The Role of Condition MonitoringWhen it comes to maintaining a car, there are several different schools of thought. Some car owners follow the manufacturer’s guidelines for maintenance, scheduling preventive checks on a regular basis. Others take their cars in for a check-up when “it just doesn’t sound right.” Still others run their cars until they break.

      Much the same can be said for maintenance of equipment in industrial plants. Some companies follow a regimented maintenance schedule; others try to anticipate problems by keeping tabs on equipment condition; and still others run equipment until a breakdown occurs. The difference is, those breakdowns can be expensive. In fact, in the average manufacturing plant, an unscheduled outage can cost anywhere from $6,000 to $90,000 per hour.

      In today’s cost-competitive, fast-changing business environment, the old adage
“If it’s not broken, don’t fix it” no longer has a place. Instead, many organizations are
evolving toward reliability-centered maintenance programs — relying on condition monitoring technology to help guide their efforts.
Taking the first step

According to Bart Bartholomew, Manager of Condition Monitoring Development for SKF USA Inc., equipment maintenance practices still vary widely among individual companies. Most, however, have shifted away from “reactive” maintenance techniques.

      “A number of factors are causing companies to rethink their maintenance practices and focus their resources on predicting and avoiding problems, instead of correcting them after they happen,” Bartholomew says. “First, most companies are operating with smaller maintenance and operations staffs that are being asked to do more. Second, they’re trying to increase their throughput and production rates, which means rotating equipment is running faster and handling larger loads than in the past. Third, companies are striving to be more competitive in general, by operating as lean as possible.”

      Taken together, these trends are driving companies to use predictive maintenance techniques — ways to avert trouble and keep operating, repair and maintenance costs to a minimum. As Bartholomew explains, the most sophisticated form of predictive maintenance is reliability-centered maintenance, a practice many companies are evolving toward today. With reliability-centered maintenance, the focus is on maximizing equipment reliability and the resulting uptime by targeting maintenance where it’s needed most. When problems do occur, the root cause is carefully documented and steps are taken to assure the same issues don’t recur.
The role of monitoring

At the heart of most reliability-centered maintenance programs is condition monitoring, a process that measures specific parameters to assess machine condition during operation. Parameters such as temperature, velocity, vibration, acoustics and lubricating oil condition all provide indicators of a machine’s operating condition and can signal impending problems. By charting regular readings on those variables through a program of condition monitoring, system operators can accurately assess machine condition and make more informed, effective decisions about maintenance.

      “Condition monitoring allows you to hone in on equipment that needs attention and avoid wasting maintenance resources on equipment that
is in good working order,” Bartholomew explains.
The resulting benefits can be sizable and far-reaching — from extending equipment service life and minimizing repairs,
to boosting productivity and reducing operating costs.

      Condition monitoring is used primarily on rotating equipment — machinery that typically involves a bearing of some kind. Drawing on its extensive experience in the bearings industry, SKF is committed to providing condition monitoring products and services that can help
customers maximize equipment reliability and minimize downtime.

      “SKF sees condition monitoring as an extension of our TFO (Trouble-Free Operation) program,” Bartholomew says. “The goal of TFO is to help customers increase productivity and maximize machine
uptime, by improving equipment reliability and preventing unnecessary bearing failures. By offering a variety of condition monitoring products and services, SKF is able to help companies apply those principles to rotating equipment.”
A matter of focus

Implementing a condition monitoring program involves two key considerations: which equipment to monitor and what form of monitoring to use. To answer the first question, organizations need to establish each machine’s level of priority, which is affected by several factors.

      “The most likely candidates for condition monitoring include equipment that is critical to production, is running at its design limit, is particularly expensive to repair or replace, or is handling dangerous material that could pose a safety risk,” Bartholomew says. Companies also should monitor equipment that typically operates unattended or at a remote site, he adds.

      When deciding what form of condition monitoring to use, companies can choose from two general categories.
Periodic monitoring involves taking measurements at regular intervals, typically with hand-held instruments, while continuous monitoring requires the use of permanently installed equipment
that logs measurements on an ongoing basis.

      Periodic monitoring involves using small, portable instruments that take a basic reading of vibration and other variables. Following a pre-defined route, a system operator or SKF technician can use such instruments as an early
warning device — looking for readings that fall outside the norm for each particular piece of equipment.

      For instance, with the SKF Vibration Pen — a pocket-sized instrument — technicians can immediately view vibration readings on an LCD read-out. (See sidebar for more details.) For a broader assessment, SKF offers a hand-held computer called MARLIN, which allows operators to periodically
monitor a number of variables. Both devices are early warning monitors that signal an impending problem.
Honing in

“More sophisticated condition monitoring programs use diagnostic tools that not only warn of a problem, but also help to identify its specific source,” Bartholomew says. Periodic monitoring tools such as SKF’s Microlog data collectors can pinpoint what is causing an unusual reading — whether misalignment, imbalance, looseness, or another factor. When combined with data analysis software, these data collectors can help system operators hone in on potential trouble spots and identify the best course of action.

      For more critical equipment, continuous monitoring devices — hard-wired directly to
rotating machinery — can
provide greater protection and peace of mind. SKF’s Machinery Condition Monitoring units provide an early warning of potential problems, with alarm levels pre-programmed to note excessive readings. SKF’s Local Monitoring Unit goes a step further — by diagnosing the cause of the unusual reading and interfacing with a special software package that walks the
operator through the process of identifying its root cause.
The data gathered can even
be sent via the Internet to
SKF specialists for their review and analysis.

      No matter what form of monitoring a company chooses, one of the most important steps is to chart the data and look for trends in the readings, Bartholomew says. Each machine has its own “signature,” which indicates what is considered normal operating condition for that particular piece of equipment. By
starting with a baseline and charting trends over time,
system operators can easily spot changes that signal a deviation from the equipment’s “normal” readings.

      “When an equipment failure results in unexpected
downtime, the costs can be significant, involving not only equipment repair and replacement, but additional labor expenses, lost production, and lost opportunity,” Bartholomew says. “By providing a full range of condition monitoring solutions, SKF can help customers avoid those unexpected costs, improve their productivity, and ultimately compete better in their in-
dustries.”