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Mass Flow Meter for Hot Oil and Thermal Fluids
Quick Answer: A Coriolis mass flow meter is the most reliable instrument for measuring hot oil and thermal fluids from 200°C to 350°C. It provides direct mass reading in kg/h or t/h, independent of fluid viscosity or density shifts. Silver Instruments supplies direct mass meters in DN15 to DN80, built from forged 316L stainless steel and rated for ATEX Zone 1 environments.
Why Volume Measurement Fails in Thermal Oil Loops
Volumetric flow meters like turbine or oval gear types struggle with heat transfer fluids. Their readings drift with temperature because the oil expands and contracts. A fluid at 30°C and at 310°C can have a volume difference of 10% or more. To get true mass flow, you need a separate density input and a flow computer. Most maintenance teams skip that setup because it adds complexity and still gives an inferred value.
Coriolis meters bypass this whole problem. They vibrate one or two measuring tubes and detect the Coriolis force generated by mass moving through them. That means you get the mass directly. No density tables, no temperature compensation logic, no extra transmitters. We have seen a chemical plant in Thailand replace a wobble-disc meter on a hot oil loop at 265°C with a Silver Instruments DN40 Coriolis unit. The mass balance error across their reactor jacket dropped from 3% to under 0.3% immediately.
Silver Instruments Coriolis Meters for Hot Fluids
Our range for hot oil and thermal fluid applications starts at DN15 and goes up to DN80. The wetted material is 316L stainless steel, with Hastelloy C-22 available for corrosive heat transfer salts. Standard process temperature limits go up to 200°C for the integral transmitter version. With a remote transmitter and a separation kit, the sensor handles fluid temperatures up to 350°C. The remote design moves the electronics away from the hot pipe, so the amplifier stays within its specified 60°C ambient limit.
Each meter comes with a factory calibration certificate traceable to ISO 17025 for mass flow, density, and temperature. The output is a standard 4-20 mA HART signal, with pulse and Modbus RTU as options. Because many thermal oil systems operate in solvent recovery or refinery areas, we offer ATEX and IECEx certification for Zone 1 and Zone 2.
Real World Examples from Our Sales Log
Here is the thing. A snack food plant in Indonesia runs food-grade thermal oil at 240°C through a fryer heat exchanger. Their plate heat exchanger kept clogging and no one could figure out the exact heat balance. They installed a DN25 Coriolis meter from us on the oil supply line. The direct mass reading showed flow pulsations from a worn gear pump. Fixing that pump saved them 18 days of production downtime a year.
A bitumen blending facility in Saudi Arabia asked us for a meter that could handle hot asphalt binder at 180°C with viscosity around 500 cP. They needed it to measure mass flow into the mixing drum, not volume. They chose a DN50 remote Coriolis with a steam trace jacket option. The meter paid for itself in six months through reduced binder overconsumption.
In practice, engineers also use our Coriolis meters for heat metering in district heating plants. You can measure the thermal fluid mass flow on the primary side and multiply by the temperature difference to get an accurate heat flow in kW or MW. The PT100 sensor inside the Coriolis tube gives the fluid temperature directly, so the PLC calculates the heat t
Installation Tips for Hot Oil Mass Flow Meters
Most engineers skip this part but it matters. With thermal oil above 200°C, the pipe expands significantly. Always install flexible hoses or expansion loops near the meter flanges. Support the pipe on both sides so the sensor is not under tensile stress at operating temperature. Also, avoid insulation on the electronics housing. Insulate the pipe and the sensor body but leave the transmitter exposed to natural convection cooling.
Zero calibration must be done at working temperature. A cold zero proves nothing because the tube stiffness changes with heat. Run the hot oil through the meter until the case temperature stabilizes, shut the isolation valves, and then push the zero button through the display or via HART. We see many sites skip this step and then complain about a small offset.
For thermal fluids with trace amounts of coke or fine particulates, install a Y-strainer with a 0.5 mm mesh upstream. The Coriolis tube ID is small so a blocked tube ends up giving a density alarm. The electronics can trigger that alarm through the relay output to signal a maintenance check.
Frequently Asked Questions
Can I use an electromagnetic flow meter for hot oil?
No. Thermal oil and hot oils are non-conductive hydrocarbons. A magmeter needs a minimum conductivity of 5 μS/cm. Hot oil has a conductivity near zero. The only practical inline mass meter for this fluid is a Coriolis or a thermal mass flow meter for small gas-phase systems. For liquid thermal oils, Coriolis is the standard.
What is the pressure drop on a Coriolis meter at high temperature?
Pressure drop depends on the flow rate, viscosity, and tube geometry. For a typical DN25 Coriolis meter flowing 2,000 kg/h of thermal oil at 30 cP, you can expect around 0.3 bar to 0.6 bar loss. We provide a pressure drop curve in the datasheet along with the quote. Send us your flow range and we will calculate it for your fluid.
Do I need a straight pipe run upstream?
No. One advantage of Coriolis meters is that they are insensitive to flow profile. You can mount the meter right after a 90° elbow or a pump discharge. There is no requirement for 10D or 20D straight runs. This saves a lot of space in the pipe rack of a thermal oil skid.
How do I measure the heat flow in a thermal fluid circuit?
Use a Coriolis meter with a built-in RTD for mass flow and supply temperature. Add a separate PT100 on the return line. The PLC or energy calculator subtracts the temperatures and multiplies by mass flow and specific heat capacity. Silver Instruments offers an integration guide for common PLC brands to set up this loop.
What maintenance is needed on these meters?
Almost none. There are no moving parts in the flow tube. The only checks are to verify the zero point every three months at operating temperature and to inspect the transmitter cable gland for tightness. The electronics do not drift. If the meter shows a density reading that does not match lab values, check for a thin coating inside the tube and clean with a solvent flush.
Request a quote: For a firm price and delivery time, email your hot oil temperature (°C), pressure (bar), pipe size (DN), and required flow range (kg/h or t/h) to [email protected]. We will send you a datasheet and a competitive quote within one working day. See our Coriolis mass flow meter product page on flow-meter.com.au for more installation drawings and CAD files.
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