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Reliability Centred Maintenance (RCM) in action: apron feeders

Tuesday, 15 June 2021 08:00

In mining operations, apron feeders are generally located under RoM bins or underground in a dusty, hot or wet tunnel fed from a RoM stockpile, and are typically used to provide the means of moving coarse material when it first enters a processing plant. The location of the assets and the nature of the coarse material they move means that they are subject to often harsh operating conditions and wear over time. As these assets are typically not in a redundant configuration, a functional failure can potentially cause undesirable production losses. Consequently, as part of an Asset Management strategy for apron feeders, an appropriate maintenance program needs to be developed that maximises uptime and ensures that preventive maintenance is both applicable and effective.

Developing your maintenance strategy

The criticality of an equipment item (in terms of the potential consequences of its failure) typically determines the level of rigour to be applied in developing the preventive maintenance program for that equipment. In this case, as Apron Feeders tend to be critical in terms of their impact on production output, the maintenance program would ideally be developed using a Reliability Centred Maintenance approach that considers all possible failures. However, as a minimum, original manufacturer recommendations can often provide a starting point that can be adapted to suit individual site needs. While an apron feeder is comprised of many sub-systems and assemblies that require consideration for maintenance, let’s just look at the example of the master link.

Example: choosing an effective strategy for master link maintenance

Apron feeders, especially ones that use Caterpillar chains, have a component called a "master link". The function of the master link is to provide a method of attachment that provides an easy way to replace individual sections of the drive chain. Consequently, several master links are typically found in the full length of the drive chain.

A master link comprises of a split chain link, bolted together. The bolts are required to be fitted dry without thread lubricant and tightened to a stated torque using a torque wrench.

Strategy 1: Condition monitoring

The integrity and on-going required functional performance of the master link could be assured through periodic inspection (condition monitoring) established as part of the maintenance program. However, in order to perform the inspection, the following would need to be performed:

  • The master link to be worked on, needs to be positioned at the rear of the feeder, clear of the feed chute.
  • Machine guards need to be removed to allow access to the chain;
  • Three flight plates, each with around eight securing bolts, need to be removed to obtain access to the master link securing bolt heads. As these are heavy items, lifting gear will be required to help remove and then reinstall them;
  • Any built up material will need to be removed to allow inspection of the master link for any damage or cracks; and
  • The torque on the master link securing bolts needs to be checked and adjusted as needed.

The flights and machine guards then need to be re-installed when returning the apron feeder back to operational use. In re-installing the flight plates, each of the flight plate securing bolts also need to be tightened. If one bolt is incorrectly fitted or not properly tightened, the chance of a loosened bolt catching on the structure and causing a chain failure is very high. In RCM terms, the chances of a Failure Pattern Type F (early life failure following the inspection) is high – in other words, there is a high probability that the “preventive” maintenance task could actually cause the failure to occur, rather than prevent it.

Six Failure Patterns of RCM

Figure 1 - Failure Patterns

To minimise this risk, any instruction developed for performing the inspection should consider incorporating hold points for Supervisor QA when the task of fitting and tightening the flights bolts is reached, thereby reducing the risk of human error introducing an unwanted failure mode but at the cost of more time needed to complete the inspection activity. The frequency of performing this inspection is determined by the PF Interval associated with the failure mode, which in this case would depend upon factors such as the operating cycle for the apron feeder and type of coarse material that is loaded onto the feeder.

PF Interval

Figure 2 - PF Interval

Overall, the process of performing the inspection would consume a significant amount of time and resources and potentially introduce other human-error based modes of failure, not to mention the planned downtime that would need to be scheduled to perform the inspection. Consequently, the applicability of the maintenance operation in addressing the failure mode needs to be balanced against its effectiveness to the business as a whole.

Strategy 2: Fixed interval replacement

Alternatively, if it can be clearly demonstrated that the failure mode is age-related – that is, that the conditional probability of this failure mode occurring increases with age, and that we can state with a reasonably high degree of certainty the age at which the probability of this failure mode occurring starts to rapidly increase in this particular application (that is, it complies with Failure Pattern B in Figure 1), then fixed interval replacement of the link may be both applicable and effective. However, to support this strategy, sufficient good-quality data would be required regarding the frequency of this failure mode occurring. In most organisations, data to this level of granularity is simply not available, so adopting this strategy also comes with some risks.

