Azbil Corporation
6
Model
KFPA
, KFT - Field Mount type Pressure Indicating Controllers
2-2-2: Control mechanism
The control mechanism consists of a controller unit, a reset unit, and a rate unit.
Different combinations of these units are possible to attain different control actions.
Controller unit
Displacement of the deviation link is fed via the flapper pin of the feedback link to the
flapper, so that its gap with respect to the nozzle is varied and consequently the nozzle
back pressure is varied. The nozzle back pressure is boosted by the pilot relay and
delivered as the pneumatic output signal of the controller. This output signal is led to
the feedback chamber in order to return the flapper-to-nozzle gap to that existed before
this displacement took place. Ultimately the controller output pressure is balanced at a
value in a certain proportion to the deviation.
Setting of proportional band can be done by turning the proportional band dial which
varies the crossing angle between flapper and deviation link (feedback link).
Figure 3
Proportional band
setting dial
Index
Link length
adjusting screw
Flapper adjusting pin
Stopper pin
Dial stopper
Feedback link
adjusting pin
Feedback room
Reset room
