Bray 6A Series O&M Manual - Manual (Page 28)

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Series 6A Operation & Maintenance – Troubleshooting
6A O & M : 28
Fault profile (symptoms) Possible cause(s) Remedial measures
In stationary automatic mode
(constant setpoint) and in manual
mode, both piezo valves contin-
ually switch alternately, and the
actuator oscillates around a mean
value.
Sticking friction of the packing gland from the
control valve or actuator too large
Reduce friction or increase dead zone of positioner (param-
eter ”dEbA”) until the oscillation stops
Looseness (play) in the positioner/actuator/con-
trol valve system
Part-turn actuator: Check for firm seating of set screw on cou-
pling wheel
Linear actuator: Check for firm seating of lever on positioner
shaft
Correct any other play between the actuator and the control
valve
Actuator is too fast
Positioner doesn’t move control
valve to the stop (at 20 mA)
Supply pressure too low. Load on the feeding
controller or system output is too low
Increase supply pressure, insert ballast converter
Select 3/4-wire mode
Remedial Measures Table 4
Remedial Measures Table 5
Fault profile (symptoms) Possible cause(s) Remedial measures
Zero point displaces sporadi-
cally (> 3%).
Impact or shock loads result in accelerations
so high that the friction clutch moves, e.g.
due to ”vapor shocks” in vapor lines
Rectify the causes for shock loads
Re-initialize the positioner
The device function has com-
pletely failed: no view even
on the digital display.
Electrical auxiliary power supply is not
adequate
Check the electrical auxiliary power supply
In case of very high continuous loads due to
vibrations (oscillations):
Screws of the electrical connecting terminals
may be loose
Electrical connecting terminals and/or elec-
tronic components may be knocked out
Tighten the screws firmly x
Repair
1)
For prevention: install the positioner on the damping pads