Prooftesting instrument mechanic

Figure 10-25 An instrument mechanic prooftests a critical instrument panel.

Figure 12.27 An instrument mechanic prooftesting a flammable vapor detector in a tank farm.

Six independent groups of technical personnel provide prooftesting services. Prooftesting is performed by electricians, critical-metering mechanics, refrigeration mechanics, analyzer-repair technicians, instrument-maintenance personnel, and chemical process operators. 

Class 1 safety instrumentation loops include alarms and trips on storage tanks containing flammable or toxic liquids, devices to control high temperature and high pressure on exothermic-reaction vessels, and control mechanisms for low-flow, high-temperature fluids on fired heaters. Other Class 1 instruments include alarms that warn of flame failure on fired heaters, and vapor detectors for emergency valve isolation and sprinkler-system activation. All of these alarms, shutdown valves, and other critical instruments are regularly prooftested on a well-defined schedule. 

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