Flowserve DFP17 - Manual (Page 5)

WCAIM2037 DataFlo Digital Electronic Positioner DFP17 Installation, Operation and Maintenance Instructions 5
Flow Control
Worcester Actuation Systems
1.2 Environmental Considerations
a CAUTION: The DataFlo Digital Electronic Positioner is sensitive to
electrical noise on signal or supply lines and in the environment.
For maximum positioner sensitivity, the electrical noise level
should be as low as possible. Follow installation, calibration and
adjustment guidelines carefully and use shielded wire as stated
in section 1.2.3.
Flowserve recommends that all products which must be stored prior
to installation, be stored indoors, in an environment suitable for
human occupancy. Do not store product in areas where exposure to
relative humidity above 85%, acid or alkali fumes, radiation above
normal background, ultraviolet light, or temperatures above 120˚F or
below 40˚F may occur. Do not store within 50 feet of any source of
ozone.
Temperature and humidity are the two most important factors that
determine the usefulness and life of electronic equipment.
1.2.1 Temperature
Operating solid state electronic equipment near or beyond
its high temperature ratings is the primary cause for most
failures. It is, therefore, very important that the user be
aware of and take into consideration, factors that affect the
temperature at which the electronic circuits will operate.
Operating an electronic device at or below its low
temperature rating generally results in a unit operating
poorly or not at all, but it will usually resume normal
operation as soon as rated operating temperatures are
reached. Low temperature problems can be easily cured by
addition of a thermostatically controlled heater to the unit’s
housing.
The Worcester/McCANNA DataFlo Digital Electronic
Positioner is rated for operation between -40˚F (with heater
and thermostat) and 160˚F. When using the Positioner
inside the Worcester/McCANNA 75 Series actuators, a
maximum ambient temperature of 115˚F is required to
ensure the circuit board maximum temperature of 160˚F is
not exceeded.
1.2.2 Humidity
Most electronic equipment has a reasonable degree of
inherent humidity protection and additional protection is
supplied by the manufacturer, in the form of moisture
proofing and fungicidal coatings.
Such protection, and the 3 to 4 watts of heat generated by
the circuit board assembly will generally suffice for
environments where the average relative humidity is in the
area of 80% or less and ambient temperatures are in the
order of 70˚F average.
Where relative humidity is consistently 80 to 90% and the
ambient temperature is subject to large variations,
consideration should be given to installing a heater and
thermostat option in the enclosure. The heater should not
increase the enclosure temperature to the point where the
circuit board assembly’s temperature rating of 160˚F is
exceeded.
In those instances where the internal heater would bring
the circuit board operating temperature near or above its
maximum rating, the user might consider purging the
enclosure with a cool, dry gas. The initial costs can usually
be paid off quickly in the form of greatly extended
equipment life, low maintenance needs, and much less
process downtime.
1.2.3 Input Circuit Noise Protection
Shielded wiring should be used for all signal input circuit
wiring regardless of length.
With separately housed positioners, the wiring from the
feedback potentiometer to remote positioner, would be
considered as signal input wiring and should also be
shielded wire.
The shields should never be used in place of one of the
input wires, and the shields should be grounded to
equipment housings at one end of the wiring run only.
Grounding both ends of shielding can eliminate the
shielding benefits because of current ground loops. If two
or more shielded cables come to the positioner from
different locations, ground the shields at the positioner.