The volume displacer-type roll consists of a chilled cast-iron shell with a large central bore, bolted-on flanged journals, and a steel volume displacer inserted in the roll bore. This creates a 0.3" to 0.4" wide annulus between the displacer and roll body. The heating fluid is diverted to the annulus where it heats the outer diameter of the roll. The large diameter of the roll bore increases the area available for heat transfer, reduces the distance heat must travel in order to affect the roll surface temperature, and reduces the overall weight of the roll.

Advantages of the Aquitherm™-V type roll are apparent when high length-to-diameter ratios and high speeds are required. Higher critical speeds are obtainable with this design. Dynamic balancing is also improved as the roll can be balanced in three-planes. This produces an exceptionally smooth running calender roll.

The Aquitherm™-P type calender roll consists of a chilled cast iron roll body with peripherally drilled fluid passages and bolted-on flanged journals. These passages are located just below the outer chill layer.

The peripheral drilled fluid passages may be configured as Mono-Pass (one peripheral hole per pass), Duo-Pass (two adjacent peripheral holes per pass), Tri-Pass (three adjacent peripheral holes per pass in series), or Tri-Pass-II™ (three adjacent peripheral holes, the heating media enters the two outer holes and returns in the middle hole at twice the velocity).The patented Tri-Pass-II™ design has more efficient transfer of heat, which allows operation at higher thermal loads and temperatures. This also keeps the central bore empty, reducing overall weight.

The heating medium can be hot water (typically 250 degrees F. surface temperature) or hot oil (typically 400 degrees F. surface temperature). For high temperatures, special alloyed chilled cast iron is used, which has higher tensile strength, a fine-grained structure, and a more uniform chill that enhances heat transfer. This special alloy also inhibits corrosion.
Insulation is used to protect the bearings from excessive heat, and to reduce unevenness at the paper web edges. On large diameter, long oil-heated calender rolls, temperature drop compensation inserts (T.D.C.), inserted in the peripheral fluid passages, increase the velocity of the oil passing through, contributing to the roll's thermal efficiency.

Rolls can be configured for either Mono Flow or Duo Flow rotary joints.

The Aquitherm™-PS type calender roll consists of a chilled cast iron roll body with peripherally drilled fluid passages, bolted-on flanged journals, and siphon tubes. In operation, saturated steam is passed directly through the peripherally drilled fluid passages. Steam condenses in the bores, transferring heat to the roll body. Condensate is collected by the siphon tubes and removed through the bore of the roll.
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).
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.

The Aquitherm™-PSW type calender roll consists of a chilled cast iron roll body with peripherally drilled fluid passages, bolted-on flanged journals, siphon tubes, and a steam / water valve. When heated with water, the calender roll functions as an Aquitherm™-P type roll. When heated with steam, the calender roll functions as an Aquitherm™-PS type roll. This offers the mill greater flexibility in roll heating and cooling and in matching the heat required to the various grades of product produced.

When heating with water, water enters the roll through the center bore (or center siphon pipe), where the water pressure opens the steam / water valve and water is directed through the peripheral fluid passages transferring heat to the roll surface.

When heating with steam, the process is reversed. Steam is directed through the peripheral fluid passages first keeping the steam / water valve closed. Condensate is collected through the siphon tubes into the center siphon pipe and exited.