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Plenary Lecture

Properties of Covering Materials of Roller Used in
Cotton Roller Gin

Professor Vijayan Gurumurthy Iyer
Chief Co-ordinator (EDC)
Dr. M. G. R. University
13/14 A ,Tharachand Nagar Second Street
Virugambakkam, Chennai-92

Abstract: Cotton ginning process is the mechanical separation of cotton fibres from the seed-cotton (kapas). The roller ginning process for cotton was invented by Fones McCarthy in 1840. This process mechanically separates cotton fibres from seeds by means of one or more rollers to which fibres adhere while the seeds are impeded and struck off or pulled loose. Most of the ginning operations is performed by using double roller (DR) gins which serve an important role in the ginning industries. The roller is the major component of DR gins and one requiring considerable attention. The peculiar gripping action or adherence of the cotton fibres to roller covering surface is an important element in the success of roller ginning process.
In the conventional ginning process, the chrome composite leather-clad (CCLC) rollers emit chromium into environment due to the constant dust-producing grinding action. This contaminates the cotton and its products beyond the safe limit prescribed by International Organisation for Standarization (ISO) 14000 standards. CCLC rollers contain about 18,000 to 36,000 mg/kg (ppm) total chromium in trivalent and hexavalent forms, which are toxic to human health and carcinogenic. Current roller gins manufactured by companies in India and abroad commonly employ CCLC rollers. Since semi-finished chrome leather washers, which contain 3% to 4% chromium, are being used by roller ginning mills in India, Africa, Tanzania, China and Egypt, attention has been drawn to the contamination and pollution aspects of the process. This roller covering wears completely out with usage and repairing the roller consists of re-covering it. Specifically, due to persistent rubbing of the leather-clad roller over the stationary knife during the ginning process, the lint is contaminated with about 140 to 1,990 ppm of chromium, and the spun yarns and cotton by-products contain about 100 to 200 ppm, far in excess of the ISO standards limit of 0. 1 ppm. The use of CCLC rollers in the ginning process also causes air pollution due to chrome-specific dust (CSD) in the mill environment and is responsible for synergistic health complications (chromium based diseases and byssinosis) among gin and mill workers. Chromium in CSD and contaminated cotton products acts on human in three ways such as (1) local action as dermatitis or absorption through skin, (2) direct inhalation and (3) ingestion or absorption into the stomach. Toxic effects are produced by prolonged contact with airborne, solid or liquid chromium contamination and pollution, even in small quantities.
Presently, there are about 4,900 cotton ginning mills and they gin 65% of the seed-cotton produced in major eight cotton growing states in India. As per the rough estimate during field survey and discussions with ginning mill management, presently, there are about 2,13,000 CCLC rollers, which comprise of 1,70,40,000 CCLC washers and they are used for a cotton season of three months. There are about 7,60,000 people working in roller ginning industries in India.
Walrus hide, which was used till 1940 in United States of America, was thought to be unequalled for roller coverings. Research and experiments show the possibility of obtaining a substitute. A literature survey was carried out to help meet the objective of designing and developing eco-friendly alternatives. Various eco-friendly alternative roller covering materials and methods have been studied and deviced, such as vegetable tanned leather, eco-friendly tanned leather, alternative rubber and rubber-processing technologies, and modification of the present CCLC roller ginning system. This research is an attempt to eliminate the contamination of cotton and its products , air pollution in cotton ginning and textile mills, and other ginning problems at the source through the design and development of an eco-friendly , pollution-free chromeless roller. Gin roller packing made of multiple layers of cotton fabric bonded together with a rubber compound has been found to be very promising.
The objectives of this research were to :
• Define the physical properties of a roller material which contribute to its energy consumption , ginning rate potential, eco-friendly quality lint cotton, and to search for a better roller covering material.
• Identify and study the environmental problems asssociated with the CCLC rollers currently employed in cotton roller ginning mills.
• Design and develop an eco-friendly, chromefree roller and evaluate its performance with particular reference to the environmental, technical, and commercial aspects of ginning mills.
A special laboratory-built, 200 mm wide, McCarthy-type reciprocating-knife gin referred to here as a gin roller investigation device (GRID) was designed to test and investigate the various roller materials. The GRID was designed to make speeds, pressures, and adjustments measurable and controllable. Fifteen different gin rollers were constructed to provide a range of material characteristics for testing. Ten different types of gin roller covering materials were used: (1) rubber with cotton fabric packing, (2) vegetable tanned leather disks, (3) chrome tanned leather disks, (4) cotton packing, (5) rubber and cork packing, (6) polypropylene packing, (7) coconut coir buffing disks, (8) cotton buffing disks, (9) walrus covering disks and (10) walrus and cotton packing.
Ginning investigations were carried out to study and search the better gin roller covering material for commercial DR gins with good material properties with respect to good fibre production and quality and to design and develop eco-friendly alternatives. Various alternative roller covering materials, namely,vegetable tanned leather, eco-friendly tanned leather, including rubber and rubber-processing technology and modifying the present CCLC roller ginning system have been studied. In a DR gin, two spirally grooved leather rollers, pressed against stationary knives, are made to rotate at a definite speed. Two moving knives, known as the beaters oscillate by means of a crank or eccentic shaft, close to the leather rollers. When the seed-cotton (or kapas) is fed to the gin in action, fibres adhere to the rough surface of the roller and are carried in between the stationary knife and the roller such that the fibres are partially gripped between them. The oscillating knife beats the seeds and separates the fibres which are gripped from the seed end. This process is repeated a number of times and due to the ‘push and pull’ action, the fibres are separated from the seeds, carried forward on the roller and dropped out of the gin. The ginned seeds drop down through the slots provided in the seed grid. Ginning rate potential and ginning efficiency depends upon the number of effective working strokes on the moving knives.
Seven types of roller covering materials with different rubber compounds and multiple fabrics composition were tested in GRID and DR gins. The RCF rollers made with these experimental covering materials were tested (1) to establish the existence of ginning rate potential and good lint cotton quality production , (2) to find shortcomings in gin performances such as roller life, rate of wear and tear , temperature, lint contamination and maintenance aspects. This chrome-free RCF rollers were found successful in ginning out seed-cotton in an environment friendly way, while maintaining high ginning rate potential, good cotton technological parameters such as fibre,yarn and fabric properties. The chromium contamination levels for cotton and its products were well above allowable limits for all samples, except the cotton samples ginned with RCF roller gin rollers. On the basis of the design and development of various rollers and subsequent performance evaluations, the chrome-free RCF roller has been demonstrated to be superior with reference to technical, commercial and eco-friendliness aspects of the cotton ginning industry. This improved technology is suitable for commercialization. Although the initial cost of the RCF roller is eleven times that of the CCLC roller, this high price is compensated by benefits. The RCF roller is durable with an estimated life of seven years (compared to a few months for CCLC rollers), and the following additional advantages:
• Negligible wear and tear and very low maintenance requriements .
• Output is about one and half times more than that of CCLC rollers because the RCF roller has a surface finish conducive to high ginning efficiency.
• A reduction in the weight of the rollers of 50% could reduce 25% consumption in electrical energy compared to CCLC roller ginneries.
• Noise level is reduced by 4 to 7 dB(A) due to inherent properties and cushioning effects.
• Eco-friendly cotton and cotton-by products are obtained.
• Labour output per hour is 2. 4 standard performance rating which is twice that of CCLC-equipped mills.
• Medical expenses for treating affected workers are decreased by a factor of 23 .

