User Manual
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Siemens Control device PN40, safety function to DIN EN 14597 CE1N4388en
Smart Infrastructure 2020-01-09
Subcritical range
Supercritical range
%42%100
p
pp
1
31
−
%42%100
P
pp
1
31
−
Pressure ratio < 42% subcritical
Pressure ratio 42% supercritical
(not recommended)
k
)pp(p
m
4.4k
313
vs
−
=
k
p
m
8.8k
1
vs
=
m
= steam quantity in kg/h
k = factor for superheating of steam = 1 + 0.0012 · T (k = 1 for saturated steam)
T = temperature differential in K between saturated steam and superheated steam
Example
given
saturated steam 151.8 °C
p
1
= 500 kPa (5 bar)
m
= 460 kg/h
pressure ratio = 30 %
saturated steam 151.8 °C
p
1
= 500 kPa (5 bar)
m
= 460 kg/h
pressure ratio = 42 %
(supercritical permitted)
required
k
vs
, valve type
k
vs
, valve type
procedure
100
p30
pp
1
13
−=
)bar5.3(kPa350
100
50030
500p
3
=
−=
h/m83.81
)350500(350
460
4.4k
3
vs
=
−
=
h/m09.81
500
460
8.8k
3
vs
==
selected
k
vs
= 10 m
3
/h MKB632.40-12
k
vs
= 8 m
3
/h MKB632.25-7.5
Engineering notes
We recommend installation in the return pipe, as the temperatures in this pipe are
lower for applications in heating systems, which in turn, extends the stem sealing
gland's life.
In open circuits the valve plug may seize as the result of scale deposits. We rec-
ommend that the valve should be exercised at regular intervals (two to three times
per week).
A strainer MUST be fitted at the valve inlet
Ensure cavitation free flow (refer to page 7).
To ensure the reliability of the valve, we recommend the fitting of a strainer at the
valve inlet even in closed circuits.
The use of these valves for steam is subject to specific parameters: Observe dia-
gram for steam on page 8 and "Technical data" on page 12!
Conduct the electrical connections in accordance with local regulations on electri-
cal installations as well as the internal or connection diagrams.
Safety regulations and restrictions designed to ensure the safety of people
and property must be observed at all times!
Calculation of the k
vs
value for steam
Caution