Flowserve I90 Series - Manual (Page 7)

WCAIM2053 Pulsair Loop-Powered Positioner Modular Accessory System (Series I90/L90) 7
The Pulsair Loop-Powered positioner board 4-20 mA signal
input circuit is protected with a 63 mA fuse. The intrinsically
safe version of the circuit board does not have a fuse,
however, due to the requirements imposed by intrinsic
safety practices.
Technical Data
Ambient Temperature: Circuit Board Temperature:
Resistance to Vibration: 2 g’s – 0 to 100 Hertz
Nominal Signal Range: 4 to 20 milliamp
Minimum Current to
Maintain Power Supply: 3.6 milliamp
Load Voltage: 14[V] - ((i[mA] - 4)/2.67)[V]
+ .05[kohm] x i[mA]
Static Destruction Limit: +/-40 mA
Dynamic Destruction Limit
1.2/50 usec, 82 ohm: +/-500 V
Internal Capacitance: Negligible
Internal Inductance: Negligible
2. ENVIRONMENTAL CONSIDERATIONS
a. General
Caution: The Worcester/McCANNA Pulsair Loop-
Powered Positioner M.A.S. circuit board is relatively
insensitive to electrical noise on signal lines, and from
noise in the environment. Follow installation,
calibration, and adjustment guidelines carefully and
use shielded wire as stated in paragraph III.A.2.d.
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
in areas where exposure to relative humidity levels above
85 percent, 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 span of
electronic equipment.
b. Temperature
Operating solid-state electronic equipment near or
beyond its high temperature rating 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 Pulsair-Loop Powered
Positioner M.A.S. circuit board is rated for operation
between 0°F and 176°F. Do not exceed an ambient
temperature of 170°F. in order to ensure that the interior
of the sealed M.A.S. housing does not exceed 176°F.
CAUTION: Exposure to direct sunlight can result in
internal temperatures up to 40°F higher than ambient
conditions.
c. Humidity
Most electronic equipment has a reasonable degree of
inherent humidity protection and additional protection is
supplied by Flowserve in the form of a moisture proofing
and fungicidal coating.
Such protection will generally suffice for environments
where the average relative humidity is in the area of 80
percent or less and ambient temperatures are in the order
of 70°F average. Where relative humidity is consistently
80 to 90 percent and the ambient temperature is subject
to large variations, a desiccant can be used to control
humidity. The desiccant will need to be changed
periodically to maintain its effectiveness.
In those instances where high ambient temperature would
bring the internal operating temperature near or above its
maximum rating, the user should 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, reduced maintenance needs and much
less process downtime.
d. Shielding – Grounding of Shielding
Shielded wiring should be used for all signal input
circuit wiring.
The shields should never be used in place of one of the
input wires, and the shields normally 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 ground loops. If two or more
shielded cables come to the positioner from different
locations, they must be grounded at the positioner. For
intrinsically safe Pulsair, using zener barriers, grounded
shield must be connected to a zener barrier ground.
3. ELECTRONIC CIRCUIT BOARD BASICS
a. Circuit Board Configurations
There are two basic circuit board configurations. Both
versions contain the same basic input, logic and solenoid
control circuitry. The difference is in between the two is
intrinsic safety. One version of the circuit is not
intrinsically safe primarily due to the presence of a fuse
on the circuit board, while the intrinsically safe version
does not have the fuse.
Flow Control Division
Worcester Controls