Aquitherm™ - PS, D.A.S.H. (Direct Advanced Steam Heated)
The peripherally drilled-type steam heated calender roll consists of a peripherally drilled chilled cast iron roll body, bolted-on flanged journals, and siphon tubes. In operation, saturated steam is passed directly through the peripherally drilled fluid passages, which are approximately 2 inches below the outer surface of the roll and under the chilled zone. There the steam condenses on the metal of the bores and transfers its heat to the roll body. Condensate, which acts as an insulator, is collected by the siphon tubes and removed through the bore of the roll, allowing for more efficient heating.
The peripheral holes are usually configured as Duo-Pass (two adjacent peripheral holes per pass), or Tri-Pass (three adjacent peripheral holes per pass in series).
With mono-flow rotary joints, the heating fluid enters one end of the roll, passes through the peripheral hole(s) and exits through the other end of the roll. With a duo-flow rotary joint (fluid entering and exiting the same end), the fluid enters one end of the roll, passes through the peripheral holes and exits through the same end of the roll as it entered.
Advantages of direct steam heating are:
- steam condenses at identical temperatures everywhere in the roll, producing a uniform surface temperature across the entire face
- steam is readily available in most paper mills allowing for a smaller, less costly control system and components
- steam delivers a higher roll surface temperature than water
- steam is clean.
Peripherally Drilled, Steam Heated:D.A.S.H.
(Direct Advanced Steam Heated)
TriPass-Duoflow (Driven) Shown; Can also be TriPass-Monflow