Predictive maintenance benefits

Another method used by some plants to acquire data is hand-held transducers. This approach is not recommended if it is possible to use any other method. Hand-held transducers do not provide the accuracy and repeatability required to gain maximum benefit from a predictive maintenance program. If this technique must be used, extreme care should be exercised to ensure that the same location, orientation, and compressive load are used for every measurement. Illustrates a hand-held device. 

The only useful function of broadband analysis is longterm trending of the gross overall condition of machinery. Typically, sets of alert/alarm limits are established to monitor the overall condition of the machine-trains in a predictive maintenance program. However, this approach has limited value and, when used exclusively, severely limits the ability to achieve the full benefit of a comprehensive program. 

A side benefit of predictive maintenance is the automatic ability to monitor the mean-time-between-failures, MTBF. This data provides the means to determine the most cost-effective time to replace machinery rather than continue to absorb high maintenance costs. The MTBF of plant equipment is reduced each time a major repair or rebuild occurs. Predictive maintenance will automatically display the reduction of MTBF over the life of the machine. When the MTBF reaches the point that continued operation and maintenance costs exceed replacement cost, the machine should be replaced. 

Several other benefits can be derived from a viable predictive maintenance management program verification of new equipment condition, verification of repairs and rebuild work and product quality improvement. 

The overall benefits of predictive maintenance management have proven to substantially improve the overall operation of both manufacturing and process plants. In all surveyed cases, the benefits derived from using condition-based management have offset the capital equipment cost required to implement the program within the first three months. Use of microprocessor-based predictive maintenance techniques has further reduced the annual operating... 

Vibration analysis is the dominant technique used for predictive maintenance management. Since the greatest population of typical plant equipment is mechanical, this technique has the widest application and benefits in a total plant program. This technique uses the noise or vibration created by mechanical equipment and in some cases by plant systems to determine their actual condition. 

The chapters on establishing and maintaining a total plant predictive maintenance program will provide the practical knowledge required implementing a cost-effective vibration-based program that will provide maximum benefits. 

Many of the predictive systems manufacturers are strictly hardware and software oriented. Therefore, they offer minimal training and no application training or technical support. Few plants can achieve minimum benefits from predictive maintenance without training and some degree of technical support. It is therefore imperative that the selected system or system vendors provide a comprehensive support package that includes both training and technical support. 

The second method uses dynamic limits that monitor the rate of change in the measurement parameters. This type of monitoring can detect minor deviations in the rate that a machine or system is degrading and anticipate when an alarm will be reached. The use of dynamic limits will greatly enhance the automatic diagnostic capabilities of a predictive maintenance system and reduce the manual effort required to gain maximum benefits. 

To be successful, a predictive maintenance program must be able to quantify the cost-benefit generated by the program. This can be achieved if the program is properly established, uses the proper predictive maintenance techniques and has measurable benefits. The amount of effort expended to initially establish the program plant is directly proportional to its success or failure. Proper implementation of a predictive maintenance program must include the items listed in Sections 50.5.1-50.5.5. 

To meet the above challenges, two ftmdamental initiatives are under way, namely, shifts to reliability-centered maintenance and predictive maintenance. Broadly speaking, prior to the maintenance revolution, the utilities maintenance approach had essentially been one of preventive maintenance on all components after fixed time intervals, irrespective of the components criticality and actual condition. The shortcomings of this approach included the following (1) overly conservative maintenance requirements, (2) limited gains in reliability from investments in maintenance, (3) inadequate preventive maintenance on key components, and (4) added risk of worker exposure to radiation through unnecessary maintenance. Anticipated benefits of the revised approach are related not only to reduced maintenance costs but also to improved overall operational reliability. 

In order to be successful any maintenance department needs strong internal customer—suppher partnerships. Such partnerships require opportunity for mutual benefits, predictable performance by each partner, and communication across links. 

Inhaled corticosteroids do have a role in COPD. They should be prescribed for patients with an FEV, <50% predicted, with two or more exacerbations in 12 months that require antibiotics or oral corticosteroids. These patients are still breathless despite monotherapy with a long-acting beta2-agonist. Maintenance use of oral corticosteroids is not recommended, but some patients with advanced COPD may require them. Oral corticosteroids should be used in all patients admitted to hospital with an exacerbation of COPD. There is insufficient evidence to establish the minimum dose of inhaled corticosteroids to obtain benefit (NICE, 2004). 

These findings prompted the development and evaluation of the currently available form of inhaled tobramycin, which is sterile and free of preservatives. The benefit of maintenance therapy with this inhaled tobramycin is supported by the results from two 24-week, multicenter, randomized, double blind, placebo-controlled clinical trials [6]. In these studies, patients with cystic fibrosis were at least six years of age, with an FEVj between 25% and 75% predicted. All subjects had evidence of colonization with Pseudomonas aeruginosa. Exclusion criteria included an elevated serum creatinine or colonization with Burkholderia cepacia, which is typically resistant to tobramycin. Subjects in the active treatment arm received inhaled tobramycin 300 mg twice daily through... 

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