Burkert 8697 Pneumatic Control Unit

Figure 1: Burkert Type 8697 CLASSIC Drive position feedback sensor

The Burkert Type 8697 serves as a pneumatic position feedback and control unit, specifically engineered for the decentralized automation of process valves. It accurately detects the valve's position using mechanical or inductive limit switches. Its suitability for the food, beverage, and pharmaceutical sectors is enhanced by its easy-to-clean housing, robust IP protection, and materials resistant to chemicals. This article discusses the technical specifications and features of Burkert 8697 pneumatic control unit.

Is Burkert Type 8697 the right controller for you?

The Burkert Type 8697 offers a compact design that integrates a pilot valve with manual override and control air routing within the actuator. This design eliminates the need for external tubing, streamlining installation and maintenance processes. Here are some additional considerations to determine if the Type 8697 fits an application:

• Decentralized automation needs:
  • Burkert Type 8697 is specifically designed for decentralized automation for ELEMENT process valves Type 21xx and CLASSIC process valves Type 20xx, ensuring compatibility and streamlined integration.
  • When used in conjunction with Burkert ELEMENT actuators, it facilitates spring chamber aeration, effectively preventing contamination of the actuator chamber from external sources.
• Hygienic processing environments: With its easy-to-clean housing, IP protection, and chemically resistant materials, the Type 8697 is ideal for applications in hygienic processing environments where cleanliness and material compatibility are critical.
• Automatic adjustment of final position feedback: This feature ensures accurate valve positioning, enhancing process reliability and control precision. This feedback unit is straightforward to install on an actuator, offering an efficient alternative to the traditional solenoid valve.
• ATEX approval requirements: For applications in potentially explosive atmospheres, the Type 8697 comes with ATEX II cat. 3G/D and cat. 2D/G approval, making it suitable for use in these environments.
• Visual and electrical feedback: The unit provides both visual feedback via LEDs and electrical position feedback, facilitating easy monitoring of valve status and integration with control systems.

Technical specifications

• Materials: The control unit has a PPS body, EPDM seals and cover made of PC.
• Commissioning: The commissioning process involves an automatic mechanical setting of valve end positions. A manual override is available for added control flexibility. The design also includes an integrated pilot valve.
• Status display: The device and valve status are indicated through colored LEDs, and there is an optical position indicator (mechanical) for precise monitoring.
• Position sensor/feedback:
  • The control unit includes four micro switches for detecting positions, divided into two sets based on voltage and current ratings: two switches for low voltage (0 to 48 V AC/DC, max. 2 A) and two for higher voltage (50 to 250 V AC/DC, max. 2 A).
  • There are also four initiators (sensors) for position detection, divided into two types: two are PNP initiators suitable for 24 V DC systems, featuring a 3-wire connection and LEDs for status indication, and two are NAMUR initiators designed for 8.2 V DC systems, with a 2-wire connection and LEDs.
  • The control unit is compatible with linear actuators, supporting a valve spindle stroke range of 2 to 36 mm.

Electrical data

• Operating voltage: The pilot valve operates at 24 V DC with a ±10% tolerance and a residual ripple of 10% DC, consuming 1 watt of power, and it meets Protection Class 3 as specified by DIN EN 61140.
• Electrical connection:
  • Multipole M12, 8 pin
  • Cable gland M16 x 1.5 (cable Ø 4 - 8 mm) with terminal screws for cable cross-sections 0.14 - 1.5 mm²

Pneumatic data

• Control medium: Neutral gasses, air, quality class according to ISO 8573-1
  • Dust content: Class 7 (< 40 µm particle size)
  • Particle density: Class 5 (< 10 mg/m3)
  • Pressure dew point: Class 3 (< -20 °C or min. 10 °C below the lowest operating temperature)
  • Oil content: Class X (< 25 mg/m3)
  • Supply pressure: 3 - 7 bar
  • Pilot air ports: The pilot air ports offer two connection options - a G ⅛ threaded connection in stainless steel or a push-in connector for pipes with a diameter of 6 mm or ¼ inch.
• Positioning system:
  • Circuit function: Single-acting
  • Air capacity: The air capacity is 7 liters per minute (L/min) for aeration and ventilation, measured as the flow rate when the pressure drops from 7 to 6 bar absolute.

Approvals and certificates

• Conforms with EMC directive 2014/30/EU
• Ignition protection:
  • II 3D Ex tc IIIC T135 °C Dc
  • II 3G Ex ec IIC T4 Gc
  • II 2D Ex ia IIIC T135 °C Db
  • II 2G Ex ia IIC T4 Gb
• UL, cULus certificate
• ATEX and IECEx certificates are available

Environment and installation

• Installation: As required, ideally with actuator in a vertical position
• Operating environment:
  • Ambient temperature (max.): 0 to +55 °C (32 to 131 °F) with pilot valve, -20 to +60 °C (-4 to 140 °F) without pilot valve
  • Degree of protection: IP65/IP67 according to EN 60529, 4X according to NEMA 250 standard
  • Operating altitude: Up to 2000 m above sea level