Refrigerating Specialties Division
2
penalty in the suction line. The CK-6D will positively
close the suction line allowing for defrost to occur. The
dual position feature permits the evaporator pressure to
equalize with the suction pressure after a defrost cycle
has occurred. The intermediate stage allows for this
equalization to occur in a controlled manner without
the need for an externally piped equalizing solenoid.
The CK-6D is unique control valve that also incorporates
a built-in mechanical fail-safe feature which prevents
the undesirable effects of an immediate opening of the
valve in the event of an electrical power failure while
the evaporator is in defrost.
Principles of Operation
The CK-6D is a normally open valve which uses discharge
gas to power the valve closed. For closing of the CK-6D,
either energize both solenoid coils simultaneously, or
energize solenoid coil #2 initially allowing condenser
gas pressure or pressure from another source to act
on the secondary piston forcing it down and closing the
valve to the 1st stage. Then while keeping solenoid coil
#2 energized, solenoid coil #1 is energized allowing gas
pressure to act on the primary piston forcing it down,
compressing the spring fully, and firmly seating on the
valve seat bead. Refrigerating Specialties recommends
utilizing an oil free source of gas such as that from
the top of the high-pressure receiver, or rotary screw
compressor system. The valve will not close unless
pressure above the pistons exceeds the downstream
pressure by at least .35 bar (5 psi). If an attempt is made
to fully close the valve by only energizing solenoid coil
#1, a far greater amount of pressure will be required
to act upon the main piston.
For line equalization solenoid coil #1 is de-energized,
while solenoid coil #2 remains energized, allowing
the primary piston to move up to the bottom of the
secondary piston, allowing for evaporator equalization
after defrost. The length of time the valve is left in the
equalization position is controlled by the time set in the
equalization stage on the defrost controller.
After the termination of the hot gas injection period,
any style of suction stop valve must reopen in order
for refrigeration to resume. For the CK-6D to open,
the valve’s pilot solenoids de-energize, thereby inter-
rupting the pilot stream flow of discharge gas to the
top of the valve's pistons. The main valve will open
to it's intermediate position, however, since residual
pressure in the coil is transmitted through the pilot
regulator to the top of the top piston. [Note: The pilot
regulator should be adjusted to maintain a minimal
set point, approximately 10 psi.] De-energizing only
the solenoid feeding the lower piston will allow some
flow to pass and equalize pressures between the coil
and the suction line. It is imperative to allow sufficient
time for this equalization. The ability of the CK-6D to
resist opening fully during an interruption of power,
while an evaporator is in the process of defrosting, is
its single greatest advantage. Where power failures
can occur with any frequency, consideration should be
given to this unique valve. By design, a standard CK-2
or a competitive valve of similar design would open
immediately as residual coil pressure surges through
the valve should power to the pilot solenoid suddenly
be interrupted during a defrost. The design of the
CK-6D prevents this from occurring and prevents the
dangerous consequences to the system under these
conditions.
Adjustment
The pilot regulator should be adjusted to maintain a
minimum set point of about 10 psi. This represents
approximately 1/2 turn clockwise of the adjusting stem
starting with the stem turned completely out.
Manual Lift Stem
If it is desired to hold open the CK-6D Dual Position
Suction Stop Valve manually, remove the Sealing cap
and turn the Lifting Stem inward as far as possible.
Valve cannot close now until the Seat Lift Stem is once
again turned out.
Installation
Protect inside of valve from dirt and chips during in-
stallation.
In low temperature applications the CK-6D should be
powered with an oil free source of gas such as that
from the top of the high-pressure receiver or a rotary
screw compressor system. The CK-6D should not be
used at temperatures below -30°C (-25°F) if an oil
free source of high-pressure gas cannot be utilized to
power the valve.
The CK-6D Dual Position Suction Stop Valve may be in-
stalled on its side or vertically upright in either vertical
or horizontal pipe lines. When used on suction lines the
arrow on the valve body should point in the direction
of normal fluid flow. When used on either gas or liquid
legs of a flooded evaporator the arrow on the valve body
should point from the evaporator to the surge drum.
The solenoid sequencing should be as follows.
To fully close the valve:
Energize both solenoid coils simultaneously, or ener-
gize solenoid coil #2, then solenoid coil#1.