Max. Δp is t he physical limit of diffe rential pressure the valve will cl ose against. Max. Δp for ste m application is 6 bar.
2)
The recommen ded Δp is based on the generati on of noise, plug erosion e tc.
Max. re commended Δp is 4 bar.
If max. c losing pressure is smaller tha n 4 bar than the recommended Δ p is the same as closing Δp.
3)
Values in parenth eses [ ] are based on the force of the ac tuator AMV(E) 25 SU/SD only.
Before mounting the valve be sure that the pipes
are clean and free from abrasion.
It is essential that the pipes are lined up squarely
with the valve at each connection and that they
are free from vibrations.
Adapter for
VFS 2 DN 15 -50
Always install the valve with the arrow on the
body in the same direction as the ow. In order to
avoid turbulence, which will aect the measuring
accuracy, it is recommended to have a straight
length of pipe up and down stream from the
valve as shown (D - diameter of pipe).
Install the motorized control valves with the
actuator in a vertical or horizontal position in
accordance to recommendations described in
Installation above.
Note that the actuator may be rotated up to 360°
with respect to the valve body by loosening the
retaining fixture. After this operation retighten.
Leave sufficient clearance to facilitate the
dismantling of the actuator from the valve body
for maintenance purposes.
Note that the actuator may be rotated up to 360°
with respect to the valve body by loosening the
retaining fixture. After this operation retighten.
AMV(E)
FVR/FVF
2D
5D
Note:
Install a strainer upstream of the valve
(e.g. Danfoss FVR/FVF)
FLOW Pressure d rop kPa (100 kPa = 1 bar = ~10 m H2O) Specif ic gravity
Examples:
1 For fluids with specific gravity of 1
(e.g. water)
Design data:
Flow rate: 6 m3/h
System pressure drop: 55 kPa
Locate the horizontal line representing a flow
rate of 6 m3/h (line A-A). The valve authority is
given by the equation:
Where:
p1 = pressure drop across the fully open valve
p2 = pressure drop across the rest of the circuit
with a full open valve
The ideal valve would give a pressure drop equal
to the system pressure drop (i.e. an authority of
0.5):
If p1 = p2
In this example an authority of 0.5 would be
given by a valve having a pressure drop of 55
kPa at that flow rate (point B). The intersection
of line A–A with a vertical line drawn from B lies
between two diagonal lines; this means that no
ideally-sized valve is available. The intersection
of line A–A with the diagonal lines gives the
pressure drops stated by real, rather than ideal,
valves. In this case, a valve with kVS 6.3 would give
a pressure drop of 90.7 kPa (point C):
The largest valve, with kVS 10, would give a
pressure drop of 36 kPa (point D):
Generally, the smaller valve would be selected
(resulting in a valve authority higher than 0.5
and therefore improved control). However, this
will increase the total pressure and should be
checked by the system designer for compatibility
with available pump heads, etc. The ideal
authority is 0.5 with a preferred range of
between 0.4 and 0.7.
2 For fluids with specific gravity (S.G. )
different from 1
Design data:
Flow rate: 6 m3/h of fluid, S.G. 0.9
System pressure drop: 10 kPa
For this example, the left hand axis of the
diagram must be ignored. Starting from the
right hand axis, the flow rate of 6 m3/h is located
(point E). The intersection of the diagonal line
from point E with a vertical line from S.G. = 0.9
(point F) gives the starting point for the effective
flow rate line G-G. The process then continues as
for Example 1, so 10 kPa intersects G-G nearest
to the kVS 16 diagonal. The intersection of G-G
with kVS 16 gives a valve pressure drop of 12.7 kPa
(point H).
Max. p in low pressure steam application variance from 0.5 bar to 6 bar (see page 2)
mass flow of saturated water steam (kg/h)
Critical Pressure Drop (kPa)
Critical Pressure Drop (kPa)
Absolute Inlet Pressure
Saturated Sream Temperature
Superheat °C
mass flow of superheated water steam (kg/h)
Steam valve sizing is based on 40 % of the
absolute steam pressure (immediately upstream
of the valve), being dropped across the valve
when fully open. At this condition the steam
is travelling at or close to its critical velocity
(approx. 300 m/s) and throttling will occur over
the full valve stroke. If the steam is travelling
slower than this then the first part of the valve
stroke will merely increase the velocity of the
steam without reducing the volumetric flow.
The absolute inlet pressure is 500 kPa. 40% of
this is 200 kPa.
Locate the diagonal line corresponding to the
pressure drop of 200 kPa (line A-A).
Read the absolute inlet pressure on the lower left
hand scale (point B), and draw a horizontal line
across until it meets the pressure drop diagonal
(A-A) at point C.
From this point extend a vertical line upwards
until it meets the horizontal line representing
the steam flow of 1000 kg/h from point D. The
intersection of this is point E.
The nearest diagonal kVS line above this is line F-F
with a kVS of 25 (point E’). If the ideal valve size
is not available the next largest size should be
selected to ensure design flow.
The pressure drop through valve at the flow rate
is found by the intersection of the 1000kg/h
line with F-F (point E’) and dropping a vertical;
this actually hits the horizontal line for 500 kPa
(point E’’) inlet pressure at a pressure drop
diagonal of 70 kPa. This is only 14 % of the inlet
pressure and the control quality will not be
good until the valve has partially closed. As with
all steam valves this compromise is necessary
since the next smaller valve would not pass the
required flow (maximum flow would have been
about 600 kg/h).
The maximum flow for same inlet pressure
is found by extending the vertical line (C-E)
through point E until it crosses the kVS 25 line F-F
(point E’’’) and reading off the flow (1700 kg/h).
2 For superheated steam
Design data:
Flow rate: 500 kg/h
Absolute inlet pressure: 5 bar (500 kPa)
Steam temperature: 190 °C
The procedure for superheated steam is much
the same as for saturated steam, but uses a
different flow scale which slightly elevates the
readings according to the degree of superheat.
- follow dotted line -
As before, the diagonal pressure drop line
A-A is located as before for 40 % of 500
(200 kg/h). The horizontal inlet pressure line
through point B is now extended to the left to
read off the corresponding saturated steam
temperature at point G (150 °C). The difference
between the saturated steam temperature and
the superheated steam temperature is
190 °C - 150 °C = 40 °C.
The superheated steam flow is found on the
upper right hand scale, point H, and the diagonal
line is followed down from here until it meets
a vertical line from the steam temperature
elevation (40 °C) at point J.
As before, the horizontal line through point B is
drawn to cut line A-A at point C and the point
where the vertical line from this point meets the
horizontal line from point J is the operating point
(point K). This horizontal line, J-K, is the corrected
flow line. The nearest diagonal line above this is
for kVS 10 (point K’). A vertical line
the intersection of J-K with the 10 kVS line intersects
the 500 kPa inlet pressure line (point K’’) at a
pressure drop diagonal of about 150 kPa. This
is about 30% of the inlet pressure which will
give reasonable control quality (compared to
recommended ratio of 40%).