(1) The positioner will not work correctly if the positioner is not engaged properly in the actuator.
Check the positioner to actuator coupling to see if the positioner
and actuator are mated correctly.
ii) Linear
(1) Slop – can result when the actuator to positioner components
are loose or improperly connected. A linear arm is what converts
the linear motion to a rotary motion for the positioner. If there is
slop or play in the assembly, it can cause the positioner not to perform correctly. A rule of thumb
when mounting on linear actuators is when at 50% of input signal the linear arm should be at
mid stroke, thus making a 90 angle with the linear arm and the valve stem.
2) Hunting or Oscillation
a) Spool Valve
(1) Remove the spool valve and blow out with air. If air is not available wipe
down with cloth. Something every soft, like a pipe cleaner should be used
to clean the inside of the spool block itself. Once cleaned the spool piece
should slide very easily within the housing. Place spool valve back into
positioner making sure that the top of the spool piece is connected
correctly on the balance arm.
(a) DO NOT USE WD40 or OIL BASED LUBRICANTS TO CLEAN
SPOOL PIECE.
(2) Due to our superior air delivery sometimes on small actuators this can cause
hunting to occur. This can also occur when dealing with damper drives as well,
do to the weight and stroke of the damper.
(a) If there are doubts on which spool valve to order call our service
center at 205.678.0507
(b) Replace standard spool valve with the Low Gain spool valve. VAC
will do an exchange at no cost.
