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The technical data herein is for general information only. Product suitability should be based solely upon customer’s detailed knowledge and experience with their
application.
Series 6A Installation, Operation & Maintenance – Introduction
6A O & M : 4
INTRODUCTION
The Bray S6A is a microcontroller based positioner for pneumatic
actuators. The S6A converts an analog current signal into
a valve position pressure signal and offers positioner, valve
and actuator diagnostics using a variety of communication
protocols. Optional modules can be added for full range valve
position feedback, valve open/close verification, preset alarm
warnings and electromagnetic compatibility.
Principles of Operation
The operation of the S6A can be described in three parts; the
user defined setpoint, the pneumatic actuator air supply, and
the S6A internal controller. The user defined setpoint, which is
provided by the incoming analog signal or the communication
protocol, tells the positioner where to set the actuator. The
pneumatic actuators air supply provides the power to work
the valve, and the S6A internal microcontroller monitors the
actuator position and provides diagnostics to the end user.
When the microcontroller sees a deviation between the actual
position of the actuator and the provided setpoint it will
pulse the internal piezo electric valve in order to let air fill
the corresponding actuator chambers and drive the actuator
from the pneumatic supply lines. Once this deviation is within
a desired tolerance or “dead band” the microcontroller will
stop the pulsing. Using this process, the S6A only consumes
air when it is needed, meaning it will pay for itself within a
short period of time.
Electrical Operation
The standard S6A requires 4 to 20mA loop power for all
of the internal electronics. It can be installed in a two wire,
three wire, or four wire architecture. There is no need to run
separate power and signal wiring. The S6A positioners with
communication modules get their power directly from the
network. All of the wiring diagrams for the different versions
of the S6A and any optional modules are shown in the “Field
Connections” portion of this manual.
Mechanical Operation
The S6A requires a pneumatic supply in the range of 20 - 102 psi
(1.4 - 7 BAR). Using this pneumatic supply, the S6A will posi-
tion the actuator and valve precisely where it needs to be
to regulate the process. Once in the settled state, the S6A
has one of the lowest air bleed rates in the market. The S6A
requires a pneumatic supply rated at Class 2 in accordance
with ISO 8573-1. An optional filter can be installed upstream
of the S6A to clean incoming air. Diagrams are provided show-
ing how to make the pneumatic connections in the “Field
Connections”portion of this manual.
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