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Saving cash by machine care
LEEDS. 11 MAY 1972
Saving cash by machine care Leeds Industrial Unit of Tribology and WIRA
The down-to-earth title 'Saving cash by machine care' of this first conference run jointly by the two Leeds based industrial research centres was deliberately chosen to persuade northern industrialists that something of direct benefit to their businesses was on offer. WlRA is world renowned for its expertisein the technology of textiles and clothing. It offers comprehensive services ranging from fundamental investigations to commercially directed work covering most topics of concern to industry. Nowadays its sphere of activity extends far beyond the British wool textile industry, and this more outward looking attitude is typified by its links with the Industrial Unit of Tribology at Leeds University. To Dr Ambler, a director of a West Riding worsted spinning firm, goes the credit for initiating this conference. He saw it as a way of educating manufacturers in the benefits to be obtaine," from sound tribological practice in its widest sense by indicating the possibilities and state-of-theart in this field. Dr Ambler set the scene by asserting that 'in the wool textile industry as elsewhere, far too little attention has been paid to combating machinery wear. Not only is the repair or replacement of worn machinery expensive but worn parts can often do untold damage to the product itself'. Mr W. H. Wilson of the Leeds Industrial Unit of Tribology reminded his audience of the savings to industry possible if the available knowledge were applied to the reduction of machine wear. Much of the £345 million savings through reduced maintenance, replacement and breakdown costs estimated by Jost in his report six years ago still remain to be realised. Organizations like the Industrial Units of Tribology are doing their best but without the commitment of more of industry's own resources progress will remain slow. Indeed at times of economic hardship the situation may even get worse through the skimping of essential maintenance. Such a policy can only aggravate the position in the medium to long term, Mr Wilson then gave some case histories from the Leeds Industrial Tribology Unit which included advice on improved mould material which saved the client thousands of pounds through reduced wear, investigation followed by a test programme in connection with a worm gear drive on earth moving equipment, redesign of a fly shuttle loom which resulted in a 15% increase in ouput through reduced downtime, a design study for an improved ring spinning ring and traveller, the use of monitoring techniques to detect deterioration in performance and imminent failure involving sensing devices or routine analysis of the lubricant, several instances of damage caused by using the incorrect lubricant, by contamination of the lubricant, by insufficient and even by too much lubricant. Problems frequently met concemed the lubrication and wear of conveyor and stenter chains operating at elevated temperatures. Of the rolling contact bearing problems perhaps the most interesting was a bearing in a stand-by motor severely damaged and yet never run, a perfect example of 'false brinelling' induced by vibration generated by an adjacent air conditioning system fan and drive motor.
Mr W. Haidinger gave the delegates a unique opportunity to hear a frank and authoritative account of the experiences of a major textile group, Coats Patons, in introducing planned maintenance to its factories. The first attempt, in which a conventional planned maintenance scheme was instituted, ended by costing, directly and indirectly through lost production far more than any savings produced by reduced unscheduled downtime. The final solution placed emphasis on special training and status for maintenance men. In their equipment was provided a stethoscope (requiring 'a good ear for music' and three months training for its effective use) for maintaining a listening watch on bearings in critical components. It was at the suggestion of the trades union representative that both electrical and mechanical maintenance was carried out by the same man. A demonstration of how, given determination and good sense, together with a spirit of co-operation between trade unions and management, a satisfactory scheme suited to the needs of the situation can be worked out. In complete contrast with the very practical application of tribology involved in planned maintenance, was Mr T. C. Askwith's talk on the basic principles of tribology. His relaxed presentation was appreciated by his audience who could see the relevance of knowing how to tell the difference between running-in and wearing out, of why it is important to maintain a low shear strength layer between rubbing surfaces, almost irrespective of what the layer might comprise, and so on. The interest stimulated showed itself in the large number of questions posed at the end of the session. Of greatest interest