Drive shaft failure

Any oil seen around the drive shaft is an indication that a drive shaft seal may need replacement. Unusual noise and/or heat may indicate bearings that may need to be changed or a failure of the internal lubrication system. Typically, the first section of a pump that will show wear from abrasive particulate matter that may have entered will be the discharge valves and will be indicated with drops in pressure. 

The second failure involves an error made during the weld repair of an electric motor drive shaft, which again resulted in a fatigue failure. 

Failure of a Steel Coal-Conveyor Drive Shaft This failure was because of a transverse crack that passed through the right keyway near the center of the keyway (Sastri et al. (19), p. 499, Fig. 7.50). The shaft was cut to open the crack and expose the corroded mating surfaces. Two sets of crack arrest marks were concentric to each... 

The failure of the conveyor drive shaft can be prevented by the use of proteetive coatings or other means of shielding the shaft from a corrosive medium. 

Electronic slack rope Mechanical slack rope Rock winder inter-trip Auxiliary drive shaft shaft failure Ecam fault No start and stall Relay X check Slowdown failure GEC over speed Headgear overwind Brakes rubbing Escort fault Brakes worn... 

RCCA ejection accidents caused by mechanical failure of a control rod mechanism pressure housing, resulting in the ejection of an RCCA and drive shaft. The consequence of this mechanical failure is a rapid positive reactivity insertion together with an adverse core power distribution, possibly leading to localised fuel rod damage. 

It is important to seal the glands on the turbine shaft, and a typical arrangement is illustrated in Figure 14-24. Thrust bearing failures can be serious problems for steam turbines and other mechanical drives, as well as the bearings used on the driven equipment. 

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. 

Repeated twisting of the spindle s tube or the solid shaft used in jackshafts results in a reduction in the flexible drive s stiffness. When this occurs, the drive loses some of its ability to absorb torsional transients. As a result, damage may result to the driven unit. Unfortunately, the limits of single-channel, frequency-domain data acquisition prevents accurate measurement of this failure mode. Most of the abnormal vibration that results from fatigue occurs in the relatively brief time interval associated with startup, when radical speed changes occur, or during shutdown of the machine-train. As a result, this type of data acquisition and analysis cannot adequately capture these... 

Bucket elevators. The bucket elevators lift catalyst, at 900-1000°F., about 200 ft. Each elevator consists of two chains with a continuous line of alloy-steel buckets loosely supported between them (217). The upper shaft is fixed in position but the bottom shaft can move to offset thermal expansion and wear of the chain. Chain speeds are 90 to 125 ft./minute at catalyst-circulation rates of 100 to 150 tons/hour. Power requirement is 60 to 80 horsepower (241). Differential band brakes protect against reverse rotation in case of a power failure. Sprockets with renewable teeth were used at first (217), but a traction-wheel drive was later substituted because wear is more evenly distributed and life is longer (241). Repair techniques have been developed for extending chain life (316). Graphite is used to lubricate the chains (239). The upper shaft and main bearings are water-cooled and the bearings are lubricated with oil. 

The shaft seals preventing gas leaks, the brush-contact unit and the electric drive tachometer generator attachment unit have been also modified. Owing to the actions taken the failures of the pumps causing the abnormal operating conditions have been avoided since the 15th cycle (since December, 1985). 

In general, there seems to be no consensus on the siting of a drive. The main objections for bottom-driven bioreactors is the possibility of a catastrophic failure of the shaft seals providing a major release. Many authors favour top-driven bioreactors from a containment viewpoint. 

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