8
SECTION 2ITEM 1040
DATED NOVEMBER 2012
SUPERCEDES MAY 2010
6.3.1 Record the size of the valve and stem position using the
Flow Indicator Scale (at right). Calculate percentage of
valveopeningreferringtotablebelow:
Valve
Size 21⁄23 4 5 6 8 10 12
No. of Rings
(valve full open) 5 5 6 9 10 12 18 28
6.3.2 Measure and record the differential pressure across the
valve in the throttled position.
6.3.3 Locate percentage of valve opening on the bottom scale of
FlowCharacteristic Curve (Fig 6). Projectline vertically
up to intersect with the Valve Characteristic Curve and
fromthispointprojectlinehorizontallyacrosstotheleft
ofthe chart and recordthepercentageofmaximumflow
rate.
6.3.4On the Triple Duty Performance Curve (Fig. 5) locate
the differential pressure obtained in Step 6.3.2 and
project line horizontally across to intercept with Valve
Performance Curve. Drop a line vertically down to read
theflowrateatthebottomofthechart.
6.35 To calculate flow rate of valve in the throttled position,
multiplythe flow rate fromStep 6.3.4 by thepercentage
flowratefromStep6.32dividedby100.
Example: Valve size 4 inch.
DifferentialPressureis5.4ft.(1.65m).
Number of rings open = 3. Therefore: 3 rings ÷ 6 rings x
100 = 50% throttled.
From the Triple Duty Performance Curve (Fig. 5), a 4
inchvalvewith5.4ft.pressuredrop(1.65m)representsa
flowof400USgpm(25.2l/s).
FromFlowCharacteristicCurve (Fig. 6), a 4 inch valve,
50%open,represents34%ofmaximumflow.
Approximate flow of a 4 inch valve, with a 5.4 ft. (1.65
m)pressuredropwhen50%throttledis:
400 x 34=136USgpmorinmetric25.2 x 34 = 8.57l/s
100 100
Note: To prevent premature valve failure it is not recommended
that the valve operate in the throttled position with more than
25 ft. pressure differential. Instead the pump impeller should
betrimmedorvalveslocatedelsewhereinthesystembeusedto
partiallythrottletheflow.
FLOW INDICATOR SCALE:
The valve stem with its grooved rings
and positioning sleeve indicates the
throttled position of the valve. The
quarter turn graduations on the sleeve,
with the scribed line on the stem
providesforapprox.flowmeasurement.
Note: The valve is shipped in the closed position. The
indicator on the plastic sleeve is aligned with the vertical
scribed line on the stem.
7.0 OPERATION:
7.1 To assure tight shut off the valve must be closed using a
wrenchwith25to30ft./lbs.oftorque.
7.2 Toassuretrouble-freecheckvalveoperationandshutoff
operation, the valve should be periodically opened and
closedtokeepvalveseatandvalvediscguidestemfreeof
build up of system contaminants.
8.0 REPACKING OF 3DV UNDER FULL SYSTEM
PRESSURE:
8.1 Should it be necessary, stem “O” Ring can be changed
under full system pressure. Caution: Safety glasses
shouldbeworn.
8.2 Record the valve setting.
8.3 Turn the valve stem counter-clockwise until the valve
is fully open and will not turn any further. Torque to a
maximumforceof45ft./lbs.Thiswillensuregoodmetal-
to-metalcontactandminimumleakage.
8.4 Thevalve bonnetmaynow beremoved.Theremay bea
slight leakage. As the metal-to-metal back seating does
notprovideadrip-tightseal.
8.5 Cleanexposedportionofvalvestem(Donotscratch).
8.6 Removeandreplacethe“O”Ringandgasket.
8.7 Install the valve bonnet.
8.8 Tighteningvalvebonnetisnecessarytostopanyleaks.
8.9 Open valve to balance set point as recorded in 8.2.
9.0 MAX. NUMBER OF TURNS FULL OPEN VALVE:
Note:Onvalvesizes2-1⁄2"and 3", full open position of valve
is5turns.Howevervalvewillopento5-1⁄2turnswhichisjust
backofseatingofvalve.
10.0 SEAT REPLACEMENT:
10.1 Drain system and remove valve from piping.
10.2 Remove the body bolts from the body using an Allen Key.
10.3 Remove seat and “O” Ring. “O” Ring is not used on
valves 8" and larger.
10.4 Inspect and clean “O” Ring cavity and install new “O”
Ring and seat. Valve disc stem also should be inspected
and replaced if worn. Valve stem “O” Ring should be
replaced at this time. Refer to section 8.
Inherent Flow
Characteristic Curve
with Valve in
Throttled Position
Fig. 6
