A Guide to Dynamic Weighing for Industry The Institute of Measurement and Control 87 Gower Street London WC1E 6AF October 2010 A Guide to Dynamic Weighing for Industry PANEL RESPONSIBLE FOR THIS GUIDE The Weighing & Force Measurement Panel reporting to the Learned Society Board of the Institute of Measurement and Control has prepared this Guide. The persons listed below served as members of the Weighing & Force Measurement Panel in preparing this Guide: Dr T Allgeier Flintec UK Ltd Mr J Anthony UK Weighing Federation Mr M Baker Sherborne Sensors Ltd Mr A Bowen AB Measurement and Control Solutions Mr P Dixon National Measurement Office Professor U Erdem Consultant, UE Consulting Mr P Harrison United Kingdom Accreditation Service Mr M Hopkins Procon Engineering Ltd Mr A Knott National Physical Laboratory Mr S Maclean Sherborne Sensors Ltd Professor J Pugh Glasgow Caledonian University Mr D Smith Avery Weigh-Tronix Mr A Urwin The Quality Scheme for Ready Mixed Concrete Mr C Whittingham M & C Engineers Mr B Yarwood Consultant, Dynamic Weighing Mr P Zecchin Nova Weigh Ltd The Weighing & Force Measurement Panel would like to express its thanks to the specialists who contributed to the preparation of the following sections: Section 3.2.1.3 Mr N Clark of Ishida Europe Ltd Section 5.2.1 Mr R W Stokes of Central Weighing Ltd Section 5.2.2 Mr D McLennan of Railweight Ltd Section 5.2.3 Mr D Pewter and Mr G Dorney of Herbert Industrial Ltd The Institute is grateful to members, specialists, and their organisations for providing relevant illustrations, and also to other providers of figures and photographs, including Eastern Instruments Inc and Gericke GmbH. This Guide is subject to review at any time by the responsible technical group of the Institute. The Institute welcomes all comments on this Guide and requests that these should be addressed to the Institute. DISCLAIMER This Guide represents the professional judgement of the members of the Weighing & Force Measurement Panel and the external contributors listed above. The Institute shall not be responsible to anyone for the use of or reliance upon this Guide by anyone. The Institute shall not incur any obligation or liability for damages, including consequential damages, arising out of or in connection with the use of, interpretation of, or reliance upon this Guide. Publication reference number WFMP1010 Page 2 of 83 A Guide to Dynamic Weighing for Industry TABLE OF CONTENTS Page 1. FOREWORD .......................................................................................................................................6 2. SCOPE OF DOCUMENT ....................................................................................................................7 3. DISCRETE MASS DELIVERY SYSTEMS........................................................................................10 3.1 PROCESS BATCH WEIGHERS .............................................................................................10 3.1.1 Application .......................................................................................................................11 3.1.2 Construction.....................................................................................................................14 3.1.3 Typical Performance........................................................................................................14 3.1.4 Factors Affecting Accuracy ..............................................................................................16 3.1.5 Calibration/Verification.....................................................................................................17 3.2 GRAVIMETRIC FILLING MACHINES ......................................................................................17 3.2.1 Net Weighers ..............................................................................................................................17 3.2.1.1 Conventional Net Weighers...............................................................................................18 3.2.1.1.1 Application.........................................................................................................18 3.2.1.1.2 Construction ......................................................................................................19 3.2.1.1.3 Typical Performance .........................................................................................20 3.2.1.1.4 Factors Affecting Accuracy ...............................................................................20 3.2.1.1.5 Calibration/Verification ......................................................................................21 3.2.1.2 Weigh-Out Weighers.........................................................................................................21 3.2.1.2.1 Application.........................................................................................................21 3.2.1.2.2 Construction ......................................................................................................21 3.2.1.2.3 Performance......................................................................................................21 3.2.1.2.4 Factors Affecting Accuracy ...............................................................................21 3.2.1.2.5 Calibration/Verification ......................................................................................21 3.2.1.3 Selective Combinational Weighers..................................................................................22 3.2.1.3.1 Application.........................................................................................................22 3.2.1.3.2 Construction ......................................................................................................22 3.2.1.3.3 Typical Performance. ........................................................................................25 3.2.1.3.4 Factors affecting Performance ..........................................................................26 3.2.1.3.5 Calibration/Verification. .....................................................................................27 3.2.2 Gross Weighers..........................................................................................................................28 3.2.2.1 Application.........................................................................................................28 3.2.2.2 Construction ......................................................................................................28 3.2.2.3 Typical Performance .........................................................................................29 3.2.2.4 Factors Affecting Accuracy ...............................................................................29 3.2.2.5 Calibration/Verification ......................................................................................30 4. DISCONTINUOUS TOTALISING WEIGHERS .................................................................................31 4.1 SHIPPING AND RECEIVING WEIGHERS ................................................................................31 4.1.1 Application .......................................................................................................................31 4.1.2 Construction.....................................................................................................................31 4.1.3 Typical Performance........................................................................................................32 4.1.4 Factors Affecting Accuracy ..............................................................................................32 4.1.5 Calibration/Verification.....................................................................................................33 4.2 IN-PROCESS WEIGHERS ....................................................................................................34 4.2.1 Application .......................................................................................................................34 4.2.2 Construction.....................................................................................................................34 4.2.3 Typical Performance........................................................................................................34 4.2.4 Factors Affecting Accuracy. .............................................................................................34 4.2.5 Calibration/Verification.....................................................................................................35 Page 3 of 83 A Guide to Dynamic Weighing for Industry 5. IN-MOTION WEIGHING SYSTEMS..................................................................................................36 5.1 CONTINUOUS WEIGHING SYSTEMS.....................................................................................36 5.1.1 Belt Weighers .............................................................................................................................36 5.1.1.1 Application.........................................................................................................36 5.1.1.2 Construction ......................................................................................................37 5.1.1.3 Typical Performance .........................................................................................38 5.1.1.4 Factors Affecting Accuracy ...............................................................................39