The Velan Theory
The Velan Bimetallic, Thermostatic steam trap was developed by A.K. Velan
in 1946. The trap was a major innovation because it makes use of the
pressure of the system to clear the lines of air and non-condensable gases
during startup and uses the heat of the steam to close the trap when the system
reaches saturated temperature.
The closing forces of the bimetallic elements closely follow the steam curve
because of the Velan patented multi-segmented design. The force of
line pressure acting on the valve ball holds it open when air or condensate
is in the trap. Engineering calculations determine the force needed to close
the trap for a given application. The closing force of the Velan
bimetallic element is designed to allow the trap to remain open up to 15-20
deg F below saturated temperature. At saturated temperature and in superheat
conditions, the trap is completely closed. This prevents live steam from entering
the return system and causing great difficulties with the condensate return
equipment along with large losses of energy.
DISCHARGE CONDENSATE NEAR-TO-STEAM TEMPERATURE