Flowserve 3400IQ Digital Positioner - Manual (Page 64)

Logix 3400IQ Digital Positioner FCD LGENIM3401-00 – 06/06
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12. Reconnect the field wiring to the user interface board terminals.
13. Install the main PCB into the housing. Insert the retaining screw through the board into the
threaded boss and tighten evenly, using a Phillips screwdriver. Do not overtighten.
14. Install the plastic board cover. Insert the three retaining screws through the plastic cover into the
threaded boss and tighten evenly, using a Phillips screwdriver. Do not overtighten (see Figure
16).
15. Reinstall the UI wire connection (see Figure 12).
16. Reinstall all covers.
9 Optional Vented Design
NOTE: See Figures 19 and 20
A standard Logix 3400IQ positioner is vented directly to the atmosphere. When supply air is
substituted with sweet natural gas, piping must be used to route the exhausted natural gas to a safe
environment. This piping system may cause some positioner back pressure in the main chamber
(from the modulator and regulator) and spool chamber (from the actuator). Back pressure limitations
are described below.
Two chambers must be vented on the Logix 3400IQ positioners: the main housing chamber and the
spool valve chamber (Figures 20 and 21). The main chamber vent is located on the backside of the
positioner (see Figure 20). Vented-design Logix 3400IQ positioners are supplied from the factory
with a fitting installed in the main chamber vent. Connect the necessary tubing/piping to this fitting to
route the exhausted natural gas to a safe environment.
The maximum allowable back pressure from the collection device on the main housing vent is 2.0
psig (0.14 barg). Vent flow rate is 0.5 std ft
3 /min (1.4 std liter/min).
c WARNING: The back pressure in the main housing must never rise above 2.0 psig (0.14
barg).