Moog D680 Series - Background; Pilot Pressure and Flow Calculation

46Rev. C, April 2017
BACKGROUND Moog D680 Series Proportional Control Valves
PILOT PRESSURE AND FLOW CALCULATION
46
BACKGROUND
Rev. C, April 2017
Moog D680 Series Proportional Control Valves
PILOT PRESSURE AND FLOW CALCULATION
Pilot Pressure
To achieve reliable functioning of the valves we
recommend the following pilot pressure p:
• p
x
> 10 bar (150 psi) over T or Y
• For valves with stub shaft spools p
x
> = p
P
• For valves with stub standard spools p
x
> = 0.3 x p
P
p
P
= Pressure at port P of the valve (supply pressure)
Note: The pilot pressure range (see technical data) must be
observed.
Flow Calculation
When the valve is open, the prevailing flow is dependent
not only on the spool position, (i.e. the opening cross
section of the valve), but also on the pressure drop at the
individual lands. When the valve is deflected at 100 %, it
delivers the rated flow with the rated pressure drop.
Flow chart
The rated flow of a proportional valve corresponds to a
pressure drop of 5 bar (75 psi) per land, equating to 10 bar
(145 psi) for two lands. When a valve is opened at 100 %,
the flow can be calculated as a function of the actual
pressure drop with the aid of the formula or taken from
the diagram.
The actual flow in the valve ports must not exceed a mean
flow velocity of approximately 30 m/s (96.5 ft/s) due to
the risk of cavitation.
When operating the valves close to these application
limits, it is necessary to drill the ports to the maximum
possible diameters (see specifications for the respective
valve).
Q = Q
N
.
p
p
N
Q [l/min (gpm)] actual flow
Q
N
[l/min (gpm)] rated flow
Δp [bar (psi)] actual pressure drop per spool land
Δp
N
[bar (psi)] rated pressure drop per spool land
1,500 l/min (390 gpm)
1,000 l/min (260 gpm)
550 l/min (143 gpm)
60 l/min (15.6 gpm)
30
(450)
20
(300)
10
(150)
5
(75)
70
(1,000)
100
(1,450)
Valve pressure drop
p [bar (psi)]
Flow rate l/min (gpm)
3,000 (780)
4,500 (1,170)
2,000 (520)
1,500 (390)
1,000 (260)
800 (208)
500 (130)
300 (78)
200 (52)
150 (39)
100 (26)
80 (20.2)
50 (13)
20 (5.2)
30 (7.8)
50
(750)
Nominal pressure drop
p
N
= 10 bar (150 psi)
D685-
P15
D685-
P10
D684-
P05/N05
D683-
P03/N03
D682-
P02
D682-
P01
D681-
P80
D681-
P60
D681-
P30
Q
max
= 3,600 l/min (936 gqm)
Q
max
= 1,500 l/min (390 gqm)
Q
max
= 1,100 l/min (286 gqm)
Q
max
= 600 l/min (156 gqm)
Q
max
= 180 l/min (46.8 gqm)
150 l/min (39 gpm)
30 l/min (7.8 gpm)
350 l/min (91 gpm)
80 l/min (20.8 gpm)
250 l/min (65 gpm)