Strategy 3: Run to fail

A third alternative strategy could be to consider a ‘run to fail’ approach with a contingency work pack in place with:

  • An instruction developed for the removal and replacement of the failed master link;
  • The development of an inspection for the specialist tools to be used to remove the master link (a track pin press, correctly sized for the chain);
  • Identification of all tools and supporting equipment needed to complete the repair, and
  • Stocks of master links in the warehouse as a catalogue inventory item.

There is no one right approach, but whether it is scheduled inspection, fixed interval replacement or run to fail, the approach to be used needs to be determined based on the effectiveness of each strategy in meeting business outcomes, which in turn depends on the criticality of the apron feeder to overall operations. Another option would be to totally remove or reduce the number of master links in a chain, thereby reducing the need for maintenance, however, such and idea would need proper engineering analysis as part of a formal management of change process.

Other failure modes to consider

Some other failure modes worthy of consideration include:

Tail roller wear

Roller wear is typically caused by spill carried back into the tail by the chain. The spillage is caused by the sacrificial skirting on the feed chute being allowed to become worn away. In general, the smaller the gap between the sacrificial skirting and the flight plates, the less the spillage. Spillage also has direct influence on the tracking of the feeder and wear on the chains, , rollers, drive sprocket and tail rollers and therefore has a large financial impact on the maintenance budget, as well as the huge effort required to change-out the major components of the feeder. A periodic inspection and condition assessment/replacement program on the sacrificial skirting will support minimising the instance and impact of spillage and thereby help reduce component wear and increase component life.

Chain stretch

Chain stretch on an apron feeder can eventually reach the point that the chain stretches past its design point and snaps, causing significant down time. An appropriate inspection should be developed to take measurements on determining when chain tension needs to be adjusted and links replaced. A go-no-go gauge is available from OEMs to support measurement.

Snapped carry roller shafts

For some types of apron feeder, the design uses a large steel shaft with carry rollers pressed onto the ends of the shaft rather than the small single rollers to carry the chain as is typical in a Caterpillar based design. In one instance in our experience, a catastrophic failure occurred when one of the shafts snapped at a roller. The roller was carried down the chain until it stopped at the tail, jamming the tail roller. With no master links installed due to the chains being part of the flights, the drive kept trying to turn the feeder causing the tail of the apron feeder to break away from the structure and lift upwards like a banana until the chain broke. Even after the chain failure, the drive continued to operate causing the feed hopper to drop through the discharge chute, overloading the mill feed conveyor, bursting the discharge chute, burying the feeder, until the heap was high enough to block the feed hopper. This catastrophic failure resulted in five days of plant downtime while the apron feeder was repaired. If this type of design is installed, appropriate maintenance strategies need to be developed to ensure the integrity and continuing operation of the carry rollers.

Work management process failure

Sites will have often developed appropriate and effective maintenance programs for their apron feeders with detailed inspection sheets and comprehensive reporting that can include photographs, marked-up diagrams, and recorded measurements that would support subsequent decision making and the next course of required action. However, these inspections are of little value and present a risk to the business if the subsequent decision making is not made by an appropriate competent and authorised individual who can determine the course of action once a defect has been identified. This is where the Maintenance Planner and/or Supervisor needs to ensure that, when closing the associated Work Order, not only are all relevant details captured in the CMMS but that the relevant inspection reports are forwarded to an appropriate competent and authorised individual for subsequent decision making, i.e. not just placed in an archival storage box.

Where to from here?

Using this example of apron feeder maintenance, we can see how all process equipment are able to cause major production issues and costs if not properly maintained. Having the correct strategies in place to support your business needs can ensure that production downtime is minimised within accepted limits. As an asset management, maintenance and reliability consultancy, Assetivity can assist you developing and implementing the required strategies to ensure your assets are supporting you business objectives. Speaking to one of our expert consultants is an excellent way to start, as we can help to examine your specific challenges and provide advice on what action should be taken.

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How to align reward systems with strategic goals: Moving from a repair-focused to a reliability-focused culture

Tuesday, 08 June 2021 08:00

This is the third in a series of 6 articles on moving from a repair-focused to a reliability-focused culture. The full series includes:

Foster motivated attitudes towards change

Any form of change initiative must successfully address the question of “what’s in it for me” for those being asked to change. In other words, there must be some form of greater reward for individuals and groups if they adopt the new, desired behaviours, than if they continue to behave in the old, undesirable way. These rewards can be both financial and non-financial, but the most successful change initiatives incorporate a blend of the two.

It is also important to assess the existing financial and non-financial reward systems, and identify any elements of the existing reward systems which are incompatible with the desired behaviours.

