Safety critical instruments

Experience with inherent safety reviews indicates that project investment costs are frequently reduced as a result of this exercise. Eliminating equipment and reducing the need for safety critical instrumentation are typically the main contributors to investment reduction. Capturing these potential savings depends greatly on the timing of the reviews. 

Covers mechanical integrity programs for safety critical instruments and safety relief... 

Mechanical Programs for Safety-Critical Instruments and Safety Relief Valves... 

Another Company—A Different Emphasis on Safety Critical Instrument Systems... 

Critical Consequence—Class 1. Safety Critical instruments whose failure would either cause, or fail to inform of, situations resulting in accidental fire, explosion, uncontrolled release of dangerous materials, reportable environmental releases, or major property or production losses. The safety critical instruments assigned a Class 1 include those that have been mandated as such by regulating agencies an in-house technical safety review committee reliability studies and specific shutdown systems and specific alarms deemed critical by operations supervisors. 

Class 2 Safety Critical instruments include alarms or trips on refrigeration systems, rectifiers, cooling towers, kettles, and stills. [8]... 

When repairs are successfully completed and the safety critical instrument is restored, the Lead Operator will remove the out-of-service tag from the control board. 

Delays to Safety Critical Instrument Test and Equipment Inspection Frequencies... 

Practical Information on Aging of Pressure Vessels, Tanks, Piping, and Safety Critical Instruments... 

Practical Information on Safety, Critical Instruments, Pressure Vessels, Tanks, and Piping... 

Serious Consequences—Class 2. Safety Critical instruments whose failure could either cause, or fail to inform of, serious conditions involving environmental releases,... 

Class 2 Safety Critical instruments include alarms or trips on refrigeration systems, rectifiers, cooling towers, kettles, and stills. [71 Normal Consequences—Class 3. Instrument systems that are used to alert the chemical pracess operator of a nonhazardous abnormal condition that might otherwise be undetected. The failure to react to one of these alarms may create an off-spec ificalion product such as a low-temperature alarm on certain distillation columns. These systems are not included in the prooftest program. 

When repairs are successfully completed and the safety critical instrument is restored, the Lead Operator will remove the out-of-service tag from the control board. He fills out the blank, which indicates the date when the instrument was restored, and tapes the small slip into the logbook. 

Another company - a different emphasis on safety critical instrument systems... 

Delays to safety critical instrument test and equipment inspection frequencies... 

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