13.5.4 System drains
Both the live steam and bled-steam supply lines must be adequately drained at all times. Drain lines usually include a dirt trap at the take-off tapping and some form of steam trap arrangement.
Under normal conditions, water is drained away via the steam trap to a drain vessel. However, steam traps have a history of poor reliability and, in the case of the bled-steam supply line, are often inadequate to cope with the water flow at low-loads. Water traps are therefore always provided with valved by-passes, sized to pass the maximum possible flow under all operating conditions.