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Design Out For Reliability & Long Term Profitability

Dibyendu De
Principal Consultant, Reliability Management Consultant, Kolkata, India
Email: rmc@satyam.net.in or dde@rmcglobal.com

Abstract

How do companies prosper? Most of us know the answers. Reduce costs. Improve quality. Utilize existing
technology to the maximum. Unfortunately, most of the present methods do not fulfill the objectives
comprehensively. For example, Total Productive Maintenance (TPM) accepts a machine as it is and tries to
ensure basic maintenance and operating conditions to prevent accelerated degradation and failures. On the
other hand, Reliability Centred Maintenance (RCM), now an integral part of TPM development, tries to
prevent or take safeguards against the consequences of failures and operate the machines within their
design limits. However, the RCM process may be best described as a method of living with the imperfect
which leads to reducing operating costs from their present levels but rarely tackles the root design
imperfections 1.

The new approach presented in this paper called Design Out for Reliability (DOFR) goes straight to the core
of reliability issue to address design shortcomings by introducing improvements. This is a better method
when compared to the existing methods since one only needs to make the improvement once to gain
ongoing benefits. In contrast the use of Condition Based Maintenance (CBM) or Time Based Maintenance
(TBM) is an ongoing activity with recurring costs which aims at reducing the effects of unreliability, not
improving the reliability itself 1. The key feature of the new approach DOFR is to tackle unreliability not its
effects or consequences? That is we tackle the root cause that causes problems in business operations not
its symptoms.

However, there are two prerequisites for implementation of DOFR. First, a management team that believes
in innovation and is market driven. Second, the approach would need investigators who are very competent
and knowledgeable and are provided the time and funds to do the analysis/synthesis to make the
improvements 1. Clearly it may be applied to companies that see the entire operation of an organisation as a
dynamic system and believe that the investment will pay for itself.

With DOFR, we apply the concept of redesign to all types of potential failures that causes problems in
business performance. However, in this paper, we would only discuss the issue of equipment reliability with
examples since in modern manufacturing ‘managing equipment effectively’ is a fundamental factor of
production. In the now traditional approach only those failures that were not age related and were also not
susceptible to condition monitoring were treated to reliability improvement through design out. DOFR
extends this to all modes of failure related to equipment that affect business performance.

1. Introduction

Improving reliability means freedom from failures. This is done by improving the life of a component,
machine or event. There are various types of failures in an organisation. Equipment fails. Quality fails.
Process fails. Product fails and so does safety. Needless to stress that improvement in one aspect leads to
the improvement of other aspects as well. However, there still remains a need to develop reliability of each
of these aspects individually. Whatever aspect, the organisation chooses to improve, the improvement in
reliability has far reaching effects like the following:

DOFR redesigns equipment management system customized for an organisation. 2. TBM. Innovative capability and Knowledge base of an organisation. Thus DOFR as an approach overcomes such difficulties. not improving the reliability itself. It does not attempt to improve or extend the useful life to the maximum possible limit. it relates various faults and connects other issues of organisational growth and performance. Improvement in Human Talent. the answers to ‘How a company becomes a winner in the market place’ lies within the organisation itself and improvement of reliability in all aspects of the organisation holds the key to such answers since there would always be a physical limit on ‘economies of scale’ and ‘scaling up of technology’. both CBM and TBM are not very concerned with ‘good operations’. Moreover. RCM. On the other hand. 4. Reduction of cost and improvement in profits 2. Moreover. present maintenance planning is also not very concerned about improving the other important issues of organisational performance like quality. The use of CBM or TBM in contrast. and the consequences of those failures. It helps determine the most appropriate. Moreover. . Improvement in Productivity and Cost effectiveness of internal processes of an organisation. The main objectives of RCM are to reduce operating costs from existing levels and reduce the consequence of equipment failures. It treats problems in an isolated way as they surface thru small improvements – called ‘Kaizens’. In short. not directly the failures. fails to discover/anticipate potential problems thru system study (studying equipment as a whole) and solve potential modes of failures simultaneously (in one go). shortcomings and limitations. It is more concerned with detection rather than aim for a permanent solution to the problem. Similarly. It therefore. It tackles a part of the problem but not the whole. cost-effective proactive maintenance strategies to counter the effects or consequences of such failures. TPM …. DOFR approach goes straight to the core of reliability issue to address design shortcomings by introducing improvements. 1. Hence. technology improvement and the like. markets and products 3. is an ongoing activity and with recurring costs which aims at reducing the effects of unreliability. the practitioners of CBM are not very inclined to establish relationships between the various problems or disturbing factors. The key feature of DOFR approach is to tackle unreliability not its effects or consequences. Improvement in Information management Clearly. In addition. Improvement in Quality. TPM aims to restore equipment to its original condition and maintain good operating condition and maintenance skills to prevent failures from taking place. This is because CBM focuses on detection of various faults that develop during operation. We would examine the effects of DOFR on organisational performance and leadership position thru examples. a necessary effort for a permanent solution. the present maintenance management strategy and planning is flawed and gives a very limited impact on organisational performance. 6. RCM may be described as a method of living with the imperfect which leads to reducing operating costs from their present levels but rarely tackles the root design imperfections 1. This is a better approach because one only needs to make the improvement once to gain ongoing benefits and reduce maintenance activities. Therefore. TBM is concerned with discarding/replacing a machinery element at predetermined interval with the assumption that the useful life of the element is over. Improvement in Technology. CBM. The process focuses on the root cause not its symptoms. RCM is a method of studying ways in which a system’s functions can fail. Safety and Environment 5.

