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Gas Flow Meter Symbol Reference: Standard ISA Drawing Icons for P&ID Engineering Blueprints
Quick Answer: A gas flow meter on a P&ID is not a single icon. It is a set of ISA 5.1 symbols that show the flow element, the transmitter, and the controller. Use FE for the flow element, FT for the flow transmitter, FQ for a totalizer, and FC or FIC for a control loop. Send us your pressure (bar), temperature (°C), pipe size (DN), and flow range, and Silver Instruments will help you choose a gas flow meter that fits the drawing and the process.
Why the ISA Symbol Reference Matters for Gas Flow
P&ID engineering blueprints follow ISA 5.1 and ISA 5.3 for instrument symbols. A gas flow meter symbol reference tells the piping designer, the EPC contractor, and the plant engineer what to install and how to connect it. Most engineers skip this part until a shutdown goes wrong because the P&ID did not show a pressure tap or the wrong signal type. We have seen this on customer sites many times.
A gas flow meter symbol has two parts. The primary element sits in the pipe. The secondary instrument sits in the field or in a control room. For a vortex flow meter, the flow element and transmitter may be in one device. The P&ID still shows an FE bubble and an FT bubble in many projects. The line between them can be an electrical signal, a 4-20 mA HART signal, or a digital output.
Common Gas Flow Meter Symbols and Letter Codes
The ISA letter codes are the core of any gas flow meter symbol reference. FT means flow transmitter. FE means flow element. FI means flow indicator. FR means flow recorder. FQ means flow totalizer. FC means flow controller. FIC adds an indicator to the controller. Add a tag number like FT-101 or FE-101. In practice, a natural gas metering skid may use FE-201 for an orifice plate, FT-201 for the differential pressure transmitter, and FQ-201 for the totalizer in the PLC.
Here is the thing. ISA bubbles do not show the meter technology. A thermal mass flow meter and a Coriolis gas flow meter can both use FT. The spec sheet, the line list, or the instrument data sheet tells the vendor which technology to supply. Do not expect the P&ID symbol itself to say Coriolis, vortex, or ultrasonic. You add that in the equipment description or the P&ID note.
Matching Meter Types to Gas P&ID Drawings
Vortex flow meters fit many gas applications. Compressed air, steam, natural gas, and flare gas in DN15 to DN300 pipes are common. A vortex meter has no moving parts and works in ATEX Zone 1 areas. The P&ID symbol often shows a flow element in the pipe with an FT bubble nearby.
Thermal mass flow meters are common for low flow gas measurement. Biogas, aeration air, and natural gas to burners are good examples. These meters give a direct mass flow signal in kg/h. The P&ID symbol uses FT or FQ. For small pilot plants, a DN15 insertion probe may be enough.
Coriolis mass flow meters are used when gas mass flow accuracy matters. They can measure from very low flow to high flow, often in kg/h or standard cubic meters per hour. A Coriolis meter may appear as FT or as a mass flow totalizer FQ. On a P&ID, the symbol often sits in a line with a pressure transmitter PT and a temperature transmitter TT for flow correction.
Ultrasonic flow meters handle large pipes and low pressure drop gas lines. Flare gas, stack gas, and custody transfer lines sometimes use ultrasonic. The symbol is still an FE or FT. Do not assume the symbol tells you the meter type.
Oval gear flow meters are for liquid fuels and oils, not dry gas. A paint manufacturer in Southeast Asia needed a gas flow meter symbol reference for a solvent vapor recovery line. The final P&ID used a vortex flow meter for the vapor stream and an oval gear flow meter for the liquid solvent return with viscosity near 2 cP.
Pressure and Temperature Compensation in Gas Flow Loops
Gas volume changes with pressure and temperature. Because of this, many gas flo
Field Mounted vs Panel Mounted Symbols
A plain ISA bubble means a field mounted instrument. A bubble with a horizontal line means panel or DCS mounted. This detail matters when you order a gas flow meter. A field mounted vortex meter may need a local display. A panel mounted totalizer may be in the control room. On gas P&ID drawings, you will often see FT in the field and FQ in the control room. The line between them is a signal line, not a process line.
Last year a customer in Vietnam asked us to check a P&ID for a compressed air line. The drawing showed a field mounted FT, but the instrument list had a panel mounted totalizer. The mismatch caused a rewire. Most engineers skip this part if the control system integrator handles the loop drawing. But the P&ID is the reference for maintenance later.
How to Specify a Gas Flow Meter from a P&ID
Start from the process line and the tag number. Check the pipe size, the flow range, the pressure in bar, the temperature in °C, and the gas type. Then check the ISA bubble function letters. If the P&ID shows FQ, you need a totalizer output. If it shows FT, you need a live flow signal. If it shows FIC, you need a control loop with a valve. Send us these details and Silver Instruments will check the meter range and the output.
Tell us the pipe size in DN, the flow range in kg/h, the operating pressure in bar, and the operating temperature in °C. For hazardous areas, such as natural gas or solvent vapor, specify ATEX Zone 1 or Zone 2. For custody transfer, specify the accuracy class and the standards you must follow. We will quote a gas flow meter that matches the P&ID loop.
Silver Instruments Gas Flow Meter Support
Silver Automation Instruments supplies Coriolis mass flow meters, electromagnetic flow meters, ultrasonic flow meters, vortex flow meters, oval gear flow meters, thermal mass flow meters, pressure transmitters, and paperless recorders. The main markets are Southeast Asia, Oceania, Latin America, Africa, and the Middle East. Industries include oil and gas, water and wastewater, chemical, food and beverage, and marine.
For a fast quote, send us your pressure (bar), temperature (°C), pipe size (DN), and flow range. Call Silver Instruments at +86-25-68650347, WhatsApp +86-25-52155837, or WeChat +86 15365082610. You can also check the product range at flow-meter.com.au.
FAQ: Gas Flow Meter Symbols on P&ID
What is FT on a gas P&ID?
FT means flow transmitter. It sends a continuous flow signal, usually 4-20 mA HART, to a PLC or DCS.
What is FE on a gas P&ID?
FE means flow element. It is the part in the pipe that creates a measurable flow signal. Examples include a vortex shedding bar, a thermal sensor, or an ultrasonic transducer set.
Does ISA show the gas flow meter type?
No. ISA 5.1 function letters show what the instrument does, not the technology. You add the meter type in the line list, the data sheet, or a drawing note.
What is the difference between FQ and FT?
FT gives a live flow rate in units such as kg/h or standard cubic meters per hour. FQ gives an accumulated total, often in kg or standard cubic meters.
Do gas flow meters need pressure and temperature compensation?
Many gas volume meters need a PT and a TT for compensation to standard or normal conditions. Thermal mass and Coriolis meters give mass flow directly, so compensation may not be required. Check the P&ID for PT and TT symbols in the same loop.
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