Steam & Condensate Introduction
Typical Ways Steam Traps are Installed ... and how this affects the differential pressure.
Depending on the installation of the steam trap, the pressure at the outlet of the trap can vary significantly. It is important to understand the trap Outlet Pressure as this will affect the differential pressure used for sizing and selecting the appropriate steam trap. Furthermore, there could be instances where steam supply pressure to the inlet of the trap is insufficient to "push" the condensate into the return line. The following diagrams show: 1) discharging condensate to atmosphere, 2) discharging condensate into gravity return line, and 3) discharging condensate into an elevated and/or pressurized return line.
1) Discharging Condensate to Atmosphere:
Discharging condensate to atmosphere is often done in larger facilities when it may not be cost-effective or practical to install long lengths of condensate return lines back to the boiler. The Pressure in the steam main. In our case, 50psig Outlet Pressure: Since we are discharging steam trap to atmosphere, 0.0psig Inlet Pressure: Steam Pressure “pushes” the condensate through the steam trap allowing it to discharge out of the system (0 PSIG)
50 psig
Inlet Pressure
50 psig
0 psig Outlet Pressure
Inlet Pressure (Steam)
Outlet Pressure (Condensate)
–
=
Differential Pressure
Condensate Discharge to Atmosphere
TD600S Thermodynamic Steam Trap
50 psig
– 0.0psig
= 50 psi
2) Discharging Condensate to Gravity Return Line (Connected to Vented Receiver):
50 psig
It is always preferable to drain condensate in the direction of gravity to a condensate return line which leads into a vented receiver for condensate collection. In most situations the vented receiver vents to atmosphere, and is therefore at a pressure of 0.0 psig. Steam Pressure “pushes” the condensate through the steam trap allowing it to discharge into gravity return line (0 PSIG)
Inlet Pressure
Venting Flash Steam
50 psig
Outlet Pressure
0 psig
The Pressure in the steam main. In our case, 50 psig
Inlet Pressure:
Inlet Pressure
50 psig
Since the steam trap is being discharged to a properly sized condensate return line that leads to a vented receiver, we assume 0.0psig
Outlet Pressure:
Condensate flows by gravity to the vented receiver
0 psig
0 psig Outlet Pressure
Vented Receiver
Inlet Pressure (Steam)
Outlet Pressure (Condensate)
–
=
Differential Pressure
50 psig
– 0.0psig
= 50 psi
Pump
Condensate returns back to boiler
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