Burkert Type 8791 - Manual (Page 13)

13
Description of System
• mounting
on linear actuator according to NAMUR recommendation (DIN IEC 534 T6) or on rotary actuator according to
VDI/VDE 3845.
• Optional
Remote version for DIN rail mounting or for mounting bracket
5.1.2. combination with valve types and mounting versions
The positioner Types 8791 can be mounted on different proportional valves. For example on valves with linear
(piston), membrane or rotary actuator. The actuators can be single-acting or double-acting.
• For single-acting actuators, only one chamber is aerated and deaerated during actuation. The generated
pressure works against a spring. The piston moves until there is an equilibrium of forces between compressive
force and spring force. To do this, one of the two air connections must be sealed with a threaded plug.
• For double-acting actuators the chambers on both sides of the piston are pressurised. In this case, one
chamber is aerated when the other one is deaerated and vice versa. In this design, no spring is installed in the
actuator.
Two basic device versions are offered for the positioner Type 8791; they differ in the attachment option and in the
position sensor.
Device version 1: compact
An internal position sensor is used which is designed as a rotary potentiometer. The positioner is attached directly
to the actuator.
Device version 2: remote
An external position sensor (linear or rotative) via a digital interface. The positioner is attached to a wall either with
a DIN rail or with a mounting bracket (remote design).
5.1.3. Optionally external position feedback with inductive
proximity switch
The positioner type 8791 can be fitted with an external position feedback (see data sheet / accessories).
The installation and the setting are described in the installation instructions which are enclosed with the external
position feedback.
The installation instructions can also be found on the Internet.
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Type 8791