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Design and Development of Improved Impact Huller Machine.

Anthony, Manoj Kumar Y. and Kumar, M. and Shivakumara, M. (2012) Design and Development of Improved Impact Huller Machine. [Student Project Report] (Submitted)

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Abstract

Dehulling is the process of removal of the hulls from cereals like paddy, oats, millets, oil seeds like mustard, sun flower seeds etc. Basic principles of dehulling/ dehusking generally are a combination of the following:  Compression and shear (employed in splitting and stripping of husk from grains- as in a rubber roll sheller used for paddy dehusking),  Abrasion and friction (as in abrasive disc hullers/polishers)  Friction (as in metal roller huskers/polishers) and  Impact and friction According to the principle of operation, there are different types of hullers. Impact type hullers employ a mechanism to accelerate the grains at a high velocity and impinging them against a metal/elastomer plate. An impact/ centrifugal huller essentially consists of a high speed impeller enclosed in a housing. The inner lining of the housing is generally covered with rubber or any other elastomer. Grains are fed to the centre of the impeller. Guided by the vanes of the rotating impeller these grains are thrown out of the impeller due to the centrifugal forces. Grains ejected from the impeller collide against the rubber/elastomer ring. The impact forces induced during the collision result in stripping of the hulls from the grains. Impact hullers are versatile and can be adapted to dehull a variety of cereals, millets, oil seeds, nuts etc. Impact force applied on the grains is the most important parameter in the dehulling of grains and this is a function of the diameter of the impeller, rpm and the configuration of the vanes. Impact dehullers available in the Indian market are of a fixed size, rpm and the vane profile is also considered a standard. But, this restricts the versatility of the machine because the force required to dehull different grains vary. Also for different moisture of the grains rpm needs to be different. For example, with an impeller of 203.2 mm diameter (8” dia.), the optimum rpm of the impeller for dehulling of paddy is 2300-2800. For very small grains like millets, the optimum speed range would be 3600-4000 rpm. Higher the moisture content rpm required would be higher. The huller has to be run at optimal speed range to get the required dehulling efficiency. Higher speeds result in higher dehulling percent but the breakage would be higher resulting in lower efficiency and yield. Speeds lower than the optimal range result in lower dehulling percent and more unhulled grains. Higher the rpm, vibration and noise produced would be higher and the noise level measured would be beyond 80 dB. Existing machines are of constant speed and are suitable for limited applications. Aim of the present project is to ‘Design and develop improved impact huller’ to increase its range of applications. It is aimed to design and develop hullers of different impeller diameters. It is also targeted to incorporate a speed variatior (variac / invertor). Accordingly, the shaft, impeller and the casing would be redesigned to reduce the rpm of the impeller, vibration and noise produced during the dehulling operation.

Item Type: Student Project Report
Uncontrolled Keywords: Dehulling, centrifugal huller, cereals
Subjects: 600 Technology > 08 Food technology > 04 Milling
Divisions: Grain Science and Technology
Depositing User: Food Sci. & Technol. Information Services
Date Deposited: 03 Apr 2014 04:42
Last Modified: 03 Apr 2014 04:42
URI: http://ir.cftri.com/id/eprint/11419

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