1、Best Practices Entry: Best Practice Info:a71 Committee Approval Date: 2000-04-24a71 Center Point of Contact: KSCa71 Submitted by: Wilson HarkinsSubject: Predictive Maintenance Program Practice: Predictive maintenance is a technique that allows for a systematic method of monitoring and trending of eq
2、uipment condition. This activity takes place while equipment is on-line and provides early warning of equipment operation approaching out of limit conditions.Programs that Certify Usage: This practice has been used by the Kennedy Space Center Shuttle Processing Contractor and Base Operations Contrac
3、tor Predictive Maintenance Programs for Ground Support and Facilities Equipment, U. S. Industry (Utility, Manufacturing, Processing, etc.).Center to Contact for Information: KSCImplementation Method: This Lesson Learned is based on Maintainability Technique number OPS-13 from NASA Technical Memorand
4、um 4628, Recommended Techniques for Effective Maintainability. Predictive maintenance allows for scheduling of maintenance when it is required and when it will have the least effect on scheduled activities requiring support of the equipment in question. Unexpected equipment breakdowns and scheduled
5、maintenance downtime for periodic disassembly and inspection to determine equipment condition are virtually eliminated. Additional discussion of the benefits of predictive maintenance is provided in the following pages.Predictive maintenance is a technique which checks the “health“ of an item while
6、it is operating using one or more sophisticated tools. The capabilities for predictive maintenance exist because of Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-the availability of desktop computers, and the increased sophistication of equipment m
7、onitoring instruments. Too much or too little maintenance is avoided because the equipment is monitored on a regular basis providing trend data that can be used to project probable machine alarm dates. According to the Electric Power Research Institute (EPRI), the annual maintenance cost of such a p
8、rogram is reduced by 50% or more to between $7 and $9 per horsepower.Predictive maintenance has received a great deal of attention in the past five years or more. U. S. industry spent $200 billion in 1985 alone, to maintain plants and equipment. Studies by the EPRI show that the annual maintenance c
9、ost of repairing machinery when it breaks down (corrective maintenance) is $17 to $18 per horsepower. Contrasted to that is preventive maintenance, which uses statistics to determine the probable health of equipment. However, in the real world, machines do not follow averages. The result is usually
10、“over maintenance“ or “under maintenance.“ The EPRI Studies show that the annual maintenance cost per horsepower using preventive maintenance is between $11 and $13. As was stated earlier, the EPRI study shows that predictive maintenance reduces manual maintenance costs to between $7 and $9 per hors
11、epower.Benefits from implementing a Predictive Maintenance Program include:a71 Condition of equipment under a predictive maintenance program is known, permitting repairs to be planned and carried out without interrupting scheduled support activities.a71 Reduced maintenance costs are realized through
12、 the use of predictive maintenance. Maintenance needs can be anticipated and planned. Maintenance activities are more efficiently planned from a standpoint of manpower, parts, and tools. Catastrophic failures, which impose secondary, expensive damage, are also avoided.a71 Improved equipment performa
13、nce is achieved through the use of predictive maintenance. Predictive maintenance measures equipment condition so that corrections can be made before performance is compromised.a71 Predictive maintenance provides several potential areas for energy savings. Elimination of high energy vibration source
14、s such as misalignment and imbalance will reduce machine power consumption. Motor phase imbalance, which increases power consumption can be corrected resulting in savings in power and increased motor life.Technical DescriptionPredictive (or condition-based) maintenance is an outgrowth of a preventiv
15、e maintenance program. Todays state of the art technologies, readily available user friendly desk top computers, and increased sophistication of equipment monitoring instruments, now make it possible to have a reliable and cost effective predictive maintenance program.The first step in developing an
16、 effective predictive maintenance program is to determine the cost of the maintenance program such as cost for maintenance personnel, repairs, spares and cost associated with losses incurred due to equipment being down. The next step is to identify the number of man-Provided by IHSNot for ResaleNo r
17、eproduction or networking permitted without license from IHS-,-,-hours required to monitor the equipment. Simple machinery (motors, pumps, or fans) will require fewer points to accurately detect developing problems than more complex equipment, such as turbines or generators. By counting the pieces o
18、f equipment and the number of measurement points, you can estimate the level of manpower required.More critical equipment may require more frequent monitoring, which will increase manpower requirements. The monitoring frequency is a function of the critical nature of the equipment; so the next step
19、is to set up an equipment classification system. For example:a71 Class 1 - essential equipment - includes equipment that must be on-line to continue all or a major part of a process. Loss of this equipment would have a major impact on safety, productivity and availability. Also included in this grou
20、p would be equipment that has a high repair cost, or a long lead time for ordering repair parts.a71 Class 2 - critical equipment - includes equipment that would limit a major part of a process, and equipment with high initial replacement costs, or chronic maintenance problems.a71 Class 3- serious eq
21、uipment - includes equipment that is not critical to process, but require monitoring to ensure acceptable process performance.a71 Class 4 - other equipment - includes high speed or high load machinery that is prone to premature failure because of its severe operating mode, but is not considered crit
22、ical to the process.Once equipment has been properly grouped, the data acquisition schedules and routes can be established; and projected manpower levels determined. If sufficient staff is not available, the potential savings from the program must justify additional personnel.Besides salaries, costs
23、 should include the cost of diagnostic and analytical equipment, office space, and any overhead costs that will be charged to the group. Costs should also include training and additional skill development. Training costs can range from a few hundred to a few thousand dollars in the first year; depen
24、ding on the level of experience and the size of the staff.A typical predictive maintenance system contains four main components: a microprocessor based data collector, a host computer, software and transducers. Each is an important element and it is important that they function well as a total syste
25、m. Some important characteristics of the integrated system to consider are:a71 User friendly software and hardware. The predictive maintenance program will often be staffed with technicians and engineers that understand the mechanics of machine operation but not necessarily computers. Hardware and s
