Samson 3761, Монтаж и эксплуатация

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2.2 Selecting and aligning the
cam disc
The positioner is delivered with a 90° linear
cam disc. If a different control characteristic
is required, replace the existing cam disc
with a cam disc listed in the table below.
The default setting of the cam disc depends
on the valve design (butterfly valve, ball
valve, etc.) and rotary actuator version used.
For proper assignment refer to Figs. 5
and 6.
Fig. 5 shows how to adjust the cam disc for
control valves with rotary actuators that are
equipped with spring-return mechanism. The
fail-safe action "valve CLOSED" or "valve
OPEN" without supply pressure is deter-
mined by how the actuator is attached to the
valve.
For example, SAMSON's Type 3278 Actua-
tor can be mounted on a butterfly valve with
the shaft attached to either the left or the
right actuator flange.
Fig. 6 shows how to adjust the cam disc
when a double-acting, springless rotary ac-
tuator is used. The direction of rotation, ei-
ther counterclockwise or clockwise (looking
from the positioner onto the actuator shaft),
depends on how the rotary actuator is
mounted on the valve and how the two sig-
nal pressure outputs
1
38 and
2
38 are as-
signed to the connections y1 and y2 of the
rotary actuator.
Depending on the rotary actuator's direction
of rotation (counterclockwise or clockwise),
the starting point of the cam section that
must be passed through is either on the
front
A
or the back
B
of the cam disc.
10
EB 8386 EN
Attachment to rotary actuators
Cam discs Order no.
Linear cam disc, 90° 0050-0093
Equal percentage cam disc, 90° 0050-0095
Linear cam disc, 70° for butterfly valves 0050-0108
Equal percentage cam disc, 70° for butterfly valves 0050-0110
Linear cam disc, 75° for VETEC rotary plug valves 0050-0102
Equal percentage cam disc, 75° for VETEC rotary plug valves 0050-0104
Linear cam disc, 90° for Type 3310 Segmented Ball Valves 0050-0114
Equal percentage cam disc, 90° for Type 3310 Segmented Ball Valves 0050-0116
Linear cam disc, 70° for Type 3310 Segmented Ball Valves with reverse flow 0050-0126
Equal percentage cam disc, 70° for Type 3310 Segmented Ball Valve with reverse flow 0050-0128
Linear cam disc, 55° for Type 3310 Segmented Ball Valve with reduced opening angle 0050-0118
Equal percentage cam disc, 55° for Type 3310 with reduced opening angle 0050-0120