Metso NE Series, Инструкция по установке, обслуживанию и эксплуатации

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7 NE 72 en 3
1 INTRODUCTION
1.1 General view
The NE700 electro-pneumatic posiotioner is used for posi-
tioning double or single acting actuator.
1.2 Principle of operation
Operation is based on the torque balance. Force coil (152)
located in the field of the permanent magnet (168) creates
a torque proportional to the signal current on the balance
beam (164).
The feed-back spring (41) causes a counter-torque propor-
tional to the actuator position; this position is transmited
via the actuator shaft, the coupling (52), the feed-back shaft
(26), the cam plate (29) and the lever (33) as a relative dis-
placement to the lower end of the feed-back spring (41).
The nozzle (166) senses the torque balance on the beam
(164). When the input signal increases, the balance beam
(164) approaches the nozzle (166) and the nozzle pressure
rises. This causes the diaphragm piston (8), the beam (5)
and the spool (44.2) to move downward. The pilot valve (44)
distributes supply air (S) to the upper side of the actuator
piston via channel C2, and from the lower side via channel
C1 through the pilot valve (44) to the exhaust port. The
actuator piston moves until the balance beam is in equilib-
rium. At this point the actuator is exactly in the position
required by the input signal.
The spring (40) causes a negative feed-back between the
first amplification stage (nozzle 166 and restriction 24) and
the second (pilot valve assembly 44). By changing the lower
fastening point for the spring (40) on the balance beam
(164), the dynamics of the positioner can be adapted to suit
the actuator size.
The zero adjustment (61) is mechanical and the range
adjustment (35.6) is electrical.
The differential diaphragms effectively offset the effect of
fluctuations in the supply pressure.
Parts list for Figure 1:
Item Part
5 Beam
8 Diaphragm piston
24 Restriction
26 Feed-back shaft
29 Camplate
33 Lever
35.6 Range adjustment
40 Internal feed-back spring
41 Feed-back spring
44.1 Pilot valve body
44.2 Pilot valve spool
46 Changeover piece
52 Coupling
61 Zero adjustment
152 Force coil
164 Balance beam
166 Nozzle
168 Permanent magnet
1.3 Marking of positioner
The positioner has an adhesive ID plate, see Fig. 2.
The ID plate contains the following information (from top to
bottom):

Full type designation of the positioner

Input signal

Input resistance

Max. supply pressure

Enclosure class

Ambient temperature range

Manufacturing series number
An additional plate, Fig. 3, has markings:

Filter regulator (-K)

Temperature range

Conduit entry (-L, -I or -NJ)
Fig. 1 Schematic diagram
Fig. 2 ID plate
Fig. 3 Additional plate