B&C Technologies DI-225 Industrial - Manual (Page 30)

E. STEAM DAMPER ACTUATOR SYSTEM
This system consists of a hinged damper plate, pneumatic piston, and 24-volt solenoid valve
with a needle valve to control the speed of the piston actuation.
On a call for heat, a 24-volt signal is applied to the 3-way/2-position solenoid valve. This signal
switches the valve so that compressed air is sent to the piston. The piston rod extends, pushing
the hinged steam damper plate to the open position. This allows room air to be drawn through
the hot steam coil and then through the basket (tumbler).
When the temperature set point has been reached, the 24-volt signal is removed from the
solenoid valve, so that the solenoid valve blocks the air supply to the piston and the air in the
piston is bled to the atmosphere. The spring in the piston now retracts the piston rod, closing
the steam damper. The steam damper plate now covers the steam coil and allows room air to
bypass the coil before entering the basket (tumbler) For a rapid cool down.
The steam damper plate should open and close slowly and smoothly. This speed can be
modulated by adjusting the needle valve knob. Turning the knob clockwise restricts the
compressed airflow and slows down the steam damper movement. counterclockwise
adjustment speeds up the steam damper motion. Upon completion of adjustment, tighten the
needle valve’s locking nut.