Agromisa 
Interdev Agroalimentaire  

Comparison disk and rubber roller rice hullers and some addresses of providers

	Type de fiche	Techniques/Technologies
	Mise en œuvre	Agromisa(Pays Bas)
	
	Zone géographique	Global; 
	Mots clés	USINAGE DU RIZ

	Echelle d’action	Ville; Village

Contexte
In 1996 Agromisa was requested to send documentation and price quotations for rice hullers by an officer of Medicins sans Frontieres in Zaire (Congo). 
A list of addresses was provided, based on the publication "Small-scale food processing, a guide to appropriate equipment (by Fellows & Hampton, published by IT publications and CTA, 1992).
&The addresses have been approached for a cross-check on availability, prices etc.
Finally the spokesperson from Zambia ordered a machine from Belgium, that was produced in the Netherlands, the S100 of Votex. This machine is no longer in production, but a description of the laregr model S400 is attached in the linked Equipment file.
Problématique / Objectifs
Small disk hullers can be operated manually. The abrasive surface of tyhe disks can be replaced easily and manufactured locally.
Rubber roll hullers require more energy, are normally machine operated and have a higher cost of replacement, since rubber rolls have to be ordered from the manufacturer or importer of the equipment. However, the quality and efficiency of milling is better.
Description/Mise en oeuvre
A disk huller has two horizontal parallel disks, coated with an abrasive. The upper disc is fixed  and has a hole in the center, through which the rice is added. The lower disk turns at a distance of less than the length of a grain of rice. If the distance between the disks is too big, the rice is hulled insufficiently. If the distance is too small, a lot of breakage occurs. The hull is scraped off by the abrasive surface. The huller works well when grain-sizes are similar and without beard. This type of machine can often be operated manually. The abrasive layer is the part most susceptible to wear, but it can be replaced easily and manufactured locally. However, if rice with mixed sizes (lengths) is entered, the percentage broken rice is high, a lot of germ is removed and the silver coat is ripped off the grain.A Rubber Roll Huller has two moving rubber rolls in the center of the machine. The rolls turn at different speeds, at a distance smaller than the width of the grain. The hull is stripped off the grain in a gentler way than in the disk huller. The percentage broken grains is smaller. However, this huller is more suitable for round-grain rices, since the duration of the contact between roller and grain is considerably longer with long grain rice, leading to a faster wear of the rubber rolls. Wear of the rubber rolls is the most important disadvantage of this system anyway, normally around 800 tons of rice can be milled before they have to be replaced. Halfway their productive lifespan they have to be changed so the upper roll replaces the lower and vice versa. Buying rubber rolls well in advance is not a solution to possible problems in a timely supply of replacement rolls: Storage will already affect the quality of the rolls, and reduce their time of operation.

Before deciding to procure any one of these machines, it is recommended to calculate whether the investment costs can be recovered. How many days will the machine be in operation. Can the repairs and maintenance be done locally, are spare parts available in time?

Auteur : Rob Witte
Saisie le : 05/09/2001
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