Consider personal rewards when creating order from chaos

Another way of viewing the journey from repair-focused to reliability-focused culture is that outlined by Ledet, as illustrated in Figure 2. There are several things to point out in this model, in terms of incentives and rewards. First, put yourself in the position of being a tradesperson in a reactive maintenance environment. There are a number of personal rewards associated with working in this type of environment, such as:

  • The challenge and variety associated with never knowing what you will be working on next
  • The financial rewards associated with overtime and callouts
  • The personal rewards associated with being the “hero” that can fix breakdowns as quickly as possible, and get the plant back on-line
  • The satisfaction of being able to, at short notice, respond to the demands of production personnel – some would call this having a “customer focus”

 

Figure 2

 

If you then move into the Planned maintenance phase, with its focus on systems, rules, procedures and discipline, then all of these rewards disappear. In its place, from a tradesperson’s view, is routine, inspections, and minimal challenge. As one tradesperson once said to me – “It’s like Groundhog Day”. While there may be some people who relish the certainty that goes with this routine and discipline, it is unlikely to be the same type of person that thrives in the semi-chaos of a reactive maintenance environment – so there is a need to provide tradespeople with different rewards to replace those which they are now missing out on.

Money talks

A clear candidate, in order to align rewards with desired behaviour, is to remove the payment of overtime for callouts and for performing unplanned work. The best maintenance organisations in Australia now pay tradespeople a fixed salary, rather than hourly rates, thereby removing the financial reward associated with breakdowns and after-hours rework. At another organisation, moving tradespeople from hourly rates to fixed salaries had an immediate effect on shopfloor attitudes to callouts – where previously, tradespeople would, without question, attend to a callout, on the change, tradespeople would question the need for a callout, and take a proactive role in minimising the number of callouts required.

Other rewards that could be provided include the payment of bonuses for the achievement of target levels of planned work, reliability targets or other measures of desired performance – or providing awards or celebrations for these achievements, in the same way as many organisations already do for the achievement of safety targets.

Managing upskilling as a reward

Once the organisation moves from the planned maintenance phase into the proactive environment, then the opportunity exists to provide additional non-financial rewards associated with involvement in problem solving, the acquisition of additional skills associated with a focus on precision maintenance and the minimisation of rework – but even here, managers need to be sensitive to the possible concerns of tradespeople that their involvement in these types of activities will ultimately lead to downsizing of the workforce and them, or their workmates, being made redundant. Once again, those organisations that have been successful in moving into this phase frequently use contractors to perform less critical, and less skilled, maintenance tasks, and use this pool of contract labour as the source for any job reductions – thereby minimising any negative feelings that tradespeople may have towards involvement in these activities.

Conclusion

What about the situation in your organisation? Put yourself in the heads of your people – engineers, maintenance supervisors, tradespeople, production supervisors, planners? What are the financial and non-financial rewards that these individuals receive from the work that they do? Are these consistent with the new behaviours and culture that you are trying to encourage? What can you do to remove financial and non-financial rewards that are inconsistent with desired behaviours? What can you do to introduce financial and non-financial rewards that encourage new, desired behaviours? Unless you successfully address the question of “what is in it for me”, then any process and systems changes will ultimately be unsuccessful.

If you are looking for further tips to shift your organisation from a reactive to proactive culture, the other articles in this series may be able to help:

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How to build a business case for reliability improvement: Moving from a repair-focused to a reliability-focused culture

Tuesday, 01 June 2021 08:00

This is the second in a series of 6 articles on moving from a repair-focused to a reliability-focused culture. The full series includes:

Introduction

For Senior Executives to incorporate Reliability Improvement as a core element of their strategic plan, there must be a sound business case. Let’s examine how you might estimate the costs and benefits associated with a Reliability Improvement program.

Estimating the Costs of the Program

The cost of the program will very strongly depend on how well your current processes, practices, documentation and systems align with good reliability practices. For that reason, we strongly recommend that any organisation considering a Reliability Improvement program first perform a gap analysis against good practice. While this can be done using internal resources, this will often lack credibility at senior executive level, and so we recommend engaging external consultants to perform this gap assessment. This is a service that Assetivity provides, and we have performed more than 70 such gap assessments across a wide range of industries. Contact us if you would like more information.

Once you have identified the gaps that exist, you will need to develop an improvement roadmap which can then be used to develop a fully costed implementation plan. The costs may include an allowance for the cost of internal labour, as well as any external consultants or contractors that may need to be engaged. Once again, Assetivity can assist in this area if you feel that you do not have the required competence or experience internally to develop these plans.

