Prooftesting program

All of the effort expended in designing plant-safety systems is of little value unless accompanied by an adequate prooftest program and regular maintenance. These safety systems—consisting of such components as safety-relief valves, tank vents, critical alarms, and protective isolation and shutdown devices—do not operate on a continuous basis. Rather, they are only called into service periodically to warn of, or to prevent, conditions that could lead to plant accidents. [8]... 

A prooftest program cannot be left to someone s memory. It must follow a well-structured format to accomplish the essential steps, regardless of the myriad of other activities and distractions that tend to absorb all the supervisors and mechanics time. 

When PPG Lake Charles first initiated its prooftest program, efforts to classify which safety devices were truly critical were not defined specific enough. Hence, the original program allowed too many instruments into the test system which created a top-heavy burden. To prevent this from happening, the following information should be developed for critical loops [8]... 

It takes years to develop and fine-tune a prooftest program. Time is required to identify all of the instrument loops that need to be included, and more time is needed to systematically collect or develop data sheets containing basic operational information for each device or loop. During the development stage, test methods need to be defined, and the appropriate personnel responsible for testing must be identified and trained. Finally, test frequencies must be decided. 

In 1998, the PPG Lake Charles facility has about 3,200 loops in its prooftest program. Over the past 20 years the prooftesting definitions have been revised, refined, rewritten, and revised again. There are still three classes in the prooftest program. 

In the case where the final element is not tested, Operations performs a functional check of that loops final trip element during the next routine startup or shutdown of the process unit. Operations then takes test credit for the final element prooftest, which is listed separately as their responsibility on the Prooftest Program. 

Normal Consequences—Class 3- Instrument systems that are used to alert the chemical process operator of a nonhazardous abnormal condition that might otherwise be undetected. The failure to react to one of these alarms may create an off-specification product such as a low temperature alarm on certain distillation columns. These systems are not included in the prooftest program. 

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