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Flow Meter Symbol ISO Reference: Interpreting Standardized Technical Engineering Blueprints
Quick Answer: Flow meter symbols on engineering blueprints follow ISO 14617 and ISA-5.1 for most P&ID drawings. A circle with FI means flow indicator. A circle with FT means flow transmitter. Always check the drawing legend first because symbols for Coriolis, electromagnetic, ultrasonic, and vortex meters vary by project and country.
ISO Standards Behind Flow Meter Symbols
ISO 14617 is the main reference for graphical symbols on diagrams. Part 6 covers measurement and control functions. ISO 10628 is also used in chemical and petrochemical plants. Many projects in Southeast Asia and the Middle East reference these standards in the title block. In practice, a project in Malaysia or Vietnam may use ISA-5.1 letter codes with ISO style symbols. You need to read the legend before you order or install a flow meter.
Common P&ID Flow Meter Symbols
Most flow meter symbols look like a circle. The difference is in the inside marks and the letter code next to the circle. A plain circle with FI is a flow indicator. A circle with FT is a flow transmitter. A circle with FE is a flow element, often a primary sensor. When you see FIT, that means flow indicator transmitter with a local display and a 4-20 mA HART output. In many drawings, the symbol also includes a small square or a wavy line. That tells you the type of flow meter the engineer wants.
Specific Meter Type Symbols You Will See
Electromagnetic flowmeter symbols often have two small horizontal lines inside a circle. Some drawings use a label MAG or EMF next to the tag. Coriolis flowmeter symbols can be a circle with two inward arrows or a small loop above the circle. Ultrasonic flowmeter symbols may show a clamp-on transducer pair outside the pipe line. Vortex flowmeter symbols sometimes include a small triangle or a stylized V inside the circle. Oval gear flowmeter symbols are less common on P&ID. They appear as two overlapping ovals or a circle with gear teeth marks. Thermal mass flowmeter symbols often appear as a circle with a dot and an arrow for gas flow direction.
Letter Codes and Loop Numbers
ISA-5.1 assigns the first letter F for flow. The second letter tells you the function. I means indicator. T means transmitter. E means element. Q means quantity or totalizer. C means controller. V means valve. A flow loop number like 101FIT is common in oil and gas projects in Latin America and Africa. The number links the field device to the control system. When you see 101FIT on a drawing, you need one flow transmitter with local indication. It should send a 4-20 mA signal to DCS or PLC. If the drawing shows 101FQ, you need a totalizer function,
Real Project Mistakes and How to Avoid Them
Most engineers skip this part. They trust the symbol and order the meter. We have seen this on customer sites many times. Last year a customer in Vietnam asked for a steam flow meter based on a P&ID symbol that looked like a vortex meter. The legend actually called for a differential pressure flow meter with an orifice plate. The vendor sent the wrong meter and the startup was delayed by three weeks. Check the legend first. Then check the pipe size, fluid, temperature, and pressure. Send those details to the supplier before you buy.
Matching Symbols to Silver Instruments Models
Silver Automation Instruments supplies flow meters that match most P&ID symbols. For a circle with FT and a wavy line for conductive liquids, use an electromagnetic flowmeter. Sizes cover DN10 to DN600. The liquid needs at least 5 µS/cm conductivity. For high viscosity liquids and oval gear symbols, choose an oval gear flowmeter. It works from 2 cP up to 2000 cP. For gas flow with temperature changes, use a thermal mass flowmeter. It covers pipe sizes from DN15 to DN200. Add a PT100 input if the gas temperature changes more than 30 °C. For ATEX Zone 1 areas, ask for an Ex d or Ex ia version. For custody transfer or high accuracy mass flow, use a Coriolis flowmeter. It reads kg/h, density, and temperature on one screen.
FAQ
What is the ISO standard for flow meter symbols? ISO 14617 is the main standard for graphical symbols on diagrams. ISO 10628 is common in chemical and petrochemical projects.
What does FI mean on a P&ID? FI means flow indicator. It shows local flow rate only. It does not send a signal to the control system.
What does FT mean on a drawing? FT means flow transmitter. It sends a 4-20 mA HART or pulse signal to PLC or DCS. Some FT tags also have local indication, written as FIT.
How do I specify a flow meter from a P&ID symbol? Read the legend first. Note the tag number, pipe size DN, fluid type, flow range, pressure, temperature, and required output. Send these details to the supplier with a photo of the symbol.
Does Silver Automation Instruments help with symbol interpretation? Yes. Send a clear photo of the P&ID section or the symbol. A sales engineer will identify the meter type and recommend a model. Tel: +86-25-68650347. Whatsapp: +86-25-52155837. WeChat: +86 15365082610.
For a fast quote on an electromagnetic, Coriolis, ultrasonic, vortex, oval gear, or thermal mass flow meter, send us your pipe size (DN), fluid, flow range, pressure (bar), temperature (°C), and the P&ID symbol. Tel: +86-25-68650347. Whatsapp: +86-25-52155837. WeChat: +86 15365082610.
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