SIZING D36 WATER
PRESSURE VALVE
- 133 -
5 10 15 20 25
SIZING D36 WATER PRESSURE REDUCING VALVE
EXAMPLE
SPECIFIED CONDITIONS
Initial Pressure = 100 PSIG
Reduced No Flow Pressure = 50 PSIG (lock-up pressure)
Capacity Required = 30 GPM
Allowable Droop = 10-15 PSIG
1. Enter Capacities vs. Droop Chart, below, at 30 GPM. Move
up until you intersect a curve line (possibly more than one
curve). e.g. points (a), (b)…etc.
The lowest point indicates the minimum size valve required
(
3
/4") at a droop of approximately 16 psi.
2. Enter Flow vs. Velocity Chart (left) at 30 GPM and move up
until you reach the
3
/4
" pipe size curve. Move downward and
note that the velocity is approximately 18.5 ft./sec., which is
unacceptably high.
At the point of intersection of 30 GPM with the next valve
curve (1"), the velocity will be approximately 11 ft./sec.,
which is closer to the recommended value.
Referring back to the Capacities vs. Droop Chart, you will
find that the droop for a 1" valve is only 11 psig, which is also
more acceptable.
SELECT A 1" TYPE D36
NOTE: The capacities shown in the Capacities vs. Droop
Chart are based on a difference of 50 psig or more between
the initial pressure and the regulator lock-up pressure.
Where this difference is less than 50 psig, deduct 20% from
the capacity obtained.
GENERAL CONSIDERATIONS
When sizing a water valve, the following points should be
considered:
(a) The recommended velocity in the pipe (8-10 ft./sec.)
(b) The droop which is the fall-off pressure below the no flow
pressure setting.
CAPACITIES VS. DROOP CHART
FLOW VS. VELOCITY CHART
(Specific Gravity of 1)
GALLONS PER MINUTE
VELOCITY FT./SEC.
DROOP PSIG
3
/
4"1
1
/
4"1
1
/
2"2"1"
1
/
2"
0
2
4
6
8
10
20
40
60
80
100
200
400
500
2"
11/2"
11/4"
1"
3
/4"
1
/
2"
SCHEDULE 40 PIPE SIZE
FLOW IN GALLONS PER MINUTE
VALVE INFO
PAGE 104
0
5
10
15
20
10
b
a
20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170
Loading...