Val-Matic Swing Check Valve - Manual (Page 3)

VAL-MATIC'S SWING CHECK VALVE
OPERATION, MAINTENANCE AND INSTALLATION
Page 3 of 13
VALVE CONSTRUCTION
The Swing Check Valve housing consists of a
body section having integrally cast inlet and outlet
flanges. The top portion of the body has a large
integrally cast flanged access port, to which the
top access cover is bolted. The size of this access
port permits full access to the disc and seat
components for maintenance or replacement.
The flow area through the body inlet, body seat
ring and the body outlet is equal to 100% of the
nominal inside area of the standard pipe. The
center portion of the body is expanded to allow for
the area that is occupied by the disc and because
of the expanded area thru the center of the valve,
the disc at 20 to 25 degrees open reaches a full
flow area.
FLOW
STOP
BOLT
COVER
DISC
BODY
HINGE
PIN
YOKE ARM
FIGURE 1. SWING CHECK VALVE
The body has two eccentrically located hinge pin
trunnions that contain the hinge bushings and
hinge packing. A continuous stainless steel hinge
pin passes through the bushings and the disc yoke
arm. The disc yoke arm is keyed to the hinge to
lock them together rotationally. The disc is
attached to the disc arm with two stainless steel
pins, making the disc and disc yoke arm a solid
assembly. The Buna-N disc seal ring fits into a
recessed register in the face of the disc and is
captured and retained by a large circular retaining
ring or segments and stainless steel screws. The
Buna-N disc seal has O-ring type sealing beads
that provide low pressure sealing when it contacts
the stainless steel seat ring, located in a machined
register in the body. The seat ring has a groove on
its outside diameter, which accepts an O-ring, that
creates a seal between the interface of the inside
diameter of the body register and the outside
diameter of the seat ring.
The stainless steel body seat ring is threaded into
the body in 2” through 12” sizes and retained to
the body with stainless steel set screws that
engage a groove within the body seat register in
larger sizes. The exterior portion of the body has
machined mounting pads on each side of the
valve. The lower portion of the air cushion
assembly is mounted to these pads. An additional
pad accepts a spring assembly.
The counterweight arm assembly is keyed to the
extended portion of the pivot shaft. The
counterweight arm assembly has additional
keyways to allow for multiple mounting positions
such as horizontal or about 30° below when
closed. The counterweights are located on the
counterweight arm and are secured to the lever
with a bolt.
The body and the top cover are provided with
plugged ports. The body port serves as a drain
port and the top cover's port serves as a
connection point for an automatic air release valve
or as a vent port. A drain valve may also be
connected to the body port.
DESCRIPTION OF OPERATION
The valve is designed to prevent reverse flow
automatically. During system flow conditions, the
movement of the fluid forces the disc to the open
position allowing 100% un-restricted flow area
through the valve. Under reverse flow conditions,
the disc automatically returns to the closed
position to prevent reverse flow.
Upon pump start-up the forward flow of the water
will start to rotate the disc about the hinge until the
disc contacts the stop bolt in the valve body. The
disc rotates through a 60 to 70 degree arc from
the closed to the fully open position. On pump
shut down the forward velocity of the water will
start to diminish, as the forward velocity of the
water is further reduced, the disc will start its travel
to the closed position. When the forward velocity
of the water reaches zero, the disc has moved to
the closed position and the reversal of the flow is
checked. Under these ideal hydraulic conditions
the valve should close without water hammer.
However, ideal hydraulic conditions are not always
predictable and the potential for water hammer
exists. If the reversal of flow happens before the