CGE676 Chapter 1 - Maintenance & Reliability Engineering PDF

MAINTENANCE & RELIABILITY ENGINEERING CGE676 Chapter 1 Concept of Reliability and Maintenance Engineering Faculty of Chemical Engineering Introduction Course Outcomes (CO) Describe the terms, concept and objectives of reliability engineering a...

MAINTENANCE & RELIABILITY ENGINEERING CGE676 Chapter 1 Concept of Reliability and Maintenance Engineering Faculty of Chemical Engineering Introduction Course Outcomes (CO) Describe the terms, concept and objectives of reliability engineering and maintenance engineering. Analyze the maintenance and reliability engineering problems and compare the best tools or solutions. Select the best tools to be used in maintenance and reliability engineering and justify its applications. Faculty of Chemical Engineering Chapter 1 Course Learning Outcomes Define Reliability Engineering Define objectives of Reliability Engineering Describe the theory and concepts of Reliability Engineering Apply basic mathematics of probability and statistical in engineering problems Faculty of Chemical Engineering  Development of maintenance & reliability engineering First generation maintenance (pre-WW2) Industry not highly mechanized so downtime not particularly important. Most equipment simple and over-designed Reliable and easy to repair. Eventually just wore out. Only systematic maintenance required - simple cleaning, servicing and lubrication. Philosophy: “Fix it when it breaks!” Reproduced with permission from Andrew K. S. Jardine Faculty of Chemical Engineering Second generation maintenance (WW2 to mid-70’s) More mechanisation and concern over downtime. Idea that failures could and should be prevented. Awareness of “burn-in” failure mode Bath-tub curve Increase in m) aintenance costs as a proportion of total operating costs. Development of first planning and scheduling tools. Philosophy: Preventative overhauls Reproduced with permission from Andrew K. S. Jardine Faculty of Chemical Engineering  3rd generation maintenance (mid-70’s +) Aircraft data identifies 6 different failure mode patterns. Growth of mechanisation and automation increases focus on plant availability and reliability. Effect of failures on HS&E becomes important as regulations tighten. Cost of maintenance increases: Often 1st or 2nd highest of all operating costs. New techniques become available to collect data that would enable maintainers to: To predict failures - Predictive Maintenance Optimise maintenance decisions - Asset Management Reproduced with permission from Andrew K. S. Jardine Faculty of Chemical Engineering So…Reliability… Can be defined as - The probability that an item/system will perform a required function without failure under stated conditions for a stated period of time Can also be expressed as the number of failures over a period A time dependent characteristic. It can only be determined after an elapsed time but can be predicted at any time. It is the probability that a product or service will operate properly for a specified period of time (design life) under the design operating conditions without failure. Faculty of Chemical Engineering Key variables for reliability Since reliability is defined as a probability, its definition will be based on a few key (random) variables, e.g. Time to failure Time between failures Number of failures in a given period of time Faculty of Chemical Engineering How reliability is measured? The probability of an item that does not fail in a time interval (0,t], survival probability Beside being measured as a probability, reliability can be quantified via e.g. the following parameters or metrics: Mean number of failures in a given time (failure rate) Mean time between failures (MTBF) – the average time between successive failures. Mean time to failure (MTTF) - the average time that elapses until a failure occurs. Faculty of Chemical Engineering Theory and basic concepts Qualitative reliability FTA, FMEA, FMECA Quantitative reliability Statistical reliability Physics-based reliability Maintenance Time-based maintenance Condition-based maintenance Faculty of Chemical Engineering  What is reliability? The probability that an item/system will perform a required function without failure under stated conditions for a stated period of time Symbol: R(t) General expression: Series configuration Parallel Configuration A number between 0 and t Faculty of Chemical Engineering Theory and basic concepts of RE What is….? Failure rate (λ) - the number of units failing per unit time. MTBF (Mean Operating Time Between Failures) The expectation of the operating time between failures Applies to equipment that is going to be repaired and returned to service MTBF = 1/ λ = Total time/number of failures MTTF (Mean Time To Failure) Expectation of the time to failure Applies to parts that will be thrown away on failing MTTF = 1/ λ = Total time/number of units under test Faculty of Chemical Engineering Theory and basic concepts of RE…(con’t) What is….? Bathtub curve – failure or hazard rate profile Faculty of Chemical Engineering Theory and basic concepts of RE…(con’t) What is….? Bathtub curve – failure or hazard rate profile Early failure period: At the start of the operating period, sometimes a higher failure rate is observed which decreases with time. Early failures occur due to manufacturing processes and material weaknesses that do not result in failures in tests (before shipping). Constant failure rate period: After the early failure period, the failures occur with varying failure causes that result in an effective constant failure rate during the useful life. Wear-out failure period: The final period that shows an increasing rate of failures due to the dominating effects of wear-out, ageing or fatigue. Faculty of Chemical Engineering Tutorial Question Theory and basic concepts of RE 1. A mechanical system had five random failures occur in an observation interval of 1,000 productive hours. Calculate failure rate and Mean Time Between Failure (MTBF) of the system. Faculty of Chemical Engineering Theory and basic concepts of RE 2. Assume that a system is composed of five independent and identical subsystems in series. The constant failure rate of each subsystem is 0.0025 failures per hour. Calculate the reliability of the system for a 50-hour mission and the system mean time to failure. Faculty of Chemical Engineering Theory and basic concepts of RE 3. A manufacturing plant produced 10 products within one day. For quality and assurance purposes, three identical products had been tested starting from t=0 until all failed. 