was the treatment of surfaces to improve their scuff resistance or resistance to abrasion where there was contact with fibres. For scuff resistance the need was to keep the clean metal surfaces apart with a layer, preferably possessing a low shear strength; what this layer comprised did not otherwise matter very much. Machine care is a highly cost sensitive subject and most of the speakers touched on costs and potential savings. The final talk by Mr R. Nield of UMIST, a practical engineer turned economist, was a valuable exposition of the practical economics of plant engineering and machine care. In addition to substantial overall savings resulting from a correctly conceived and properly run scheme, planned maintenance makes budgeting easier and permits the use of budgetary control procedure. Such a scheme may well increase the total maintenance expenditure, initially at least, but against that should be set the significantly reduced cost of unit production achieved and the valuable by-product of improved cost awareness and control. Speakers from Shell Mex and BP, Tecalemit, and Eutectic proved very instructive and gave the point of view of col ,ponent and service suppliers active in the field of applied tribology. Mr T. D. King of Eutectic said that by using maintenance welding for recovering worn or damaged machine components savings in the money tied up in stocks of spare parts could be achieved. Mr A. Unsworth a bio-engineer from the University of Leeds had the frequently difficult task of interesting TRIBOLOGY August 1972
181
delegates straight after lunch. His dryly humerous presentation of the work being done to replace diseased knee and shoulder joints together with some excellent and lurid anatomical slides held the audience's attention and prevented the dropping of heavy eyelids. Attendance at the conference was over sixty people from thirty-eight organizations, a large proportion of whom were the type of person it was hoped to attract: namely engineers and managers from the textile industry and local firms. The true measure of the success of this new venture will be the effect it has on the actions of the delegates when they return to their working environments and the profit ensuing when they put some of the ideas into practice. In the meantime it is only possible to judge from the approving
comments and prediction that there would be much greater support when the next conference is held.
W. H. Wilson Conference papers
'Basic principles', T. C. Askwith (Leeds Industrial Unit of Tribology) 'Lubricants', W. N. Atherton (Shell Mex and BP Ltd) 'Automatic lubrication', G. Williams (Tecalemit Ltd) 'Case histories', W. H. Wilson (Leeds Industrial Unit of Tribology) 'Renovation of worn machinery parts', T. D. King (Eutectic Ltd) 'The human view', A. Unsworth (University of Leeds) 'Modern planned mill maintenance', W. Haidinger (Coats Patons Ltd) 'Economics'. R. Nield (UMIST)
PARIS. 15-18 MAY 1972
Seals GAMI, 3 rue Fernard Hainaut, 93 - St Ouen, France
The subject of the second spring session on industrial mechanics, organized by the Groupement pour L'Avancement de la Mecanique Industrielle (GAMI) was seals. There were twenty-eight reports, followed by a round-table discussion on dynamic seals. The subject was limited to allow detailed treatment of certain areas. Thus, neither vacuum sealing nor seal testing were discussed in detail. On the other hand, the general lines of a universal concept of sealing devices, either static or dynamic, were brought out, and a study was made of problems concerning them. This was set out in the exellent inaugural address by P. Rapin (Automobiles Peugeot). It was followed by a report on the specific aspects in the nuclear field by X. Elie and R. Martin (CEA) who described some solutions for various reactors. In the static seal range, an interesting description of ptfe isostatic seals was made by M. Rouger (Hispano-Suiza) and a report on high-pressure seals (280 bar) used on the Concorde by M. Hons-Olivier (Impervia). Inflated seals, liquefiable seals, electric isolating seals, sectional seals, and flexible seals as well as a calculation procedure for O-rings by computer were the subject of very well documentated presentations. The case of a sodium environment was studied particularly by M. Vercasson, Nedelec and de Montardy (EDF). Pressurized water-tank tightness using hollow metallic O-rings with improved contact due to a sort suver coating was discussed by Creusot-Loire. Automobile seals were not forgotten; M. Fiermonte (Fiat) discussed sealing rings for rotating shafts, and M. Stadelmann (Elring) cylinder head gaskets. These problems seem to be less simple to solve in modern engines than one would think because of mechanical stresses and thermal effects. Sealing of machine tools has less acute problems, but manufacturers are seeking new solutions in the use of hydrostatic devices (CERMO). Dynamic seals were the subject of a dozen of surveys, which had been co-ordinated beforehand by M. Le Blan (Alcatel).
