Plant shutdown

For normal plant shutdown, reactor power and plant output are reduced by manual insertion of control rods. After turbine load is reduced to a minimum value, steam flow is maintained through the bypass valve and the generator is disconnected from the system. 

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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 semiregenerative procedure for catalyst regeneration varies slightly between catalyst vendors however, it typically follows these general steps plant shutdown, carbon bum, oxidation and chlorination, nitrogen purge, reduction, and plant start-up. During the plant shutdown, Hquid hydrocarbons... 

In addition to environmental and safety factors, some of the early decline in manufacture was hastened by a series of plant shutdowns between 1971 and 1973 resulting primarily from the high costs of the acetylene-based process. No new production capacity is planned in the United States for the foreseeable future. 

Actuators often provide a failsafe function. In the event of an interruption in the powder source, the actuator will place the valve in a predetermined safe position, iisiiallv either full open or full closed. Safety systems are often designed to trigger local failsafe action at specific valves to cause a needed action to occur, vv4uch rnav not be a complete process or plant shutdown. 

Other Effects Stream concentration can have important effects on corrosion rates. Unfortunately, corrosion rates are seldom linear with concentration over wide ranges. In equipment such as distillation columns, reactors, and evaporators, concentration can change continuously, makiug prediction of corrosion rates rather difficult. Concentration is important during plant shutdown presence of moisture that collects during cooling can turn innocuous chemicals into dangerous corrosives. 

Another area where probes can be used effectively is in monitoring of deposits such as scale. One method of measurement is detecting specific ions that contribute to scale buildup or fouling another is measuring the ac tual layers. Scale and fouling often devastate the corrosion resistance of a system, leading to a costly corrosion-related plant shutdown. 

Some solutions may not be practical, or economical, or timely and consistent with production. You could be forced to live with cavitation until the next plant shutdown to make the neces.sary corrections. In the meantime, the cavitation shock waves and vibrations will travel through the impeller, down the shaft to the mechanical seal faces, and onto the shaft bearings. We offer some. specific recommendations for surviving cavitation shock waves and vibrations in Chapters 13 and 14 on Mechanical Seals. 

Often in the field, designs must be done quickly, for example, during an unexpected plant shutdown. For such cases, shortcut design methods are invaluable. The field invariably has the best perspective on how designs will perform for startup, shutdown, upset, or offload conditions. Experience factors come into play for field review of these design aspects. 

According to 10 CFR 50,73, the holder of an operating license for a nuclear power plant (the licensee) must submit an LER for a reportable event, within 30 days after discovery. An event b reportable regardless of the plant mode, power level, structure, system, or component that initiated the event. In addition the licensee must report the completion of any nuclear plant shutdown required by the plant s Technical Specifications or any operation or condition prohibited by the plant s Technical Specifications, or any deviation from the plant s Technical Specifications. LERs are available on the Internet at http //www.nrc.gov/NRR/DAILY/97mmdddr.htm, where inrn is the... 

A plant shutdown has been scheduled for the week of May 16. We are evaluating the impact of this shutdown on our schedule. 

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 ... 

Causes of Ammonia Plant Shutdowns Chemical Process Records of 5884 shutdowns over 98 years Ammonia Plant 47. 

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. 

A leading utility in tlie nortlieast had requested out-of-compliance information to better schedule outages (plant shutdowns). The time to failure, T, of a bus section was assumed to have a Weibuill distribution, tlie parameters of which were estimated by the metliod of maximum likelihood on tlie basis of observed bus section failures shown in Table 21.6.1 for tlie utility s 5x8... 

How does the program cater for seasonal work (e.g. plant shutdowns, holidays) ... 

Where low-cost labor is available, operators can provide intensive manual cleaning during the annual plant shutdown period. However, this is not a model for operational efficiency, and low-cost labor is seldom that low when quality and productivity is factored in. In the long run, it usually is far better to aim for a higher operational standard from the beginning. 

Most waterside problems develop insidiously. Over time, scale and other types of deposit are gradually formed on internal heat transfer surfaces, which gradually raises the cost of providing heat energy. Some types of deposition can be very difficult and costly to remove. Corrosion wastes away the fabric of the plant (sometimes very quickly) and may produce an unexpected and untimely boiler plant shutdown, with a consequential loss of space heating, electricity, or process manufacturing capability. Likewise, fouling reduces the size of waterways and increases boiler operational problems. 

Hardness breakthrough can be particularly troublesome at those small, hard-working facilities that employ just one automatic softener. The problem may develop gradually and go unnoticed for some time. This may be because the softened water is not tested daily or, more usually, because the soft water is tested soon after resin regeneration rather than immediately before the point of exhaustion (which may be many hours later, but perhaps still 2 or 3 hours before the end of a working shift or plant shutdown). 

Williams, G.P., Causes of ammonia plant shutdowns, Chem. Eng. Prog., 74, 9,1978. 

During a 16-day vacation and plant shutdown, urinary excretion accounted for 90% elimination in those with high initial PCP levels (i.e., >0.1 mg/L) to 67% elimination in those with initial urinary levels of 0.02-0.1 mg PCP/L, and to 34% reduction in workers with <0.02 mg/L Tb 1/2 was estimated at 33 h in urine and 30 h in plasma (Kalman and Horstman 1983)... 

OSHA officers finding conditions of imminent danger may request plant shutdowns. 

Modern data acquisition and evaluation help to optimise the plant under review within a short period of time, to eradicate faults in plant operation and to determine the best materials for the operation of the chlorine electrolysis plant being examined. In this way, inter-relationships are examined between the energy consumption and variables such as membrane types, anode and cathode coatings, temperature, pressure, and concentrations as well as plant shutdowns, brine impurities, materials of construction and manufacturers. It is conceivable that other inter-relationships will come to light that have so far not been considered. 

The plant was running smoothly when a common trouble alarm on the cooling tower fans sounded. The outdoor operators investigated, discovered a fire, called the fire department, and initiated a plant shutdown. The fire was extinguished in about 2 hours. 

The plant shutdown (which distracted the operators and made the electric fire water pump unavailable) was caused by a thunderstorm that tripped the primary feeder and no backup feeder was installed. The unit should be designed to shutdown safely on loss of power. (Process hazards analysis)... 

The sulfuric acid plant has boiler blowdown and cooling tower blowdown waste streams, which are uncontaminated. However, accidental spills of acid can and do occur, and when they do, the spills contaminate the blowdown streams. Therefore, neutralization facilities should be supplied for the blowdown waste streams (Table 15), which involves the installation of a reliable pH or conductivity continuous-monitoring unit on the plant effluent stream. The second part of the system is a retaining area through which non-contaminated effluent normally flows. The detection and alarm system, when activated, causes a plant shutdown that allows location of the failure and initiation of necessary repairs. Such a system, therefore, provides the continuous protection of natural drainage waters, as well as the means to correct a process disruption. 

D Plant shutdown Direct fines product stock-out >500... 

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