higher difficulty and two problems from each category are selected as illustrations. Material Incompatibility of spares. energy transfer. Local factors 7. Such causes are the basis of failures. design of an industrial machine is a matter of trade offs. Though there are many cases. DOFR Redesign the shaft with One time cost.3. since industrial equipment design cannot be standardized as functional requirements and local requirement vary from case to case. Moreover. design morphology. the underlying cause of the first six causes as listed above is Root Design Imperfections. 6. Human Factors 3. No diameter & change original shaft recurring cost. intermediate difficulty. Recurring cost RCM Monitor the shaft for Cost lower than If opportunities are not available then there fractures and replace Traditional method is a loss of productivity otherwise only a during opportunity by not eliminated cost of replacement is incurred. Then the overall effect of DOFR in an industry is shown and discussed. Maintenance free. Life enhanced to 10 years. Natural Degradation 2. material. the problems are divided into three types: simple. The objective of DOFR is to remove or tackle all such imperfection in a step by step manner by following a systematic but flexible methodology. Simple Examples: a) Problem: A shaft fractures within 3 to 6 months of operation from the bearing shoulder area. Hence at times. delays and wastages in an organisation where technology is one of main factors of production. Reasons for Equipment failures 2 The reasons for equipment failures may be summed up in the following manner: 1. inappropriate signals etc. Root Design Imperfections like unclear parameter definition. Tackling delays. The methodology is flexible in the sense that it varies in relation to an organisation’s degree of reliance on technology to produce its products and slowly over time evolves a customized system relevant to an organisation to meet its business challenges. No loss of shoulders < 5% change in Cost equal to productivity due to shaft breakage. compromises and optimization and at times invalid assumptions leading to imperfections. Table 1 Method Actions Cost Effects Traditional Replace shaft as it breaks High Loss of productivity. . This is more so. low inventory. Variation in Operating Parameters 5. 4. wastages and failures is the answer to enhanced organisational performance since there is always an effective upper limit to ‘economy of scale’ and ‘equipment scaling’ once a factory is set up. Hence. However. Recurring Cost. all cannot be discussed due to space limitations. Tolerance Stacking 4. Life cycle costs much lower. Cases and Examples The concept of DOFR may be illustrated thru real life cases and examples. considerable investments are needed to improve economy of scale. material incompatibility.

