12
Pressure
and
Pressure
Loss
Ratio
Minimum
and
Maximum
Pressures
The
minimum
inlet
pressures
are:
!
Water
-
20
psig
(1.4
bar)
!
Steam
-
20
psig
(1.4
bar)
Note:
Low
inlet
pressures
will
significantly
reduce
outlet
flow.
The
maximum
static
pressures
are:
!
Water
-
150
psig
(10
bar)
!
Steam
-
150
psig
(10
bar)
Pressure
Loss
Ratios:
!
Maximum
pressure
loss
across
the
mixing
valve
(inlet
to
outlet):
60
psi
(4
bar)
!
Minimum
pressure
loss
across
the
mixing
valve
(inlet
to
outlet):
7
psi
(.4
bar)
!
Maximum
pressure
loss
ratio
is
10:1
in
favor
of
either
supply.
!
Pressure
Loss
Ratio
(PLR)
is
the
ratio
of
steam
and
cold
water
supply
pressures
minus
the
back
pressure
caused
by
the
outlet
fittings
and
additional
pipework,
hose,
or
nozzle.
Example:
If
the
back
pressure
developed
at
the
valve
outlet
was
45
psi
(3
bar)
and
the
steam
pressure
is
100
psi
(6.6
bar)
with
a
water
pressure
of
50
psi
(3.3
bar)
the
calculation
for
PLR
would
be:
100
-
45
=
55
psi
and
50
-
45
=
5
psi
Thus,
the
pressure
loss
ratio
is:
55:
5
or
11:1*.
6.6
bar
-
3
bar
=
3.6
bar
and
3.3
bar
-
3
bar
=
.3
bar
Thus,
the
pressure
loss
ratio
is:
55:
5
or
11:1*.
*This
unit
will
not
operate
effectively.
Do
not
confuse
the
Pressure
Loss
Ratio
with
the
Inlet
Pressure
Differential
Ratio,
which
is
the
ratio
of
inlet
pressures
only
(100:50
or
2:1)
and
does
not
take
into
account
the
back
pressure.
For
optimum
performance,
keep
any
restriction
at
the
valve
outlet
to
a
minimum.
Tips:
1. The
shorter
the
hose
and
minimal
kinks
the
better
the
mixing
valve
'
s
performance.
2. Use
the
least
restrictive
nozzle
obtainable.
3. Ensure
that
pressure
or
temperature
gauges
do
not
restrict
the
mixed
water
flow.
4. The
lower
the
pressure
loss
on
the
mixing
valve
or
hose
station
outlet,
the
greater
the
flow
rate
and
cleaning
power.
5. Excessive
back
pressure
at
the
valve
outlet
will
affect
the
ability
of
the
mixing
valve
to
properly
control
the
temperature
and
may
cause
premature
diaphragm
wear.
