Confirmation of pressure level after the steam trap
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It is easy to understand that, when using a steam heat exchanger, the pressure level before the drain valve is determined based on the inlet pressure; but how is the pressure after the drain valve determined? Does the vent of the steam trap discharge directly to the atmosphere, at atmospheric pressure, or at atmospheric pressure plus the pressure loss in the piping, or based on the inlet air pressure? Who can provide an explanation? There must be a source!
The back pressure, or the pressure acting on the steam trap, is determined by the method of condensate discharge. If the condensate is discharged directly into the atmosphere, then the back pressure is 0. If the condensate is recycled, and considering that saturated condensate will flash in a low-pressure environment, a certain back pressure will be generated. The actual operating pressure of the steam trap is the pressure difference between the inlet pressure and this back pressure.
The standards and specifications have been identified: HG/T 20570.21 Technical Regulations for the Engineering Design of Process Systems, and GBT 50812-2013 Design Code for Steam Condensate Systems in Chemical Plants