ABB TZIDC Commissioning Instructions page 30

Pneumatic connection
All pneumatic piping connections are located on the right-hand side of the positioner. Tapped
holes are provided to connect the pneumatic pipes, G1/4 or 1/4-18 NPT. The positioner is
labeled according to the available tapped holes. The corresponding pipe connections must be
included.
The level of supply air pressure required to apply the actuating force should be adjusted
according to the actuating pressure in the actuator. The positioner operating range is between
1.4 ... 6 bar (20 ... 90 psi).
IMPORTANT (NOTE)
With control systems for double-acting spring return actuators, modulation problems may
occur due to the spring force combining with the compression force. The pressure values in
the springless chamber may exceed those of the supply air as a result of the compression
induced by the spring force. This may cause two effects:
Effect 1
The pressure values in the springless chamber exceed the max. permissible limit values.
The diaphragms in the I/P module or the actuator may sustain damage leading to device
failure as a result.
Effect 2
The pressure in the springless chamber is higher than the service pressure.
If this is the case and if the line to the springless chamber is actuated by the positioner, the
excess pressure will first be redirected towards the supply air, and the actuator will move
briefly (and inadvertently) in the wrong direction.
In order to ensure that this behavior cannot occur, it is recommended to install a pressure
compensation valve between the springless chamber and the supply air for these types of
applications. It enables the increased pressure to be transferred back to the air inlet line.
The opening pressure of the check valve should be < 250 mbar.
Join the pipe connections according to the following designation:
Designation
30
Pipe connection
- Supply air, pressure 1.4 ... 6 bar (20 ... 90 psi)
OUT1 Actuating pressure for actuator
OUT2 Actuating pressure for actuator (2nd connection with double-acting actuator)
TZIDC, TZIDC-110, TZIDC-120 CI/TZIDC/110/120-EN