BURKERT 20087355 Type 8745 is a mass flow controller (MFC) / mass flow meter (MFM) suitable for controlling the mass flow of large gas quantities. The specific model 20087355 is configured for air with a nominal flow rate of 400 Nl/min, operating at 24 V DC with a G 3/4" internal thread and 4-20 mA analog signals. Type 8745 can be configured as MFM or MFC according to demand. 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

Feature	Description
Operating medium	Neutral, pure gases (Air for 20087355)
Medium temperature	-10 °C to +70 °C (-10 °C to +60 °C with oxygen)
Operating voltage	24 V DC (±10% voltage tolerance)
Housing material	PC (polycarbonate)
Base block material	Aluminium (for 20087355) or stainless steel 1.4404/316L
Seal material	FKM (for 20087355) or EPDM (depending on gas)
Degree of protection	IP20
Installation position	Horizontal or vertical (vertical, flow upwards for 20087355)

Approvals and Conformities

• North America: Optional UL Listed for USA and Canada according to UL 61010-1 and CAN/CSA-C22.2 No. 61010-1.
• Foods and Beverages/Hygiene: FDA compliant (Code of Federal Regulations), USP Class VI (biocompatible), EC Regulation 1935/2004.
• Oxygen: Optional suitability for gaseous oxygen.

Product Connections

Analogue Interface

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

Performance Specifications

Nominal Flow Rate of Typical Gases

INFO

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

Gas	Min. QN [l/min]	Max. QN [l/min]
Air	20	2500
Argon	20	1600
Carbon dioxide	20	800
Nitrogen	20	2500
Oxygen	20	2500
Methane	20	1200

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

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). 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. 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.