System safety criteria

MIL-STD-882 establishes system safety criteria guidelines to assist in the determination of hazard severity. The hazard severity categories listed in Table 2.1 provide... 

During the concept phase, historical data and technical forecasts are developed as a base for a system hazard analysis. A Preliminary Hazard Analysis (PHA) is conducted during this phase. At the gross level, a Risk Analysis (RA) is performed to ascertain the need for hazard control and to develop system-safety criteria. Safety management will be doing the initial work on the System Safety Program Plan (SSPP). Three basic questions must be answered by the time the concept phase is completed ... 

Demonstrate compliance with the system safety criteria and design and operational requirements. 

As an example for a subsequent level, the second level qualification criteria for criterion A 1 (suitability assurance) are given in table SI. Table S 2 gives the second level criteria of a part (namely the quality assurance part) of first level criterion A 2 (product assurance). The second part would be a table for V V, which has not been included, as only the principle of the qualification process is shown in this paper. For the same reason, also the further details of the first level criteria documentation, product safety, system safety, interface, compensation by operating experience, error reporting, and modification are not elaborated. Thus the GOTO. .. and other references in the description part of the tables, which are the pointers to the more detailed criteria are in most cases empty. 

The tables S 1 and S 2 in this example are dealing only with the first level criterion suitability assurance and one part of the aspects of the first level criterion product assurance , i.e. with software quality assurance. The other part of the criterion product assurance is verification and validation, V V, which also has to be broken down in more detailed criteria. Also the other first level criteria of tables 3, 4 and 5, i.e. dociunentation, product safety, system safety, interface, compensation by operating experience, error reporting, and modification should be detailed into appropriate levels of refinement. Examples for this process can be foimd in [7]. 

Criterion 35 - Emergency core cooling. A system to provide abundant emergency core cooling shall be provided. The system safety function shall be... 

Criterion 38 - Containment heat removal. A system to remove heat from the reactor containment shall be provided. The system safety function shall be to reduce rapidly, consistent with the functioning of other associated systems, the containment pressure and temperature following any loss-of-coolant accident and maintain them at acceptably low levels. 

Emphasis is placed upon the functional reliability concept, introduced in (Burgazzi 2003) and enhanced in (Apostolakis et al. 2005, Burgazzi 2007) where the failure probability of the system is assessed by comparison with the threshold or limit values for any significant system characteristic parameters, according to a defined safety criterion, as highlighted in the... 

The first safety criterion to be used was the rule which limited hand assembly to those partial arrays which, udten reflected by a large polyethylene slab, had multiplications not greater than 10, en this rule proved to be overly restrictive, an effort was made to remove thie reflector from the safety criterion. The prclosed rule youM allow hand assembly of any unreflected system having a multiplication of 10 or less. This was considered to be a reasonable application of the guidance stated in Ref. 1. 

The flight safety science uses such concepts as the SP safety, aircraft system safety, and aviation (air) safety. The aircraft safety determines an aircraft capability under complex operation conditions to stay within a risk range nor exceeding a criterion value. 

In order to account for the effects of uncertainties and potential undesirable performance of a structure during its lifetime, reliability offers the means for quantifying the level of safety associated with a structural system. A criterion widely used for characterizing safety of a structure is the first-excursion probability (see, e.g., Soong and Grigoriu, 1993). This probability measures the chances that uncertain structural responses exceed in magnitude prescribed thresholds within a specified time interval. That is, first-excursion probability measures the chances of occurrence of the following event F (which is termed in the sequence as failure event) ... 

Another criterion is the effective enforcement of an operating ban imposed on a carrier by a third country predicated upon substantiated deficiencies related to international safety standards. Yet another is substantiated accident-related information or serious incident-related information indicating latent systemic safety deficiencies. The lack of ability and/or willingness of a carrier to address safety deficiencies that is demonstrated by lack of transparency or failure to communicate in a timely manner in response to a query by an EU member State regarding a carrier s safety practices and record and an inappropriate or insufficient corrective action plan are also criteria that would prompt inclusion in the black list. 

Evaluate Effectiveness on the Basis of Outputs and Acceptance Once the system has been implemented on its chosen site, its effectiveness needs to be evaluated at frequent intervals so that corrective action can be taken in the event of problems. The first criterion for success is that the system must generate unique insights into the causes of errors and accidents, which would not otherwise have been apparent. Second, the system must demonstrate a capability to specify remedial strategies that, in the long term, lead to enhanced safety, environmental impact and plant losses. Finally, the system must be owned by the workforce to the extent that its value is accepted and it demonstrates its capability to be self-sustaining. 

Some would say that this is the current state of the art. Much of the necessary library could be assembled from test systems that have been extensively evaluated and have already undergone extensive validation (Gad, 2000, 2001). Three critical steps must be taken for the eventual fulfillment of these objectives (1) acceptance of a scientific approach to the problem of safety assessment (2) development of an operative validation and acceptance process for new test procedures (3) clear enunciation of an acceptance criterion for new test designs by regulatory authorities. 

With these four strategies comphance with Part 11 can be cost-effectively integrated into the management of any automated laboratory, and while primary consideration must be paid to compliance with requirements and to adding safety controls as necessary beyond those requirements, cost-effectiveness can appropriately be utdized as a third-level criterion in laboratory system selection, design, and management. 

Structural analysis of the solid rocket case-grain system using experimentally determined propellant response properties may permit a complete description of the combined stresses and resultant deformations, but a statement expressing the ability of the propellant to withstand these stresses is also required. Such a statement, which relates the physical state at which failure occurs to some material parameters, is called a failure criterion. The criterion for failure permits a prediction of safety margins expected under motor operation and handling and defines the loading regimes where abnormal operations will occur with intolerable frequency. 

No clear guidelines exist for the appropriate use of performance impairment test systems for work eligibility. There is general agreement that in situations in which worker or public safety is potentially influenced by a worker s performance, impairment test systems are justified. However, no clear criteria for identifying safety issues are available.9 The use of such tests as a means of managing worker productivity is less universally accepted, and if used as an employee evaluation criterion, such tests should be given careful scrutiny. 

However, several exothermic reactions are characterized by moderate or low values of the B number here, the transition stages from safe to runaway conditions may cover a quite wide range of the parameter values, and the choice of the boundaries for the safe region is very discretional. Hence, not surprisingly, the main discrepancies among the different criteria are found at low B numbers [14, 15]. Moreover, in this case, runaway is a less dramatic phenomenon posing the problem to decide whether a bland explosion still represents a safety issue. In this case, an effective runaway criterion should be more properly determined on the basis of the actual ability of the system to comply with certain levels of temperature and pressure. 

Department of Energy systems analysis should specifically include safety, and it should be understood to be an overriding criterion. 

The objective of the dynamic optimization is to determine, for a dynamic system, a set of decision variable time profiles (pressure, temperature, flowrate, heat duty etc.) that optimise a given performance criterion, subject to specified constraints (safety, environmental and operating constraints). 

Note that an important word in this criterion is contribute . The system does not need to be directly responsible for harm to make it safety-related. In the majority of cases there will be a human being between the system and the patient. This individual will typically have professional responsibihties and be required to apply chnical judgement. Essentially, an HIT system can only be one contributor to a chain of events that result in harm. 

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