Flowserve 90 Series Solenoid Block Kit - Manual (Page 5)

Flow Control Division
Worcester Controls
WCAIM2043 Solenoid Block Kit for Series 90 Modular Accessory System 5
Cut one capacitor lead to 1 1 /
4
" long; leave the other lead at its
standard 1 3 /
4
" length. Cut two pieces of insulating tubing
(fluoropolymer – approximately 1 /
32
" I.D.) to 1" and 1 1 /
2
" long,
respectively, and place on the capacitor leads. Position the
capacitor under the terminal bracket and route the leads into
the internal side of terminals A and B. The shorter lead goes
into terminal A. The leads are strong enough to hold the
capacitor in place.
2. 12 or 24 VDC OPERATION – Connect the black wire from the
lead wire/connector to the “internal” side of terminal A
(negative DC power) on the side terminal strip. Connect the
red wire to the internal side of terminal B (positive DC power).
b. SINGLE-ACTING AND DOUBLE-ACTING MODULATING TYPE
(POSITIONER/CONTROLLER)
1. Follow the wiring diagrams shown on the next page closely.
Note that the spring-return version uses a pressure switch
that opens when air pressure below approximately 35 psi
is detected.
CAUTION: It is important that the power source be
connected properly to the M.A.S. terminal strip. This
terminal strip is the one located next to the solenoid block
assembly. Terminal A of this strip is to have the negative or
neutral wire connected to it. Terminal B is to have the
positive or hot wire connected to it. The board has a diode
and a fuse installed to prevent damage, as in the case of
reverse voltage polarity, but if the diode happens to be
defective, the damage could be done before the fuse blows.
2. Purpose of Pressure Switch in Fail-Safe M.A.S.
Positioner/Controller Packages.
In order to position a Series 39 spring-return actuator, it is
necessary to trap air in the actuator between the pistons. This
air balances the spring force to keep the actuator in position.
One of the three-way solenoid valves used on the SR-PC
Block is used to permit air into the actuator’s center chamber
to drive the actuator open. This solenoid valve (solenoid “B”)
is normally de-energized. The other solenoid valve on the SR-
PC Block is used to trap the air in the actuator’s center
chamber. In order to make the actuator fail-safe, this valve
(solenoid “A”) is kept normally energized so that on loss of
power, the valve will de-energize, thus allowing the air to vent
from the actuator and the springs to drive it to the fail-safe
position. To make the actuator fail-safe on loss of air pressure
we need a means to detect that we have in fact lost air
pressure. This is the function of the pressure switch. Air line
pressure above 40 psi will keep the pressure switch closed
and therefore keep the two solenoid valves connected to the
power supply as required. However, on a loss of air pressure,
the “close” solenoid (solenoid “A”) is de-energized no matter
what position the circuit board is calling for, and thus the
valve and actuator will move to the fail-safe position. In fact,
the “open” solenoid (solenoid “B”) is also disconnected from
the power supply to prevent venting air continuously—as long
as there is air pressure in the supply line and the circuit board
is trying to drive the valve open.