The H prefix denotes hand or manual operation and prefixing all devices with H keeps one loop number with all devices together.
The HY is a position transmitter and HZI displays the actual valve position not just the controller output signal a.k.a. implied valve position.
The FC suggest that the valve closes upon loss of instrument air or 4-20 mA signal. TSO suggests tight shutoff.  Typically control valves do not provide the positive shutoff required for block valves such as shutdown or isolation.  The valve symbol is a butterfly valve.  Some double and tripple offset valves can be throttled and provide tight shutoff.  TSO typically requires Class V or VI shutoff per FCI 70-2 / IEC 534-4.
HZSO and HZSC are position switches.  The O and C may not be exactly per ISA but they are the normal industry standard for open and closed position switches.  The switch is wired to the SIS may could use position verification in the logic.  A link such as TIA 485 or Ethernet permits the position to be displayed on the DCS screen.
HIC is the operator throttling adjustment from the DCS screen.  The solenoid HY is actuated by the SIS to trip the valve closed upon the process event as identified in a logic interlock scheme labeled I-2.
The symbol reflects a diaphragm positioner and handwheel.  If very large it could actually be a spring opposed piston.  The valve tag is HV-1000 etc. but the data sheet must direct the seller to provide nameplates with all of the tag numbers and to reflect them on the vendor drawings.  Don't hold your breath as the sellers rarely comply with specifications.  However, you may never know unless you are fortunate enough to follow the project to the field for construction support, better still for commissioning and STARTUP.

MORE NEWS