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Failure Prevention Efforts
3 Failure Prevention Efforts
If the number of machinery failures in a certain plant is too large, everybody will concentrate on the “firefighting” and may lose sight of the whole situation. The safe, fast, cheap, and effective repair of failed machines is only part of the job. Even though the lessons learned through the analysis of failures should be incorporated into the day-to-day life of the plant, it should be considered a reactive action, as it is done after the fact. Effective proactive actions also should take place in a competitive plant. Some examples follow; an in-depth discussion is beyond the scope of this book: 1. Predictive maintenance, such as vibration and performance monitoring and analysis. 2. Preventive maintenance, such as cleaning and lubrication. 3. Spare parts management. 4. Operator and mechanics training. 5. Reliability-centered maintenance. 6. Benchmarking, to know the objectives. 25
26
Introduction to Failure Analysis
This chapter contains a brief discussion of how to organize a plant to avoid equipment failures, using the information obtained through a failure analysis program and other methods.
3.1 Types of Failures Spend some time in a process machinery repair shop and you will be amazed by the vast amount of different types of failures that can exist. Each piece of equipment has dozens, maybe hundreds of parts. Each part may fail in several different ways. Each process plant has hundreds of machines installed. If all the possible failure modes of all the components of all the machines are put together, too large a number of possibilities is created. The normal way to handle big problems is to divide them into smaller ones and solve the most important one first. Therefore, similar types of failure modes can be grouped and a common solution applied to them. For example, reduced mechanical seal life is a common problem within the processing industry. Many strategies can be used to face this issue, including standardization, design reviews, and so forth. A failure source to analyze carefully is human error. The quantity of errors made by a person is a function of the level of training, motivation, stress, and the support provided that person by the instruments and supervisors. This source of failure includes maintenance and operation errors caused by the ineffective action of the involved persons. Some general rules to avoid human errors include these: 1. Do not assign people for continuous observation of process parameters; this is best done by a computer. 2. All possible operation tasks should be automated, including emergency operations. 3. Every person involved should be trained, and this training reinforced from time to time. Periodic auditing can prove a powerful tool to avoid problems. 4. Adequate tools and equipment should be provided.
Failure Prevention Efforts
27
3.2 Prevention of Failures The next step after a successful failure analysis is the implementation of preventive measures. A word of caution: No design, operation, or maintenance modifications should be done without a careful examination of all the consequences of the modification, including a risk analysis. Preventive action can be quite varied, ranging from the modification of an operating procedure to the replacement of the failed machine. The huge number of possibilities makes it impossible to do more than just mention some examples: 1. Component standardization has enormous advantages—reduction of inventory, standardization of maintenance and operation procedures, and reduction of mean time to repair. Many components can be standardized easily, like mechanical seals, couplings, antifriction bearings, small turbine governors, and lubrication oil. The introduction of a state-of-the-art component can solve many reliability problems, especially in older plants using outdated equipment. 2. Operation and maintenance procedures can be modified to reduce failures. 3. Machines and installations may need design modifications, such as installation of new mechanical seals or more effective lubricants, improvements in the bearing housing sealing, modifications in control systems to avoid cavitation, or installation of modern antisurge systems. The effective implementation of the preventive action depends on the importance of the problem to the plant. In the process plant industry, problems related to safety, environment, production reliability, and cost are ranked very high on the priority scale. When the results are evaluated, the use of key performance indicators (KPI) can be helpful. The most useful KPI to evaluate rotating machinery are mean time between failures, mean time to repair (MTTR), and maintenance cost. Of course, safety and environmental indicators are included.
28
Introduction to Failure Analysis
3.3 Machinery Monitoring and Anticipatory Action Failure analysis is a powerful tool to improve machinery reliability. Nevertheless, keep in mind that it is not necessary to wait for any machinery failure to apply the best practices known to the industry. In addition to analyzing failures and implementing preventive action, it is necessary to avoid foreseeable failures. This is the reasoning behind preventive and predictive maintenance strategies. Therefore, machine monitoring programs should be instituted as soon as possible. The same should be done with preventive maintenance programs, operator and mechanic training, and the like. Machine monitoring should include 1. Performance monitoring, with periodic or on-line monitoring of head, efficiency, absorbed power, and a comparison to baseline values. 2. Condition monitoring, including vibration, bearing temperature, oil temperature, noise, seal leakage, rod drop, valve temperature, and the like. 3. Preventive maintenance, such as lubrication, cleaning, and periodic inspections. 4. Critical machinery without spare components should be monitored continuously.
3.5 Operator’s Role in Machinery Reliability Many times, process plant operators are blamed for machinery failures. Although this may be true in some places, the best plants recognize that the operators play an extremely important role in machinery reliability. This can be easily understood when we compare a careless driver with a conscientious one, normally the latter will have fewer problems with a car. The same applies to process plant operators, who should be trained and motivated on how to get the most out of the equipment.
Failure Prevention Efforts
29
Some examples of actions taken by a reliability focused plant, in addition to providing operator training and other working conditions, are 1. Instructing the operators about the design limits of the equipment and the consequences of off-design operation. 2. Instructing the operators on how the machines are designed and built, so they can understand the possible consequences of their acts. 3. Installing automatic monitoring of process and condition parameters, with adequate alarms and automated trips. This keeps operators doing what a computer cannot do for them, that is, inspecting the plant to make sure everything is working well. 4. Involving plant operators in all jobs related to reliability, for example, discussion of the predictive maintenance strategy and failure analysis.