DOFR Redesign with oil One time cost. Life approximately one year. No account the principles of Moment of cost. Table 3 Method Actions Cost Effects Traditional Replace motor as and when it burns High Loss of productivity. Life cycle cost much lower. Creates a lot of dust and causes secondary damages to other elements of the conveyor system. burns out randomly (approximately once a year) and the belts become slack at regular interval (more-or-less after every three months or so). Recurring out and adjust/replace belts regularly. d) Problem: Dry hot abrasive material falling on a rubber conveyor belt from a chute. the shaft for method otherwise cost of replacement is fractures and replace during incurred. Recurring cost and when it breaks. otherwise only a cost of during opportunity Recurring cost remains. replacement is incurred.b) Problem: A grease lubricated bearing of a high speed fan seizes frequently. RCM Monitor bearing life Cost lower than Traditional If opportunities are not available with vibration method (since opportunity then there is a loss of productivity monitoring and replace utilized) but not eliminated. Makes inspection difficult due to unhygienic condition and dusty atmosphere in an enclosed space. Replace Traditional then there is a loss of productivity belts every three months. Inertia and radius of gyration. Maintenance free. RCM Monitor motor to determine the Cost same as If opportunities are not available optimum replacement time. Problems of intermediate difficulty: c) Problem: A motor driving a crusher main shaft thru pulley and belt mechanism. Maintenance free. Recurring Cost. cost. . recurring cost. Life enhanced to three years. opportunity DOFR Redesign the pulley size taking into Low one time No loss of productivity. No lubricating system loss of productivity No recurring since D x N > 3500. Recurring Cost. cost. Table 2 Method Actions Cost Effects Traditional Replace bearing as High Loss of productivity. low inventory.

High found or after a breakdown. RCM No definite answer. Secondary damages high. recurring cost. High damaged were inventory. There were 28 reported cases in a period of one year. The average current consumption was 12 amps which at times shot to 18 amps. No loss of productivity. No cleanliness levels and monitor wear of solution. High and costly bearings. No velocity of falling material to that of the belt. tolerances and eccentricity during fitting. DOFR Use heater in the lubrication sump to lower No cost. Low inventory. Problems of Higher Difficulty: e) Problem: In a steel mill. f) Problem: In a particular conveyor of a steel mill. Table 5 Method Actions Cost Effects Traditional Pay attention to lubrication. Table 4 Method Actions Cost Effects Traditional No definite answer. No recurring cost. High fitting and tolerances. Maintenance effort nil. Very low inventory. RCM No answer. Inspect whatever best was cost. which was not possible due to inventory. Pay attention to maintenance efforts. the motors usually tripped at least once a month. Clean regularly by High Loss of productivity. High maintenance effort. DOFR Redesign the system by matching the Practically No loss of productivity. no cost. There were cases of many bush bearing failures and failure of other components. within 93 to 95 cSt. journal bearings seized rather randomly. No maintenance effort. maintenance effort. Recurring planning and strategies. cost. Probably monitor High Productivity loss continues. High inventory. Life enhanced to more than 4 viscosity of the oil entering the bearings years. No reduction in inaccessibility and costs. Replace when the bearings recurring costs. Only better maintenance High Loss of productivity. Secondary damages high. possible and replace when defects were High inventory. No secondary damages. High maintenance imported efforts. . Recurring casual workers. Pay attention to Very high as High loss of productivity.

No failures of other system. replace. inspect. After an integrated effort of the application of DOFR the number of failures came down to one failure per month for the critical machines (46 in number). High maintenance efforts. of Breakdowns(Avg/month) 30 Number 20 No. This company was having on the average of 24 failures a month with their critical machines. But the system is still far from perfect. No. . High. Average current consumption entire equipment as a dropped to 8 amps. the solution costs. The graph (1) below illustrates the result achieved over a period of four years. RCM Monitor. High recurring Monitoring did not help. Higher did not work inventory. High recurring costs. Table 6 Method Actions Cost Effects Traditional Lubricate. Higher inventory not reduce. replace High. The accompanying table (Table 7) presents a comparative analysis of the some important parameters of improvement. No maintenance effort. Overall effect of DOFR: When DOFR was applied to a chemical company the results were impressive. DOFR Redesign thru small viable Very low No tripping observed for five months after modifications taking the modifications. More work is to be done to achieve better results. since Loss of productivity. since Loss of productivity continues. Less inventory. components. of Breakdowns(Avg/mo 10 nth) 0 1st Yr 2nd Yr 3rd Yr 4th Yr Years Graph 1 The graph also shows the consistency achieved. High failures did maintenance efforts.

