Maintenance mechanical

As we ve di,seussed, system design is responsible for much of cavitation. Yet, the maintenanee mechanic is responsible for stopping and preventing eavitation. And certainly, it s the maintenance mechanic who has to deal with the results of cavitation, the constant changing of bearings, meehanical seals, damaged impellers, wear rings and other pump parts. 

Along with the sounds, evidence and signs of cavitation, there is a broad range of other information and signals available to the maintenance mechanic. Almost all mechanics have seen the gouge and scratch marks, and signs of heat on the pump when disassembled in the shop. Sadly, most mechanics are never trained to interpret these marks. 

Maintenance (Mechanical Integrity) —Pre-Startup Review —Management of Change —Safety Audits — Accident Investigation... 

Inadequate or incorrect maintenance. Mechanical devices such as vacuum breakers and flame arrestors require routine maintenance attention to ensure that they provide their intended protective function. Incorrect maintenance (e.g., changing the vacuum breaker set pressure) could defeat the intended protection. 

Colgin, L. M., and R. R. Reddel. 1999. Telomere maintenance mechanisms and cellular immortalization. Curr Opin Genet Dev 9(1) 97—103. 

FIGURE 4—22. Neurons appear to have a normal maintenance mechanism for their dendritic tree by which they are able to prune, or remove, old, unused, or useless synapses and dendrites (normal mechanism shown in Fig. 1—23). One postulated mechanism for some degenerative diseases is that this otherwise normal pruning mechanism may get out of control, eventually rendering the neuron useless or even killing it by pruning it to death. ... 

At this section of the plant in the past, chemical process operators (not maintenance mechanics) handled the tank-filling step in the hydrotest process. Operators would typically drape a fire hose into an oversize roof nozzle and fill the tank from the nearest hydrant. In this case, it was reported the two mechanics asked their maintenance supervisor if they could connect the hose to a flanged lower-valved nozzle on the tank. The supervisor remembers requesting the mechanics to roll a blind flange at the top for venting purposes if they used the lower nozzle for filling. There must have been a miscommunication. Obviously the mechanics failed to understand the dynamics of the filling operation when they chose to open only the two 1/2-inch top vents. 

A Latin American chemical plant experienced a catastrophic fire and series of Boiling Liquid Expanding Vapor Explosions (BLEVEs) that resulted in the loss of one life and 5 million in direct damages (1977 dollars). The initial vapor cloud occurred as a maintenance mechanic started to remove a pneumatic actuator from the liquid discharge line below a tank of flashing flammable liquid that had a boiling point of 7° F (—14° C). 

The alert mechanic informed the operations supervisors of the failures. Operations shut down the furnace. Maintenance mechanics replaced the bolts with the properly-specified high-strength stud bolts prior to any serious releases. 

The procedure was to clear the transfer fine of the waxy material with compressed air supply just before the transfer fine was put in service. On the evening of the accident, an operator connected an air hose to a 90 psig (6 bar) supply to clear the entire 200 meters (600 ft.) of feed line. The operator then walked to the elevated tank to determine if air could be heard rushing out of the tank vent. He heard nothing. The operator spoke to two maintenance employees working near the end of the 20-m3 (700 ft3 or 5,300 gallon) tank and left the area to find his supervisor. Shortly after that, one end of the tank blew off, and the two maintenance mechanics plunged some 40 ft. (12 m) to their deaths. [7]... 

According to the ambiguous instructions written in the log for the operator, he should have pressured up the ammonia condenser to compressed air system pressure. Next, he should block off the air supply and discharge ammonia fumes to the atmosphere. The operator pressurized the ammonia-laden condenser to full air system pressure, but unfortunately did not block it off. Therefore at the beginning of the day when the arriving maintenance mechanics... 

This is the more normal test situation. For processes where prooftesting the final trip or control element cannot be made available (such as testing a furnace shutdown system), the maintenance mechanics perform a prooftest as described above (complete loop test) with the exception of testing the final trip or control element. All components in the loop including the final element are visually inspected for physical condition. Maintenance takes test credit for the portion of the loop prooftested. 

Do all of the affected individuals including the engineers, supervisors, chemical process operators, maintenance mechanics, purchasing employees, etc., understand that there is a management of change policy ... 

Most inorganic membranes are mechanically stronger than their organic counterparts. However, installation, repair and maintenance, mechanical vibration, pressurization and other application conditions sometimes can cause problems. This is especially true with... 

Hoeijmakers J., Genome maintenance mechanisms for preventing cancer. Nature, 2001, 411, 366-374. 

Specific maintenance mechanisms ensure that the inactive X chromosome is clonally transmitted and that it remains inactive in subsequent cell divisions. Methylation of CpG islands at the beginning of genes in the inactive X chromosome appears to play an important role in suppressing gene expression the corresponding CpG islands in the active X chromosome are usually unmethylated. 

Workers skilled in doing the job are the first logical resource for a procedure review team. Operators review operating procedures. Maintenance mechanics review maintenance procedures. Laboratory technicians and chemists review laboratory procedures. This promotes employee participation and ownership in the procedure development process. 

In this chapter the properties of nonaqueous hydrocarbon foams will be reviewed and the effects of foam formation on flow of oil—gas mixtures in porous media will be discussed A laboratory technique for investigating the role of foamy-oil behavior in solution gas drive is described, and experimental verification of the in situ formation of non-aqueous foams under solution gas drive conditions is presented The experimental results show that the in situ formation of nonaqueous foam retards the formation of a continuous gas phase and dramatically increases the apparent trapped-gas saturation. This condition provides a natural pressure maintenance mechanism and leads to recovery of a much higher fraction of the original oil in place under solution gas drive. 

Results of the experimental study suggest that the formation of an oil-continuous foam may be involved in flow of heavy oil under solution gas drive. Such foam formation can be very beneficial for increasing the oil recovery. It delays the formation of a continuous gas phase, and thereby acts as a natural pressure-maintenance mechanism. In terms of the conventional solution gas drive theory, it serves to greatly increase the apparent trapped-gas saturation. 

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