Introduction to Steam

  1. Steam Trap Selection

    1. Understanding the Operating Pressure

      1. Inlet Pressure of Steam Traps


        The steam trap should not only meet the pressure specification of the equipment, but also maintain good operation if there is pressure fluctuation during operation. The condensate discharge ability of a steam trap is determined by the pressure difference at its inlet and outlet, and the inlet pressure will change depending on the steam pressure supplied to the equipment and the load fluctuations on the equipment. In particular, operating pressure may decrease a lot under light load if an automatic regulating valve is installed in the steam supply line of equipment, and the steam supply is controlled according to the load. Thus, decreasing pressure in closing regulating valve should be taken into consideration. Thus it is necessary to consider these when grasping the operating pressure of the steam trap.

      2. Back pressure of steam trap


Steam traps should also maintain good operation in reaction to the downstream (back) pressure and its variation. It is not necessary to consider back pressure if the outlet side of the steam trap is exposed to the atmosphere, but it is often connected to a long condensate discharge line, a stand up line, or a condensate recovery line. In these cases, the back pressure is generated at the outlet of steam trap due to flow resistance, hydraulic head pressure, and pressurized equipment at the recovery site. It is also important to note that a part of the condensate discharged from the steam trap becomes flash steam and generates back pressure.



The degree of back pressure must be determined when selecting a steam trap with an appropriate 'minimum working differential pressure' or 'minimum working pressure'.