Tappings for mainline steam traps should be taken through correctly sized drain pockets. This ensures effective condensate removal to allow optimum process efficiency and reduced fuel bills.

In normal operation, steam carries condensate while flowing along the mains with speeds up to 25m/s (i.e. 90km/hr).

Although commonly used drain pipes have sufficient flow capacity, they are unlikely to capture much of the condensate moving along the mains at high speeds. This can result in wet steam reaching the equipment, reducing the process efficiency and increasing fuel and steam consumption.

Instead, remove condensate by installing drain pockets as illustrated below. In drain pockets steam trap lines should be taken from a point above the bottom of the pocket. This allows space for any dirt and scale to settle, preventing it from choking the trap. This height should be atleast 25 to 30 mm from the bottom of the pocket for steam main up to 100 mm, and atleast 50 mm for larger main.

The table below provides the recommended drain pocket dimensions.