18-19 March 2010, Radisson BLU Scandinavia Hotel, Düsseldorf, Germany

Conference review - by Dr Robert McCaffrey, conference convenor

The first Global Cement Wear and Maintenance Conference has taken place in Duesseldorf, Germany. 120 delegates registered to attend, from 25 countries, and among them were delegates responsible for specification and procurement of wear protection for over 300Mt of cement production capacity in more than 90 countries. The focused networking and friendly atmosphere of the conference was popular among delegates, so much so that the conference will be repeated in May 2011 in Istanbul.

The event started with networking in the exhibition area, which featured 15 different companies in the area (see table 1). Due to the popularity of the exhibition, the exhibitors were kept busy throughout the event.

The conference started with opening remarks from Dr Robert McCaffrey, the conference convenor, who suggested that the worst of the global economic crisis has now passed, and that companies which have survived have generally optimised their operations so that they have very good prospects for future profitability when the good times return. However, Dr McCaffrey warned that – taking the Asian Crisis as a model – it may be 2020 before the levels of cement demand return to those seen in 2006 in many areas of the world.

After this sobering introduction, the first of the technical presentations at the conference was given by Ralph Viebrock of Loesche. He told delegates that his company had responded to strong demand for training from customers by setting up a learning centre (see also Global Cement Magazine March 2010), which has augmented the company’s service hubs in Germany, India and China. The hubs have been established to optimise the company’s cost structure for its customers. Ralph stated that the use of wear-resistant materials has many benefits in the cement industry, primarily the increase of reliability and availability and the increase of service lifetimes. He pointed out that metal-matrix composites (MMC), where wear-resistant ceramic plugs are inserted into a metal base, are virtually maintenance-free, since they are extremely resistant to wear and have high impact strength. In one field test on a 46.2+2 Loesche vertical roller mill, the rollers were found to be practically free of wear after running for 10,000 hours (compared to the requirement to re-hard-face standard rollers up to 17 times during the same run time). MMC rollers double the lifetime of rollers, increase the availability of the mill by 10%, reduce the risk of roller breakage and have a 50% higher cost benefit over their lifetime compared to standard rollers. In consequence, Loesche will offer MMCs as the first-choice material for its rollers in the future.

Joachim May of Kalenborn Kalprotect next introduced his company, and mentioned that it designs, manufactures and installs wear-resistant solutions. He told delegates that to fix any wear problem it was first necessary to know the characteristics of the material causing the wear, including its size, shape, density, hardness, velocity, throughout, temperature, corrosivity, type of wear (sliding, impact and so on) and a number of other factors as well. Once these controlling factors were understood, it should be possible to recommend a particular type of wear-resistant material from among those provided (by Kalenborn, naturally!). Wear protection is required throughout the plant (see illustration) and different wear-resistant materials are used in different wear situations. Six main types are provided by Kalenborn: Abresist is the ‘original’ fused cast basalt material, with a hardness of 8 on Mohr’s scale, while Kalcor is a zirconium-corundum material which measures 9 on the Mohr’s scale and which can be used at up to 1000C. Kalocer is high-alumina ceramic with similar properties to Kalcor, but which also has the ability to be made in thin sheets. Kalcret is a monolithic wear-resistance material which consists of a hard aggregate, a cement-based binder and microsilica and which has many areas of application in the cement plant. Kalmetall-W is a hard-face welding solution, while Kalmetall-C is the company’s hard-casting option. Crucially, the company also offers a number of robust solutions for the fixing into place of all these wear solutions.

Above: Busy exhibition area at the Wear and Maintenance conference

Rema Tip Top’s paper, authored by Gjorgji Balkanov, pointed out that while customers have previously focused largely on price, in the future they should more sensibly focus on not only price but also on ramp-up costs, material costs, personnel costs, downtime costs, service costs and disposal costs, in order to choose the provider of the solution with lowest total cost of ownership (TCO).

Dorival Tecco of Welding Alloys presented a three-stage graph showing the evolution of grinding efficiency for cement mills: Stage 1 was the ‘bedding-in and optimisation stage of the mill, Stage 2 was the most efficient, stable operation phase of the mill, while Stage 3 showed a decrease in the efficiency of the mill due to increasing wear. Dorival’s clear advice was that you should not operate your mill when it has entered Stage 3, since its specific energy consumption will increase and its throughput will decrease. He suggested that it is possible to decrease the length of Stage 1 by providing an engineered profile for the mill after it has been run for a short time. Taking his analogy from the seconds-long tyre change on a Formula 1 car, he suggested that rollers can be hard-faced within the time that it takes for a storage silo to discharge, meaning that the kiln does not need to be stopped.