182
TRIBOLOGY August 1972
First of all, a coherent vocabulary had been established to designate the different types of dynamic seals. For instance, instead of using the terms 'axial seals' or 'radial seals', which are to a certain extent ambiguous, one should say precisely if one talks of a seal with an 'axial leakage' or of a seal with a 'radial leakage'. Then, a doctrinal report on the creation of self-acting lift by fluid flow (hydrodynamic, hydrostatic, elastrohydrodynamic) in radial leakage seals was given by Professor Godet (INSA, Lyon), while Dr Nau (BHRA) surveyed recent developments in the field of mechanical seals. This general introduction allowed other authors to deal with their particular subject without repetition. They described original research in the field of axial leakage seals with auto-centered rings (Hispano), with floating rings (CEM), with grooves (CIT-Alcatel); viscoseals (Rateau, SOGEME, Hispano Suiza), and sealing by sublimated gaskets (Carbone Lorraine). M. Collet (Sealol) showed that friction-generated vibrations were far from being eradicated but that their effects were nevertheless controlled by judicious use of damping devices. The round-table discussion held on the last afternoon was organized like a public trial; defenders of mechanical seals against defenders of hydrodynamic seals. This round table proved that the balance was finer than either side thought. But mainly it pointed out what could have been forgotten by seal manufacturers or project engineers; reliability of mechanisms with rubbing parts remains the most important factor for the customer, who has already obtained satisfaction on all the other functional parameters described by the conditions of the contract. Sustaining the initial quality of mechanical seals during a minimum length of time which can be exactly predicted is still not possible, because the evolution of wear is not yet well known, and it is not yet possible to limit wear properly when it does occur. The texts of all the reports and the round-table discussion will be published at the end of 1972 in a special issue of Mecanique-Materiaux-Electricit&
R. Cour~l
Saving cash by machine care Leeds Industrial Unit of Tribology and WIRA
The down-to-earth title 'Saving cash by machine care' of this first conference run jointly by the two Leeds based industrial research centres was deliberately chosen to persuade northern industrialists that something of direct benefit to their businesses was on offer. WlRA is world renowned for its expertisein the technology of textiles and clothing. It offers comprehensive services ranging from fundamental investigations to commercially directed work covering most topics of concern to industry. Nowadays its sphere of activity extends far beyond the British wool textile industry, and this more outward looking attitude is typified by its links with the Industrial Unit of Tribology at Leeds University. To Dr Ambler, a director of a West Riding worsted spinning firm, goes the credit for initiating this conference. He saw it as a way of educating manufacturers in the benefits to be obtaine," from sound tribological practice in its widest sense by indicating the possibilities and state-of-theart in this field. Dr Ambler set the scene by asserting that 'in the wool textile industry as elsewhere, far too little attention has been paid to combating machinery wear. Not only is the repair or replacement of worn machinery expensive but worn parts can often do untold damage to the product itself'. Mr W. H. Wilson of the Leeds Industrial Unit of Tribology reminded his audience of the savings to industry possible if the available knowledge were applied to the reduction of machine wear. Much of the £345 million savings through reduced maintenance, replacement and breakdown costs estimated by Jost in his report six years ago still remain to be realised. Organizations like the Industrial Units of Tribology are doing their best but without the commitment of more of industry's own resources progress will remain slow. Indeed at times of economic hardship the situation may even get worse through the skimping of essential maintenance. Such a policy can only aggravate the position in the medium to long term, Mr Wilson then gave some case histories from the Leeds Industrial Tribology Unit which included advice on improved mould material which saved the client thousands of pounds through reduced wear, investigation followed by a test programme in connection with a worm gear drive on earth moving equipment, redesign of a fly shuttle loom which resulted in a 15% increase in ouput through reduced downtime, a design study for an improved ring spinning ring and traveller, the use of monitoring techniques to detect deterioration in performance and imminent failure involving sensing devices or routine analysis of the lubricant, several instances of damage caused by using the incorrect lubricant, by contamination of the lubricant, by insufficient and even by too much lubricant. Problems frequently met concemed the lubrication and wear of conveyor and stenter chains operating at elevated temperatures. Of the rolling contact bearing problems perhaps the most interesting was a bearing in a stand-by motor severely damaged and yet never run, a perfect example of 'false brinelling' induced by vibration generated by an adjacent air conditioning system fan and drive motor.
