The BURKERT 20064744 (Type 8745) is a high-performance Mass Flow Controller (MFC) designed for controlling the mass flow of large gas quantities. This specific configuration is optimized for N2 nitrogen with a nominal flow rate of 500 SLPM. It features a 24 V DC supply, G 1/4" internal thread, and a 4-20 mA analogue interface. The thermal inline sensor located directly in the main gas stream achieves very fast response times with minimal pressure loss. As the actuator, a Bürkert direct-acting proportional valve guarantees high response sensitivity.

General Technical Data

Property	Description
Seal Material	FKM (Fluor rubber)
Housing Material	PC (polycarbonate)
Base Block Material	Aluminium
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)
Analogue Interface	4...20 mA (Input impedance: <300 Ω, Maximum load: 400 Ω)
Operating Medium	N2 nitrogen (Calibration medium: Air)
Medium Temperature	-10 °C to +70 °C
Ambient Temperature	-10 °C to +50 °C
Degree of Protection	IP20
Installation Position	Horizontal or vertical

Approvals and Conformities

• North America (USA/Canada): Optional UL Listed according to UL 61010-1 and CAN/CSA-C22.2 No. 61010-1.
• Foods and Beverages/Hygiene: FDA compliance (Code of Federal Regulations), USP (United States Pharmacopeial Convention) biocompatibility, and EC Regulation 1935/2004 compliance available depending on variable codes.
• Oxygen: Optional suitability for use with gaseous oxygen.

Dimensions (Threaded Connections)

Small nominal flow rates, with internal thread

Thread (A)	Thread depth [mm]
G 1/4	12
NPT 1/4	11
G 3/8	12
NPT 3/8	11
G 1/2	15
NPT 1/2	14
G 3/4	16
NPT 3/4	15

Product Connections

Analogue Interface

D-Sub plug, 9-pin

Pin	Assignment
1	Digital input
2	GND (for supply voltage and digital input)
3	24 V
4	Relay, normally closed contact
5	Relay, reference contact
6	Set-point value input +
7	Set-point value input GND
8	Actual value output
9	Actual value output GND
Housing	Shielding

Terminal strip, 6-pin

Pin	Assignment
1	24 V
2	GND
3	Set-point value input +
4	Set-point value input GND
5	Actual value output +
6	Actual value output GND

Performance Specifications

Nominal Flow Rate of Typical Gases

INFO

All values refer to 1013.25 mbar abs and 273.15 K (0 °C) (Index N).

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

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.

Formula for calculating the pressure loss in an MFM: $\Delta P_{Gas} = \Delta P_{Air} \sqrt{\frac{\rho_{NGas}}{\rho_{NAir}}}$

Derating Diagram for Electromotive Variants

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 is a measure of the heat dissipation and represents the primary measured variable.

Adequate flow conditioning within the MFC and calibration with high-quality flow standards ensure that the amount of gas flowing through per time unit can be derived from the primary signal with a high degree of accuracy.

Safety Information

Electrostatically sensitive components: The device contains electronic components that are susceptible to the effects of electrostatic discharging (ESD). Do not touch electronic components when the supply voltage is connected. 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 and vent or empty the lines.