Shell ice is formed on 6" diameter stainless steel tapered evaporators. Water cascades across both the inner and outer tube surfaces, which allows the machine to operate efficiently. Once the desired ice thickness has been reached (operator adjustable), the automatic controls will terminate the flow of liquid refrigerant to the evaporators and initiate the flow of hot gas refrigerant. The introduction of hot gas forms a thin layer of water between the ice and the tube surface allowing gravity to pull the ice easily off the evaporator tubes. As the ice slides off the tubes, the discharge auger (or beater bar depending on the style of icemaker) removes the ice from the machine. Once again, gravity or another mechanical delivery device will take the ice to storage. Any free water on the shell ice surface will quickly refreeze on the sub-cooled shell ice, leaving dry, hard ice fragments.
*Note: This operating principle describes the Berg Shell Icemaker. Other shell ice machines might work differently and produce different results.