Mr W. Haidinger gave the delegates a unique opportunity to hear a frank and authoritative account of the experiences of a major textile group, Coats Patons, in introducing planned maintenance to its factories. The first attempt, in which a conventional planned maintenance scheme was instituted, ended by costing, directly and indirectly through lost production far more than any savings produced by reduced unscheduled downtime. The final solution placed emphasis on special training and status for maintenance men. In their equipment was provided a stethoscope (requiring 'a good ear for music' and three months training for its effective use) for maintaining a listening watch on bearings in critical components. It was at the suggestion of the trades union representative that both electrical and mechanical maintenance was carried out by the same man. A demonstration of how, given determination and good sense, together with a spirit of co-operation between trade unions and management, a satisfactory scheme suited to the needs of the situation can be worked out. In complete contrast with the very practical application of tribology involved in planned maintenance, was Mr T. C. Askwith's talk on the basic principles of tribology. His relaxed presentation was appreciated by his audience who could see the relevance of knowing how to tell the difference between running-in and wearing out, of why it is important to maintain a low shear strength layer between rubbing surfaces, almost irrespective of what the layer might comprise, and so on. The interest stimulated showed itself in the large number of questions posed at the end of the session. Of greatest interest was the treatment of surfaces to improve their scuff resistance or resistance to abrasion where there was contact with fibres. For scuff resistance the need was to keep the clean metal surfaces apart with a layer, preferably possessing a low shear strength; what this layer comprised did not otherwise matter very much. Machine care is a highly cost sensitive subject and most of the speakers touched on costs and potential savings. The final talk by Mr R. Nield of UMIST, a practical engineer turned economist, was a valuable exposition of the practical economics of plant engineering and machine care. In addition to substantial overall savings resulting from a correctly conceived and properly run scheme, planned maintenance makes budgeting easier and permits the use of budgetary control procedure. Such a scheme may well increase the total maintenance expenditure, initially at least, but against that should be set the significantly reduced cost of unit production achieved and the valuable by-product of improved cost awareness and control. Speakers from Shell Mex and BP, Tecalemit, and Eutectic proved very instructive and gave the point of view of col ,ponent and service suppliers active in the field of applied tribology. Mr T. D. King of Eutectic said that by using maintenance welding for recovering worn or damaged machine components savings in the money tied up in stocks of spare parts could be achieved. Mr A. Unsworth a bio-engineer from the University of Leeds had the frequently difficult task of interesting TRIBOLOGY August 1972
181
delegates straight after lunch. His dryly humerous presentation of the work being done to replace diseased knee and shoulder joints together with some excellent and lurid anatomical slides held the audience's attention and prevented the dropping of heavy eyelids. Attendance at the conference was over sixty people from thirty-eight organizations, a large proportion of whom were the type of person it was hoped to attract: namely engineers and managers from the textile industry and local firms. The true measure of the success of this new venture will be the effect it has on the actions of the delegates when they return to their working environments and the profit ensuing when they put some of the ideas into practice. In the meantime it is only possible to judge from the approving
comments and prediction that there would be much greater support when the next conference is held.
