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Equipment reliability can be improved and maintenance costs controlled by obtaining and utilizing better information about the condition of equipment and by changing outdated practices
Does this sound familiar? Because of constant breakdowns with the aging water and wastewater infrastructure in a large urban area, it is almost impossible to keep up with routine scheduled maintenance. Service interruptions are inevitable and the rising cost of emergency repairs is erasing any hope of fiscal responsibility.
Here’s another frequently heard scenario. The rapid growth of a large city in the south is overwhelming the current water distribution system and straining the already overworked staff.
Reliability is decreasing, costs are rising, maintenance crews are shrinking, and overtime for emergencies is going through the roof. Does anyone have a solution?
Actually, there are several solutions based on the proper application of technology and work processes. While specific requirements may vary depending on the situation, a typical list includes the need for greater equipment reliability, increased capacity for existing equipment, more effective maintenance, less overtime, and lower costs, of course. Various approaches are possible, but they generally boil down to one or a combination of the following:
Obtaining diagnostic information
Technology exists today to automatically obtain field-based information about the health and well being of a whole range of critically important pieces of machinery in water and wastewater treatment plants. Such information can be the basis for maintenance decisions leading to long-term, high-level performance.
One platform for optimizing asset availability and performance is Emerson’s AMS suite of software applications including the Machinery Health Manager, Intelligent Device Manager and Equipment Performance Monitor.
All types of rotating machinery, including motors, pumps, fans, turbines, and compressors can be continuously monitored online or on a periodic basis for changing vibration patterns—a sure sign of impending trouble. The problem is that most continuous monitoring systems only alarm when vibration becomes excessive, but provide no in-depth predictive information. The software evaluates the data from online condition monitoring, assigns a severity, and issues early warnings and diagnostic information as to the root cause. The warning and diagnostic information can automatically show up in the plant’s control system or come in the form of an e-mail or page. It could be radial rubbing, water induction, differential expansion, misalignment, coupling problems, balance, or lubrication issues. Other information sources, including oil analysis, infrared thermography, and historical data, are utilized by this software to provide a true picture of the operating condition of rotating assets and their potential for failure.
Device Manager may be an effective means of acquiring, processing, and presenting diagnostic information generated by field instruments, including transmitters, analyzers, and valve positioners.
According to the ARC Advisory Group, an independent organization providing strategic planning and technology assessment services, this software has become the standard for predictive maintenance of field devices. It communicates with both Hart and Foundation Fieldbus instruments to obtain essential information on their condition and that of equipment to which they are attached. Device alerts identify potential process problems, so corrective measures can be implemented in time to prevent costly shutdowns.
Performance Monitor uses thermodynamic models to compare the actual performance of machines such as blowers and variable speed pumps with their ideal performance. The data is automatically analyzed, and results are presented as trends, graphs, and cost summaries showing amounts being lost due to poor performance. This type of monitoring complements condition monitoring as a means of diagnosing problems in mechanical equipment.
The information captured by each of these technologies can be used in various ways to extend equipment life, reduce maintenance costs and increases overall process reliability. Plant workers gain a new perspective on the current condition of their rotating machinery, valves, and instrumentation, enabling them to take appropriate action as necessary to prevent unexpected failures and emergencies. Achieving these benefits is not difficult, but it requires an understanding of new approaches to maintenance that may not have been widely practiced in the past.
At a time when two-thirds of trips to the field by maintenance personnel typically result in no corrective action and nearly one-third of all dollars spent on maintenance is wasted, better procedures are clearly needed. Too many plants are managed reactively, which is the most expensive of all types of maintenance. If operators suspect a problem, they react by sending a maintenance person out to check. When something fails, everyone reacts in frenzy, spending whatever is necessary to get the plant up and running.
In an effort to stem the tide of failures or extend the mean time between failure, equipment manufacturers recommend preventive maintenance, and plant personnel are assigned to carry out suggested procedures. While this is an improvement over reactive maintenance, it’s time consuming and expensive. For one thing, manufacturers protect their interests by recommending that their equipment receives far more attention than may actually be necessary. If every PM task were carried out as called for by the manufacturers, no maintenance staff would be large enough, and little other work would get done.
A far more efficient system called reliability-based maintenance was first developed by Emerson in the 1980’s. Under this concept, all machinery is prioritized in order of importance to the overall mission. Obviously, certain pumps, valves, and instruments are critically important and must be maintained for maximum reliability, but it may not be necessary to give that same level of care to every piece of equipment. Some may even be allowed to run to failure with minimal attention if that will not adversely affect the overall operation of the treatment plant.
The idea is to efficiently allocate resources where they are most needed. Many old, schedule-based maintenance tasks can be delayed or totally eliminated. Using available diagnostic tools, managers can make more informed decisions as to when repair work should be done. Armed with never-before-available information on the actual condition of operating equipment, plant personnel can determine with reasonable accuracy when each pump, valve, or instrument will next need maintenance in order to preserve its performance. The idea is to service equipment at the proper time to minimize physical deterioration and unexpected failures while maintaining acceptable performance as long as possible. This is the essence of predictive maintenance, which is a practical outgrowth of the availability of accurate past and current operating information on process equipment. Such information was hard to get in the past, largely because the technologies described above simply did not exist.
However, software-based monitoring technologies are now making predictive maintenance programs much easier to execute.
It does little good to buy and install the latest diagnostic systems unless appropriate work practices are put in place. Too many companies invest in technology and expect a big payback without training personnel to utilize the information and without changing maintenance practices accordingly. Personnel must accept what technology is telling them and be willing to adopt new work routines to benefit from the change.
For example, a vibration monitoring and lube oil analysis program was started years ago in a midwestern power plant with the expectation that some maintenance tasks could be eliminated. But, that didn’t happen; instead, the old preventive maintenance program was continued, and new PMs were even added. The maintenance workload actually increased to the point that technicians could not get important work done.
Technology must be used to save a significant number of man-hours while providing greater protection for equipment or the investment in diagnostic systems will be wasted. Once an advanced technology is installed and employees are trained in its use, managers need to examine existing practices to see what tasks can be streamlined or eliminated.
Does it work?
It’s working for the city of Detroit Water & Sewage Department where an Reliability based maintenance program was instituted to combat a combination of an aging infrastructure, a growing number of emergencies, and a shrinking maintenance team. Multiple diagnostic technologies (vibration, oil analysis, infrared thermography, etc.) helped maintenance personnel identify machinery health problems early, allowing a favorable scheduling of repair activities. As a result, pumping availability has increased and OEM-recommended periodic maintenance has been cut back significantly.
It’s also working in the Tarrant Regional Water District in Texas, where “run to failure is no longer an acceptable option—not when continuous, online condition monitoring is available to trigger reliability centered maintenance,” according on one official.
“It is just too costly to let those big pumps run until something breaks.”
As a result, unexpected critical mechanical failures have been minimized, emergency costs have been reduced 20% and staffing requirements for new pumping stations in the growing district were cut in half.
Another growing city in the west has experienced a 35% reduction in emergency maintenance and a 28% reduction in preventive maintenance hours in its water purification and distribution system. Their predictive maintenance program is based on monitoring critical equipment to determine machinery health and identify problems prior to failure. The reduction of emergency maintenance resulted in increased reliability, reduced repair costs, and fewer service disruptions. By continually seeking ways to replace preventive or reactive maintenance with predictive, reliability-based maintenance, these cities and many others have found that the practical application of advanced monitoring technology results in greater equipment reliability along with reduced maintenance costs.