Outages

It has developed a real time method to compare successive non-destructive inspections of the steam generator tubes in nuclear power plants. Each tube provides a safety barrier between the primary and secondary coolant circuits. Each steam generator contains several thousands of tubes whose structural integrity must be ensured through the lifetime of the plant, Therefore, Laborelec performs extensive nondestructive tests after each plant outage. 

The calculation setup screens list a good selection of the options that are most widely used. However, it is not a complete list. The user also chooses which queue to use on the remote machine and can set queue resource limits. All of this is turned into a script with queue commands and the job input file. The user can edit this script manually before it is run. Once the job is submitted, the inputs are transferred to the server machine, the job is run and the results can be sent back to the local machine. The server can be configured to work with an NQS queue system. The system administrator and users have a reasonable amount of control in configuring how the jobs are run and where files are stored. The administrator should look carefully at this configuration and must consider where results will be sent in the case of a failed job or network outage. 

In addition, iu May 1988 an iucident at Shell s Norco plant (54) limited production. These outages hastened many customers to switch over to other solvent substitutes. The price of MEKia October 1994 was about 0.88/kg. Supply fluctuations caused the price to range from 0.55 to 1.10 /kg siace the early 1980s. 

A PPM program is needed to avoid equipment failures, utiHty outages, and production intermptions. From a cost savings angle it is extremely important to do preventive maintenance in order to avoid breakdowns. Periodic inspections and a good lubrication program uncover conditions that could lead to breakdowns. When problems are found eady, they can be taken care of without work intermption and costly repairs. Sometimes faciHty managers are so afraid of downtime that preventive maintenance is done too often. In other cases production does not allow adequate time to provide proper maintenance. 

In addition, because of the extreme variation in the bulk density of products, use of the standard 19-L (5-gal), 38-L (10-gal), 61-L (16-gal), 114-L (30-gal), and 208-L (55-gal) metal dmms often results in excessive outage. Fiber dmms, in contrast, are available in a wide range of sizes, and can be sized to meet product volumes, thus allowing for Httle outage as weU as saving storage and shipping space. 

Approximately 25—30% of a reactor s fuel is removed and replaced during plaimed refueling outages, which normally occur every 12 to 18 months. Spent fuel is highly radioactive because it contains by-products from nuclear fission created during reactor operation. A characteristic of these radioactive materials is that they gradually decay, losing their radioactive properties at a set rate. Each radioactive component has a different rate of decay known as its half-life, which is the time it takes for a material to lose half of its radioactivity. The radioactive components in spent nuclear fuel include cobalt-60 (5-yr half-Hfe), cesium-137 (30-yr half-Hfe), and plutonium-239 (24,400-yr half-Hfe). 

The goals of the F EI are to raise awareness of loss potential and identify ways to reduce potential severity and potential dollar loss in a cost-effective manner. TLe index number has significance as a comparison and in calculations to estimate the maximum probable property damage (MPPD). It also provides a method for measuring tbe effect of outage (plant being shut down) on the business. It is easy for users to get credible results with a small amount of training. 

Maintenance and Reliability Preventive maintenance requires that all engines be shut down at periodic intervals for inspection and repair. For properly maintained heavy-duty engines availability is over 97 percent, with maintenance costs of 2.50 to 5 per horse-power-year and lubricating-oil consumption of 1 to 2 gal/hp-year. While this represents a high degree of reliability, outages of heavy-duty engines are more frequent than those of electric motors or steam turbines. 

During prolonged outages, remove wet packing and clean gasketed surfaces thoroughly. 

It would not be expected that crevice corrosion could easily occur in demineralized water. However, this exchanger was subject to extended outages with no lay-up procedures. Under such conditions, crevice attack is more likely. 

A routine inspection of the tube bundle during a plant outage revealed fine cracks of the type shown in Fig. 9.11. Scattered longitudinal cracks were observed along the lengths of most tubes. The external surface was covered with a thin film of black copper oxide and deposits. The bundle had been exposed to ammonia levels that produced 14 ppm of ammonia in the accumulated condensate. 

Cooling water system corrosion causes immediate and delayed problems. Difficulties spread from a failure like ripples from a pebble thrown into a pool. A single failure may force an unscheduled outage, redirect worker efforts, contaminate product, compromise safety, increase equipment expense, violate pollution regulations, and decrease productivity. 

Overcurrent protection is normally not provided in generator and generator transformers to save the machines from likely outages on momentary overlo.ids. In the event of overloading, the normal practice is to shed some of the loads on the transmission network. 

All such loads generate harmonics and cause variations in the fundamental power frequency of the supply sy.stem which leads to distortion in the sinusoidal waveform of the voltage. This distortion may affect the quality of the supply system (voltage) beyond desirable limits, A non-sinusoidal and distorted supply system may adversely affect the different loads connected on the system, besides leading to outage of the sy.stem itself. 

While the former would stress the generator windings, the latter may cause a voltage swing during a load rejection or load fluctuation and result in a line outage. These features, if not controlled, may render the system unstable. Overvoltages must therefore be controlled within an acceptable limit. Table 24..3 prescribes one such limit. 

For the system to remain stable under all conditions of loading, switching, or any other line disturbances it is essential that an uncompensated line is loaded at much below this level. Otherwise disturbances of a minor nature may result in undampened oscillations, and may even swing the receiving-end voltage beyond acceptable limits. It may even cause an outage of the system. It is therefore not practicable to operate an uncompensated line to its optimum level. For this we will analyse this equation for sin 0 and sin S as follows. 

Reliability of shunt or series power capacitors is of utmost importance for the security of the system on which they are installed. Their failure may disturb the system or result in a system outage. 

Note Similarly, load lines can be drawn on a load rejection, or the generator or the line outages. 

For loads, such as on motors where the capacitor unit is being switched with the machine, or where close monitoring of the capacitor health is a prerequisite to avoid an eventual outage of the capacitor unit by gradual depletion of its capacitance, internally protected capacitor units may be preferred. 

In this case the next switching may almost be instant to retain the stability of the system and save it from an outage. A static switching (Section 24,10) alone may be the correct solution for such applications. 

Synchronous generator helps power factor Outage of generator or expander does not affect production... 

In many cases, the most frequent cause of equipment outage is the lubrication system. Because magnetic bearings do not wear out, and do eliminate oil, pumps, filters, coolers, and regulating and mixing valves, the potential for improved reliability is obvious. Reliability is also enhanced by the control system, which offers continuous real-time protection. The system automatically shuts down before machinery damage can occur. 

S = Seheduled outage hours for planned maintenanee F= Foreed outage hours or unplanned outage due to repair. 

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