Reliability problems

The specific results of well over 1 year of continued monitoring will be discussed in a second paper. It is pointed out here that the AEBIL monitoring system installed in the power plant for the above monitoring purposes has efficiently and continuedly performed during this time interval, with no instrumentation reliability problems. 

It should be emphasized at this point that the speed of response is cnti-cal. The pressure transient pressure should not fall to less than 50% of the difference in pressure between the standby pump start pressure and the low oil pressure trip pressure. This is normally achievable with good design practice and the use of a switch and direct wiring. There is some tendency to use a transmitter and control through a remote computer. The latter arrangement is difficult to check on a shop test and normally is too slow to meet the requirement. An accumulator can be added and must be used if the requirement cannot be met. This additional hardware contributes to higher initial cost and possible reliability problems in the future. The direct switch method is therefore highly recommended. 

Several steps can be taken to maximize the run time for the reciprocating compressor. Since wear is a function of rubbing speed, the piston speed can be kept to a minimum. Chapter 3 made recommendations for piston speed. Reliability problems due to valves are reputed to account tor 40% of the maintenance cost of the compressor. Valves are the single largest cause for unplanned shutdowns. Basically, valve life can he increased by keeping the speed of the compressor as low as practical. At 360 rpm, the valves are operated six times a second. At 1,200 rpm, ihc valves operate 20 times a second or 1,728,000 times in a day. It is not difficult to understand why the valves are considered critical. To keep the reliability in mind, valve type, material selection and application considerations such as volume ratio, gas corrosiveness, and gas cleanliness need attention by the experts. One final note is that while lubrication is an asset to the rubbing parts, it is not necessarily good for valve reliability. 

Reciprocating compressor pulsations were covered in Chapter 3, but neeti to be mentioned with the discussions on reliability. Problems with reciprocating compressor pulsations and the potential for acoustic and mechanical resonances are very similar to those experienced with helical-lobe compressors. The significant difference is the frequencies are much lower and the number of discrete frequencies per compressor aie much less. However, piping vibrations can occur and there is always a... 

Fluctuations in the inlet and discharge pressures indicate potential system problems that may adversely affect performance and reliability. Pressure fluctuations are generally caused by changes in the ambient environment, turbulent flow, or restrictions caused by partially blocked inlet filters. Any of these problems will result in performance and reliability problems if not corrected. 

Most reliability problems associated with positive clutches fall into two categories mechanical damage and fatigue failures. 

Widespread concern with the significance of the results and their interpretation Ruggedness and reliability problems with equipment Concern with intrinsic safety of equipment... 

Plant reliability problems are associated with excessive downtimes due to component failure or scheduled maintenance requirement. Development needs include ... 

The last need translates into the requirement that plant sizes need to be consistent with the needs of utilities and other industries. To date, a detailed market study that clearly defines this need does not exist. Also, economy and efficiency means that plants that can be mass-produced and deployed on a modular basis must be developed. Finally, start-up and reliability problems can only be overcome by standardizing operations, which, as noted early on, will increase both investor and customer confidence. 

There have also been revivals of the steam car. Robert McCulloch, the chain-saw millionaire, spent part of his fortune on a steam prototype, called the Paxton Phoenix, between 1951 and 1954. William Lear of Learjet fame, spent 15 million in 1969 on a turbine bus and a 250-horsepower turbine steam car. Both used quiet, efficient steam engines although the bus had reliability problems and poor gas mileage. Lear also tried to enter a steam car into the 1969 Indianapolis 500. The British firm of Austin-Healey was also working on a steam car in 1969. It had four-wheel drive. However, even prosperous entrepreneurs like McCulloch and Lear found that they lacked the means and support structure to successfully mass market a competitive car. Alternative power systems would have to wait until air-quality regulations resulted in some breakthroughs with hybrid and even fuel-cell cars. 

System theory can be applied to incident investigation, reliability problems, quality problems, and other business losses. One of several reasons why system theory has received broad recognition relative to incident investigation is that it builds directly on current, verified process safety principles. In process safety, as in all other systems used to control risk to a business, there are three basic keys to controlling the risk (see Figure 3-4) ... 

Experience indicates that an important part of a normal process development is definition of solutions to operability and reliability problems that have been identified. The EDS process development is no exception. Potential mechanical problems associated with feed slurry preheat, slurry pumping, high pressure letdown valves and vacuum bottoms pumping have been identified and will be addressed in the 250 T/D pilot plant program. In addition, several process problems associated with the variety of coals processed have been identified and solutions defined. The status of both pilot plant construction and definition of solutions to process problems is presented in this paper. 

I hope that the Commission s decision will be favorable because, although I would argue that high Btu gas from coal is not now economically competitive, we must proceed in order to reduce the technical and economic uncertainties. We must move on with the construction of one, two or a very small number of commercial-size plants so that we can learn about the real economics, and the real technical and reliability problems. 

And yet, for more them four years after its very successful First National Bank of Omaha project, SurePower was not able to sell a second high-reliability system. The interrelated reasons for this go to the heart of the reason why fuel cells will have difficulty using reliability problems as a path to commercialization. 

As with all water-based extinguishing systems, there are temperature considerations associated with water-spray systems. In cold climates where freezing is a potential problem, selection of a water-spray system should not only be based on potential benefits, but also on the possibility of reliability problems. Care should be taken in the design to ensure that the... 

In the early 1950s several groups built experimental electronic calculators based on transistors, and in the UK a team at Manchester University built an experimental transistor computer between 1953 and 1955. This was at a time when new manufacturing techniques were being introduced which overcame many of the reliability problems which had plagued the early transistors, and in 1956 an adaptation of the Manchester experimental computer was marketed as the Metropolitan Vickers... 

In order for a polyimide to be useful as an interlevel dielectric or protective overcoat (passivant), additional demanding property requirements must be met In the case of the passivant, the material must be an excellent electrical insulator, must adhere well to the substrate, and must provide a barrier for transport of chemical species that could attack the underlying device. It has been demonstrated that polyimide filrns can be excellent bulk barriers to contaminant ion motion (such as sodium) [10], but polyimides do absorb moisture [11,12], and if the absorbed moisture affects adhesion to the substrate, then reliability problems can result at sites where adhesion fails. However, in the absence of adhesion failure, the bulk electrical resistance of the polyimide at ordinary device operating temperatures and voltages appears to be high enough to prevent electrochemical corrosion [13]. 

Several other types of encapsulants have been evaluated for use by the semiconductor industry. Polyphenylene sulfide, a thermoplastic, has the advantage of good thermal characteristics and a low viscosity for device encapsulation. In addition, since it is a thermoplastic, the molded runners can be reused. This improves the material utilization and reduces cost. Unfortunately, this material also contains a significant amount of impurities that caused device reliability problems and efforts to remove them have met with mixed success. 

Data for, and estimates of, D( and failure thickness are obviously important to the designer or analyst in spotting potential detonation reliability problems where explosive charges or systems must be minimized in size and weight. 

Si (epitaxial) precipitation in contact areas to silicon [Hirashita et al.140). The main problem here is an increase in contact resistance, especially in small contacts, thus leading to device reliability problems. 

But the rise of the transistor quickly revealed an even more urgent problem large electronic systems were quite unreliable because each transistor was placed into the system as an individual component. No amount of quality control could overcome the reliability problems created by the manual interconnection of all these components. Once again, the problem was most severe in defense applications, and the Department of Defense was prepared to pay well for a solution. Once again, the industry leaders were well funded, and once again an outside company invented the... 

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