Estimating the Benefits of the Program

This is likely to be a more difficult exercise than estimating the costs. Nevertheless, it needs to be done. The benefits may be both quantitative and able to be expressed in financial terms or may be more qualitative or unable to be expressed in financial terms. In this section we will discuss the quantitative, financial benefits. The benefits of improved Reliability include such elements as:

  • Increased Production Output
  • Reduced Operating Costs
  • Reduced Maintenance Costs
  • Deferred Capital Expenditure
  • Reduced Working Capital Requirements
  • Increased Product/Service Quality
  • Reduced Scrap/Waste

However you will need to estimate how much improvement there will be in these elements and convert this into financial terms. So you will need to consider such questions as:

  • How much is 1% extra production output worth to your organisation?
  • How much will reducing maintenance costs by 1% save (and will there be any increase in risks as a result)?
  • What is the $ value of improving product or service quality?

One model that can assist in performing this evaluation (at least for “for profit” organisations) is the Economic Value Add driver tree. Explaining how this works in detail is beyond the scope of this paper, but more information can be found online at various places, including valq.com/blogs/value-driver-tree-introduction-101/.

Essentially Economic Value Add (EVA) is a measure of the value of an organisation. It can be calculated by breaking it down into various subcomponents and then adding, subtracting or dividing these components by each other in order to derive the EVA. A sample of an EVA driver tree is illustrated in Figure 1.

Figure 1. EVA Driver Tree

Using this EVA driver tree it is possible to calculate the impact on EVA of changes to several factors, such as:

  • Increased Sales
  • Reductions in Costs
  • Reductions in Fixed Asset Values
  • Reductions in Working Capital/Current Assets

All of these changes will drive up EVA, but by differing amounts, depending on the specific organisation. This can then be used as a guide to identify the priority areas where improvements will provide the greatest overall financial benefit to the organisation. If you would like assistance to develop an EVA Driver tree for your organization, once again, contact us.

 

If you are looking for further tips to shift your organisation from a reactive to proactive culture, the other articles in this series may be able to help:

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How to ensure a long-term strategic focus: Moving from a repair-focused to a reliability-focused culture

Tuesday, 25 May 2021 08:00

This is the first in a series of 6 articles on moving from a repair-focused to a reliability-focused culture. The full series includes:

Introduction

Most maintenance organisations are looking to move their culture from a repair-focused culture to a reliability-focused organisation – but what are the characteristics of each of these types of culture? Some of these characteristics are listed in the following table.

Repair-focused Reliability-focused
Fix it Improve it
Firefight Predict, Plan, Schedule
Tradesman Business Team Member
Manage defects Eliminate Defects
Reduce Maintenance Cost Increase Uptime
Program of the month Continuous Improvement
Believe failures are inevitable Believe failures are exceptional
Give priority to breakdowns Give priority to eliminating failures
Many failures Few failures
Low level of planned work High level of planned work
High level of rework Low levels of rework
Poor reliability High reliability
High maintenance costs Low maintenance cost
Short term plans Long term plans
Become non-profitable Attract new investments

 

This series of articles outlines six prerequisites for moving from the left-hand column to the right-hand column of this table.

How to ensure a long-term strategic focus

The first point to make about Organisational Culture is that changing it is not a short-term activity. Significant, sustainable change in organisational culture takes at least 5 years and potentially up to 10 years in some organisations. Given the propensity of some organisations today to rotate managers through operational positions with a two-to-three-year spell in any one position, it is unlikely that any one manager will succeed in significantly and sustainably changing the culture within their area of responsibility – but many try.

What is required is a constancy of purpose that transcends short-term fluctuations in organisational circumstances, and changes in personnel. This, therefore, requires the achievement of a reliability-focused culture to be a core element of the organisation’s strategic vision and plan. And this, in turn, requires the senior leadership team (potentially including the board of directors) to be convinced of the merits of this initiative – not just one individual. We will discuss how to go about achieving this later in this paper.

Further, if success is to be achieved, it is essential that the strategic vision is communicated throughout the organisation, and that the sense of purpose is “internalised” within all personnel within the organisation – everyone is committed to, and driven by, the achievement of this purpose, or goal. For this to occur, the purpose or goal must be inspirational – it must appeal to our higher order psychological needs and wishes. It goes without saying, that for this purpose to appeal to us, achievement of the goal must provide “something in it for us” for all within the organisation. And a critical role required of a leader within the organisation is to formulate this goal with reference to the needs of those working within the organisation, build commitment to the goal, and use the goal to shape the future organisation. While a sound business case for the improvement initiative is necessary, it is not sufficient. If we want true commitment from all employees, it needs to be supported by emotionally appealing reasons for change. For a more in-depth discussion of selling the value of reliability to senior executives (and others), see our article on selling the value of reliability improvement to senior management.

