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Failures of ?Gearbox and Drives?

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It is a pain area for the plant management team when the gear drive fails and it is more difficult to arrive at the correct cause of failure. S Sengupta & A Ray Chowdhury from Sprat Consultancy elaborates on some of the common causes of failures, also suggests remedial measures.

The idea of putting pen to paper regarding gear drives seems to be a daunting task. One is apprehensive as to where to begin and to what degree to write is a nerve racking proposition as majority of the readers are qualified, sound practical engineers who are associated with industrial plants such as cement, power, metals, etc. Experience confirms that a meaningful insight on the subject requires around three working days and if fourth day could be added by way of site visit with discussions on practical problems, works out a ?win-win? situation for all.

An endeavour is however being made to jot down some thoughts that may serve as pre curser from selection to use of drives. The order of narration is not sacrosanct and not all encompassing. It is just a brief write up on few attributes hoping it will provoke the mind of concerned personnel be it users or project/technical personnel. Use of gear drives in a system does not imply just operational; it encompasses what happens within a drive train and requirements to achieve desired performance life hence design life.

In many instances over the past 38 years, we have come across failures in drives caused by lack of insight or foresight or lack of correct data or its understanding during selection of drive. A common failure, but not frequent, is lack of perception of what all is to be handled &/or power required to drive the system.

An example that readily comes to mind is in a greenfield cement plant around early 1980s: the external consultant confirmed motor power, application, operating hours per day, etc. and wanted a drive with a safety factor (SF) of 2.5. This particular gear drive was 1 amongst 65 others. It was the only one that was prone to frequent failure to the tune of once every three months. Review of actual operating data confirmed actual power consumed was 40 per cent higher than confirmed during project design & planning leading to premature failures.

Another instance of premature failures observed in a cement plant in Western India of a twin drive bucket elevator where input drive was through fluid coupling. After a year of satisfactory operation failures commenced with regularity in one of the gear drives in the arrangement. As they were imported gearboxes not much hue and cry was raised initially. Replacements from two indigenous producers also failed in the same manner and frequency leading to a pantomime at the plant. Analysis of the drive arrangement confirmed power consumed by individual drives differed by over six per cent. In such a scenario, failure was inevitable and plant further confirmed that after a year one drive motor had burnt out requiring rewinding. Rewinding is common accepted process but what is equally important is that in a twin drive synchronisation of input power is of utmost importance of within two per cent variance. Since synchronise of input power no further failures occurred over a decade.

There are many other instances of failures we often recollect as observed over the last four decades. In all instances failures have taken place for:

  • Incomplete or inadequate clarity of specification at initial stage.
  • Lack of appreciation of specification, which is more dangerous.
  • Hypothesis by OEM of likely operational parameters viz a viz specification thus incorrect supply.
  • Augmenting capacity after year/s of use and not sharing data with supplier or supplier not appreciating information conveyed which must be well defined.

In short whatever are the circumstances in life (we consider gear drives also a form of life) it takes two to speak the truth to form an understanding and thus realisation. In the field of machine dynamics the same applies; dialogue between user and supplier must be continual and without inhibition or prejudice. In other words partnership is required with frank exchanges, irrespective of how insignificant the information may appear, to eliminate misgivings consequently failures.

The more this realisation dawns on all in a B2B scenario and quicker the better for all concerned resulting in reliability of operations. Failures are phenomena that cannot be totally ruled out even with best intentions of user and supplier. Any failure, irrespective of its occurrence, within or beyond the warranty period or after extended period of use is relevant at all times towards better and improved designs unless failure occurs beyond design life of rolling elements. This information should be shared with factual details unambiguously.

It is common for most designers to design critical drives, irrespective of type/size &/or application considering a life of 100,000 hours for gears/pinions and around 60,000 hours for bearings. Indirectly, to a large extent, bearing life sets the set point for case hardened and ground gears/pinions although theoretically it has an infinite life.