1st product failed at 10 hrs, 2nd product failed at 12 hours and 3rd product failed at 13 hours. Calculate average MTTF for the product. Faculty of Chemical Engineering MAINTENANCE & RELIABILITY ENGINEERING CGE676 Chapter 1 Concept of Reliability and Maintenance Engineering Faculty of Chemical Engineering Introduction Course Outcomes (CO) Describe the terms, concept and objectives of reliability engineering and maintenance engineering. Analyze the maintenance and reliability engineering problems and compare the best tools or solutions. Select the best tools to be used in maintenance and reliability engineering and justify its applications. Faculty of Chemical Engineering For better understanding For example, if there is a vapor release, but no please see this video: source of ignition, then there will be no https://www.youtube.com/wa explosion. However, if there is both a release tch?v=MfWpMrEOlJ8&t=109s and a source of ignition, then an explosion will result. Reason’s Swiss Cheese model Reason developed the "Swiss cheese model" to illustrate how analyses of major accidents and catastrophic systems failures tend to reveal multiple, smaller failures leading up to the actual hazard. In the model, each slice of cheese represents a safety barrier or precaution relevant to a particular hazard. Poor Reliability Reliability What is reliability? “ability of an item to perform a required function under given conditions for a given time interval” IEC 60050 “… the probability that an item will perform a required function without failure under stated conditions for a stated period of time…” Smith, D.J. (2005) Faculty of Chemical Engineering Reliability What is reliability? “ability of an item to perform a required function under given conditions for a given time interval” IEC 60050 “… the probability that an item will perform a required function without failure under stated conditions for a stated period of time…” Smith, D.J. (2005) The probability that an item/system will perform a required function without failure under stated conditions for a stated period of time Faculty of Chemical Engineering Reliability Objectives of Reliability Engineering To apply engineering knowledge and specialist techniques to prevent or reduce the likelihood or frequency of failure To identify and correct the causes of failures that do occur, despite of the efforts to prevent them To determine ways of coping with failures that do occur, if their causes have not been corrected To apply methods for estimating the likely reliability of new designs, and for analysing reliability data Faculty of Chemical Engineering oil refinery and offshore rig incidents by looking for causes that are specifically related to maintenance activities or systems https://www.youtube.com/watch?v=St09jyDOuX0 https://www.youtube.com/watch?v=goSEyGNfiPM  Tesoro Martinez Refinery Sulfuric Acid Spill In early 2014, there were two incidents of sulfuric acid release, which caused worker injuries in the Alkylation Unit of the Tesoro Martinez Refinery. The first incident resulted in a release of 84,000 pounds of sulfuric acid and caused burns to two employees with the potential for far more severe consequences. The second resulted in a spray of acid that injured an additional two workers. Alkylation units contain both highly aggressive acid catalysts and light hydrocarbons, creating a combination of hazards with the potential for severe consequences. Both incidents at the Tesoro refinery occurred during the performance of non-routine maintenance work. The investigation report highlights the inherent increase in risk when conducting work that is unfamiliar and where procedures and work instructions may not be well known and understood. https://www.youtube.com/watch?v=8vPaQYM-tWs  Macondo Blowout and Explosion Deepwater Horizon Rig on April 20, 2010, in the Gulf of Mexico, in which 11 people lost their lives and 17 others suffered serious physical injuries. The CSB released their report in April 2016, which highlighted some learnings related to maintenance functions. Technical findings in the report indicated that one of the emergency disconnect systems (the blue pod) was not functional at the time of the incident. Miswiring of a solenoid caused a critical battery to be drained, therefore rendering the blue pod inoperable. Each piece of equipment handed over to operations for commissioning after maintenance or project work is accompanied by a handover pack. As part of this handover pack, every discipline signs off to verify that the equipment is in good condition and functions as per design. A handover pack for a single solenoid is certainly https://www.youtube.com/watch?v=9NQ8Leh not the highest profile pack in the commissioning UWSE phase of a new project or after a turnaround. However, the failure of this particular solenoid was one of the contributing factors to a significant disaster. Caribbean Petroleum Refining Tank Explosion and Fire On October 23, 2009, a large explosion at the Caribbean Petroleum Refinery in Puerto Rico caused extensive damage to 17 petroleum storage tanks as well as severe damage extending into the neighborhood beyond the refinery. The incident occurred during the offloading of gasoline from a tanker ship to the tank farm. The tank being filled actually overflowed, resulting in a vapor cloud release and subsequent explosion. One maintenance-related cause identified in the CSB report is worthy of some attention - a simple failure of the tank side gauge transmitter. When the transmitter failed, data was no longer transmitted to the computer system and trends were not visible to the operator to indicate the overfilling of the tank. It was reported at the time that the level transmitters were often out of service. understand the importance of continuous improvement and the determination to resolve ongoing maintenance issues (bad actors). These https://www.youtube.com/watch?v=2Bn4Krb- lessons can have a significant impact on reducing HoI the risk of an incident.  