P&ID symbols.
Reference for the symbols Tagsight reads on P&IDs: field instruments, panel instruments, valves, actuators, control loops, off-page connectors, and equipment shapes. Each symbol page describes how it appears on the drawing and how the extractor handles it.
Instrument mounting symbols.
- Behind-panel mounted instrumentAn instrument symbol with a dashed horizontal line bisecting the circle, denoting an instrument mounted behind the panel. Inside the cabinet, not directly acces.
- Field-mounted instrumentA simple circle on a P&ID denoting a discrete instrument located in the field, accessible to the operator at the point of installation rather than mounted on a.
- Panel-mounted instrumentAn instrument symbol with a solid horizontal line bisecting the circle, denoting an instrument mounted in the primary control panel and directly accessible to t.
- Shared-display BPCS function blockA hexagon containing a tag denotes a function executing in the shared-display Basic Process Control System, BPCS, the DCS or PLC that runs the regulatory loops..
- SIS logic solver functionA rounded square with an inscribed diamond marks a Safety Instrumented System, SIS function, the protective layer that takes the process to a safe state when a.
primary-element.
- Coriolis flow meterA U-tube or curved bent pipe with the inlet and outlet returning to the same plane. Coriolis meters report mass flow directly, plus density and temperature as s.
- Level sight glassA vertical glass tube against a vessel wall, tagged LG. Mechanical-only level indication for the operator at the equipment. No wires, no PLC channel, never on t.
- Local pressure gaugePI in an instrument circle on a pipe tap marks a local mechanical pressure gauge. Mechanical-only like the level sight glass, intended for operator local indica.
- Magnetic flow meterA pipe section labeled MAG with a pair of inline electromagnetic coils. Magmeters work on conductive fluids and produce a clean linear signal without moving par.
- Orifice plate, flow elementA vertical line bisecting the pipe represents an orifice plate flow element. Pair it with a differential pressure transmitter, PDT or FT and you have one of the.
- RTD sensor, Pt100, Pt1000TE, RTD inside an instrument circle. Resistance temperature detectors are the dominant primary element below 600 °C because they drift less than thermocouples a.
- Thermocouple primary elementTE inside an instrument circle is the standard tag for a thermocouple primary element. Thermocouples cover the highest temperature range in process work, especi.
- ThermowellA protective sheath that the temperature element inserts into. Tagged TW separately from the TE that lives inside it. Same physical location, two distinct items.
- Venturi flow elementA pipe section with a tapered constriction in the middle. Venturi tubes recover pressure better than orifice plates, which matters on services where the permane.
valve-actuated.
- Control valve, pneumatic diaphragmA globe-valve body topped by a rectangular diaphragm bonnet. The most common control-valve symbology on a process P&ID. The air signal in the upper rectangle mo.
- Motor-operated valve, MOVA valve body topped by a small circle with the letter M denotes motor-operated actuation. MOVs handle large block valves, ESD service, and remote isolation wher.
- Pressure safety valve, reliefAn angle-pattern body with a coiled spring bonnet on top. The spring sets the cracking pressure. Once relieved, the disc reseats. PSVs are mechanical safety dev.
- Solenoid valveA globe-valve body with a small rectangle on top containing the letter S. Solenoid valves switch on a discrete signal. You'll find them on instrument-air supply.
valve-body.
- Ball valveA circle inscribed in a square represents the ball-valve body. Quarter-turn operation makes ball valves the dominant emergency-shutdown choice on modern P&IDs.
- Butterfly valveAn ellipse with a diagonal disc inside represents a butterfly valve. Compact, low-cost, suitable for large diameters where a globe or ball would be unwieldy.
- Check valveA triangle pointing in the direction of intended flow. Check valves prevent reverse flow and are mechanical-only. No PLC channel, no actuator.
- Gate valveA bowtie body with a vertical stem and handwheel marks a gate valve. Gate valves are isolation devices, fully open or fully closed, never modulated.
- Globe valveTwo triangles meeting apex-to-apex form the standard globe-valve body symbol. Globe valves throttle flow well and dominate control-valve service because of it.
Symbol not listed.
If a symbol type you encounter on drawings is not covered here, send a note and we will document the extraction behavior.