PAPTAC - C.11P
SHIVE CONTENT OF MECHANICAL PULPS (Somerville Fractionator Method)
|Publication Date:||1 April 2011|
The presence of mechanical pulp shives in newsprint and other papers containing mechanical pulp has been shown to be a major source of runnability problems on paper machines and in the pressroom.
The method for shives determination presented here is very similar to a method recommended to the Technical Section, the Paper Maker's Association of Great Britain and Ireland, July 1936 (Ref. 1), following a very thorough investigation. It makes no attempt to classify the undesirable material in detail, but such a refinement should be within the reach of any user of the method if desired. The dimensional limits dividing acceptable pulp from objectionable material are arbitrary. This method has been designed to ensure as far as possible that no useful material is included in the rejects and that no objectionable material remains in the accepted pulp.
The type of screen plate specified in this method is designed for mechanical pulp only and is not suitable for chemical or chemimechanical pulps. Although it is sometimes used with such pulps, the amount of rejects determined in this case cannot always be taken as an accurate estimate of shives. This is because, in many cases, a significant amount of useful material is retained on the screen, and causes the measured percent weight of shives to be erroneously high.