BURKERT Type 8746 (SKU 20142867) is a Mass Flow Controller (MFC) / Mass Flow Meter (MFM) for gases, suitable for a wide range of applications, e.g., metal and glass manufacturing or processing, fermentation processes, test benches, or filling systems and packaging machines. The specific SKU 20142867 is configured for Ar argon with a nominal flow rate of 600 Nl/min, featuring a G 1/2" internal thread, 24V DC supply, and 4-20 mA analogue communication.

Type 8746 is available in two variants: a variant with several analogue or digital communication interfaces and a variant with a pure CANopen-based interface. The thermal inline sensor is located directly in the main flow and achieves fast response times and a high level of measuring accuracy with long-term stable calibration. As the actuator, a Bürkert direct-acting, electromagnetic proportional valve or motor valve guarantees high response sensitivity.

General Technical Data

Product properties	Description
Seal	FKM or EPDM (depending on gas)
Housing	Die-cast aluminium (painted)
Base block	Aluminium or stainless steel 1.4404/316L
Wetted parts (sensor)	Stainless steel 1.4404/316L, Al₂O₃, PPS GF40, epoxy resin, silicon, silicon nitride
Operating voltage	24 V DC (±10% voltage tolerance, ±2% residual ripple)
Operating medium	Neutral, pure gases (others on request)
Medium temperature	-10 °C to +70 °C (-10 °C to +60 °C with oxygen)
Degree of protection	IP65
Ambient temperature	-10 °C to +50 °C (higher temperatures on request)

Variant with Electromagnetic Proportional Valve

Type 8746 can be configured as MFC or MFM as required. The MFC variant uses direct-acting proportional valves of the 287x series. These electromagnetic proportional valves are normally closed and stand for highest measuring accuracy and repeatability with settling times resp. response times of a few hundred milliseconds.

Performance data	Description
Nominal flow range (Q_N)	MFC: 20...1500 I_N/min (N₂) MFM: ≤ 2500 I_N/min (N₂)
Operating pressure	MFM: max. 25 bar MFC: max. 25 bar (depends on medium and nominal valve size)
Measuring accuracy	±1.5% MV ±0.3% FS (under calibration conditions)
Repeatability	±0.1% FS
Turndown ratio	1:50
Settling time (t95)	< 500 ms
Power consumption	MFM: max. 2 W MFC: max. 10.5...29.5 W (depending on valve type)

Variant with Electromotive Proportional Valve

Type 8746 with electromotive proportional valve is especially suitable for applications with high inlet pressures up to 22 bar or high flow rates (with low pressure loss). Thanks to their very low holding power, these valves can drastically reduce a system’s energy consumption. When de-energised, the motor valves remain in position.

Performance data	Description
Nominal flow range (Q_N)	20...2500 I_N/min (N₂)
Operating pressure	MFM: max. 25 bar MFC: max. 25 bar
Measuring accuracy	±2% MV ±0.5% FS (under calibration conditions)
Repeatability	±0.5% FS
Turndown ratio	1:50
Settling time (t95)	< 5 s
Power consumption	MFM: max. 2 W MFC: max. 10.5 W (Valve holding power is < 1 W)

Approvals and Conformities

• Explosion protection (Optional): ATEX II 3G Ex ec IIC T4 Gc / II 3D Ex tc IIIC T135 °C Dc; IECEx EPS 22.0066X.
• North America: Optional UL Listed for the USA and Canada (UL 61010-1).
• Foods and beverages/Hygiene: FDA (Code of Federal Regulations), USP (United States Pharmacopeial Convention) Class VI, EC Regulation 1935/2004.
• Oxygen: Optional suitability for use with gaseous oxygen.

Product Connections

Analogue Interface

M12 socket, 5-pin (A-coded):

1. Digital input GND
2. Digital input +
3. Relay, reference contact
4. Relay, normally closed contact
5. Relay, normally open contact

M12 plug, 5-pin (A-coded):

1. GND for the analogue output (for MFM) or GND for the analogue output and set-point value input (for MFC)
2. 24 V
3. GND for supply voltage
4. Set-point value input (not connected for MFM)
5. Analogue output for measured value

Performance Specifications

MFM Pressure Loss Diagram

The diagram shows an example of the pressure loss curves with air flowing through. To determine the pressure loss of other gases, the corresponding air equivalent must first be calculated and the base block used for the other gas must be taken into account.

Derating Diagram for Electromotive Variants

Nominal Flow Rate of Typical Gases

Gas	Min. Q_N [l/min]	Max. Q_N [l/min]
Acetylene	20	320 (from 65 l/min with air calibration)
Ammonia	8	1000
Argon	20	1600
Carbon dioxide	20	800
Air	20	2500
Methane	20	1200
Propane	20	200
Oxygen	20	2500
Nitrogen	20	2500

(All values refer to 1013.25 mbar abs and 273.15 K / 0 °C)

Product Operation

Measurement Principle

This sensor works as a hot-film anemometer in the so-called CTA operational mode (Constant Temperature Anemometer). Two resistors with a precisely specified temperature coefficient located directly in the media flow and three further resistors are connected to form a measuring bridge. The first resistor in the gas flow measures the fluid temperature, while the second, low-value resistor is always heated just enough to keep it at a fixed, specified excess temperature with respect to the fluid temperature. The heating current required for this purpose is a measure of heat dissipation and represents the primary measured quantity.

Safety Information

• Electrostatically sensitive components: The device contains electronic components that are susceptible to the effects of electrostatic discharging (ESD). Meet the requirements specified by EN 61340-5-1.
• Electric shock: Touching live parts can result in severe electric shock. Before working on the device or system, switch off the power supply.
• Medium under pressure: Medium under pressure can seriously injure people. Before working on the device or system, switch off the pressure. Vent or empty the lines.