As it is essential to clear condensate as it forms, the first choice is a float-thermostatic trap. A separator will remove the suspended droplets as well as the condensate layer and provide drier steam for heating and processes (Figure 11.11.2). Separators are normally fitted line size. Typical recommended drain pocket dimensions, relative to steam main pipe sizes are given in Table 11.11.1. Use a properly sized pocket into which fast moving condensate can fall - as shown in Figure 11.11.1. Horizontal runs must not be drained through a small pipe connection in the bottom of the pipe. Thermodynamic traps are very robust and offer long life and efficient operation in exposed conditions. The condensate loads associated with mains drainage are relatively small hence a low capacity thermodynamic trap is more suitable. This is undesirable if the traps are of the blast discharge type, and the practice of discharging into flooded lines should be avoided to deter waterhammer. If the condensate returns are flooded, as they often are, severe waterhammer will result. Because condensate return lines often run alongside steam mains, there is a temptation to connect into them the discharges from the traps draining the main.

Steam traps should discharge into adequately sized condensate lines, falling towards a vented receiver. Both the air and water must be removed for maximum plant output. Steam mains carry water droplets in suspension in the steam, as well as a layer of condensate and air on the wall of the pipe.

Pocket tanks steam