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    9-32, Nakacho 2-chome, Musashino-shi, Tokyo, Japan    
     TEL : 81-0422-52-5586   FAX : 81-0422-52-9802 

Agent In Korea : Sung Chang Trading Co.,
     Tel : +82-2-2040-7577   Fax : +82-2-2040-7580

HEAT CALENDER ROLL

1. Introduction of Heat Roll

Although anybody did not take much interest in the roll heat generated by former calender, it was known well enough that the roll heat produces an effect on paper'ssmoothness and luster.
The reason why the heat of roll was not a matter of one's concern is that roll temperature changed up to 10¡£C or more luster of paper became unstable and heat roll was applied habitually only for forming up by calender because steam was need as a heat source for heat roll.
Recently hot roll became the object of one's attention to get paper smooth and luster with less nip pressure.
Heat roll was developed as a roll which is available to make flesh of roll cell thin as far as possible and equally temperature of roll face with using warm as heat water as a heat source.
In the past, the rotary joint which can stand rotation at high speed was not developed.
However, T company in U. S. A. have developed the joint which can fully bear high speed rotation up to 4 inch caliber and vibration of machine calender roll. It was applied to paper mill and proved it excellency. Heat roll was adopted at first as an middle roll for super calender and met with good results.
And then it was adopted to newsprint making machine in order to cope with the tendency of light weight newsprint and it is apt to be adopted to high and middle grade printing paper owing to the unexpected good results.

2. Structure and feature of Heat roll

D. Small Center Hole Type

This roll was used in the past. It price is  cheap. But it is used usually in case of forming-up because it makes big difference  between a fluid steamily inside of the roll and temperature of roll face and has some faults such as increasing in temperature change toward the shaft.

 A. Hollow Assembling Type 

 This roll is simple in structure and is used frequently for machine calender.
 The temperature difference between inside and outside of roll is limited, temperature change toward shaft is within 1¡£C and volume of warm water become in ceasing with capacious inside measurement of the  roll. And also it is equivalent for the first grade pressure tool in case of using more than 100¡£C  warm water as heat source.

B. Diskplacer Type 

 This roll is used mainly for super calender of which face needs 100¡£C temperature and more.
  Its fluid in volume becomes decreasing because the temperature change toward shaft becomes below 0.5¡£C despite small difference of external temperature of roll.
  It is not used for machine calender due to complicated structure, expensive price, unbalanced inside disk placer and maintenance problems.
  It is not equivalent for the first grade pressure tool because of pressing inside measurement.

Remark : Above all pictures are piercing type roll.
             Double passage type roll can be manufactured.

3. Examples of actual use of Heat Calender roll

1) Machine Calender

A. Hollow Assembling Type

B. Displacer Type

There are many cases that two or three units of heat roll are used for machine calender. In case that two units of roll are used, some of paper mills produce paper with less pressure by 20-30% than former NIP pressure when they are operated under equal smoothness and luster.

2) Super Calender 

Two to four units of Heat Roll are usually used for super calender. In this case, it is possible to reduce NIP pressure by 15 percent when they are operated under equal smoothness and luster.
 The quantity of pack elastic roll is reducing very  much to control temperature of middle roll.

4. Effectiveness of Heat Roll

Smoothness
Such smoothness as is obtainable from normal calendering with high NIP pressure can be derived from low NIP pressure by using heat roll.

Luster
As for luster, it is as same as smoothness.

Bulkiness
For bulkiness the influence of temperature is more powerful than that of NIP pressure.

Brightness
Brightness is affected more by influence of NIP pressure than that of temperature.
Paper brightness is not changed in accordance with temperature change but NIP pressure change affects paper brightness.

Opacity
Opacity becomes decreasing to some extent as calendering temperature is rising.
However, opacity is affected more qreatly by NIP pressure than temperature.

Suitableness of  printing
Paper calendered with less NIP pressure under high temperature makes its face rough and brings good results from printing test.
Suitableness of printing becomes better than smoothness and gross by adopting heat roll.

Improvement of difference between inside and outside
It is possible to improve the difference between two sides of smoothness, gross etc in accordance with quantity of heat roll and selection of place.

5. Merit in using heat roll

a) The time for forming-up by calender can be reduced.
b) If the smoothness is equal, stable operation can be done with less NIP pressure
   and equal luster.
c) In case of B.C Type ( Hollow assembling roll ) temperature difference between fluid in skidding and roll face becomes 3-5¡£C and it is easy to control the surface temperature.
    In case of D type ( Center Hole Type ), temperature difference between inside and outside of roll becomes 30¡£C - 40¡£C, and temperature change towered shaft becomes over 5¡£C.
d) Since temperature difference becomes within 1¡£C the roll operates under same precision as grinding.
e) Due to large quantity of flowing oil stuff within roll temperature of roll changes slightly when paper is passing through roll even though temperature of paper is not equal.
f) If temperature of roll face changes slightly cold wind can be less used. Roll can be rarely changed by using cold wind and grinding cycle can be extended owing to equal abrasion of roll.
g) Roll temperature other than heat roll difference slightly.
h) It is possible to cope with external factors so that temperature of roll face changes without restraint. It is able to improve the equality ratio of products.
I) The quantity of pack in elastic roll can be reduced very much in case of adopting two to three units of heat roll for super calender.

6. Comparative table of Heat Roll 

Heat roll has been using in large quantities in the field of paper rubber and vinyl industries.  Hollow roll for paper mill and roll for rubber and vinyl industries are excellent in precision.  There are two kinds of roll ; hollow assembling roll and roll with good thermal efficiency.  They are subject to variation according to method of manufacturing, precision of roll and price.
Please refer to following items to adopt what kind of roll for your purpose.