Driver problems

Feel A Psychological Investigation of the Novice Driver Problem. PhD thesis. Transport Research Institute, Edinburgh Napier University, Edinburgh, Scotland. With permission.)... 

Harless, D.W., and Hoffer, G.E. 2002. The antilock braking system anomaly A drinking driver problem Accident Analysis and Prevention, 34, 333—341. 

Harless, D. W. and G. E. Hoffer (2002). The antilock braking system anomaly a drinking driver problem . (fcciV/. Anal, Prev., 34, 333-341. 

The first methanol bus in the world was placed in revenue service in Auckland, New Zealand in June 1981. It was a Mercedes O 305 city bus using the M 407 hGO methanol engine. This vehicle operated in revenue service for several years with mixed results. Fuel economy on an equivalent energy basis ranged from 6 to 17% mote than diesel fuel economy. Power and torque matched the diesel engine and drivers could not detect a difference. ReHabiUty and durabihty of components was a problem. Additional demonstrations took place in Berlin, Germany and in Pretoria, South Africa, both in 1982. 

In contrast to steam turbines, in which runaway overspeediug is always a problem, pump-turbines operating at design head go to zero torque at about 130 to 140 percent of design speed. Thus, overspeed protection may not be necessary if the pump-turbine can withstand 140 to 150 percent of design speed and it is the sole driver. When a steam-turbine helper is used, it should be provided with the usual overspeed trip-out mechanism. 

Whenever the process machine operates at the same speed as its driver, the two can be directly coupled. This direct couphng stiU allows for a variable speed, through acuustments of the speed or the driver. Steam turbine speed can be easily adjusted, and electric motor speed can also be varied by the use of special drives that vaiw the frequency of the power applied to the motor. Wdiether the speed is fixed or variable, direci coupling of two machine shafts presents the problem of accommodation of misalignment. To this purpose, machines are coupled through a.flexible coupling. 

Starting up the turbocompressor installation of a nitric acid plant does not present a problem. As mentioned earlier, during the startup phase the expander is not able to contribute any power. Accordingly, electric motor drivers must initially provide power in excess of the nominal operational rating. 

Overhung rotors present an easier alignment problem beeause shaft-end alignment is neeessary only at the eoupling between the eompressor and driver. 

The low speed gear shaft and the housing must be designed to permit installation of a stub shaft for a torsiograph unit if an operational problem occurs. API 613 gives the details of the shaft end requirements for attaching a torsiograph. This should be done on all synchronous motor compressors and on multiple driver or multiple compressor case trains. 

Other sources, such as compression temperature rise, driver-induced vibration, or component problems (bows) can contribute to the machine shaking. These must be treated as they occur. As a minimum, care must be used to understand the nature of the sources to keep them from interacting with the resonant frequencies of the compressor. The best remedy to stop the excitation at the source. If this is not possible, selective tuning and proper application of damping must be used. 

Besides the inherent lateral natural frequency characteristic, compressors are also influenced by torsional natural frequencies. All torsionally flexible drive trains are subject to non-steady or oscillatory excitation torques during normal operation of the system. These excitation torques can be an inherent function of either the driver or the driven equipment and, when superimposed on the normal operating torque, may appear to be of negligible concern. However, when combined with the high inertia loads of many turbomachinery trains and a torsional resonant frequency of the system, these diminutive ripples can result in a tidal wave of problems. 

Once the driver and driven equipment have been chosen and it is deter mined that none of the items will be subject to any lateral vibration problems, the system torsional analysis is performed. If a calculated torsional natural frequency coincides with any possible source of excitation (Table 9-21, the system must be de-tuned in order to assure reliable operation. A good technique to add to the torsional analysis was presented by Doughty [8 j, and provides a means of gauging the relative sensitivity of changes in each stiffness and inertia in the system at the resonance in question. 

API again offers some help. API 671 covers the special purpose coupling as either a specification or guideline. It has been common practice for the compressor vendor to furnish the couplings. Most compressor vendors have no problem accepting this responsibility, while driver vendors sometimes prefer not to furnish them. In some compressor types, the coupling style will be somewhat influenced by the user. When torsionals become a major consideration, the vendor may have to make the choice based on system need. In all cases, the user should establish his right of approval if the vendor performs the selection. 

It is also useful to identify any drivers that may support new integrated systems—or any factors that may inhibit integration. By identifying these the team will be able to take advantage of support and work around any problems. 

The contiguous resei"voirs of gas or water that contribute the drive pressures for an oil well can cause a problem. Gas and, in some cases, water, are more mobile than oil in an oil reservoir. As a result, during production the oil-gas or oil-water surface can move toward the region of reduced pressure around the borehole. If the interface reaches the borehole, the driver fluid will enter the well and be produced along with the oil. Since gas is not as valu-... 

Because of the magnitude of the task of preparing the material for this new edition in proper detail, it has been necessary to omit several important topics that were covered in the previous edition. Topics such as corrosion and metallurgy, cost estimating, and economics are now left to the more specialized works of several fine authors. The topic of static electricity, however, is treated in the chapter on process safety, and the topic of mechanical drivers, which includes electric motors, is covered in a separate chapter because many specific items of process equipment require some type of electrical or mechanical driver. Even though some topics cannot be covered here, the author hopes that the designer will find design techniques adaptable to 75 percent to 85-1- percent of required applications and problems. 

Belt-drive fault frequencies are the frequencies of the driver, the driven unit, and the belt. In particular, frequencies at 1X the respective shaft speeds indicate faults with the balance, concentricity, and alignment of the sheaves. The belt frequency and its harmonics indicate problems with the belt. Table 44.1 summarizes the symptoms and causes of belt-drive failures, as well as corrective actions. 

The solution to these problems is to develop "smart" airbag systems that can sense the severity of a collision, the size and weight of the driver, and how far his or her head is from the steering wheel. 

Contact the local branches of agencies, such as the Epilepsy Foundation of America, for information and assistance with problems such as legal matters, insurance, driver s license, low-cost prescription services, and job training or retraining. 

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