BURKERT Type 8745 is a mass flow controller (MFC) and mass flow meter (MFM) suitable for controlling the mass flow of large gas quantities. Type 8745 can be configured as an MFM or MFC according to demand. Optionally, up to four calibration curves can be stored in the device. 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. As an MFC, Type 8745 is available in two variants: with an electromagnetic proportional valve and with an electromotive proportional valve. In addition to an analogue and an Industrial Ethernet variant, a Modbus RTU variant is also available.

General Technical Data

Property	Description
Seal Material	FKM or EPDM (depending on gas)
Housing Material	PC (polycarbonate)
Base Block Material	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)
Ambient Temperature	-10 °C to +50 °C (higher temperatures on request)
Degree of Protection	IP20

Note on Electromotive Valves

When using the electromotive proportional valve, the minimum medium temperature is 0 °C. The device additionally includes a PEEK valve seat seal (Type 3280 DN 4) or an Al₂O₃ valve seat seal (Type 3285).

Product Variants

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
Nominal flow range (QN)	MFC: 20...1500 lN/min (N₂) MFM: ≤ 2500 lN/min (N₂)
Operating pressure	MFM: max. 25 bar MFC: max. 25 bar
Measuring accuracy	±1.5% MV ±0.3% FS
Repeatability	±0.1% FS
Turndown ratio	1:50
Settling time (t95)	< 500 ms
Power consumption	Max. 4 W (as MFM) Max. 12.5...31.5 W (as MFC)

Variant with Electromotive Proportional Valve

Type 8745 with an electromotive proportional valve is especially suitable for applications with high inlet pressures of up to 22 bar or high flow rates (at a low pressure drop). The motor’s power consumption to hold a specific opening position is nearly zero, which can reduce the energy consumption of a plant dramatically.

Performance Data	Specification
Nominal flow range (QN)	20...2500 lN/min (N₂)
Operating pressure	MFM: max. 22 bar MFC: depends on medium and nominal valve size
Measuring accuracy	± 2% MV ± 0.5% FS
Repeatability	± 0.5% FS
Turndown ratio	1:50
Settling time (t95)	< 5 s
Power consumption	Max. 4 W (as MFM) Max. 12 W (as MFC)

Approvals and Conformities

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

Product Connections

Industrial Ethernet

Analogue

Modbus RTU

Performance Specifications

Nominal Flow Rate of Typical Gases

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

Gas	Min. QN [l/min]	Max. QN [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

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.

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 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.