The resulting heat loss causes some steam to condense back to water. When steam reaches the heat exchanger, heat passes from the steam to the substance to be heated such as air, water, food, or chemicals. Maximum heat transfer in the heat exchanger is highly desirable. Heat radiation from the distribution system causes condensate to form. Steam traps, at natural low points or ahead of control valves, remove the condensate before it becomes a barrier to heat transfer.
Hot condensate is returned through the traps to the boiler for reuse.
To achieve maximum efficiency of the energy transfer, hot condensate should be removed from steam lines and heat transfer equipment as fast as it forms and returned to the boiler for regeneration into steam. It costs far less to raise the temperature of hot condensate to the boiling point than to elevate cool makeup water to the boiling point. Steam moves rapidly in mains and supply lines-often at speeds greater than 90 mph. A buildup of condensate in these lines can be pushed along by fast-moving steam. At minimum, water hammer will produce an annoying sound.