Bray 6A Series O&M Manual - Manual (Page 4)

All information herein is proprietary and confidential and may not be copied or reproduced without the expressed written consent of BRAY INTERNATIONAL, Inc.
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 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 position
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 sup-
ply 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 showing how to make the pneumatic con-
nections in the “Field Connections”portion of this manual.