The question therefore arises why premature failures occur within warranty period or shortly thereafter. One of the primary reasons for failure beyond warranty period is governed by the quality of lubricating oil being used. Often quality is misunderstood with viscosity grade. Quality per ?say? has no relation to viscosity grade; it refers to the cleanliness of the oil.

  • Lubricating oil needs to be maintained clean and the desired level is NAS6 for industrial application other than turbine drives. This value of NAS6 also applies to wind mill drives and speed increasers as opposed to high speed drives. The cleanliness value of NAS6 does not readily register with users and to some extent with suppliers of gear drives. To put it mildly, check oil directly from a sealed barrel supplied by OEM for its NAS value and you will invariably find it anywhere around NAS10 or worse. Do not assume it happens only with indigenous supplies as it is far from the truth. Checks conducted with top brand sealed oil drums, indigenous or imported, confirm this is normal and common.
  • The onus thus lies with users to appreciate why oil cleaning is required and how does it improve the performance as well as life of the gear drive. It is safe to conclude, which concurs with our observation, that organisation which maintains lubricating oils health is less prone to premature failures. They invariably enhance the life of their drives by any where up to 30% higher than others for same drive conditions. This phenomena can be observed in an organisation &/or plant to plant operations but sadly data and findings are rarely pooled.
  • Another disturbing fact is often lubricating oil is procured on price consideration only and neglect issues such as scuffing, scoring, wet-ability etc properties.
  • Cost differential between normal mineral oil containing higher levels of sulphur and phosphorous in relation to vacuum distilled mineral oils is around 75-80 per cent more but the usable life of oil, if cleanliness maintained around NAS6, will justify the extra cost as life will be minimum double of normal mineral oil. A cement plant in Eastern India has continually achieved life of three times that of normal mineral oils there by not only resulting in huge savings to the organisation by way of less oil consumption and frequent shutdowns for changing oil.
  • Do note, normal mineral oils with higher levels of sulphur and phosphorous have an greater affinity to absorb moisture from the atmosphere leading to formation of sulphuric & phosphoric acids; both are very harmful towards life of bearings, seals and last but not least internal preservative paints applied to gearbox housing walls adding to further contamination.
  • A question we need to ask our self, as buyers we seek guarantee and warranty at the drop of a hat then why not for lubricants used?
  • Another cause of failure beyond warranty period is the upkeep of breathers, seals, etc. along with external surface of the gear drive. Often it is neglected resulting in breathers getting choked &/or become an ingress point for dirt when drive is stopped. As a result we have oil seal leakages and oil contamination leading to premature failures. Such instances are quite common in conveyor drives of cement grinding section or packing plant, coal handling conveyors, etc. An excuse we at times come across for not maintaining minimal level of cleanliness is, it is not a critical drive! The same excuse is also conveyed when the gearbox is covered with dust. What fails to be appreciated by the user is damage is taking place to investments and it can has a cascading effect.
  • There are numerous other instances of failures beyond warranty period but this is nether the forum or place to address these issues.
  • Failures during warranty period can be generally summed up under following heads as trends prevailing in gear design are to raise power levels till it does not result in a failure while decreasing volumes thus weight leading to increasing problems of heat dissipation:
  • Faulty or inadequacy of design
  • Incorrect selection & use of materials for manufacture
  • Incorrect selection of bearing
  • Manufacturing errors
  • Heat treatment errors
  • Assembly errors
  • Fluctuating or incorrectly defined operating parameters
  • Variants from original specification supplied &/or contaminates
  • Use of improper or incorrect quality of lubricant

Very rarely only one of the above mentioned causes account for failure to gear drives thus understanding and assessing gear damage requires in-depth knowledge of:

  • Gear contact patterns
  • Gear tooth failure types and probable causes
  • Bearing failure types with probable reasons
  • Lubricating oils
  • Oil flow within the gear drives be it splash or forced lubrication, etc.

