High Complexity Facilities

DOE-STD-1027-92

is to review the process in a series of meetings during which the

multidisciplinary team "brainstorms" the plant design methodically by

following a sequence based on prescribed guide words and the team

leader's experience. The guide words are used to ensure that the design is

explored in every conceivable way. The HAZOP is based on the principle

that several experts with different backgrounds can interact and better

identify problems when working together than when working separately and

combining their results.

Generally, HAZOP should be used for identifying accident scenarios

associated with continuous processing which involves the control of a

significant number of parameters in order to maintain the process in steady-

state conditions and within safe limits. Such processes generally have

systems intended to monitor key parameters. Such monitoring systems may

interface with automatic control and protection systems which act to maintain

the process in a safe condition or may only trigger alarms to alert the

operator that a parameter change requires a response. Thus, such a

process can be either one that is automatically controlled and generally

expected to operate without or with a minimum of supervision, or one

requiring intense operator involvement for control. For this reason, detailed

design information (e.g., Piping & Instrumentation Diagrams) is required for

the analysis.

Fault trees may be used to complement to the HAZOP process. However,

the use of fault trees in this context does not imply that the trees should be

quantified probabilistically since the purpose is only the identification of

scenarios for release.

High Complexity Facilities

Use Integrated Event Tree and Fault Tree Techniques (ETs/FTs)

Facilities with a large number of interdependent components or systems and

fluid flow processes are highly complex. Highly interdependent systems and

components should not be taken to include basic buildings systems such as

Heating, Ventilation, and Air Conditioning (HVAC) and electrical power

distribution systems unless these systems have significant effect on the

progress of the accident sequence. Highly complex facilities include

multi-component transfer and control systems for which extensive

instrumentation and control systems are needed. Extensive redundancy at

the component, system, and safety level are also inherent in highly complex

facilities. Such processes generally cannot be completely controlled through

manual actions because the interactions between systems are too intricate

for an operator to interpret in the time required for action. Thus, these

processes are generally characterized by large-scale monitoring and

automatic control systems. Further, such facilities generally vary greatly in