Paladon PNS Series, Installation, Commissioning And Maintenance Manual, Page: 25 / 25

Doc : Q066 Rev : 10
Issued : 01/11/13 Page : 25 of 25
18.2 Normal Operating condition:
Under no fault (normal) conditions the PN, HY and DG scotch yoke actuators behave as
follows:
a) Correct pressure is supplied the pneumatic/hydraulic module; this forces the piston rod
to move linearly; operating the yoke assembly. The scotch yoke assembly will then
continue the movement of the piston rod which will compress the spring module. In this
position the valve under actuation will be open and the indicator will correctly show the
position.
b) When the actuated valve needs to be closed, the actuator must move to the ‘end’
position. The pressure input in the pneumatic/ hydraulic module will decrease, allowing
the spring to fully expand, turning the yoke assembly and putting the piston to the end
position. In this position the valve under actuation is fully closed and the indicator will
correctly show the position.
18. 3 Maintenance Requirement
The actuators are to be periodically inspected and maintained fully in accordance with Section
11 of this manual.