BURKERT 20051786 (Type 8745) is a mass flow controller (MFC) suitable for controlling the mass flow of large gas quantities, specifically configured for N2 nitrogen with a nominal flow rate of 15.00 Nm3/h. 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. This specific model features an aluminium body, FKM seals, a G 1/2" internal thread connection, and operates on 24 V DC with a 4-20 mA analogue interface.

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)
Operating Medium	N2 nitrogen (Neutral, pure gases)
Medium Temperature	-10 °C to +70 °C
Ambient Temperature	-10 °C to +50 °C
Installation Position	Horizontal or vertical (vertical, flow upwards recommended)
Degree of Protection	IP20

Variant with Electromagnetic Proportional Valve

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 of a few hundred milliseconds.

Performance Data	Specification
Valve Position	Normally closed
Measuring Accuracy	±1.5% MV, ±0.3% FS (under calibration conditions)
Repeatability	±0.1% FS
Turndown Ratio	1:50
Settling Time (t95)	< 500 ms

Variant with Electromotive Proportional Valve

Type 8745 with electromotive proportional valve is especially suitable for applications with high inlet pressures or high flow rates at a low pressure drop. The motor’s power consumption to hold a specific opening position is nearly zero. Without electrical power, the valve remains in its current position.

Performance Data	Specification
Valve Position	Normally closed
Measuring Accuracy	± 2% MV, ± 0.5% FS (under calibration conditions)
Repeatability	± 0.5% FS
Turndown Ratio	1:50
Settling Time (t95)	< 5 s

Approvals and Conformities

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

Measurement Principle

This sensor works as a hot-film anemometer in the 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 is heated just enough to keep it at a fixed excess temperature. The heating current required is a measure of the heat dissipation and represents the primary measured variable.

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.

Derating Diagram for Electromotive Variants

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

Analogue Interface (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

Safety Information

• Electrostatically sensitive components: The device contains electronic components that are susceptible to the effects of electrostatic discharging (ESD).
• 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. In the event of overpressure or pressure surges, the device or lines can burst. Before working on the device or system, switch off the pressure and vent the lines.