Dorival Tecco outlined a financial modelling spreadsheet which can calculate the optimum time to start hardfacing the wear surfaces in a mill, depending on a number of input variables but depending most crucially on whether the producer is operating in a sold-out market or is trying to produce the cement as cheaply as possible – he suggested that most producers will be in either one of these two situations. In either case, the time to take action is always before the start of Stage 3. He gave as an example the case of Hegmatan Cement in Iran, which decreased its power consumption by US$60,000 per year and decreased its wear-rate and level of vibrations, while increasing its production rate. Dorival pointed out that the cost of the energy saved by increasing grinding efficiency through timely hardfacing can equal or exceed the cost of the hardfacing undertaken.

Irina Issleib-Lubojanski of HARDTOP Giessereitechnologie GmbH – based in Magdeburg – next pointed out that monometalic parts have their limitations, in that while they can be impact-resistant they might be hard enough, or that they might be hard enough but might not be impact-resistant. Irina pointed out that Hardtop’s bi-metallic  hammers combine the best of both worlds, with wear-resistant heads and chromium-cast iron shafts which are resistant to breakage. The special hammers are produced through a complex casting procedure which leads to their higher cost, but Irina pointed out that the hammers can achieve three times the lifetime of austenitic manganese steel hammers, while not costing three times as much (and thus offering good value for money).
Klaus Holz of Fuchs Lubritech then gave a very useful presentation on the importance of correct lubrication in the cement industry. Fuchs – with 440 employees worldwide – provides lubricants for many industries, including food, insulation, plasterboard, forges and of course for the cement industry. Klaus pointed out that the most critical piece of equipment in the cement plant, in terms of lubrication, is the kiln. Riding ring lubrication is crucial, since it is never completely fixed, and the lubricant has to ensure the smooth relative movement of the ring and the kiln shell. Klaus suggested that some girth gears can run for 30 years if they are lubricated properly. In the first case, it is important to use a running-in lubricant, which can lead to an increase of 20% in the lifetime of the gear. It is also important to ensure that seals are intact, to prevent the ingress of cement dust which can promote wear (and also to take the simple precaution of putting a lid on the top of any barrels of lubricant to stop dust contamination). It is also important to remove old grease from gear boxes, since it is likely to be contaminated with not only cement dust to a certain extent, but also with metal particles from any wear.

During any checks on lubricants, it is important to measure the temperature of the gears to ensure that temperature gradients are not too high, and also to measure vibrations in the machine. Lubricant sampling must of course be representative of the lubricant in the system (and not taken from the sump), should be timely (sampling must not be delayed before being sent to the laboratory), with correct documentation, should be taken while the machine is still running (or soon after close-down) and must not be contaminated (sample containers must be scrupulously clean). Tests on the lubricant can include viscosity, its iron index (for the presence of magnetic particles), its Si content, Ca content and additive content. Through analysis of the used lubricant, many machine problems can be diagnosed – and corrected.

Christoph Clemens of German company F’IS (FAG Industrial Services) gave an interesting presentation on condition monitoring (CM) by vibration analysis (VA). Damage on a bearing typically progresses from vibration, to noise, to smoke (and thence to fire and self-destruction in the worst case). Obviously it is important to apply preventative maintenance strategies as early as possible, and this is where spectrographic vibration analysis can help to detect misalignment, bearing damage, transmission damage, potentially avoiding subsequent damage and optimisation of spare part strategies. Different problems show up as different patterns in the spectrographs – while data collection can be done after relatively short training, data analysis requires substantial experience, and trouble-shooting should be done by experts – such as F’IS.

Fabrice Ziegler of Novexa, a company based in Orleans, France, then mentioned that his company undertakes more than 50% of its activity in the cement industry. Novexa undertakes on-site machine of pinions, rollers and sleeve casings, and can reprofile gears for approximately 10% of the cost of a new gear. A number of cement producers in the audience were particularly interested in this option.

Conference dinner
The conference dinner took place at the Goldener Kessel, part of the oldest brewery in Duesseldorf, the Brauerei Ferdinand Schumacher. By happy coincidence, the event coincided with the festive brewing and consumption of a special beer, created only three times a year and leading to substantial beverage consumption, Germanic celebration and delegate carousal (below).

