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Hydraulic Symbols Flow Meter: Reading Industrial Machine Schematic Blueprints and Flow Element Placements
Quick Answer
Flow meter symbols on hydraulic schematics tell you the meter type, signal output, and location in the circuit. Read the tag number first, then check the line size and flow direction before you call a supplier. Silver Instruments can match the symbol and loop data to an electromagnetic, oval gear, or Coriolis meter for your machine.
Flow Meter Symbols on Hydraulic Schematics
On a hydraulic machine drawing, a flow meter usually appears as a circle with a flag or as a small box marked FE for flow element or FIT for flow indicator transmitter. ISA 5.1 and ISO 14617 symbols vary by plant, but most maintenance teams in Southeast Asia use a mix of both. In practice, the symbol matters less than the tag number and the process data next to it. A schematic may show a turbine type symbol, but the actual meter could be an oval gear unit if the oil viscosity is high.
Most engineers skip this part until a spare part is needed. Then they see the symbol, the tag, and the line size on the print and send a photo to a supplier. We have seen this on customer sites many times. A hydraulic power unit in Surabaya had a drawing marked with a paddle wheel symbol, but the actual line was DN25 and the flow range was 2 to 20 L/min. The replacement needed a positive displacement meter, not a paddle wheel.
Reading Flow Element Placement in Hydraulic Circuits
Placement affects accuracy. Flow meters should sit downstream of pumps and filters, but upstream of throttle valves or return lines depending on the measurement purpose. A meter on the pressure line reads pump discharge flow. A meter on the return line reads flow after actuators. A meter on a branch line reads only that branch. The schematic shows this but many prints do not include enough straight run detail. So check the actual pipe layout before you select a meter.
For high pressure hydraulic systems above 200 bar, a Coriolis mass flow meter from Silver Instruments can read mass flow directly. But you need to confirm the pressure rating, fluid temperature, and viscosity. For a phosphate ester hydraulic fluid at 65 °C and 150 bar, a stainless steel meter with no moving parts may be required. If the fluid is oil based, electromagnetic will not work. Use oval gear or Coriolis instead.
Common Mistakes When Reading Hydraulic Prints
One common mistake is assuming the symbol type is the exact technology. Another is ignoring the loop power and signal marked near the symbol. A drawing may show a 4-20 mA HART output from a flow element, but the replacement flow meter may have pulse only. That creates extra wiring and PLC changes. So check output first. We see drawings from Latin America and Africa where the field device has a HART signal, but the replacement quote is for a pulse meter. That does not work without a converter.
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Recommended Flow Meter Types for Hydraulic System Prints
If the schematic shows a flow switch or flow indicator on a hydraulic oil line, start with these technologies. An oval gear flow meter works for lube oil and hydraulic oil from 0.1 to 100 L/min, viscosity up to 1000 cP, pressure up to 250 bar, and temperature up to 120 °C. A Coriolis mass flow meter suits high accuracy fuel or hydraulic fluid mass flow in kg/h, for flows above 1 kg/h, with 4-20 mA HART and PT100 temperature compensation. An electromagnetic flow meter fits water glycol hydraulic fluid or water based coolant, but only when conductivity is above 5 µS/cm, sizes from DN15 to DN300.
How to Get a Quote Without Replacing the Wrong Meter
Send Silver Instruments the tag number, the schematic symbol photo, the pipe size in DN, the fluid type, viscosity in cP, pressure in bar, temperature in °C, and flow range in L/min or kg/h. We check the loop data and the line placement, then recommend a meter that matches the schematic and the actual process. Sometimes the print says one symbol and the field has another meter. So we ask for a photo of the nameplate.
For a quote, send us your pressure (bar), temperature (°C), pipe size (DN), and flow range. Contact Silver Automation Instruments at Tel: +86-135-1213-1526, Whatsapp: 86-135-12131526, WeChat: +86 13512131526. Website: https://flow-meter.com.au
FAQ
What does FE mean on a hydraulic schematic?
FE stands for flow element. The tag number next to it identifies the device in the plant database. The symbol type may show the technology but not always.
Can I use an electromagnetic flow meter for hydraulic oil?
No. Electromagnetic flow meters need a conductive liquid. Hydraulic oil has very low conductivity. Use an oval gear or Coriolis flow meter for oil.
How do I read the flow direction from the schematic?
The arrow on the flow meter symbol shows the normal flow direction. Install the meter in the same direction. If the arrow is missing, check the pump discharge and return line arrangement.
What signal should I check before ordering a replacement?
Check the signal type on the loop drawing. 4-20 mA HART is common for analog systems. Pulse is common for totalizer applications. Make sure the new meter output matches the PLC input.
What parameters do you need for a hydraulic flow meter quote?
Fluid type, viscosity in cP, pressure in bar, temperature in °C, pipe size in DN, flow range in L/min or kg/h, and the schematic symbol or tag number. Send these to Silver Automation Instruments.