It is not feasible to go through all these aspects in depth through this short article but to create awareness towards minimising risks of premature failures. We as such recommend use of following documents as a starting point to improve performance of gear drives thus overall operations of a plant. The documents relate to what needs to be communicated to the prospective seller and what in return you must get from them without fail.

Info. to be given By gearbox manufacturer

1.With offer for critical drives:
Design calculation in details for safety wrt wear & strength confirming material grade, etc.

2.Along with general arrangement (GA) drawing after placement of order:

  • GA drawing for all gear units, unless otherwise agreed upon, that gives full details of all manufactured part numbers and full nomenclature of proprietary parts including prefix and suffix, if any.
  • Number of teeth of each pinion and gear to facilitate vibration analysis. ?Spare parts list that can be correlated with GA drawing & the part number.
  • Approximate weight of gearbox.
  • Direction of rotation of input and output shafts.
  • GD? value of critical drives.
  • In case of pressure lubrication system water and oil flow rates with pressure range. Should also specify water and oil temperature gradient envisaged between inlet and outlet.
  • In case of cooling coil water flow rate and temperature gradient envisaged between inlet and outlet.
  • Details of interlocking, if any required to be ensured.

Note:

  • Your requirements of above data should be incorporated in your tender or enquiry or most major manufacturers will refuse to comply with the request at a later date.
  • Data of number of teeth will not only facilitate vibration analysis personnel but may facilitate in rationalising spares inventory if similar gearboxes are available in the plant or if same series gearboxes are installed of sizes that are just smaller or bigger than that on order.
  • Information to be given By a client

Following information are required to be furnished along with enquiry to finalise drive:

1. Prime mover – confirm type with full details like kW, rpm, Hz, type etc:

  • Motor
  • Turbine
  • I.C. engine

2. Input coupling – specify which:

  • Pin bush type flexible
  • Geared coupling
  • Fluid coupling
  • Bibby coupling
  • Tyre coupling
  • Any other than that mentioned above?

Note:

  • If coupling is not in the scope of gearbox supplier then its type, make, bore with tolerance of half to be mounted on gearbox are to be furnished.
  • Coupling in scope of gearbox OEM then confirm motor shaft diameter & tolerance.

3. Input through belt pulley drive – confirm following:

  • Pitch circle diameters of pulleys?
  • Direction of rotation of input shaft looking towards it?
  • Type of pulleys?

Note:
Provide sketch showing disposition of pulleys with respect to gearbox with dimensions in vertical and horizontal plane.

4. Type of gear drive:

  • Configuration of gearbox required i.e. helical, bevel/helical, RH, LH etc.
  • Operating hours per day?
  • Minimum and maximum ambient temperature where it is installed?
  • Place of installation i.e. open space, small confined area or large workshop?
  • Environmental condition e.g. normal, dusty, etc.

Note:
Mention if any other speciality is required in the drive.

5. Output coupling – specify which:

  • Pin bush type flexible
  • Geared coupling
  • Any other than that mentioned above?

Note:

  • If coupling is not in the scope of gearbox supplier then its type, make, bore with tolerance of half to be mounted on gearbox are to be furnished.
  • Coupling in scope of gearbox OEM; confirm machine shaft diameter & tolerance.

6. Output through Sprocket Drive:

  • Pitch circle dia of sprockets?
  • Direction of rotation of output shaft looking towards it?
  • Maximum pull of chain?

Note:
Provide sketch showing disposition of sprockets with respect to gearbox with dimensions in vertical and horizontal plane.

7. Driven machine details:

  • Cement mill, coal mill, sugar mill, belt conveyor, kiln, etc.
  • Confirm if it is twin drive, etc.
  • If possible specify OEM details of equipment manufacturer.

