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.

Configuration Management

If a device needs to be replaced, the memory card can be removed from the defective device and inserted into the new device. This transfers all data from the device to be replaced to the new device, enabling easy device exchange.

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
Degree of Protection	IP20

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 the highest measuring accuracy and repeatability with settling times of a few hundred milliseconds.

• Valve Position: Normally closed
• Nominal Flow Range (Q_N): MFC: 20...1500 lN/min (N₂); MFM: ≤ 2500 lN/min (N₂)
• Operating Pressure: Max. 25 bar
• Measuring Accuracy: ±1.5% MV, ±0.3% FS
• 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.

• Valve Position: Normally closed
• Nominal Flow Range (Q_N): 20...2500 lN/min (N₂)
• Operating Pressure: MFM: max. 22 bar
• Measuring Accuracy: ± 2% MV, ± 0.5% FS
• Settling Time (t95): < 5 s
• Power Consumption: Max. 4 W (as MFM); Max. 12 W (as MFC)

Measuring Accuracy

If the operating medium differs from the calibration medium, the actual measuring accuracy may deviate from the specified value. If natural gas is used as the operating medium, the measuring accuracy depends on the composition of the natural gas, which can vary depending on origin and season.

Approvals and Conformities

• North America: Optional UL Listed for the USA and Canada (UL 61010-1, CAN/CSA-C22.2 No. 61010-1).
• FDA: All wetted materials are compliant with the Code of Federal Regulations published by the FDA.
• USP: All wetted materials are biocompatible according to the United States Pharmacopeial Convention.
• EC 1935/2004: All wetted materials are compliant with EC Regulation 1935/2004/EC.
• Oxygen: Optional suitability for use with gaseous oxygen.

Product Connections

Industrial Ethernet

Pin	Assignment
1	FE (functional earth)
2	DGND
3	24 V

Analogue

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

Performance Specifications

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

MFM Pressure Loss Diagram

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.

Safety Information

Electrostatically Sensitive Components

The device contains electronic components that are susceptible to the effects of electrostatic discharging (ESD). Components that come into contact with electrostatically charged persons or objects are at risk.

Electric Shock Hazard

Touching live parts can result in severe electric shock. Before working on the device or system, switch off the power supply and secure it against reactivation.

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 or empty the lines.

Hot Surfaces

The surface of the device can become hot with fast-switching actuators or with hot media. Wear suitable protective gloves and keep highly flammable substances away from the device.