The manufacturing technology, design engineering features , and assembly experience show that the RCF roller covering can be selected with the following characteristics: hardness of 106 BHN (type Brinell Hardness Number), 7 to 10 layers of fabrics 20 mm length, and fabric thickness of fabrics 1. 2 mm, The rubber compound is resilient and fibre bristles protrude 0. 76 mm beyond the rubber surface is maintained in spite of wear.
• As a result, an eco-friendly roller ginning process has been developed for replacing the conventional CCLC roller ginning process to eliminate the chromium contamination and pollution from cotton ginning mills. This process meets the requirements of ISO 14000 environmental standards while maintaining high-quality spun yarns and woven fabrics to meet ISO 9000 standards. With RCF rollers, ginning mills and textile mills, will be freed from chrome-related contamination and pollution problems, and from chrome-related health hazards. The products have been tested commercially and found to be better in all aspects with reference to cotton technological parameters, dye-catching properties, and physical and chemical properties. Eco-friendly RCF rollers could be successfully used commercially as an improved alternative in ginning mills for a cleaner environment, which benefits society, mill owners, clients, workers , employees and the Government.

Brief Biography of the Speaker:
Dr. Vijayan Gurumurthy Iyer has got about 27 years experience in research, teaching, and industry out of which seven years at the level of Professor. He has been serving in Dr.M.G.R. University, Chennai as Professor and as the Chief co-ordinator of AICTE-EDC project. He has obtained his Master’s and Ph.D. degrees in Environmental Science and Mechanical Engineering from Indian School of Mines University, Dhanbad . He was a post doctoral researcher of World Scientific and Engineering Academy and Society (WSEAS), Greece. The Yorker International University, Italy has awarded him with an honorary doctorate in Engineering on 29 th June, 2008. He is going to submit his Doctor of Science , D.Sc. thesis to Jadavpur University , kolkata, India .
He has published more than 96 research publications in his professional field which includes 32 research papers in reputed journals and 56 papers in reputed conference proceedings. His publications have cited in 87 citation indices of national and international journals. He has nine awards in his credit. He has been listed in many international biographical references of repute such as Marquis Who’s Who in Asia , Marquis Who’s Who in the World , Marquis Who’s Who in America , IBC’s Dictionary of International Biography, Cambridge Blue Book,2000 Outstanding intellectuals of the 21 st Century, ABI’s Great Minds of 21 st Century, ABI’s 500 Great Leaders. He is a research supervisor of Anna University and Dr.M.G.R. University for guiding M.S and Ph.D. scholars. He has guided more than 27 projects. He is a reviewer of three international journals, viz., WSEAS, ASABE and Environmental monitor. He has fellowships from five institutions and life memberships of ten institutions. Felowhsips include 1.Fellow of Institution of Engineers (India) Grade- F.I.E.(I), F-110329/2 ,Chartered Engineer (India) , C.Eng. (I), Professional Engineer (India) P.Eng. Arbitrator. 2.Fellow of Institution of Valuers (India) Approved Valuer , Grade- F.I.V., F-9446, 3.Fellow of Textile Association, F.T.A., F-3556 , 4.Fellow of All India Management Association, FIMA, F-200620434, 5. Fellow of Madras Management Association, F.M.M.A., , 6. Fellow of Mining Engineers’ Association of India.




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