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SECTION 2 ITEM 1040
DATED NOVEMBER 2012
SUPERCEDES MAY 2010
6.3.4 On the Triple Duty Performance Curve (Fig. 2) 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 the flow rate at
the bottom of the chart.
6.35 To calculate flow rate of valve in the throttled position,
multiply the flow rate from Step 6.3.4 by the percentage
flow rate from Step 6.32 divided by 100.
Example: Valve size 4 inch.
Differential Pressure is 5.4 ft. (1.65 m).
Number of rings open = 3. Therefore: 3 rings ÷ 6 rings x
100 = 50% throttled.
From the Triple Duty Performance Curve (Fig. 5), a 4 inch
valve with 5.4 ft. pressure drop (1.65 m) represents a flow
of 400 USgpm (25.2 l/s).
From Flow Characteristic Curve (Fig. 6), a 4 inch valve,
50% open, represents 34% of maximum flow.
Approximate flow of a 4 inch valve, with a 5.4 ft. (1.65 m)
pressure drop when 50% throttled is:
400 x 34 = 136 USgpm or in metric 25.2 x 34 = 8.57l/s
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 be
trimmed or valves located elsewhere in the system be used to
partially throttle the flow.
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 provides for approximate flow
measurement.
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
wrench with 25 to 30 ft./lbs. of torque.
7.2 To assure trouble-free check valve operation and shut off
operation, the valve should be periodically opened and
closed to keep valve seat and valve disc guide stem free of
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
should be worn.
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
8.4 The valve bonnet may now be removed. There may be a
8.5 Clean exposed portion of valve stem (Do not scratch).
8.6 Remove and replace the "O" Ring and gasket.
8.7 Install the valve bonnet.
8.8 Tightening valve bonnet is necessary to stop any leaks.
8.9 Open valve to balance set point as recorded in 8.2.
9.0 MAXIMUM NUMBER OF TURNS FULL OPEN
Note: On valve sizes 2-
is 5 turns. However valve will open to 5-
back of seating of valve.
10.0 SEAT REPLACEMENT:
100
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.
10.4 Inspect and clean "O" Ring cavity and install new "O"
4
maximum force of 45 ft./lbs. This will ensure good metal-
to-metal contact and minimum leakage.
slight leakage. As the metal-to-metal back seating does
not provide a drip-tight seal.
VALVE:
⁄
" and 3", full open position of valve
1
2
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.
⁄
turns which is just
1
2
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