Unwanted energy flow

There are unwanted energy flows or exposures to hazardous environments. (If there are no unwanted energy flows or exposures to hazardous environments, no incidents can occur that result in harm or damage.)... 

MORT conceives the accident occurred when an unwanted energy flow or environmental condition that results in adverse consequences reaches persons and/or objects. MORT combines this concept and others into a functional accident definition as follows An unwanted transfer of energy or environmental condition because of lack of or inadequate barriers and/or controls, producing injury to persons and/or damage to property or the process [p. 2]. 

After an accident occurs, the first step in the MORT process is to consider the adequacy of the amelioration process, their intent being to limit the severity of the consequences. Then MORT users would determine the unwanted energy flows or hazardous environmental conditions, whether barriers and controls were less than adequate, and whether vulnerable people or property were exposed. 

If controlling the hazards through improved design or engineering is impossible or impractical, the next course of action should be to use physical guards or barriers to separate potential unwanted energy flows or other hazards from potential targets. 

The HazOp study is also similar to the ETBA in that it traces energy flows through a facility, studies barriers to control energy flows, and identifies the targets of unwanted energy flows. 

The sides of the accident triangle that are discussed in the MORT program are the unwanted energy flow, barriers that are less than adequate to prevent or control the energy flow, and targets (persons or objects) in the energy path (Fig. 13-1). This approach is the basis for ETBA, which systematically analyzes these three factors and their interrelations. 

Identify and evaluate the barriers that are in place to control the energy and the potential targets of any unwanted energy flow that could occur if the barriers fail. 

Determine the risk associated with each potential unwanted energy flow and express this risk in terms of a risk assessment code (RAC). 

Column 3—Targets. List the persons or objects at this particular location that could be in the path of an unwanted energy flow. Quantify if possible (number of people, value of property). Include other systems and subsystems that could be adversely affected by the unwanted energy flow. 

Column 4—RAC. Enter the risk assessment code associated with this particular unwanted energy flow. List a separate RAC for each potential target. 

Column 5—Comments/Barrier Evoluation. Provide comments on the adequacy of the existing barriers to control potential unwanted energy flows at that particular location. If appropriate, include comments on compliance with applicable codes, standards, and regulations. 

This configuration is consistent with the accident triangle (Fig. 18-8) and the definitions of incident as an unwanted energy flow and of accident as an unwanted energy flow that results in adverse consequences. 

Figure 18-9 Unwanted energy flow. Many accidents are the result of a series of unwanted energy flows, barrier failures, and vulnerable targets.

For analysis purposes, the changes under the accident block make little difference. The three main branches on the specific control factors side continue to be the contributory events that allowed the unwanted energy flow (or hazardous environment), the LTA barriers, and the targets in the energy path (or vulnerable to the hazardous environment). 

The items to evaluate to determine the adequacy of the controls designed to prevent unwanted energy flows and exposures to hazardous environments include the technical information system, maintenance and inspection programs, direct supervision and services provided by higher levels of supervision, and the functional operability of facilities (Fig. 18-11). 

Figure 18-13 Targets. This branch addresses the persons and/or objects which are the targets of the unwanted energy flow (or harmful environmental condition).

Prevent second accident Were the losses limited to those that resulted from the initial unwanted energy flow Were rescue or other emergency response personnel injured Was unnecessary damage to property done during the rescue effort ... 

Assuming an accident did, in fact, occur, the next branches to be analyzed are those that may have contributed to the unwanted energy flow (Fig. 18-16). Higher supervision services are provided by levels of supervision between the... 

A general approach to common cause failure analysis is to identify critical systems or components and then use energy trace and barrier analysis (ETBA) to evaluate vulnerability to common environmental hazards, unwanted energy flows, and barrier failures (see Chapter 13). 

The eventual target s) of unwanted or uncontrolled energy flow targets may be either people or objects)... 

Structural control systems must be designed using rather small-scale models but are applied in the real structure with a theoretically infinite number of eigenmodes. Unwanted interaction or energy flow from the control system to neglected but excitable structural modes may occur and lead to loss of performance or even instability. This effect is known as spillover [17]. 

Energy Trace and Barrier Analysis A system safety analytical technique used to evaluate the flow of energy through a system and analyze the effectiveness of existing barriers within the system which are intended to prevent unwanted transfers of that energy flow. 

There are unwanted energy flows or exposures to harmful environments. 

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