Flowserve RT92 Series - Manual (Page 2)

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I. INTRODUCTION
The Flowserve Worcester RTU (Remote Terminal Unit) Interface Card
is designed for use with the low power Worcester Series 75 DC
Electric Actuators. The low power actuators are those with standard
DC motors mounted on 15-second gearboxes. This increases duty
cycle while lowering current draw for a given torque output. The RTU
card acts as an interface between the customer’s RTU and the
actuator’s DC motors. Its primary function is to protect the
customer’s DC solar power supply in the event of a stuck valve or
some other condition that could cause an overcurrent condition. It
does this by electronically disconnecting the motor drive circuits
when an overcurrent condition exists. Removing the control signal
and reapplying it resets the logic in the drive circuits.
II. GENERAL
A. Environmental Considerations
CAUTION: The RTU Interface is relatively insensitive to electrical
noise on signal or supply lines and in the environment. Follow
installation, calibration and adjustment guidelines carefully and
use shielded wire as stated in paragraph 4.
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. 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.
At high temperatures, some components will destruct completely
when their maximum temperature is exceeded, others will cease
operation at temperatures above ratings and will return to
operation at normal temperatures, but may have been
permanently changed in one or another parameter causing a
device to operate poorly, and may also cause greatly reduced
component life.
2. Circuit Board Temperature Considerations:
The Worcester RTU Interface is rated for operation between
-40°F and 160°F. When using the interface inside the Worcester
75 Series actuators, do not exceed a maximum ambient
temperature limit of 115°F in order to ensure that the circuit
board maximum temperature of 160°F is not exceeded.
3. 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 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 with only
occasional short term exposure to temperatures up to 90°F.
Where relative humidity is consistently 80 to 90% and the
ambient temperature is high or subject to large variations,
considerations 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’s 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.
4. Input Circuit Noise Protection:
Shielded wiring should be used for all signal input circuit wiring
regardless of length.
With a separately housed interface board, the wiring from the
feedback potentiometer to the remote interface board is
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 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
current ground loops. If two or more shielded cables come to the
RTU card from different locations, ground the shields at the RTU
card location.
III. ELECTRONIC CIRCUIT BOARD
A. General
Figures 1 through 3 show the location of major components of
the various RTU cards. The RTU card is wired into the terminal
strip through two amphenol 6-pin quick disconnects. This makes
it very quick and easy to replace a circuit board in the field.
B. Circuit Board Configurations
There are three basic circuit board configurations. All versions
contain the same basic input, logic, and motor control circuitry
including overcurrent trip. The difference is in the type of output
indication desired. The first version (Figure 1) has no output
indication circuitry. The second version (Figure 2) is set up to
provide a 0-5 volt position indication output. The third version
(Figure 3) is set up to provide a relay trip condition indication
(positive, negative, or contact closure). The three boards are
physically different in this respect and are not interchangeable.
All three versions will work with either 12 VDC or 24 VDC.
Flow Control
Worcester Actuation Systems