Certified Control System Technicians (CCSTs) calibrate, document, troubleshoot, and repair/replace instrumentation for systems that measure and control level, temperature, pressure, flow, and other process variables.
As outlined in ANSI/ISA 5.1-2009, Instrumentation Symbols and Identification, an instrument that is monitored on the control system HMI and is part of a safety instrumented system (SIS) loop would be represented by which type of symbol on a process and instrumentation diagram?
A. A circle contained in a box with a horizontal dashed line through the circle.
B. A hexagon with a double-dashed line through it, not contained in a box.
C. A diamond contained in a box with a horizontal solid line through the diamond.
D. There is no representation for a SIS instrument given in ANSI/ISA 5.1-2009.
The correct answer is C,“A diamond contained in a box with a horizontal solid line through the diamond.”
The diamond symbol was first defined for safety instrumented systems with the release of ANSI/ISA 5.1-2009. Per previous releases, a box around the instrument “bubble” with a solid horizontal line through it indicates that the measurement or control element is normally accessible to the operator from the main operator console, typically a human-machine interface (HMI) screen in modern control systems.
Reference: Goettsche, L.D. (Editor), Maintenance of Instruments and Systems, Second Edition, ISA, 2005.
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