Position faults

As stated earlier, two types of fault trees will be constructed to demonstrate the use of this system safety analytical technique. The first, which will be referred to as a positive fault tree analysis, will identify the events necessary to achieve a top desired event of no accidents. The second, or negative fault tree, will be constructed to show those events or conditions that will lead to a top undesired event of a fire in a manufacturing facility. 

Sp < 9 Provide redundancy for the operation or a positive fault detector... 

The verification of the functional safety concept should be supported by a draft FMEA (see Fig. 4.23) or as illustrated by a positive fault tree. A hierarchically stmctured FMEA would be able to support the verification very well according to the VDA approach. 

A hierarchical functional decomposition could be applied similar to a positive Fault Tree Analysis , if be applying with the lowest function DeMorgan s law , a complete set of malfunction for the lowest malfunction could be evaluated. If these malfunctions would be analyzed from the bottom to the top (potential violations of safety goals) verification for completeness could be demonstrated. This bottom-up approach could be done by means of an FMEA, so that additional safety mechanism could be defined as measures of the FMEA (Fig. 4.67). 

The general list of factors influencing the uncertainty in the gross rock volume included the shape of structure, dip of flanks, position of bounding faults, position of internal faults, and depth of fluid contacts (in this case the OWC). In the above example, the owe is penetrated by two wells, and the dip of the structure can be determined from the measurements made in the wells which in turn will allow calibration of fhe 3D seismic. 

The impact of a knowledge-based application may appear in many ways improved competitive position, quality improvement, improvement in efficiency, cost reduction, and reduction in downtime, to name a few. Some of these benefits may be hard to quantify others may not be quantifiable at all. For example, the actual benefit derived from a diagnostic advisory system may not be apparent if the process behaves normally. To quantify the benefits, a careful post-audit may have to be done, taking into account the number of faults averted, and comparing the frequency of faults before and after implementation. 

High set instantaneous overcun-ent through the positive sequence network. An initial delay of a few cycles is introduced to avoid a trip during a start, whereas it will trip instantly on a phase fault, cable fault or a short-circuit. 

The magnitudes of symmetrical and non-symmetrical fault currents, under different conditions of fault and configurations of faulty circuits, can be determined from Table 13.5, where Z] = Positive phase sequence impedance, measured under symmetrical load conditions. The following values may be considered ... 

Note The impedances marked on Figure 13.1.6 refer to positive phase. sequence impedances only. Faults that are non-symmelrical alone... 

For a switching device (which has not been previously tested for a short-circuit test). This should be closed and held in the normal service position. The test voltage (that would generate the required level of fault current) may be applied on one set of terminals, the other terminals being shorted. The test may be continued until the short-circuit device operates to clear the fault, but in no case for less than 10 cycles. In LT assemblies the point where the short-circuit is created should be 2 0.4 m from the nearest point of supply. 

Not applicable. But if the In the event of a leakage is in the conipies- leakage, the breaker will sed air supply system, the still be in a position to breaker may not interrupt interrupt the normal on fault, depending upon currents the air pressure the system is able to maintain on a leakage... 

In a phase-to-phase fault, however, the system will be composed of two balanced systems, one with positive sequence and the other with negative sequence components. The phasors of these two systems individually will add up to zero, and once again, as in the above case, there will be no residual quantities through the neutral or the ground circuit, except for the transient and spillover quantities. 

Z = positive sequence equivalent system impedance, Q/phase at the location of the fault = negative sequence equivalent system impedance, fj/phase at the location of the fault. 

Insulators The conductors are resilient mounted on post insulators, to hold them in the centre (Figure 31.3) and dampen the forces, during normal operation or on fault. The conductors are held in position to have free movement axially but they have almost no movement... 

Contacts with other pipelines or grounds can be localized to within a few hundred meters by pipe current measurements. Contacts with foreign pipelines or cables can also be found by measuring potential at the fittings of the other line while the protection current of the cathodically protected pipeline is switched on and off. While the potential of unconnected pipelines will assume more positive values when the protection current is switched on, the cathodic current may also enter any line in contact with the cathodically protected pipeline and thus shift its potential to more negative values. Should the contacting line not be located by this method, fault location can be attempted with direct or alternating current. 

Positive Displacement c. Spurious Start/Command fault... 

Foolwall—lhe block that occupies the position beneath the fault, regardless of whether the hanging wall ha.s moved up or dowm. 

Fault traps—involve the movement of the reservoir rock formation to a position where the formation across the fault plane provides a seal preventing further migration of hydrocarbons (see Figure 2-48). 

Plan and schedule sequences of operating steps to bring the plant at the desired operating level, e.g., recover from safety fallback position, return to feasible operation after a fault. 

Other kinds of defects could give rise to peak broadening, for example the staking faults. In this case, the equation taking into account this phenomenon depends on the peculiar structure of the crystals and the analysis can be more complex some defects, in fact, introduce profile asymmetry and a shift in the position of some selected peaks [26]. 

Among crystals with stacking faults the lack of a periodic order is restricted to one dimension this is called a one-dimensional disorder. If only a few layer positions occur and all of them are projected into one layer, we obtain an averaged structure. Its symmetry can be described with a space group, albeit with partially occupied atomic positions. The real symmetry is restricted to the symmetry of an individual layer. The layer is a three-dimensional object, but it only has translational symmetry in two dimensions. Its symmetry is that of a layer group there exist 80 layer-group types. 

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