ICS  65.060.01  
 
Reference number  
DRS  268-1: 2020  
© RSB 2020  
  
 RWANDA 
STANDARD  DRS  
268-1 
2nd edition  
2020 -June  
 
Agro -processing machines — 
Specification  — 
Part 1:  
Rice thresher  
   
DRS  268-1: 2020  
©RSB 2020 - All rights reserved                  ii 
 In order to match with technological development and to keep continuous progress in industries, 
standards are subject to periodic review. Users shall ascertain that they are in possession of the latest 
edition  
 
 
 
 
 
 
 
 
© RSB 2020  
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized 
in any form or by any means, electronic or mechanical, including photocopying and microfilm, without 
prior written permission from R SB. 
Requests for permission to reprodu ce this document should be addressed to : 
Rwanda Standards  Board  
P.O Box 7099 Kigali -Rwanda  
KK 15 Rd, 49  
Tel. +250 788303492  
Toll Free: 3250  
E-mail: info@rsb.gov.rw  
Website: www.rsb.gov.rw  
ePortal: www.portal.rsb.gov.rw   DRS  268-1: 2020  
iii                ©RSB 2020  - All rights reserved  
 Contents  Page 
Foreword  ................................ ................................ ................................ ................................ ............................  iv 
1 Scope  ................................ ................................ ................................ ................................ ......................  1 
2 Normative references  ................................ ................................ ................................ ............................  1 
3 Terms and definitions  ................................ ................................ ................................ ...........................  1 
4 Classification  ................................ ................................ ................................ ................................ .........  3 
5 Materials of construction  ................................ ................................ ................................ ......................  3 
6 Performance and other requirements  ................................ ................................ ...............................  43 
7 Workmanship and finish  ................................ ................................ ................................ .......................  4 
8 Maintenance and operation  ................................ ................................ ................................ ..................  5 
9 Sampling and testing  ................................ ................................ ................................ ............................  5 
10 Marking  ................................ ................................ ................................ ................................ ...................  5 
 DRS  268-1: 2020  
©RSB 2020 - All rights reserved                  iv 
 Foreword   
Rwanda Standard s are prepared  by Technical Committees and approved by R wanda Standards Board (RSB) 
Board  of Directors in  accordance with the procedures of RSB, in compliance with Annex 3 of the WTO/TBT 
agreement on the preparation, adoption and application of standards.  
The main task of technical committees is to prepare national standards.  Final Draft Rwanda S tandards 
adopted by Technical committ ees are ratified  by me mbers of RSB Board of Director s for publication and 
gazettment as Rwanda Standards.  
DRS  268-1 was prepared by Technical Committee RSB/TC 047, Steel aluminium and related product . 
In the preparation of this standard, reference was made to the following standard  (s): 
1) XYZ: Title  
2) XYZ:  Title 
The assistance de rived from the above source is hereby acknowledged with thanks.  
This second  edition cancels and replaces the first  edition (RS  268-1: 2015 ) which has been technically 
revised.  
DRS  268 consists of the following parts, under the general title Agro-processing  machine s — Specification : 
 Part 2: Power operated maize sheller  
 Part 3: Rice mill  
 Part 4: Heated air mechanical grain dryer  
 Part 5: Maize mill  
 
Committee membership  
The following organizations were represented on the Technical Committee on Steel aluminium and related 
products (RSB/TC 047) in the preparation of this standard.  
University of Rwanda/college of science and technology  
University of Rwanda/College of agriculture animal science and veterinary medicine  
  DRS  268-1: 2020  
v                ©RSB 2020  - All rights reserved  
 Kabizu business group  
Rwanda Polytechnic/IPRC Kigali  
Rwanda Polytechnic/IPRC Ngoma  
Rwanda Polytechnic/IPRC Musanze  
RWANTECH Boilers  
Rwanda Inspectorate and c ompetition authority (RICA)  
Rwanda Institute for Conservation Agriculture  (RICA)  
ACER Ltd  
Machine Engineering and Training Company Ltd  
Rwanda  Standards Board  (RSB) – Secretariat  DRS  268-1: 2020  
1                ©RSB 2020  - All rights reserved  
 Agro-processing  machines — Specification — Part 1: Rice thresher  
1 Scope   
This Draft Rwanda Standard specifies the classification, requirements, sampling and methods of test for rice 
thresher . 
2 Normative references   
The following documents are referred to in the text in such a way that some or all of their content constitutes 
requirements of this document.  For dated references, only the edition cited applies. Fo r undated references, 
the latest edition of the referenced document (including any amendments) applies.  
RS 269 -1, Agroprocessing machines  —Test methods — Part 1: Rice thresher   
RS 241,  Agriculture machinery  — Methods of sampling  
RS 236, Acoustics — Noise pollution — Tolerance limit  
RS 340, Food processing machines — Specifications  
3 Terms and definitions   
For the purposes of this standard, the follow ing terms and definitions apply  
3.1  
blower loss  
ratio of the weight of grains blown with the chaff by the th resher fan, to the weight of the total grain input of the 
thresher, expressed in percent  
3.2  
chaff  
empty grains and crushed straw being discharged from the threshing chamber  
3.3  
grain -straw ratio/ grain content  
ratio of the weight of the grains present in the panicles, to the total weight of the grain and straw in the same 
sample text of the definition  
  
