Bimba PCS - Manual (Page 25)

www.bimba.com Technical Assistance: 800-44-BIMBA 25
Problem:
Solution: The change in command signal is too small.
Ensure that the change in command signal is large enough to cause the
actuator to move outside of the deadband. If the change in signal is too small
(smaller than the adjusted deadband), the actuator will not respond.
Problem:
Solution: The Zero adjustment is too high and/or Span adjustment is too low.
Refer to the Installation Section of the manual that pertains to the Zero and
Span Adjustments and make the proper adjustments.
The Actuator is not Repeatable or Stable
Problem:
Solution:
PCS system parameters are not adjusted properly.
Follow the Installation instructions to make the appropriate system
adjustments for your application parameters, ensuring that the deadband and
decel adjustments are adjusted according to the application requirements.
Improper adjustments may cause actuator overshoot (deadband is too small),
non-repeatability (deadband is too big), sluggishness or instability.
Problem:
Solution: The actuator and PCS system are not sized properly.
Refer to the Application Sizing Chart in the PCS catalog to ensure the
actuator and PCS system are sized properly for the application requirements.
Problem:
Solution: Noisy Command Signal.
Provide an analog 0-10 VDC command signal that has less than 5 mV of
ripple. Employ proper wiring techniques to ensure signal noise is kept to a
minimum (use shielded cables, proper grounding methods, etc.)
Problem:
Solution: The Electrical Power Supply is supplying less than the required 23.5 VDC.
Utilize a DC power supply that can supply the minimum 23.5 VDC required
by the PCS. At voltages less than 23.5 VDC, the system performance will
degrade.
Problem:
Solution: Inadequately sized air line between the actuator and PCS valves.
Application testing yielded best results with 0.093 I.D. air line tube for
1-1/16” and 1-1/2” bore actuators and 0.170 I.D. air line tube for 2” bore
actuators. Smaller or larger I.D. tubing may result in less position
repeatability.
Problem:
Solution: Air lines between the actuator and PCS valves are too soft or compliant.
Avoid using soft easy to expand air tubing. Use harder tubing such as nylon
or metal.
Problem:
Solution: Air lines between the actuator and PCS valves are too long.
Longer air lines cause the system to be less accurate. Always use the shortest
air lines as possible (< 18”). The system will work with longer lines, but may
not be stable or responsive enough for application requirements. Option N
allows you to mount the valves close to the actuator with the PCS electronics
mounted separately.
Problem:
Solution: Air Supply pressure is too low (Below 70 psi)
Turn air supply up to at least 70 psi. If the air supply experiences pressure
drops due to excess air demand in the building’s air supply system, an air
reservoir may be required.