Maintenance plant shutdown

In addition, NDT plays an important part in industrial maintenance. During plant shutdowns for instance, many thousands of ultrasonic wall thickness measurements are taken on piping, vessels, furnace tubes etc. All these thickness readings have to go into extensive data bases, and this process is, thanks to modem computers and data loggers, ever more automated. 

The Chemical Process Industry (CPI) uses various quantitative and qualitative techniques to assess the reliability and risk of process equipment, process systems, and chemical manufacturing operations. These techniques identify the interactions of equipment, systems, and persons that have potentially undesirable consequences. In the case of reliability analyses, the undesirable consequences (e.g., plant shutdown, excessive downtime, or production of off-specification product) are those incidents which reduce system profitability through loss of production and increased maintenance costs. In the case of risk analyses, the primary concerns are human injuries, environmental impacts, and system damage caused by occurrence of fires, explosions, toxic material releases, and related hazards. Quantification of risk in terms of the severity of the consequences and the likelihood of occurrence provides the manager of the system with an important decisionmaking tool. By using the results of a quantitative risk analysis, we are better able to answer such questions as, Which of several candidate systems poses the least risk Are risk reduction modifications necessary and What modifications would be most effective in reducing risk ... 

This report addresses ammonia plant shutdowns over the listed time period in 40 countries. It provides a basis for comparing plant performance area by area leading to better control of reliability efforts while reducing maintenance and unplanned shutdown costs. Data are presented for shutdowns due to power, equipment, instrumentation, feedstock and product inventory control. 

While frequent testing of the valves is necessary as seen before, everyone wants to reduce the downtime of the process. When a plant shutdown is planned, the valves can be dismantled and brought to the maintenance shop for testing on the test bench and eventual overhaul. 

Cost-reduction projects are aimed at reducing the cost of production of an existing plant. The most common cost-reduction investments are for preventive maintenance, in which equipment is replaced, repaired, or cleaned after a planned interval and before the equipment deteriorates to the point where it could impact process performance or safety. Most preventive maintenance projects are small and are handled through the plant maintenance budget, but some can be very large, expensive projects requiring a major plant shutdown, for example, replacing the fired tubes in a main... 

B. Work order controls We have found that the most cost-effective plants have a systematized approach to identifying, prioritizing, planning, scheduhng, executing, and recording routine maintenance. This would include plant shutdowns. 

The quantity of work to be done must be defined by the appropriate time period, which could be by as little as a 15-minute interval for cashiers and as long as a day for paper mills. For continuous process industries, such as chemical plants and some mining processes, the definition of what is needed is relatively easy to determine. Even so, the work must be defined by the hour and day of the year to allow for maintenance and shutdowns for holidays. There are many other industries that also have a well-known stable demand for work profile—for example, prisons, long-term health care facilities, and many manufacturing systems, such as assembly lines. At the other end of the scale are situations such as retad outlets and telephone operators, that have a demand that varies constantly during the day, and from day to day, and from season to season. Many of the organizations with such a fluctuating demand pattern have a detailed data bank of historic data, usually by the 15-minute interval. These data can be used to predict the work requirements for future time periods. 

Corrosion is the destructive attack of a material by reaction with its environment. The serious consequences of the corrosion process have become a problem of worldwide significance. In addition to our everyday encounters with this form of degradation, corrosion causes plant shutdowns, waste of valuable resources, loss or contamination of product, reduction in efficiency, costly maintenance, and expensive overdesign it also jeopardizes safety and inhibits technological progress [3]. 

When corrosion is effectively managed, there will be leakage reduction, less plant shutdown, and less unplanned activities for maintenance [2], Therefore, a facility s reliability should not be overlooked, and this can be achieved in the following ways [3,4] ... 

Member 1 Series of major process safety incidents, environmental releases, and plant shutdowns in petrochemical plant 1 Early retirement of competent personnel, major investment project, neglected maintenance... 

Unintermpted supply of raw materials, additives, catalysts, etc., is required for production, while spare parts are required for timely maintenance. This in turn depends on the stock of usable raw materials and spares available in stores (to quickly repair the machinery whenever required). Spares are also required during annual plant shutdown or during overhauling period for replacements of worn out or damaged components. 

A shutdown level-1 PSA has almost completed. The reliability of the decay heat removal system (DHRS) during the plant shutdown (refueling and maintenance) was evaluated. There are several system trains out of service because of the scheduled maintenance so that it reduces redundancy of the safety functions. We considered several candidates of accident management (AM) measures as an operator recovery action under accident condition. As a result of this study, it concluded that these AM candidates were effective for the DHRS to maintain high reliability in cooperation with a long grace period. 

The pressurizer heaters are single unit, direct immersion heaters that protrude vertically into the pressurizer through sleeves welded in the lower head. Each heater is internally restrained from high amplitude vibrations and can be individually removed for maintenance during plant shutdown. 

Section 9.5.2. The system normally used for plant shutdown operation and maintenance is the Intraplant Sound-Powered Telephone System. Phone jacks connect specific areas of the plant and the control room, and the system is powered from diesel-backed power sources. The communications panel in the control room is described in CESSAR-DC Section 18.7.4.13. 

The equipment arranged in the protective shell requires no maintenance during plant operation. The equipment is arranged so that it is easy to carry out routine repair and maintenance works during scheduled plant shutdowns. 

Operational life Startup from a normal or controlled shutdown is part of the safety procedure. There may be three types of shutdown plaimed, emergency, and shutdown for maintenance, as indicated in Clause 2.1.1. Each of these has certain safety issues associated with it, so, these types of plant shutdown along with startup from emergency shutdown should be checked. 

If a deviation is found for an individual valve, in-situ testing is done during a plant shutdown. The information gained from in-situ testing is analysed and then used in maintenance programmes. 

The probabilistic safety assessment is developed as an integral PSA model covering all Plant Operational States (POS) of the plant, covering full power, low power and shutdown states. The reference model considers 15 POSs to include the 6 operational modes combined with the typical configurations of the units during maintenance in shutdown states. The determination of these POSs was carried out on the basis of operational experience on other Slovak NPPs and includes plant-specific peculiarities deriving from detail design development. 

Make maintenance planning more flexible, by providing, wherever possible, viable alternatives to unplanned shutdowns and to immediate component replace or repair actions. Increased flexibility of maintenance planning, by conditionally running under surveillance components with potential or incipient stmctural integrity problems, means improved plant availability, reduced energy replacement and maintenance costs. 

In plant maintenance, the availability of quantitative and non-invasive screening NDT methods will reduce the time needed for shutdowns and increase the intervals between them. Modem NDT methods will become just as important a tool for Risk Based Inspection approaches and maintenance planning as operational parameters and degradation mechanisms already are. 

Water chemistry is important to the safe and reflable operation of a nuclear power plant. Improper conditions can lead to equipment and material failures which ia turn can lead to lengthy unscheduled shutdown periods for maintenance (qv) and repair operations. Water chemistry can also have an impact on the radiation levels duriag both power operations and shutdown periods. These affect the abiUty of personnel to perform plant functions. 

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