W. H. Wilson Conference papers
'Basic principles', T. C. Askwith (Leeds Industrial Unit of Tribology) 'Lubricants', W. N. Atherton (Shell Mex and BP Ltd) 'Automatic lubrication', G. Williams (Tecalemit Ltd) 'Case histories', W. H. Wilson (Leeds Industrial Unit of Tribology) 'Renovation of worn machinery parts', T. D. King (Eutectic Ltd) 'The human view', A. Unsworth (University of Leeds) 'Modern planned mill maintenance', W. Haidinger (Coats Patons Ltd) 'Economics'. R. Nield (UMIST)
PARIS. 15-18 MAY 1972
Seals GAMI, 3 rue Fernard Hainaut, 93 - St Ouen, France
The subject of the second spring session on industrial mechanics, organized by the Groupement pour L'Avancement de la Mecanique Industrielle (GAMI) was seals. There were twenty-eight reports, followed by a round-table discussion on dynamic seals. The subject was limited to allow detailed treatment of certain areas. Thus, neither vacuum sealing nor seal testing were discussed in detail. On the other hand, the general lines of a universal concept of sealing devices, either static or dynamic, were brought out, and a study was made of problems concerning them. This was set out in the exellent inaugural address by P. Rapin (Automobiles Peugeot). It was followed by a report on the specific aspects in the nuclear field by X. Elie and R. Martin (CEA) who described some solutions for various reactors. In the static seal range, an interesting description of ptfe isostatic seals was made by M. Rouger (Hispano-Suiza) and a report on high-pressure seals (280 bar) used on the Concorde by M. Hons-Olivier (Impervia). Inflated seals, liquefiable seals, electric isolating seals, sectional seals, and flexible seals as well as a calculation procedure for O-rings by computer were the subject of very well documentated presentations. The case of a sodium environment was studied particularly by M. Vercasson, Nedelec and de Montardy (EDF). Pressurized water-tank tightness using hollow metallic O-rings with improved contact due to a sort suver coating was discussed by Creusot-Loire. Automobile seals were not forgotten; M. Fiermonte (Fiat) discussed sealing rings for rotating shafts, and M. Stadelmann (Elring) cylinder head gaskets. These problems seem to be less simple to solve in modern engines than one would think because of mechanical stresses and thermal effects. Sealing of machine tools has less acute problems, but manufacturers are seeking new solutions in the use of hydrostatic devices (CERMO). Dynamic seals were the subject of a dozen of surveys, which had been co-ordinated beforehand by M. Le Blan (Alcatel).
182
TRIBOLOGY August 1972
First of all, a coherent vocabulary had been established to designate the different types of dynamic seals. For instance, instead of using the terms 'axial seals' or 'radial seals', which are to a certain extent ambiguous, one should say precisely if one talks of a seal with an 'axial leakage' or of a seal with a 'radial leakage'. Then, a doctrinal report on the creation of self-acting lift by fluid flow (hydrodynamic, hydrostatic, elastrohydrodynamic) in radial leakage seals was given by Professor Godet (INSA, Lyon), while Dr Nau (BHRA) surveyed recent developments in the field of mechanical seals. This general introduction allowed other authors to deal with their particular subject without repetition. They described original research in the field of axial leakage seals with auto-centered rings (Hispano), with floating rings (CEM), with grooves (CIT-Alcatel); viscoseals (Rateau, SOGEME, Hispano Suiza), and sealing by sublimated gaskets (Carbone Lorraine). M. Collet (Sealol) showed that friction-generated vibrations were far from being eradicated but that their effects were nevertheless controlled by judicious use of damping devices. The round-table discussion held on the last afternoon was organized like a public trial; defenders of mechanical seals against defenders of hydrodynamic seals. This round table proved that the balance was finer than either side thought. But mainly it pointed out what could have been forgotten by seal manufacturers or project engineers; reliability of mechanisms with rubbing parts remains the most important factor for the customer, who has already obtained satisfaction on all the other functional parameters described by the conditions of the contract. Sustaining the initial quality of mechanical seals during a minimum length of time which can be exactly predicted is still not possible, because the evolution of wear is not yet well known, and it is not yet possible to limit wear properly when it does occur. The texts of all the reports and the round-table discussion will be published at the end of 1972 in a special issue of Mecanique-Materiaux-Electricit&
R. Cour~l