Second day
The first presentation on the second day of the conference was given by Georg Wallrathner, who spoke about failure patterns, problem identification and problem solution in cement industry bag houses.  He showed that different fibres have different applications in the cement plant, depending on the conditions the bags are likely to experience and the characteristics of the fibres making up the bags. Repeated failure of bags can be seen as an indication of local problems, such as high gas volumes or the location of cold spots with subsequent condensation and corrosion. Georg pointed out that used bags should be replaced all at the same time (or at least all of those in the same filter chamber), and that new bags should be pre-coated with materials such as ground limestone or slaked lime, in order to reduce blinding, to prevent the bags subsequently being coated with hygroscopic dust and to reduce attack by sulphuric acid gases. Georg also helpfully pointed out that many types of used filter bag can be used as an alternative fuel in the cement kiln.
Dirk Schmidt of Intercem Engineering outlined his company’s capabilities in the supply of pre-owned or refurbished equipment, and pointed out that the company can supply entire ‘greenfield’ cement plants using any combination of new or used equipment, such as a recently completed cement plant in Ras al Khaimah in the United Arab Emirates. The company has significant expertise in dismantling, transport, sand-blasting and refurbishment, coating and logistics, and has supplied plants around the world.

Dr Stefan Seemann of KHD outlined his company’s efforts to make maintenance of the KHD roller press easier, including the provision of hydraulic hatches and lateral tracks that allow the rollers to easily be removed from the press frame. The gear box for the roller press can also be removed on rails. Echoing the sentiments of Loesche, Dr Seemann stated that the company’s stud-lining benefits from the build-up of an autogeneous wear protection layer, which can lead to lifetimes of up to 20,000h without significant maintenance (and a total lifetime estimated at 45-50,000h after reprofiling at 20,000h). To protect the rollers, very effective bar-sizers can be used to segregate large lumps before they get to the roller press, while magnetic systems can be used to avoid damage from tramp metal.

Stefan Beese of EMZ recounted his company’s capabilities in building high and low voltage motors, and reminded delegates that many types of motors for the cement industry are immediately available from stock at short notice. Stefan pointed out that today’s standard motors – designated EFF2 – will not be sold after June 2011, and that the next most efficient motor type, IE2, will become ‘illegal’ after 2015. In this way, the European regulators are forcing motor manufacturers and users to progress towards increasing electrical efficiency.

The final pair of presentations at the conference were given by authors from Phillips Kiln Services. Peter Cope, during his final presentation before his retirement, outlined the principles of kiln alignment, and pointed out that deviation from perfect alignment of only two or three millimetres can be enough to start the destruction of kiln tyres, refractories, the kiln shell, support rollers and bearings, and that mis-alignment leads to higher maintenance costs and lower kiln availability. He mentioned that the worst kiln alignment he had witnessed during his long career was ‘only’ by 30mm, a misalignment that is still not visible to the naked eye but which will quickly lead to the breakdown of the kiln. Interestingly, he also mentioned that some Russian kilns have up to nine pairs of kiln support tyres. The mind boggles.

Steven Machin – ex of Lafarge Cement Cauldon works – then outlined the new dynamic thrust balancing method of kiln re-alignment, which involves measuring the thrust forces on the rollers, rather than their position. When the force on the rollers is equal when the kiln is rotation in either direction, then the rollers have minimum (or zero) skew and are in their neutral position. Through this method, the kiln can quickly be brought into perfect alignment.
At a short prize-giving ceremony after the conference, awards were given for the best presentations, based on delegate votes. In third place was Dr Stefan Seemann with his paper on design advances on KHD roller presses. In second place with his paper on the importance of lubrication was Klaus Holz of Fuchs Lubritech, while in first place – and winner of the best presentation award – was Dorival Tecco of Welding Alloys, with his paper on hardfacing of mills, and the optimisation of maintenance scheduling.

Conclusion

Feedback from delegates and exhibitors was strongly positive, with both networking opportunities and the technical content of the event being highly praised. Such was the level of interest in the event that it will be repeated, in May 2011, in Istanbul in Turkey. A large delegation of Turkish cement producers is expected to attend, as well as cement producers and equipment vendors from around the world.

Full details are at http://www.propubs.com/wandm