©RSB 2020 - All rights reserved                  2 
  
3.4  
mechanically damaged grain  
grains that were broken and/or dehulled (partially or fully) as a result of thresh ing operation  
3.5  
purity  
ratio of the weight of clean grains, to the total weight of unclean grains sample, expressed in percent  
3.6  
scattering loss  
ratio of the weight of grains that fell out from the machine during threshing operation, to the weigh t of the total 
grain input of the thresher, expressed in percent  
3.7  
separation loss  
ratio of the weight of grains that come out of the threshing chamber with the straw, to the weight of total grain 
input of the thresher, expressed in percent  
3.8  
straw length  
cut plants length measured from the point of cut to the tip of the panicle  
3.9  
threshing efficiency  
ratio of the weight of the threshed grains collected at all outlets, to the total grain input of the thresher, 
expressed in percent  
3.10  
threshing recovery  
ratio of the weight of the threshed grains collected at the main grain outlet, to the weight of the total grain input 
of the thresher, expressed in percent  DRS  268-1: 2020  
3                ©RSB 2020  - All rights reserved  
 3.11  
total grain input  
sum of the weights of collected threshed grains and all grains loss during threshing  
3.12  
unthreshed loss  
ratio of the weight of grains that remained in the panicles of the plants fed into the threshing chamber, to the 
weight of total grain input of the thr esher, expressed in percent  
4 Classification  
The classification of rice thresher shall be based on the following:  
method of feeding;  
a) hold-on type;  
b) throw -in type;  
operation;  
c) axial flow type;  
d) through flow type;  
threshing cylinder;  
e) peg-tooth cylinder;  
f) rasp-bar cylinder; and  
g) Wire-loop cylinder.  
5 Materials of construction  
5.1 Food zone area shall be  made from food grade materials . 
5.2 Non-food zone area may be made from carbon steel that has been rendered corrosion resistant   
5.3 Construction of rice thres hing machine shall be done in accordance with RS 340.   
©RSB 2020 - All rights reserved                  4 
 6 Performance requirements  
6.1 The performance criteria for rice thresher shall be as specified in Table 1.  
criteria  Performance data  
Threshing Recovery, %, min  97.0 
Threshing Efficiency , %, min.  98.0 
Losses, %, max.  
a) Blower Loss  
b) Separation Loss  
c) Unthreshed Loss  
d) Scattering Loss  1.2 
1.3 
0.2 
0.3 
Purity, %, min.  
a) With Sifter and Fan  
b) Without Sifter and With Fan  
c) Without Cleaning Devices  97.0 
95.0 
80.0 
Mechanically Damaged Grain, %, max.  2.0 
Net Cracked Grain, %, max.  5.0 
6.2 The maximum level for Noise Level, [db] (A) for threshing machine shall be as specified in RS 236. 6.3 
Sealed type bearings shall be used as protection against dust.   
6.4 Lubrification  shall be provided for lubrication of non -sealed type bearings and bushings.  
6.5 Belt cover or guard and provisions for belt tightening and adjustments shall be provided.  
66  Provisions for the safety of the operators in the feeding port and other moving  parts shall be included in 
the thresher.  
6.7 Threshing cylinder speed indicator should be provided.  
7 Workmanship and finish  
7.1 Rice thresher shall be free from manufacturing defects that may be detrimental to its operation.  
7.2 Any uncoated metallic sur faces susceptible to corrosion shall be painted properly.  
7.3 Rice thresher shall be free from sharp edges and surfaces that may injure the operator.  
7.4 Rotating parts should be dynamically balanced.  
7.5 Thresher shall be constructed to ease operation and cleaning.  DRS  268-1: 2020  
5                ©RSB 2020  - All rights reserved  
 8 Maintenance and operation  
8.1 Each heated - rice thresher shall be provided with a set of relevant mechanic tool kit.  
8.2 An instruction manual (User’s manual, parts catalogue and service manual) shall be provided.  
8.3 All components that re quire regular maintenance, servicing and adjustment should be easily accessible  
 
9 Sampling and testing  
9.1 Rice thresher shall be sampled for testing in accordance with RS 241.  
9.2 Rice thresher samples shall be tested in accordance with RS 269 -1.  
10 Marking  
Each rice thresher shall be marked at prominent place with the following information:  
a) name or registered trademark  of the manufacturer;  
b) brand;  
c) model;  
d) serial number;  
e);  
f) g) country of manufacture;  
h) rating power, Kw;  
i) recommended  threshing cylinder speed, rpm;  
k) safety/precautionary markings  
production capacity  
 DRS  268-1: 2020  
 
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