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SECTION 2 ITEM 1040
DATED NOVEMBER 2012
SUPERCEDES MAY 2010
Fig. 6
6.3.1 Record the size of the valve and stem position using the
Flow Indicator Scale (at right). Calculate percentage of
valve opening referring to table below:
Valve
2
⁄
3
1
2
Size
No. of Rings
5
5
(valve full open)
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
Flow Characteristic Curve (Fig 6). Project line vertically
up to intersect with the Valve Characteristic Curve and
from this point project line horizontally across to the left
of the chart and record the percentage of maximum flow
rate.
6.3.4 On 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
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.
Inherent Flow
Characteristic Curve
with Valve in
Throttled Position
4
5
6
8
10
12
6
9
10
12
18
28
100
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 approx. 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
maximum force of 45 ft./lbs. This will ensure good metal-
to-metal contact and minimum leakage.
8.4 The valve bonnet may now be removed. There may be a
slight leakage. As the metal-to-metal back seating does
not provide a drip-tight seal.
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 MAX. NUMBER OF TURNS FULL OPEN VALVE:
Note: On valve sizes 2-
⁄
1
2
is 5 turns. However valve will open to 5-
back of seating of valve.
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.
8
" and 3", full open position of valve
⁄
turns which is just
1
2
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