable limits, the risk of failure increases due to increased activity in one or more of the affected failure mechanisms (abrasion, corrosion, cavitation, etc.).
Proactive and predictive maintenance are excellent partners in the fight against unreliability. Proactive maintenance reduces the likelihood of failure and predictive maintenance reduces the severity of each failure event. One can draw an analogy to the healthcare industry. Routine monitoring and control of cholesterol is a proactive activity. If high cholesterol is detected, it does not indicate that a heart attack is in progress. However, high cholesterol does increase the rate at which the plaque builds up on the arteries, which places increased stress on the affected organ, thus accelerating activity of the failure mechanism.
An electrocardiogram (EKG), on the other hand, is a predictive monitoring activity because it targets early stage heart disease. Life insurance companies know the relationship between proactive and predictive monitoring. When an individual is negotiating for a new policy or increasing the coverage of an existing one, he is usually subjected to a battery of tests. Some of these tests are predictive in nature, designed to detect any current illnesses that might be life-threatening (heart disease, cancer, etc.). Other tests are proactive in nature, designed to evaluate the likelihood that the insured will contract a life-threatening disease during the policy period. This information is used along with other information to adjust the standard rate tables based upon age.
Life insurance and equipment reliability assurance are risk-management activities. Like several other key equipment maintenance tools, lubricant analysis has proven to be an indispensable tool in the fight against machine failure, and a significant asset in failure diagnosis and root cause analysis.
Strategic Lubricant Analysis
Lubricant analysis benefits the organization in several ways, before, during and after the occurrence of machine failure (Figure 4).
Before the onset of failure, lubricant analysis confirms that the machine contains the right lubricant and that the lubricant is physically and chemically fit for service.
It also confirms that contamination levels are within tolerable limits. These are proactive applications of lubricant analysis that extend the life of the equipment. In some cases, proactive lubrication management can extend component life more than 10 times, generating significant profits for the organization.
When a machine fails, wear debris, which is detectable using lubricant analysis, is produced well in advance of any observable operational deterioration. The early warning of lubricant analysis gives the maintenance team options. Also, lubricant analysis plays a key role in diagnosing problems once they are detected. When a problem is detected, operations typically inquires about the projected time of failure, or the probability that the machine will last until some defined date, usually the date of the next scheduled outage. While prognostics, the process of estimating the failure date, is the least precise of the condition-monitoring activities, it provides some insight. Prognostic estimates are improved when multiple data parameters are defined. Lubricant analysis plays an important role here.
When a machine fails, we sometimes fail to analyze the oil from the failed machine. The oil contains the remnants of the failure. Just as a forensic scientist uses evidence collected at the crime scene in an attempt to piece together a picture of a murder, a reliability engineer analyzes evidence collected at the scene of the failure to gain an understanding of how the machine failed and why. While uncovering the underlying root cause of failure won’t bring back the failed piece of equipment, it will make possible the deployment of root cause control measures to prevent failures.
In addition to in-service oils, lubricant analysis is an important tool in the efforts to assure the quality of new lubricant deliveries, storage effectiveness and recondition or reclamation activities. Analysis helps make certain that lubricants are fit for service.
Strategic alignment of lubricant analysis to organizational objectives should begin with an audit of the program’s component parts. The audit should identify the program’s strengths and weaknesses, and evaluate how resources are allocated. Often, the audit reveals that a machine was brought into the program for the wrong reasons. For example, plants often decide to include or exclude a machine based upon sump volume (include machines with sump volume greater than 30 gallons). Sump volume is not a mission-driven decision process. The cost of the oil is inconsequential in the big picture. The decision to include a machine for routine lubricant analysis must be based upon the effect a failure will have on production, safety or environmental compliance, the cost to repair or restore the equipment and/or the likelihood that a failure will occur.
In some cases, specialty tests might be included in the test slate because of a desire to avoid an oil change in a large system, but reservoir volume shouldn’t be the driving motivation. For example, large steam turbines have very large reservoirs and lubrication delivery systems. The rotating pressure vessel oxidation test (RPVOT) is often run on these systems to evaluate the lubricant’s ability to prevent base oil oxidation. If the base oil is degraded, a great deal of oil must be changed or reclaimed which is expensive in itself, but the time to undertake the activity is significant. Likewise, if the base oil degrades, there is a good chance that the reservoir and the piping will become varnished. The system cleanup job significantly increases the total cost of the oil change.
Mission criteria should also drive the frequency of lubricant analysis. Some machines are simply more important than others. They deserve more resources within the program. The likelihood that failure will occur and volatile lubrication challenges (high temperature, risk of contamination, etc.) are also factors that drive the analysis frequency decision.
It is not uncommon for oil analysis programs to be developed because an individual or group takes an interest, or because a manager wants to keep up with what he perceives other plants are doing. Without question, the passion of an individual or group is a necessary ingredient to success with lubricant analysis, or any other program for that matter, and nothing evokes passion as powerfully as competition. However, the program must appropriately align with the mission of the organization. Lubricant analysis programs that fail to align with the objectives of the organization may be wasteful, and are susceptible cutback targets. Program managers should periodically review the oil analysis program relative to mission of the maintenance organization, the plant and the corporation and make necessary adjustments to correct strategic misalignment to keep the program on-track for success.
Simply stated, manage the program to ensure that resources are wisely allocated to maximize the return to the organization.