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Concrete

International seminar on Advances in Bridge Management hosted in Bengaluru

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The International Seminar on “Advances in Bridge Management” took place on September 25-26, 2024, at Hotel Lalit Ashok, Bengaluru. Organised by the Indian Road Congress in association with the Ministry of Road Transport & Highways, Government of India, and the International Road Association, the seminar brought together top professionals from around the world. It was inaugurated by Nitin Gadkari Union Minister for Road Transport & Highways, Government of India.

Over the course of two days, 24 distinguished speakers shared their insights on the latest innovations and challenges in bridge construction and management. The event featured 12 international experts from countries including the USA, Canada, Germany, Hungary, Spain, France, Japan, Korea, the UK, and Australia, alongside 12 Indian speakers identified by the Indian Road Congress, Ministry of Surface Transports, and the International Road Association.

During the event, Dr S B Hegde, Professor, Department of Civil Engineering, Jain College of Engineering and Technology, Hubli and Visiting Professor, Pennsylvania State University, USA, delivered the first keynote presentation on “New and Sustainable Materials & Technologies in Bridge Construction”. “My session focused on the potential of innovative materials such as Photocatalytic Concrete, Self-Healing Concrete, Basalt Fiber-Reinforced Polymers, and Nanocomposites to improve the longevity and sustainability of India’s bridge infrastructure. This was particularly crucial as the design and construction of bridges for a 100-year service life demand advanced materials and techniques,” said Dr Hegde, who is also the Editorial Advisory Board Member of Indian Cement Review (ICR).

The response from the audience, including engineers, industry professionals, consultants, and academicians, was overwhelmingly positive. The seminar emphasised the importance of updated IRC codes, project preparation, and bridge health monitoring systems in achieving sustainable infrastructure development in India.

This seminar underscored India’s commitment to innovative solutions for infrastructure, setting the stage for future advancements in bridge management and construction.

 

 

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Concrete

Revolutionising Energy

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The April-June 2024 quarter posed a challenging period for India’s cement industry, with softer prices putting pressure on the topline of many firms. While volume growth has been steady, muted revenues underline the pressing need for a price revival, which experts anticipate in the second half of fiscal 2025. However, the dip in revenue is counterbalanced with the spirit of optimism.
Given the Indian government’s ambitious infrastructure plans, involving a $1.7 trillion investment by 2030, the Indian cement companies are set to invest $14.3 billion over the next four years in capacity expansion.
However, with growth comes responsibility. The cement sector, being one of the most energy-intensive industries, is under increasing scrutiny for its environmental impact. As India marches towards becoming a global leader in sustainable development, all leading cement companies are aligning their strategies with decarbonisation goals, setting Net Zero targets for the coming decades. This commitment reflects the larger trend of industries embracing green manufacturing operations as both an ethical responsibility and a competitive advantage.
A significant part of this transformation will be powered by renewable energy. By 2030, India’s cement sector is estimated to add up to 5 GW of renewable energy, a crucial step towards reducing the industry’s carbon footprint.
The path forward also involves adopting the principles of a circular economy, which will be pivotal in minimising waste, reusing resources, and ensuring long-term sustainability. As we look ahead, it’s clear that the cement sector’s focus on energy efficiency and sustainability will not only help meet climate targets but also foster prosperity and growth in the years to come.
Further, ASAPP Info Global Group (the publisher of ICR) is hosting the RAHSTA (Roads & Highways Sustainable Technologies & Advancements) Expo from October 9-10, 2024 at the Jio World Convention Centre, Mumbai, to showcase latest developments in technologies and materials used for road construction. To know more, visit www.RAHSTAexpo.com

Follow me on twitter @PratapPadode

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Concrete

Sustainable Procurement Practices

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Partha Dash, Managing Director, Moglix, discusses how India’s cement industry, a key player in the country’s construction growth, is at a critical juncture as it faces the challenge of balancing expansion with sustainable practices.

