Fisher 3570C - Supply Pressure Connections

3570 Series
6
CAUTION
When installing a remote vent pipe, take
care not to overtighten the pipe in the
vent connection. Excessive torque will
damage the threads in the connection.
Note
The vent connection is always plugged
with a pipe plug for Type 3570P and
3570PC positioners when mounted on
Fisher 490 Series actuators.
The connection marked VENT (see figure 2) should be
left open if the actuator is installed in the vertical posi-
tion. However, the vent must be protected against the
entrance of any foreign material that could plug it.
Check the vent periodically to be certain it is not
plugged.
If the actuator is mounted in other than the vertical
position, be sure there is a vent and drain at the low-
est point of the positioner. To do this, remove the pipe
plug (key 36, figure 10) from the cover. Then, position
the cover in such a way that the hole in the cover is at
the lowest point. Plug the vent connection because the
positioner is now vented through the cover.
Note
A remote vent is not possible with Type
3570P, 3570PC, 3571, 3576, and 3577 po-
sitioners.
If a remote vent is required, the vent line must be as
short as possible with a minimum number of bends or
elbows. Vent line piping should have a minimum inside
diameter of 3/4 inches (19 mm) for runs up to 20 feet
(6.09 meters) and a minimum inside diameter of 1-inch
(25.4 mm) for runs from 20 to 100 feet (6.09 to 30.5
meters).
Supply Pressure Connections
WARNING
Personal injury or property damage may
occur from an uncontrolled process if
the supply medium is not clean, dry,
oil-free, or non-corrosive gas. Industry
instrument air quality standards
describe acceptable dirt, oil, and
moisture content. Due to the variability
in nature of the problems these
influences can have on pneumatic
equipment, Fisher Controls has no
technical basis to recommend the level
of filtration equipment required to
prevent performance degradation of
pneumatic equipment. A filter or filter
regulator capable of removing particles
40 microns in diameter should suffice
for most applications. Use of suitable
filtration equipment and the
establishment of a maintenance cycle to
monitor its operation is recommended.
WARNING
To avoid personal injury or property
damage resulting from the sudden re-
lease of pressure, do not install the
valve assembly where service condi-
tions could exceed the limits given in
this manual or on the appropriate name-
plates. Use pressure-relieving devices
as required by government or accepted
industry codes and good engineering
practices.
CAUTION
If the supply pressure medium is corro-
sive, make sure the tubing and instru-
ment components that contact the cor-
rosive medium are of suitable corrosion-
resistant material. The use of unsuitable
materials might result in personal injury
or property damage due to the uncon-
trolled release of the corrosive media.
The connection marked SUPPLY (see figure 2) must
be provided with clean, dry air or a non-corrosive gas.
Install a 40-micron filter and suitable equipment to dry
the supply medium. Establish a maintenance cycle to
ensure that the regulator and filter are working
correctly.
The maximum allowable supply pressure to prevent
damage to the components of the positioner, actuator,
and valve is normally stamped on the actuator name-
plate. Use a suitable supply pressure regulator to re-
duce the supply pressure source to the value stamped
on the nameplate.
If this maximum supply pressure value is not available,
use a supply pressure that does not exceed any of the
following:
D The maximum supply pressure for the positioner
as shown in table 1.