Metso NP724/S1 User Manual

7 NP 72 en 11
The pilot valve spool (44.2) should slip easily in the pilot
valve body (44.1).
If the pilot valve sticks, wash the body and spool with sol-
vent.
See the exploded view for the correct installation position
of the pilot valve. The size code for the pilot valve on the
body, for example DIA 4.0, must be visible on the right side.
Check the condition of the O-rings (43, 47) and of the gas-
ket (45). The end of the leaf spring on the beam must be on
top of the pilot valve spool, Figure 7. Make sure that the end
of the beam (5) goes into the spool groove without side-
ways deflections. After tightening the nuts (49), check the
beam once again by hand to see that the pilot valve moves
readily.
8.3 Replacement of the diaphragms
Remove the feedback spring (60), loosen the screws (23)
and remove the screw (15). Replace the diaphragm (14).
Note the correct installation position for the diaphragm,
with the convolution downward. See Figure 12.
Check the condition of the washer (55) when assembling
and secure the upper spring plate (16) with e.g. Loctite.
Check that the O-ring (11) is in place. Tighten the cover
screws (23) evenly. The positioner adjustment should be
checked after replacement of diaphragm.
Note. O-ring (11) in the old construction only (manufac-
tured before 12/94)
9 TROUBLESHOOTING
1. Signal pressure change does not affect actuator position
 supply pressure too low
 signal pressure tubes leak
 diaphragm damaged
 pilot valve sticks
 changeover piece seals leak
 tube installations between positioner and actuator
 changeover piece or cam position wrong, see Fig. 6.
 actuator or valve jammed
2. The actuator reaches final position with a small signal
pressure change
 the tube installation between positioner and actua-
tor, the changeover piece or the cam position wrong.
3. Inaccurate positioning
 pilot valve dirty
 beam (5) pushes pilot valve spool sideways
 diaphragm damaged
 actuator torque too low
 supply pressure too low
 valve torque requirement increased
4. Overshooting or too slow positioning
 pilot valve dirty or wrong size, see Table 2
 supply air tube too small or supply air filter dirty
 valve sticks
10 OPTIONS
10.1 NP700/B and NP700/B1
Equipped with a flameproof enclosure I/P converter.
To be adjusted like for standard posioners. Do not make any
adjustments for the I/P converter!
10.2 NP700/GN natural gas construction
For clean "sweet" natural gas instead of compressed air. Like
standard construction but with 3/4 NPT exhaust port.
Please note: do not remove the exhaust port (4).
10.3 NP700/R dust-proof construction (IP65)
For extremely dusty environments. The protective cover (3)
behind the standard posioner is replaced with an exhaust
port. The port has a 3/4 NPT filter.
Please note: do not remove the exhaust port (3).
10.4 NP700/A with pressure gauges
A standard positioner can be equipped with a pressure
gauge block.
The block (70) is attached with tree sef-tapping screws (72).
The O-rings (71, 3 pcs.) must be in position before mount-
ing. Check tightness after mounting.
For all other constructions see Type Code, Chapter 14.
11 TOOLS
In addition to standard general tools, you need the follow-
ing equipment:
 calibration device for adjustments
12 ORDERING SPARE PARTS
When ordering spare parts, always include the following
information:
 type code, sales order number, serial number
 number of the parts list, part number, name of the
part and quantity required
This information can be found from the identification plate
or documents.
NOTE:
The pilot valve body and spool constitute a pair, and must
not be replaced separately.
Fig. 12 Replacement of diaphragms
NOTE:
gap required
11 14 55 15 22 23
5
16
60

Metso NP724/S1 Specifications

General

Brand	Metso
Model	NP724/S1
Category	Valve Positioners
Language	English