Pumps local power failure

Local power failure, such as a motor for a pump or compressor, or fan for an air cooler... 

This essentially means the failure of an individual drive of a pump, compressor, fan, and so on. Failure of a single motor does not always mean it will affect only one relief valve. Depending on the drive that fails, the relief can be substantial. The following situations should be considered carefully in evaluating the impact of local power failure ... 

Power will be purchased from a nearby company. (One of the major reasons for locating here was the presence of low-cost, plentiful power.) A gas-fired plant for 125 psig steam will be built. This must be able to supply enough power to operate agitators and cooling-water pumps associated with the reactors when there is a power failure. Gas will be purchased from a local company. Drinking water will be purchased from the community of Martins Ferry, Ohio. Process and cooling water will be obtained from the Ohio River. Both will require treatment before they can be used in the plant. 

The operation of ECCS pumps is also possible from a local key lock hand switch and from the control room but automatic signals pre-empt all others. In the event of normal power failure while the system is operating or in the process of going into operation, the system will restart from the standby sources. All system alarms annunciate in the control room. 

Because of the potential Importance of the moderator cooling system a high degree of reliability has been provided Circulation pumps are powered both vlth BPA and local electric power In the event of failure of both power systems, cooling will be supplied by raw river water on a once through basis ... 

Failure is considered both on a local basis i.e., loss of utihty supply to one item of equipment (e.g., electric power to a pump motor) and on a general basis i.e., loss of supply to all consuming equipment in a process unit (e.g., cooling water to all coolers and condensers). For the purpose of these pressure rehef design considerations, a process unit is defined as one which meets all the following criteria ... 

Generally, electricity is purchased from a local supplier. Power is required to generate motor drives for lighting and for general uses. Note tliat, in tlie typical distillation operation illustrated in Fig. 16.3.3, a power outage for the entire system would cause a less severe effect tlian failure of a reflux pump alone. 

Apart from the outer boundary the inner boundary, i.e. the degree of detail of the analysis, must be determined. With reference to the telephone example this implies the question whether screws, coils, cables etc. have to be considered or not. Does the analysis have to address the molecular or atomic level or go even further Obviously not. In practical cases the degree of detail is determined by the objective of the analysis. If we intend to find out the consequences of a pump failure, it suffices to consider the pump as a unit. This unit comprises the motor, the impeller, the power transmission and the easing as well as the local control boards and the cables to the sockets in the wall. Should, however, the failure of the pump itself be examined, the piece-parts mentioned must be eonsidered individually or even be broken down to smaller units. 

The primary loop pumps will normally be powered during operation by process generated steam in the secondary loop. During initial phases of startup and after shutdown they will be powered by steam generated by the local oil-fired boiler. In the event of failure of the local boiler the process can be shut down and maintained In the shutdown condition without fuel damage by the use of BPA electrically powered motors provided for the piurpose Any two of the five primary loop process pumps have the capability of providing adequate... 

The continuous formation and collapse of numerous bubbles at the surface of a component, created due to localized pressure changes during high-velocity fluid flow, could lead to cavitation erosiom Collapse of these bubbles is always accompanied by the emission of shockwaves and micro-jets, which will exert stress pulses on solid surfaces in the vicinity. Repetitions of shockwaves on the solid surface will eventually lead to fatigue failure, fracture and material loss (Brennen, 1995 Kwok et ai, 2000). Cavitation erosion is commonly observed in valves in nuelear power plants and in pumps in the petroleum industiy. Cavitation erosion is essentially a mechanical process. However, in many working environments, eavitation erosion and eorrosion occur simultaneously, and if eorrosion does oeeur it will accelerate the rate of eavitation erosion damage. 

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