Breakdown based maintenance

Maintenance is not merely called upon to repair failed equipment (breakdown maintenance). Over the course of time, maintenance workers have teamed with plant operations personnel to develop preventive maintenance (PM), predictive maintenance (PdM), and condition-based maintenance (CBM) programs, all in an effort to get ahead of problems occurring in plant operations, and to do so as efficiently as possible. 

OBM (operator-based maintenance), 1620 OBS, see Organizational breakdown structure Observation(s) ... 

The objective of preventive maintenance is to extend the life of an item and prevent all failures before they occur by detecting critical wear that leads to failure or breakdown. This can be accomplished by estimating a lifetime schedule for each item. The way this estimation takes place determines the type of preventive maintenance. In predetermined maintenance the estimation is static and results in static maintenance intervals. In condition-based maintenance, maintenance intervals are determined according to either the detection of a degradation mechanism by monitoring or a forecast derived from the analysis and evaluation of a number of parameters (i.e., vibration, imbalance, machine noises, power demand) of the degradation mechanism (thus, condition-based maintenance is often referred as predictive maintenance). 

In nuclear power plants approx. 5000 valves are periodically preventively, condition-based (predictive) or breakdown-based maintained. Because of this large number of valves to be maintained a high potential of improvements and cost reductions can be achieved by performing optimized maintenance methods and using innovative tools. 

Key Operating and maintenance (Q M) cost elements for the Ashkelon SWRO project are shown in Table 3.7 (Velter, 2004). The difference between the first 5 years is attributed to the use of new equipment at the first years of the plant operations and used equipment after that time. An O M cost breakdown based on experience with seawater desalination in Spain is shown in Figure 3.22 (Medina, 2004). 

The seheduling of maintenanee inspeetions and overhauls is an essential part of the total maintenanee philosophy. As we move from Breakdown or Panie maintenanee towards a performance based total productive maintenance system, total eondition monitoring and diagnosties beeomes an integral part of both operation and maintenanee. Total eondition monitoring and diagnostie examines both the meehanieal and performanee... 

Table E.4 in Appendix E provides a breakdown of the total production costs encountered in the manufacture of nitric acid. The costing is based upon paying the full market price for ammonia feed (at A 300/tonne). All tangible input and output valuesarecalculated using the results of the mass and energy balances detailed in Section 7.3. Labour requirements are evaluated assuming only two operators per shift and the usual labour maintenance requirements for nitric acid plants (see Ref. CE1 1).

Inspections of rotating equipment could be accomplished by Preventive Maintenance Programs, which assures that equipment and machine behavior follow some sort of statistical average based upon weeks of operation or throughput in the process stream. Preventive maintenance (PM) programs—the planned, periodic inspection of equipment—reduces the occurrence of unexpected problems. Preventive Maintenance Programs are much more efficient to conduct than the old-fashioned breakdown maintenance programs of previous years in which failures often occur at undesirable times, interfere with production, and may prove to be more costly to correct. [2]... 

The allocation to industrial installations is based on sectoral emissions in the period 2000-2002 and on the emissions share of the installation in the sector s emissions in that period. This basic allocation principle is adjusted to accommodate several issues. Where individual unit data are not adequate, the installation receives its baseline capacity share using an average emissions benchmark for comparable facilities. Special provision is also made for cogeneration and process emissions, special circumstances during 2000-2002 (abnormal stops due to maintenance, breakdowns, changes in the installation, strikes, adverse weather etc.), and capacity increases after 1 July 2001 leading to an increase in emissions in excess of 20%. 

The early phase of SBS is associated with large day-to-day variations in fluid and electrolyte losses. Strict output records should be assessed, as well as all intake including intravenous medications. Initially, it is recommended to start a standard PN solution that meets the patient s maintenance metabolic, fluid, and electrolyte needs, and a separate intravenous replacement solution is typically necessary to keep the patient euvolemic based on actual fluid losses. Insensible losses should be estimated between 300 and 800 mL/day above measured output, and daily urine output should be kept at least 1 L. As fluid and electrolyte losses stabilize over time it becomes possible to incorporate these replacement requirements into the PN solution. The PN solution typically is composed of standard crystalline amino acids, glucose, and intravenous lipids. A generic caloric breakdown for SBS patients based on a need of 30 to 40 kcaV kg per day may be 1.5 g/kg of protein per day, approximately 20% to 30% of calories from intravenous lipids, and the remainder of calories from carbohydrates. An example of a PN formula for the patient with SBS is given in Table 139-2. 

The major benefit to be realized from Fieldbus and intelligent instruments is primarily due to the ability to obtain on-line diagnostic information. This provides information on the performance of a control valve, for instance, or on the expected lifetime of a seal material based on the number of hours installed and the duty. These features lead to better planned maintenance (rather than preventative or run-to-breakdown maintenance), which in turn leads to lower overall maintenance costs and fewer unplanned losses of production. Validation of the on-line diagnostics will assist in the ongoing review of the validation status of the OCS. 

There are three major cost components fuel, bdler feed water (BFW) including freshwater, chemical treatment, pumping and heating, as well as fixed cost including capital and maintenance and environmental related costs. Table 17.2 shows the breakdown for these three costs based on fuel prices at 6/MMBtu. In this case, fuel cost is dominant, which accounts for 69%, and all other costs for 31%. 

Reliability and maintainability analysis, based on breakdown, repair, and periodic maintenance statistics obtained for each plant item (or even on sensible guesses from experienced people). In conjunction with economic data, the model is used to predict plant availability and economic performance while taking into account the probability of failure of individual components and the repair time. The model may be used to make optimum choices on the provision of standby equipment, equipment enhancement, operational flexibility enhancement (including optimizing the period between overhauls), maintenance facilities, intermediate tankage or stockpile capacity, and capacity margins for individual equipment items. 

You may be able to obtain mamrfacturer s information on expected risks of breakdown when purchasing eqiripment, and you can certainty find out recommended times for replacement or servicing of parts. Within a compatty, careful examination of maintenance records will give you information. Some electronically-based control systems store data on events which occitr ditring operation so they can be analysed later. 

The time scheduling system has been developed with the object of appreciably lowering the cost due to downtime (caused by breakdown or failure of machinery or equipment) of industrial installations. It is based on the principle of grouping maintenance operations together as much as possible (Fig.4). 

The major downside of reactive maintenance is unexpected and unscheduled equipment downtime. If the equipment fails and repair parts are not available, delays ensue while parts are ordered and delivered. When this is the sole type of maintenance practised, both labour and materials are used inefficiently. Labour resources are thrown at whatever breakdown is most pressing. A purely reactive maintenance programme ignores the many opportunities to influence equipment survivability. However, it can be effective if used selectively and performed as a conscious decision based on the results of an RCM analysis. Equipment that can be reactively maintained must be non-critical and will not pose any serious hazards or affect the operation of the system as a whole. 

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