Bürkert 8791, Operating Instructions Manual

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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
combination with valve types and mounting versions 5.1.2.
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 measuring system.
device version 1: compact
An internal position measuring system is used which is designed as a rotary potentiometer. The positioner is
attached directly to the actuator.
device version 2: remote
An external position measuring system (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).
english
Type 8791