Val-Matic Tilted Disc Check Valve - Manual (Page 3)

2
DESCRIPTION OF OPERATION (cont’d)
Upon pump start-up, the forward flow of water will
start to rotate the disc about the pivot pins until the
disc rotates through a 40-degree arc and contacts
the integral body stops. The partially balanced disc
assists in opening the disc and stabilizes the disc in
low-flow cases where the valve remains partially
open.
On pump shutdown, the forward velocity of the water
starts to diminish, until the disc is no longer held
against the body stops and the partially balanced
disc will move to the closed position. When the
forward velocity reaches zero, the disc will have
moved to the closed position and the reversal of flow
is checked. The 40-degree travel of the disc and the
partially balanced disc reduces the potential for
check valve slam and water hammer normally
associated with conventional swing check valves.
However, ideal hydraulic conditions are not always
predictable and the potential for water hammer can
still exist. Applications with a potential for valve slam
include high-head pumping, multiple high service
pumps, and the use of hydro-pneumatic surge tanks.
If the reversal of flow occurs before the disc has a
chance to fully close, it will be driven to the closed
position by the rapid flow reversal.
For these rapid flow reversal conditions, a bottom
mounted hydraulic dashpot can be fitted in the
bottom inspection port, provided that sufficient
clearance is provided for installation. The bottom
mounted oil dashpot will control the last 10 degrees
of disc travel between 1 and 5 seconds. A top
mounted dashpot can also be used. A top mounted
oil dashpot performs the same function as a bottom
dashpot and in addition, independently controls the
full open and closing strokes between 5 and 30
seconds to prevent line surges.
INSTALLATION
The installation of the valve is important for its
proper operation. The Tilted Disc Check Valve can
only be used for horizontal flow or vertical flow-up
applications.
Each valve is provided with a flow arrow integrally
cast on the valve body and a flow arrow printed on
the metal label attached to the valve. These flow
arrows must point in the direction the water will flow,
when the system is operating. ANSI Class 125 and
Class 250 Cast Iron valves are furnished with flat
faced flanges and should be mated with flat faced
companion flanges. The valve and adjacent piping
must be supported and aligned to prevent
cantilevered stress being transferred to the valve’s
flanges when installing the flange bolts or studs. For
raised face applications, a ductile iron valve body
should be specified.
When mating the check valve with butterfly isolation
valves, the clearance between the butterfly disc and
the fully open check valve stem must be checked. A
spacer pipe is sometimes needed. See the valve
arrangement drawing for disc clearance dimensions.
FLANGED ENDS: The flange should be mated with
flat-faced pipe flanges equipped with resilient
gaskets. When ring gaskets are used, the bolt
material shall be ASTM A307 Grade B or SAE
Grade 2 Carbon Steel. Higher strength bolts should
only be used with full-face gaskets.
INSTALLATION: Lower valve into the pipeline using
slings or chains around the valve body. Eye bolts or
bars can also be used in the bolt holes. Lubricate
the flange bolts and insert them around the flange.
Lightly turn bolts until gaps are eliminated. The
tightening of the bolts should then be done in
graduated steps using the cross-over tightening
method. Recommended lubricated torques for use
with resilient gaskets (75 durometer) is given in
Table 1. Do not exceed bolt rating or crush gasket
more than 50 percent of its thickness.
125# FLANGE DATA 250# FLANGE DATA
Valve
Size
(in)
Bolt
Dia.
(in)
Bolt
Torque
(ft-lbs)
Valve
Size
(in)
Bolt
Dia.
(in)
Bolt
Torque
(ft-lbs)
4 5/8 30-90 4 3/4 50-150
6 3/4 30-90 6 3/4 70-150
8 3/4 40-120 8 7/8 90-200
10 7/8 45-150 10 1 110-300
12 7/8 65-200 12 1 1/8 160-450
14 1 80-250 14 1 1/8 140-450
16 1 90-300 16 1 1/4 180-600
18 1 1/8 100-350 18 1 1/4 190-600
20 1 1/8 120-450 20 1 1/4 220-600
24 1 1/4 150-500 24 1 1/2 350-900
30 1 1/4 180-600 30 1 3/4 500-1500
36 1 1/2 250-750 36 2 700-2000
42 1 1/2 300-900 42 2 800-2500
48 1 1/2 400-900 48 2 900-1800
54 1 3/4 400-1200 - - -
TABLE 1. Flange Bolt Torques
CAUTION
For horizontal flow applications, the valve must
be installed with both of the eccentric pivot pin
trunnions located above the horizontal
centerline of the valve and they must be level
to the horizontal plane of the valve.
CAUTION
The valve must be mated with flat-faced
flanges or damage may result. The use of
excessive bolt torque can damage the valve.