4. Chevron Refinery Pipe Rupture and Fire A pipe rupture on the Crude Unit of the Chevron Refinery in Richmond, California on August 6, 2012, resulted in a vapor release and explosion. Eighteen employees were caught in the vapor cloud but were able to make their way to safety before ignition. Smoke and particulate clouds travelled across the surrounding community. In all, 15,000 people from the surrounding area were treated for symptoms of sore throats, breathing problems, chest pains and headaches. Approximately 20 people were admitted to hospital. The offending pipe was found to have been damaged by sulfidation corrosion, which is known to be highly aggressive on carbon steel piping. One of the key activities designed to combat this kind of failure is the implementation of routine inspections as part of the Preventative Maintenance strategy. The purpose of Preventative Maintenance routines is to monitor equipment in order to observe warning https://www.youtube.com/watch?v=QiILbGbk signs before a failure occurs. 8Qk A periodic review of PM routines is important to evaluate what checks are being done, and to determine whether these checks are the right ones that can prevent a failure from occurring  Chevron Refinery Pipe Rupture and Fire On March 9, 2012, an incident that happened on the Suncor Altares drilling rig serves to highlight the importance of adequate orientation and training when moving from one environment to another. The rig had previously been commissioned in heavy oil well conditions at shallow depths, whereas it was now deployed in drilling a deep, high-pressure gas well. During the drilling operation, a kick occurred (higher pressure in the drilled rock forces formation fluids into the well bore). The casing pressure increased above the maximum allowable level (MACP) but the drilling program did not provide work instructions for what action to take in this scenario. In addition, the Well Control program was inadequate as it only outlined MACP in general terms and was more oriented towards shallow well drilling programs. Ultimately a mechanical failure led to a blowout of the well. The drilling rig caught fire and was completely destroyed. A more thorough process for training and orientation could have prevented the blowout on Suncor Altares and is an important lesson to minimize risk for safety, environmental and production incidents.  Aftermath In just the previous five events: 84,000 pounds of sulfuric acid released into the atmosphere and acid burns to 4 employees 11 people were killed and 17 seriously injured due to an oil rig explosion a refinery explosion resulted in the loss of 17 petroleum storage tanks and surrounding buildings a pipe rupture affected 15,000 members of the community with smoke and particulates a mechanical failure, coupled with inadequate training, resulted in the complete loss of an oil rig ✓ These are the frightening consequences of failures in systems related to oil refining and offshore drilling. ✓ Every incident that occurs in a production environment provides the opportunity for us all to learn and improve our existing policies and practices in order to prevent a recurrence. ✓ Some incidents have tragic consequences and are widely discussed in the media while others may not cause such significant consequences. Nevertheless, the more we can eliminate the “holes in each slice of cheese”, the more we can reduce the possibility of a catastrophic accident. ✓ The specific maintenance causes noted in these incidents are only a few of many that could play a role in a major loss of life, property, and revenues.  Sources http://www.solufy.com/blog/critical- maintenance-lessons-from-5-major-oil-industry- accidents Maintenance Maintenance Engineering “Plant and equipment are installed and employed to do what the users want them to do. Maintenance is undertaken in a variety of forms, to ensure that the plant and equipment continues to do what the users want it to do”. (http://www-pub.iaea.org) Faculty of Chemical Engineering  Stakeholders for Maintenance 29  Maintenance terminology 30  Generic Maintenance policies 31  Expectations of Maintenance 32  Changing Maintenance techniques 33  Maintenance maturity levels 34  Maintenance strategies evolutions Focus on mainte- nance activities Reactive Proactive Maintena nce performa Use equipment- Eliminate nce the specific strategies sources Fix it before to optimize of Fix it when it breaks cost/ defects it breaks benefit of Do not fix it planned mainte- nance Focus Maximize Provide Minimize Optimize use Preempt failures by cash by rapid unscheduled of removing root causes/ running response for maintenance preventive/pr defects in a cost- assets into breakdowns downtime edictive effective manner; the ground maintenance continue to employ 35 – “avoid over equipment-specific Source: OPI team maintenance strategies ”  Maintenance plays a significant role in ILLUSTRATIVE process industries High Automotive E&P oil and gas White Goods Pulp and paper Trains (manufacture) Base metals Power generation High asset intensity increases importance Railways of good maintenance (infrastructure) practices Maintenance effort or input cost Small manufacturers Aircraft maintenance Ship manufacturers Medical devices Pharma Electronic assembly (PCB’s) Low asset intensity, where asset up time does not impact Low output significantly* High Low Importance/asset intensity * Beware of critical equipment that can adversely affect output/revenue Source: McKinsey Maintenance Therefore… The activity of equipment/item maintenance that develops concepts, criteria, and technical Maintenance requirements in conceptional and acquisition engineering phases to be used and maintained in a current status during the operating phase to assure effective maintenance support of equipment. Faculty of Chemical Engineering