It needs a management team that believes in innovation and is market driven. Parameters of Audit Before 1998 After (May 01) No 1 Reliability (Moving Reliability Index) –only 75% (24 95% (One/Zero considered for critical flow path.49 hours 1. It means that investigators need to know in depth the physical and chemical laws.87 hours 9 Maintenance Budget Rs 3. Companies need to do the improvements only once. With design imperfections removed and functionality improved. 3.10% 99. 6. quality and cost reduction (the key factors to face competition). quality is improved and the process is also made more stable. 4. Research shows that the average engineer knows 50 to 100 physical and chemical laws. principles and effects to solve engineering problems. DOFR would need investigators who are competent and knowledgeable and are provided the time and funds to do the analysis/synthesis to make the desired improvements.16 hours of the jobs would be completed within this time) 6 Maintenance Manpower 126 107 7 Spares cost Rs195.66 T/hr 1. Also note the reduction in cost as reflected in the maintenance budget (a reduction of about 58%) and the improvement in quality.66 hours 3108.4 Crores Rs 1. It follows that maintenance planning is reduced to the minimum. failures/month) failures/month) 2 MTTR (Mean Time To Repair) 4 hours 2 hours 3 Steady State Availability (Markov Analysis) 96.87 T/hr 11 Quality 3.5 % 4 Median Corrective Maintenance Time (i.64 hours the jobs would be completed within this time) 5 Maximum Corrective Maintenance Time (i. This has been possible through continuous improvement in reliability of equipment and productive system and subsequent rise in sustained productivity.e. Advantages 1. but there are over 6000 such effects described in scientific literature 3.85 Lakhs 8 Annual Mean Maintenance Labour Hours in a year 4675. Investment made in DOFR will pay for itself.83 Lakhs Rs 177. But even with lower selling price the company is making more cash gains than they did when selling prices were higher. 50% of 2. Table 7 Sr. 2.86 hours 7. Prerequisites 1. Recurring cost of maintenance is reduced to nil or minimum. Without market demands innovation is not possible since innovation is a response to customer demands. 5. 95% 10. Note that management with a sharp focus on reliability improvement of equipment achieved market leadership position from a lower position in about two years time.41 Crores 10 Production rate 1. principles and effects which can be used for solving engineering problems. 2. Thereafter the company gains ongoing benefits.e. And maintenance effort is also reduced to the minimum. .5 σ 6σ 12 Leadership Position 4Th 1st (sells at premium) It is interesting to note that over a period of five years. market forces have pushed down the company’s selling price almost to the extent of 20%.

Notes: DOFR is a part of the overall organisational reliability improvement plan which is named as ROMS TM (Reliability of Manufacturing Systems TM or Result Oriented Management Systems TM ) developed by RMC. However.. observing the system as a whole and design thinking. Oct. DOFR’s concept of redesign may be applied to all types of potential failures so that the intrinsic life (reliability) is enhanced. This of course has been the problem that has plagued CBM and indeed maintenance improvement generally 1. Discussion notes and comments of Prof. U. Operational cost is minimized. 6(3) July 2003. References 1. 2000. the companies would be not only be able to reduce their operating costs to the minimum but also achieve and sustain a very high level of quality (6σ). PP. 4. so are the delays and wastages. Minimizing Equipment ‘Failures’ To Gain Competitive Advantage. In the now traditional approach only those failures that were not age related and also not susceptible to condition monitoring were treated to reliability improvement thru design out. the approach would gain a bad name if applied by less competent/untrained people. Dibyendu De. Conclusions 1. maintenance effort is greatly reduced and maintenance planning is simplified and optimized to the barest possible. 168 9.7.. Quality losses due to malfunctioning of equipment are minimized. 3rd Edition. It would help an organisation to respond to competitive forces effectively within a short time. 6. 2. International Journal of COMADEM. . Dieter.K. Thru the application of DOFR. George E. DOFR extends this to all modes of failures affecting business performance thru the understanding of the complex interrelationships between different modes of failures. 2003. internal note of RMC 2. DOFR is a better method when compared to the existing methods since one only needs to make the improvement once to gain ongoing benefits. Chairman. On continuing application organisations would become highly competent to engineer new technology as and when the need comes to gain competitive advantage. 5. Potentially this feature may useful to downsized companies. (2003). PP. Tim Henry. Manchester. McGraw Hill International Editions. Engineering Design. Therefore. 19-24 3. 3. 8. Engineering knowledge base (a new factor of production) of the organisation is greatly improved. 7. WM Engineering Ltd.