If the number of machinery failures in a certain plant is too large, everybody will concentrate on the “firefighting” and may lose sight of the whole situation. The safe, fast, cheap, and effective repair of failed machines is only part of the job. Even though the lessons learned through the analysis of failures should be incorporated into the day-to-day life of the plant, it should be considered a reactive action, as it is done after the fact. Effective proactive actions also should take place in a competitive plant. Some examples follow; an in-depth discussion is beyond the scope of this book: 1. Predictive maintenance, such as vibration and performance monitoring and analysis. 2. Preventive maintenance, such as cleaning and lubrication. 3. Spare parts management. 4. Operator and mechanics training. 5. Reliability-centered maintenance. 6. Benchmarking, to know the objectives. 25
26
Introduction to Failure Analysis
This chapter contains a brief discussion of how to organize a plant to avoid equipment failures, using the information obtained through a failure analysis program and other methods.
3.1 Types of Failures Spend some time in a process machinery repair shop and you will be amazed by the vast amount of different types of failures that can exist. Each piece of equipment has dozens, maybe hundreds of parts. Each part may fail in several different ways. Each process plant has hundreds of machines installed. If all the possible failure modes of all the components of all the machines are put together, too large a number of possibilities is created. The normal way to handle big problems is to divide them into smaller ones and solve the most important one first. Therefore, similar types of failure modes can be grouped and a common solution applied to them. For example, reduced mechanical seal life is a common problem within the processing industry. Many strategies can be used to face this issue, including standardization, design reviews, and so forth. A failure source to analyze carefully is human error. The quantity of errors made by a person is a function of the level of training, motivation, stress, and the support provided that person by the instruments and supervisors. This source of failure includes maintenance and operation errors caused by the ineffective action of the involved persons. Some general rules to avoid human errors include these: 1. Do not assign people for continuous observation of process parameters; this is best done by a computer. 2. All possible operation tasks should be automated, including emergency operations. 3. Every person involved should be trained, and this training reinforced from time to time. Periodic auditing can prove a powerful tool to avoid problems. 4. Adequate tools and equipment should be provided.
Failure Prevention Efforts
27
3.2 Prevention of Failures The next step after a successful failure analysis is the implementation of preventive measures. A word of caution: No design, operation, or maintenance modifications should be done without a careful examination of all the consequences of the modification, including a risk analysis. Preventive action can be quite varied, ranging from the modification of an operating procedure to the replacement of the failed machine. The huge number of possibilities makes it impossible to do more than just mention some examples: 1. Component standardization has enormous advantages—reduction of inventory, standardization of maintenance and operation procedures, and reduction of mean time to repair. Many components can be standardized easily, like mechanical seals, couplings, antifriction bearings, small turbine governors, and lubrication oil. The introduction of a state-of-the-art component can solve many reliability problems, especially in older plants using outdated equipment. 2. Operation and maintenance procedures can be modified to reduce failures. 3. Machines and installations may need design modifications, such as installation of new mechanical seals or more effective lubricants, improvements in the bearing housing sealing, modifications in control systems to avoid cavitation, or installation of modern antisurge systems. The effective implementation of the preventive action depends on the importance of the problem to the plant. In the process plant industry, problems related to safety, environment, production reliability, and cost are ranked very high on the priority scale. When the results are evaluated, the use of key performance indicators (KPI) can be helpful. The most useful KPI to evaluate rotating machinery are mean time between failures, mean time to repair (MTTR), and maintenance cost. Of course, safety and environmental indicators are included.
28
Introduction to Failure Analysis
3.3 Machinery Monitoring and Anticipatory Action Failure analysis is a powerful tool to improve machinery reliability. Nevertheless, keep in mind that it is not necessary to wait for any machinery failure to apply the best practices known to the industry. In addition to analyzing failures and implementing preventive action, it is necessary to avoid foreseeable failures. This is the reasoning behind preventive and predictive maintenance strategies. Therefore, machine monitoring programs should be instituted as soon as possible. The same should be done with preventive maintenance programs, operator and mechanic training, and the like. Machine monitoring should include 1. Performance monitoring, with periodic or on-line monitoring of head, efficiency, absorbed power, and a comparison to baseline values. 2. Condition monitoring, including vibration, bearing temperature, oil temperature, noise, seal leakage, rod drop, valve temperature, and the like. 3. Preventive maintenance, such as lubrication, cleaning, and periodic inspections. 4. Critical machinery without spare components should be monitored continuously.
3.5 Operator’s Role in Machinery Reliability Many times, process plant operators are blamed for machinery failures. Although this may be true in some places, the best plants recognize that the operators play an extremely important role in machinery reliability. This can be easily understood when we compare a careless driver with a conscientious one, normally the latter will have fewer problems with a car. The same applies to process plant operators, who should be trained and motivated on how to get the most out of the equipment.
Failure Prevention Efforts
29
Some examples of actions taken by a reliability focused plant, in addition to providing operator training and other working conditions, are 1. Instructing the operators about the design limits of the equipment and the consequences of off-design operation. 2. Instructing the operators on how the machines are designed and built, so they can understand the possible consequences of their acts. 3. Installing automatic monitoring of process and condition parameters, with adequate alarms and automated trips. This keeps operators doing what a computer cannot do for them, that is, inspecting the plant to make sure everything is working well. 4. Involving plant operators in all jobs related to reliability, for example, discussion of the predictive maintenance strategy and failure analysis.