Samson 3760, Монтаж и эксплуатация

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The starting point (zero) in this case is 0.2
bar or 4 mA, the upper range value is 1 bar
or 20 mA.
In split-range operation, the controller output
signal intended to actuate two control valves
is split into half to allow each valve to pass
through its entire travel range at one half of
the signal range (e.g. first valve adjusted to
0.2 to 0.6 bar or 4 to 12 mA, and the sec-
ond valve adjusted to 0.6 to 1 bar or 12 to
20 mA).
To avoid any crossing-over, allow for a
dead band of ± 0.05 bar or ± 0.5 mA as
shown in Fig. 6.
The starting point (zero) is adjusted at the
ZERO adjustment screw (5). The reference
variable span, and thus the upper range
value is adjusted at the SPAN adjustment
screw (8).
4
In a
pneumatic
positioner, connect an air
source providing max. 1.5 bar to the
positioner input (IN SIGNAL 27) via a
remote adjuster and a pressure gauge.
4
In an electropneumatic positioner, con-
nect an ammeter to the ter11
and –12.
4
Connect compressed air to the supply in-
put (SUPPLY 9); also see section 3.1.2.
4.2 Adjustment for actuator with
fail-safe action "Actuator
stem extends"
NOTICE
To ensure that the full closing force can be
effective at the control valve, the diaphragm
chamber must be completely vented when
reaching the lower range value (direction of
action >>) or the upper range value (direc-
tion of action <> ) of the reference variable.
Therefore, set the input signal to a slightly
increased starting point of approx. 0.23 bar
(4.5 mA) when the direction of action is di-
rect >>, and to a slightly lowered starting
point of 0.97 bar (19.5 mA) when the direc-
tion of action is reverse <>.
This applies in particular to controllers and
control systems whose output signal is lim-
ited to a range of 4 to 20 mA.
Starting point (zero)
e.g. 0.23 bar (4.5 mA)
1. Turn ZERO adjustment screw (5) until
the plug stem just begins to move from
its resting position (observe plug stem at
the travel indicator).
2. Decrease input signal and increase
again slowly. Check whether the plug
stem starts moving at a starting point of
0.23 bar (4.5 mA) and correct it, if nec-
essary.
16
EB 8385 EN
Operation – Adjustment