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<p><big><font FACE="Arial">Superheated steam</font></big></p>

<p><u><font FACE="Arial" size="3">Calculation conditions:</font></u></p>

<p><font FACE="Arial" size="2">Steam must be in superheated state with temperature from 10
to 1000 °C, and pressure from 0.001 to 1000 MPa in absolute value. Turbulent flowing.
Isoentalpic throttling.<br>
Following data must be entered for calculation of valve´s Kvs value:<br>
&nbsp;&nbsp;&nbsp; Inlet pressure p1<br>
&nbsp;&nbsp;&nbsp; Outlet pressure p2<br>
&nbsp;&nbsp;&nbsp; Flow Q <br>
&nbsp;&nbsp;&nbsp; Medium temperature t<br>
Calculation can be executed simultaneously for 3 states in which the valve can be operated
- e.g. minimal, nominal, maximal flow. An optimal Kvs value is finally selected for state
in which calculated Kv value is maximal. But user may change the final Kvs value.<br>
It is necessary to select an optimal inlet and outlet pipe diameter D1 and D2. It is
convenient to make such selection in regard to medium flow speed in piping which is always
showen on the screen and applies to actually selected diameter. There is a principle that
outlet DN must be equal to or higher than inlet DN. <br>
In common operation, the medium maximum flow speed is recommended to be 15% of acoustic
velocity in given environment. If this speed is exceeded, noisiness caused by medium flow
in piping can occur and if the limit of 30% of acoustic velocity is exceeded, the greater
noisiness of flowing accompanied by shock waves. It is not possible to prevent such
noisiness by commong means of damping (orifice plates, noise dampers etc.) in this state.</p>

<p><u>Principles for plug type selection</u></p>

<p>V-ported plugs should not to be used in above - critical differential pressures with
inlet pressure p &gt;= 0,4 MPa and for regulation of saturated steam. In these cases we
recommend to use a perforated plug. The perforated plug should be also used always when
cavitation may occur due to a high differential pressure value or valve ports erosion
caused by high speed of process medium flow. If the parabolic plug is used (because of
small Kvs) for above-critical differential pressures, it is necessary to close both plug
and seat with a hard metal overlay, i.e. stellited trim.</p>
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