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Selection principles
In order to select the steam trap correctly it is necessary to not only give the nominal pressure PN and the connection dimensions DN but also to provide two other parameters:
- the maximum differential pressure of the steam trap Δpmax
- the maximum quantity of the condensate flow through the steam trap
There is an acceptable error margin while estimating the maximum condensate flow through the steam trap. However it is inadmissible to make any mistakes while determining the maximum differential pressure.
The maximum differential pressure Δpmax = p1-p2 where:
- p1 is the maximum steam pressure before the steam trap
- p2 is the minimum condensate pressure behind the steam trap
NOTE
For your convenience we have made available a free of charge computer program for the selection for the WZ stream traps.
Selection example for WZ-200
WZ-200 steam traps are made in eight different sizes of orifices - "d". The end of each curve indicates the maximum operational differential pressure of the steam trap with a nozzle "d". On the coordinate abscissa of the capacity chart for each nozzle "d" has been assigned its maximum differential pressure Δpmax . For example the nozzle d=3 mm permits the operation at Δpmax = 0,7 MPa.
CLICK ON IMAGE TO ZOOM
The maximum steam pressure before the steam trap p1=0.7 MPa, the pressure behind the steam trap p2= 0.1 MPa. The maximum differential pressure Δpmax= 0.7-0.1=0.6 MPa. We draw a vertical line (the arrow) which represents the pressure 0,6 MPa to the intersection with the line which represents one of the eight nozzles "d". In our case it will be the nozzle d=3. It means that the steam trap with nozzles above the line d=4mm or d=5mm will not work at the pressure we have been looking for. We check the real capacity of the steam trap with the nozzle d=3mm (horizontal line) which is 520kg/h. The steam trap will work ideally within the capacity limits from 0 to 520 kg/h.
Selection abnormalities
If the steam trap does not work after the installation i.e. it is completely closed - it means that it has not been chosen correctly. The real differential pressure at which the particular steam trap should work is higher than the maximum differential pressure for the particular nozzle - "d". In this case a steam trap with a smaller nozzle - "d" and a bigger pressure difference should be chosen (see the chart above).
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