Safety critical item

The first is that ISO 105 needs to make greater provision for the testing of textiles in the U V absorption bands, and the second is that provision also needs to be made for larger test specimens in order to allow for post-exposure assessment of changes in properties other than color. This could be of particular importance where the textile product is itself a safety critical item. 

Figure 12.1 shows the interactions between development and operations. At the end of the development process, the safety constraints, the results of the hazard analyses, as well as documentation of the safety-related design features and design rationale, should be passed on to those responsible for the maintenance and evolution of the system. This information forms the baseline for safe operations. For example, the identification of safety-critical items in the hazard analysis should be used as input to the maintenance process for prioritization of effort. 

Prioritize maintenance for identified safety-critical items. Enforce maintenance... 

Ensure that spare safety-critical items are in stock or can be acquired quickly. 

The use of fire-rated insulating materials to protect the integrity of stmctural steel members, risers, vessels, and other safety critical items. 

Note that, for screws engaged over the greater part of their length, only an appropriately weak grade will allow easy removal for maintenance. Furthermore, such a weak material will also allow adjustment and retention - but this technique should only be employed on safety-critical items after very careful evaluation. Occasionally, a screw needs to be made quite immovable and, for this, only the truly adhesive versions of the anaerobic family or some other suitable permanent... 

Any good quality-assurance system should also assess the quality of performance in practice as well as in theory. With no currently available, effective, non-destructive test, critical areas or components may only be assessed for voids (acoustic methods are useful here) and, where possible, proof loaded. Other than this, test coupons or parts need to accompany the components themselves through the assembly process so that appropriate, systematic destructive tests may be carried out. A check-list for safety critical items is given in Table 6.1. 

Calibration is a comparison of a measuring device with a known standard and a subsequent adjustment to eliminate any differences. Not to be confused with alignment. Calibration of safety-critical items (SCIs) is a safety concern, and may be established as a critical safety item (CSl). 

See Critical Safety Item (CSI) and Safety-Critical Item (SCI) for additional related information. 

Steel is used extensively as a construction material in pressurized boilers and ancillary piping circuits. The boiler and the attached steam/water circuits are safety-critical items on a ship. The sudden explosive release of high-pressure steam/water can have disastrous consequences. The worst boiler explosion in the Royal Navy, on board HMS Thunderer, claimed 45 lives in The subsequent inquiry... 

Such an action can also apply to the failure of safety-critical items if the item is backed up by a redundant element. 

Identified Safety Critical Items are subject to a Critical Items Control Programme. The programme provides for an elevated level of Management, Engineering, and Product Assurance attention for those items identified as critical. The items are ranked in order of criticality in order to support prioritisation for attention and resource assignment. 

Where the relevant safety requirements can be complied with, the Hazard Consequence Report continues to be processed in a nominal manner. If, for some reason, a defined safety requirement cannot be satisfactorily implemented, or its implementation cannot be verified as complying with the intent of the requirement, then once again the relevant report is identified as potentially unresolved. Furthermore, if risk assessment determines that, in spite of compliance with defined requirements, significant risk contributors remain in the design, then the relevant report is also identified as potentially unresolved. At this stage, additional safety critical items may also be identified. 

The level of management which is responsible for safety risk acceptance is based on the qualitative ranking of the risk being accepted. Ranking is achieved by taking into account hazard consequence severity categories, whether the hazard is characterised as unresolved or controlled, and the number of safety critical items associated with the risk being accepted. 

Identification of the safety critical items (e.g. red jimction boxes, large red cable markers)... 

Safety critical A term applied to a condition, event, operation, process or item which is essential to safe system operation or use (e.g. safety critical function, safety critical path, safety critical item, etc.). All interactions, elements, components, subsystems, functions, processes, interfaces, within the system that can affect a predetermined level of risk. 

Safety critical item An item whose failure can cause hazards of catastrophic or critical severity. 

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