According to research by construction blog Bimhow, the construction sector contributes to 23 per cent of air pollution, 50 per cent of the climatic change, 40 per cent of drinking water pollution, and 50 per cent of landfill wastes. Over the last decade cement has been one ubiquitous element in India’s construction growth story. As the world’s second-largest producer, we are seeing an impressive growth trajectory. Major players like Birla, Adani, Dalmia Bharat, JK Cement and Shree Cement are expanding fast, with plans to add 150-160 million tonnes of capacity over the next five years. This follows a substantial increase of 120 million tonnes in the past five years, pushing India’s total capacity to around 600 million tonnes. But with all this expansion, we have got a big question – How do we ensure sustainable procurement practices, in such an energy dependent industry?

Energy-intensive nature of cement production
Making cement takes a lot of energy. Process starts with limestone being mined, crushed, and grounded, using about 5-6 per cent of the total energy. The biggest energy use happens during clinker production, where around 94-95 per cent of the energy is used. Here is where limestone is heated to very high temperatures in a kiln, which needs a lot of energy from fossil fuels like coal and pet coke. Electricity is also used to run equipment like fans and kiln drives.
Once the clinker is made, it’s ground into cement. This grinding process uses another 5-6 per cent of the energy and usually happens at facilities close to where the cement is needed. Facilities that handle both clinker production and grinding in one place are generally more energy-efficient. Many of these places use coal-powered plants to supply the heat needed for the kilns, keeping production steady.

Transitioning to bulk cement
Making cement use more efficient is key to reducing the industry’s carbon footprint. In India, as per research by World Economic Forum around 75-80 per cent of cement is sold in 50kg bags to small-scale builders and individuals. But there’s often little insight into how this bagged cement is used. Research from the World Economic Forum also shows that about 40 per cent of this cement is mixed by hand. Builders sometimes use more cement than needed, thinking it will make the structure stronger, which increases emissions.
It’s crucial to educate these small-scale users about using cement efficiently. Builders need accurate information on mixing ratios and should be encouraged to adopt design techniques that use less cement. One idea suggested in the report is to put embodied carbon labels on cement bags to provide this information, helping to promote more sustainable practices at the grassroots level.
On the flip side, bulk cement, which now makes up 20-25 per cent of India’s cement use, has its own set of challenges and opportunities. Bulk cement is often used for large-scale projects that need high-strength concrete, which tends to be more carbon-intensive. However, it also makes it easier to mix in supplementary cementitious materials (SCM), which can reduce the carbon intensity of the cement. As bulk cement use grows, especially in big infrastructure projects, balancing structural needs with lower-carbon solutions will be crucial.

Challenges in sustainable procurement
The cement industry finds it hard to adopt sustainable procurement because many companies aren’t fully on board with it. Sometimes, sustainability isn’t a big focus for the company, which means top management doesn’t fully support it. This lack of support slows down collaboration with environmental experts and limits the adoption of green practices. Additionally, many clients still prefer traditional materials, which means there’s less demand for sustainable options.
In terms of knowledge and innovation, there’s a gap in understanding how to incorporate green procurement into existing practices. Many companies aren’t fully aware of the benefits of adopting green strategies or getting environmental certifications. This lack of knowledge also affects the public sector, where innovation in sustainable practices is often held back due to a shortage of technical support and experts.
There’s also a common belief that green procurement is more expensive, which can be a significant barrier, especially when resources for sustainable products are limited. Awareness and readiness for green practices are still low. Many people don’t fully understand the importance of sustainable procurement in construction, and there’s a lack of information about the market for green materials. Without adequate training and a clear structure for green purchasing, it’s difficult for companies to fully commit to sustainability. Moreover, existing policies and regulations aren’t strong enough to drive real change and without enforcement and incentives, the availability of green materials remains limited.

