Badger Meter SRD/SRI Valve Positioners - Manual (Page 59)

2 Is the air achievement throttle too far open with a small drive, with high supply air pressure?
Remedy: damping screw, to more significant throttling
3 Has the air supply pressure been set too high?
Remedy: reduce pressure install pressure reducer
Changing valve dynamics during behavior A):
If valve has a high friction (for example, often the case in small rotary actuators due to low air supply pressure or due to a
valve seat packing which is too tight) then the valve position gets stuck after a setpoint jump and possibly is recontrolled via
the resetting time Tn, possibly after quite some time has elapsed
Basically, the following is possible:
a) to accept a remaining deviation
b) to accept some response procedures (such as remaining in over-response for a short time, and remaining below setpoint
and trailing)
When deciding a), “Tn” should become ineffective, table value (15) Compensating “P(kp)” should be increased until the
setpoint jumps reach the setpoint within a short period of time and without significant over-response (adapt to both
movement directions)
When deciding b) start as in a) above Thereafter “Tn” is re-switched and decreased until the setpoint deviation has been
re-controlled within a short period of time and without long after-response (adapt in both movement directions) It is
recommended to maintain the Tn’s for both directions about the same
If a post oscillation occurs after a setpoint jump, “Tn” is selected too small, possibly “P(kp)“ was selected too large
The positioning time “T63”, also called valve damping, does not have an effect during AUTOSTART in Menu 2, however,
setpoint jumps in Menu 8 reach the position controller in a damped condition which then is not easily stimulated to
oscillation This behavior is also true for the setpoint input This enables setting the controller to higher “P(kp)“ values without
producing oscillations in the process On one side this helps the position control to level disturbances due to friction, changes
in load or air supply pressure changes faster On the other hand it helps the superimposed valve control circuit that neutral
times in the valve control route do no have such a big effect (stability in valve control circuit)
Changing valve dynamics during behavior B):
Increase “Tn” for both movement directions, possibly turnoff and proceed as described in behavior A) alternative b)
Operation
Page 59 August 2014 POS-UM-00010-EN-03