26、oftware must be designed for simple, straightforward operation. Error correction should be simple, but it should not allow the free form modification of data.a71 Automated data acquisition management and trending. The object of using a microprocessor based data collector and a host computer is to re
27、move the possibility of human error during Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-data input, minimize manpower requirements, and automate as much of the data handling as possible.a71 Flexibility. The system should be capable of collecting,
28、storing and presenting data such as vibration data in a variety of formats (displacement, frequency, velocity, acceleration, cpm) and providing accurate data analysis. The system should accurately accept any commercially available transducer input.a71 Reliability. The hardware and software should ha
29、ve proven field experience. Ask for a users list and find out strengths or weaknesses from people who have experience with the system.a71 Accuracy. Data must be accurate and repeatable since decisions on equipment condition will be made based on the information that is collected and analyzed.a71 Tec
30、hnical support. Training and technical support is a very important consideration. A properly configured predictive maintenance system should provide valuable information with a minimum level of manpower, and only a limited knowledge of the theory behind the predictive maintenance techniques used. Ea
31、ch system will, however, require some training in the basics of data base development and diagnostics.a71 Report generation. Maximum flexibility in format and content is important and the system should be able to generate reports at several levels of detail. Examples of the types of reports the syst
32、em should be able to produce are: a72 Exception report. This report consists of listing equipment that have exceeded one or more alarm or alert limits, missing data points, notepad observations, or equipment with a predicted failure before the next scheduled measurement date.a72 Last measurement rep
33、ort. This report is a listing of components, notepad observations, project failure time, and missed measurement points. The report would include information shown on the exception report and a complete review of all equipment.a72 A machine history report recapping total equipment history including a
34、ll components.If the system does not automatically generate these reports the manpower requirements can increase substantially.If a limiting factor is staff levels or experience; or if the cost-benefit analysis is inconclusive, a pilot program may be the best solution. Equipment vendors will help es
35、tablish a program and phase out their support as the in-house staff becomes proficient. This option allows the development of financial benefits, provides hands-on training for the in-house staff, and develops a data base. Another option is to contract with an outside company to run the program. Wit
36、h this option, the need for additional in-house staff is eliminated, as is the need for an investment in data acquisition and analysis equipment. One should avoid vendors who quote fixed price per measurement point regardless of the type of equipment. Because of the type of equipment being measured
37、complexity of the measurements will vary and also their cost. A price based on equipment type (motors, pumps vs turbines, generators) should be requested.There are numerous techniques available for implementing a Predictive Maintenance Program. Techniques that may be found in various predictive main
38、tenance programs include:Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-a71 Vibration analysis which is performed on mechanical equipment to evaluate the online condition of its mechanical parts, and effect on related pieces of equipment. Effectiven
39、ess of vibration mounts, shafts, bearings, coupling alignment and impeller balance are measured and monitored to determine if equipment is functioning properly and within specifications.a71 Ferrography Analysis, a wear particle analysis being diagnostic and predictive techniques to evaluate the on-l
40、ine condition of interacting lubricated or fluid powered parts. Lubricants or fluids are analyzed for condition, level and type of contamination. A wide array of problems with equipment, the lubricants/fluids and maintenance methods can be determined by use of ferrography. Utilization of oil analysi
41、s has and will continue to expand the existing life of critical equipment.a71 Thermography is used to analyze equipment that exhibits over-heating and heat links when not operating properly. This includes equipment as varied as circuit breaker panels, electronic circuit boards, cryogenic piping, GN2
42、heaters and many others.a71 Laser Alignment is used to detect misalignment in mechanical equipment components that can lead to accelerated wear or possible catastrophic failure. It is used to verify proper installation and even fabrication of mechanical equipment before operation. It is also used fo
43、r online monitoring to ensure proper alignment is maintained during equipment operation. Correct alignment will reduce power consumption.a71 Motor Analysis is used to determine the level of degradation in electrical motor circuits, such as individual phase resistance from power bus disconnect throug
44、h the motor windings, phase to ground resistance, inductance of motor coils and capacitance of each phase to ground. Detecting and correcting phase imbalance saves in power consumption and prevents motor core reduction.a71 Ultrasonics is that technology used to detect hidden flaws in materials, espe
45、cially metals. This technology has advanced into a completely digital and portable microprocessor-controlled ultrasonic flaw detector. It is safe and faster than using X-Ray technology to detect flaws.a71 Visual inspection where plant or maintenance engineers, on a regular basis, visually inspect ea
46、ch critical system.A comprehensive predictive maintenance program is composed of several techniques which, when combined, can predict most mechanical and electrical problems found in equipment.References1. Lockheed Space Operations Company Predictive Engineering Technology Program Implementation Pla
47、n, 10/94.2. EG&G Florida, KSC Predictive Maintenance Plan, EGG-4061130, 11/20/92.3. P/PM Technology Publications (issues from 1986 or present).4. Maintenance Technology Publications (issues from 1993 to present).Impact of Non-Practice: Provided by IHSNot for ResaleNo reproduction or networking permi
48、tted without license from IHS-,-,-Predictive maintenance is a technique which checks the “health“ of an item while it is operating using one or more sophisticated tools. The capabilities for predictive maintenance exists because of the availability of desktop computers, and the increased sophisticat
49、ion of equipment monitoring instruments. Too much or too little maintenance is avoided because the equipment is monitored on a regular basis providing trend data that can be used to project probable machine alarm dates. According to the Electric Power Research Institute (EPRI), the annual maintenance cost of such a program is reduced by 50% or more to between $7 and $9 per horsepower.Related Pr
