TRANSFER CHUTES
The Transfer Chute Design Manual For Conveyor Belt Systems By C Benjamin, P Donecker, S Huque & J Rozentals
A Review by Em Prof Peter Arnold and Dr David Hastie, Centre for Bulk Solids and Particulate Technologies Technologies Faculty Faculty of Engineering, Engineering, University of Wollongong. Wollongong.
T
here is no doubt that transfer chutes in conveying systems present operating problems far too frequently. Being a series link in the overall conveying system means that when the transfer chute fails to perform then the whole conveying system suffers. As stated by the authors, this book ‘sets out to bring together the way transfer chute design has evolved and to relate this evolution to the underlying design principles pri nciples that must be aapplied pplied if the transfer is to operate with the min imum of maintenance consequences’. consequences’. The text also examines how conflicting outcomes can be accommodated and how to assess the compromises that may have to be made. The authors are well experienced practical chute designers and operators and the book reflects their wealth of experience. They frequently point out that an effective chute design requires: Accurate Accurate calculatio calculation n of the trajecto trajectory ry Maintaining control over the bulk material flow Controlling the bulk material stream velocities and dust generation Ensuring that the presentation of the material to the receiving belt is correct. Like many similar simila r design manuals, this book has its strengths and its weaknesses. weaknesses. Its Its strengths strengths include include:: Its coverage of the various types of transfer chute that may need consideration, pointing out their advantages and disadvantages. Extensive practical design guidance relating to the various chute types. The wealth of practical information relating to such aspects as chute liners, maintenance issues, dust control and sealing issues. Its weaknesses include: The lack of comprehensive comprehensive detail that th at would allow the user of the manual to actually carry out the calculations that are required as part of the design process. The authors continually emphasise the importance of accurate trajectory calculations and they pro vide a wealth of references references relating to the topic but in the end they rely on ‘in house’ software that the manual user would need to acquire, for their calculations. Similar lack of detail exists for other calculations, for example calculating the velocities through hoods and spoons. The manual user would be forced to go to the work of others (eg AW Roberts) to carry out such calculations. The chapter on trajectories and their comparisons is lacking any comparison to experimentally measured values. It is unfortunate that with all authors having widespread background in the area of conveyor design, none has been able to supply data for comparative purposes to better gauge the accuracy (or lack thereof) of the trajectory models. Being self published the book has some presentation shortcomings, for example: References that are in error or missing ( Powell (1995) (1995) is referred referr ed to on a number of occasions but not referenced – it happens to be an Undergraduate Thesis from the University of Wollongong); Wollongong); trajectory methods by BF Goodrich, Good rich, BTR, Colijn and Connors and S-A 66 are referred to on several ocassions but •
•
•
the references are not provided; photographs that are indistinct; figures that are hard to comprehend; drawings that are reduced to such an extent that they are illegible; and the inevit able typos.
Despite Despite the above above weaknes weaknesses ses this manual manual provide provides s a valuabl valuable e insi insight ght into into the the vagaries of chute design and emphasises that the design must not be treated as trivial trivial.. In In fact fact there there is is an an unde underlyi rlying ng philoso philosophy phy that that empha emphasise sises s that that it is genera generally lly very very cost cost effec effectiv tive e to to entru entrust st the the design to a well experienced designer.
•
•
•
•
•
•
•
•
8
Australian Bulk Handling Review: September/October 2010
While the authors acknowledge acknowledge that t hat it has taken t aken them some time to bring the book to fruition, it is a pity that they have not kept up to date with the research and developments that have taken place during that ti time. me. The book contains an extensive range of references and a comprehensive bibliography, however, there are few references less than 10 years old. Two examples are: the 6th edition of the CEMA guide (2006) contains some minor changes to the way trajectories are determined but is not covered; and the use of Golka’s method (1993) (1993) of determini ng trajectories originally lacked the detail on how to determine the divergent coefficients but a subsequent publication by Golka et al. (2007) has clarified these issues. One area where it is felt that the manual i s seriously lacking is in the application application of DEM techniques to chute design. The authors conclude their brief coverage of the DEM technique by saying that they ‘believe that using DEM to look at the flow properties of a chute can assist in the design process but it is not a very strong tool’. They state that a more reliable method of testing the design of a transfer is using scale model testing. In the last 10 years great strides have been made in the development of DEM software and the application of calibration techniques to enable reliable material parameters to be incorporated in the DEM models. While DEM analysis can still be expensive so is scale model testing. With the advances made in recent years, DEM is proving to be a very valuable tool for chute design, especially when retrofit designs need to be developed. developed. Despite the above weaknesses this manual provides a valuable insight into the vagaries of chute design and emphasises that the design must not be treated as trivial. In fact t here is an underlying philosophy that emphasises that it is generally very cost effective to entrust the design to a well experienced designer. Contact: Peter Arnold, email –
[email protected]