What we need to do is to establish what Collins and Porras, in the Harvard Business Review of September/October 1996, described as the “Core Ideology” of an organisation. They argued that this “Core Ideology” could be considered to consist of two parts – Core Values (which consisted of 3-5 timeless guiding principles which require no external justification, they have intrinsic value), and a Core Purpose, which is a simple statement which captures the organisation’s reason for being, and reflects people’s idealistic reasons for doing the company’s work.

In this article, they gave examples of organisations’ core values and core purposes as follows:

Core values

Sony

  • Elevation of the Japanese culture and national status
  • Being a pioneer - not following others, doing the impossible
  • Encouraging individual ability and creativity

Walt Disney

  • No cynicism
  • Nurturing and promulgation of “wholesome American values”
  • Creativity, dreams and imagination
  • Fanatical attention to consistency and details
  • Preservation and control of the Disney magic

Core purpose

  • Sony: To experience the joy of advancing and applying technology for the benefit of the public
  • Walt Disney: To make people happy
  • 3M: To solve unsolved problems innovatively
  • Nike: To experience the emotion of competition, winning and crushing competitors

It is the role of a leader to identify and nurture these core values and purpose, and through the identification of, according to Collins and Porras, Big Hairy Audacious Goals (BHAG’s) that are consistent with these value and purpose, make them more tangible, and use them to drive the organisation forward with unity of purpose.

These BHAG’s can have several forms, including:

  • Qualitative: Democratise the automobile (Ford, early 1900’s)
  • Quantitative: Become a $125 billion company by the year 2000 (Wal-Mart, 1990)
  • Common enemy thinking: Crush Adidas (Nike, 1960’s)
  • Role model: Become the Harvard of the West (Stanford University, 1940’s)
  • Internal-transformation: Transform this division from a poorly respected internal products supplier to one of the most exciting, respected and sought-after divisions in the company (Components Support Division of a computer products company, 1989)

Consider your own organisation, for a moment. What are the core values and core purpose of your organisation and what is its BHAG? What is your organisation’s long-term plan for achieving your BHAG? If you have trouble clearly defining these, then you leave yourself open to random external influences, forever drifting from one “Program of the Month” to the next, making large scale changes in reaction to relatively minor external events.

Now that you are thinking long-term, you are ready to take the next steps towards achieving a reliability-focused culture. The next articles in this series will help you on this journey:

 

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The Do's and Don'ts of Effective Maintenance Planning

Tuesday, 01 May 2012 12:41

Most asset-intensive organisations recognise that efficient and effective maintenance Planning and Scheduling is one of those cornerstone processes that can help assure equipment reliability and assist with attaining excellence in operations.  The benefits of good Maintenance Planning and Scheduling are numerous, and include:

  • Increased productivity of tradespeople
  • Reduced equipment downtime
  • Lower spare parts holdings
  • Less Maintenance rework
  • and many more…
 

Are your KPIs supporting your processes or are they only measuring the outcomes?

Thursday, 21 January 2021 08:29

Traditionally KPIs focus on the outcomes of our various processes, if however we hope to manage those processes for more predictive outcomes, we need to develop a KPI framework that supports our processes.

 

What does a good Asset Management Strategy look like?

Thursday, 27 August 2020 09:37

 In an earlier article: Asset Management Strategy vs Strategic Asset Management Plan (SAMP) – A Practical Approach, we recommended that an organisations strategic approach to Asset Management be split amongst two documents:

  • An Asset Management Strategy, which outlines the high level, strategic approach that the organisation takes to Asset Management. In other words, how it proposes to manage its assets
  • A Strategic Asset Management Plan, which contains the longer-term, higher level strategic initiatives that the organisation must take in order to execute its Asset Management Strategy.

Taking this approach results in documents that are shorter in length and are:

  • Aimed at different audiences for different purposes, and therefore more likely to be used
  • Able to be more easily updated, and therefore more likely to be current and relevant.

In this article, we go into more detail regarding what a good Asset Management Strategy document may look like. In another article, What Does a Good Strategic Asset Management Plan Look Like?, we discuss the key elements of a good Strategic Asset Management Plan. 

 

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Are your KPIs supporting your processes or are they only measuring the outcomes?
Traditionally KPIs focus on the outcomes of our various processes, if however we hope to manage those processes for more predictive outcomes, we need...

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