Opportunities in sustainable procurement
To fully understand the opportunities in sustainable procurement, Indian construction companies need to make it a key part of their business approach. This requires strong support from top leadership, including CEOs and boards of directors. When sustainability is a central focus in a company’s goals, it not only improves environmental impact but also sets the company apart in the market. Firms that focus on green practices can attract clients who value sustainability.
Working together with industry, academic institutions and government bodies is crucial for advancing green procurement. Top institutions in India like IIMs and IITs should collaborate with agencies like the Central Pollution Control Board and the Ministry of Environment. These partnerships can help develop shared goals and standards, like ISO 14000 for Environmental Management Systems, and offer training programs across the country.
It’s crucial to help clients understand how green buildings can save money over time. These sustainable structures not only cut down on running costs but also enhance the quality of life for those who live or work in them. Organisations such as the Construction Federation of India and the Builders Association of India should promote green products, which can drive demand and reduce costs by boosting production.
The government’s role is also vital. Programmes like the Pradhan Mantri Awas Yojana should focus on using green materials to show that sustainable construction can be affordable. To encourage use of sustainable materials, giving incentives like tax breaks, just like the ones for electric vehicles, could make a big difference.
Establishing a national certification for green procurement professionals, backed by organisations like the Indian Green Building Council, can help create a skilled workforce that can lead sustainable practices in the construction industry. By seizing these opportunities, India can move toward a more sustainable future in construction.

India’s leadership in sustainable cement production
India has made impressive strides in sustainable cement production. As per a research report by JMK research and analytics in 2022, the global cement industry accounted for 26.8 per cent of industrial emissions, but Indian manufacturers have been proactive in reducing their carbon footprint. The same report also states that between 2017 and 2022, the industry cut its emissions intensity by 19.4 per cent, thanks to a rise in alternative materials like fly ash and slag Blended cements, which now make up 81 per cent of India’s output, are a big part of this progress.
Leading cement producers in India, including Ultratech Cement, Shree Cement and Dalmia Cement, have committed to reducing emissions by 20 per cent by 2030, with a long-term goal of achieving net-zero emissions by 2050. Recently, the industry introduced 150 electric trucks to reduce carbon footprints, though challenges like limited charging infrastructure and high costs remain. Still, this move is expected to cut logistics expenses by 25-40 per cent. The industry is also pushing for policy support to accelerate the adoption of electric trucks and further its sustainability goals. According to report published by India Brand and Equity Foundation, some of the major investments in renewable energy and energy storage solutions include:

  • UltraTech Cement plans to deploy 500 electric trucks and 1,000 LNG/CNG vehicles by June 2025, cutting transport emissions by 680 tonnes annually. They aim to reach 85 per cent green energy use by 2030 and boost production capacity to 200 million tonnes.
  • Shree Cement completed a 6.7 MW solar project in Haryana in September 2022.
  • Dalmia Cement aims to produce 100 per cent low-carbon cement by 2031, supported by a $405 million carbon capture investment.
  • JK Cement signed an agreement with PRESPL in October 2021 to increase the use of biomass and alternative fuels, reducing reliance on coal.

Is the impossible possible?
The Indian construction and cement industries are making prudent strides toward sustainability. Recent research shows a strong link between the use of renewable energy and economic growth, highlighting the importance of reducing reliance on traditional energy sources. The construction industry, which has a large environmental impact, must adopt greener practices to help reduce pollution and waste.
The Indian cement industry is leading the way, with plans to significantly increase its use of renewable energy by 2026. This shift not only helps reduce costs but also sets a positive example for other sectors. The focus on renewable energy, like solar and wind, and efforts to avoid new thermal power plants show a clear commitment to a more sustainable future.
As the cement industry continues to push for net-zero emissions by 2050, its proactive approach is setting a new standard. These efforts not only benefit the industry itself but also provide a roadmap for others to follow. By embracing greener practices, the cement industry is helping to pave the way for more sustainable and environmentally friendly procurement practices in India.

About the author:
Partha Dash, Managing Director, Moglix, is a sales and marketing professional with 15+ years of hands-on experience in shaping businesses especially in the emerging markets.

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