The Complete Steam Guide

What is a drop leg and why is it necessary / Why should an additional trap set be installed on the steam lead line to process equipment?

Whether it is a batch type process or a continuous process, at some point steam to the equipment will be shut off, either on account of the process requirement or during a shutdown. When steam is not needed and the steam inlet valve is shut, condensation will keep on occurring in the charged lead line leading to accumulation. If this condensate is not evacuated, it will rush into the equipment as soon as the inlet valve opens causing damage to the pipeline, accessories and the process equipment. Thus a drop leg /additional trap set is recommended to be installed on the steam lead line to the process equipment.