25
Logix
®
520MD+ and 510+ Digital Positioners FCD LGENIM0105-15-AQ – 05/16
flowserve.com
Figure 22: Linear, Single Acting, Air to Open
6.2 Connect Supply Port
The positioner ports are threaded with either G ¼ or ¼ NPTF as
indicated on the housing.
In order to maintain the recommended air quality, a coalescing filter
should always be installed in the supply gas line. An air filter is highly
recommended for all applications where dirty air is a possibility.
The positioner passage ways are equipped with small filters, which
remove medium and coarse size dirt from the pressurized air. If nec-
essary, they are easily accessible for cleaning.
A supply regulator is recommended if the customer will be using the
diagnostic features of the Logix 500+ but is not required. In applica-
tions where the supply pressure is higher than the maximum actuator
pressure rating a supply regulator is required to lower the pressure to
the actuator’s maximum rating.
6.3 Purging Single Acting Actuators
Purging allows the non-pressurized side of a single acting actuator
to fill with exhaust gas instead of atmospheric air. This configuration
helps prevent corrosion of actuator components in harsh environ-
ments. When a single acting relay is used, a special procedure can be
performed to configure the positioner to purge properly using port
A. Contact your local Flowserve Representative for more information
regarding the purging option.
6.4 Vented Design
A standard Logix 500+ 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.
The housing chamber exhaust port is located on the backside of the
positioner. The actuator exhaust port is located on the bottom of the
positioner. Both ports are tapped with either ¼ NPTF or G ¼ threads
and covered with a protective cap. To control vented gas, remove the
caps and connect the necessary tubing/piping to these ports. See
Figure 23: Exhaust Vents.
This piping system may cause some positioner back pressure. Back
pressure in the housing chamber is from the modulator and regulator.
Back pressure in the exhaust port is from the actuator.
The maximum allowable back pressure from the housing chamber is
0.14 barg (2.0 PSIG). For flow rates, see section 2.3 Air Supply.
The maximum allowable back pressure from the exhaust port is 0.55
barg (8.0 PSIG) for double acting relays and is 0.14 barg (2.0 PSIG)
for single acting relays. Higher pressure may result in decreased per-
formance. For output flow rates, see section 2.2 Pneumatic Output.
a
CAUTION:
The back pressure in the main housing must never
rise above 0.14 barg (2.0 PSIG). This could cause the positioner
to become unresponsive under some circumstances
Figure 23: Exhaust Vents
Housing
Chamber
Exhaust
(0.14 barg Max)
Actuator
Exhaust
(0.55 barg Max)
