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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:

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

Variation in Operating Parameters 5. design of an industrial machine is a matter of trade offs. 4. . Natural Degradation 2. Life cycle costs much lower. Though there are many cases. No diameter & change original shaft recurring cost. Such causes are the basis of failures. Life enhanced to 10 years. the underlying cause of the first six causes as listed above is Root Design Imperfections. This is more so. 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. Maintenance free. Human Factors 3. 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. However. since industrial equipment design cannot be standardized as functional requirements and local requirement vary from case to case. Recurring Cost. Tackling delays.3. intermediate difficulty. Then the overall effect of DOFR in an industry is shown and discussed. all cannot be discussed due to space limitations. 6. 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. Root Design Imperfections like unclear parameter definition. low inventory. 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. Tolerance Stacking 4. delays and wastages in an organisation where technology is one of main factors of production. design morphology. Material Incompatibility of spares. higher difficulty and two problems from each category are selected as illustrations. 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. the problems are divided into three types: simple. material. compromises and optimization and at times invalid assumptions leading to imperfections. material incompatibility. Hence at times. Hence. Moreover. Reasons for Equipment failures 2 The reasons for equipment failures may be summed up in the following manner: 1. No loss of shoulders < 5% change in Cost equal to productivity due to shaft breakage. inappropriate signals etc. Local factors 7. energy transfer. Simple Examples: a) Problem: A shaft fractures within 3 to 6 months of operation from the bearing shoulder area. DOFR Redesign the shaft with One time cost. Table 1 Method Actions Cost Effects Traditional Replace shaft as it breaks High Loss of productivity.

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

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

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

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. Thereafter the company gains ongoing benefits.e. but there are over 6000 such effects described in scientific literature 3.83 Lakhs Rs 177. Companies need to do the improvements only once. Table 7 Sr. 6. 2. Prerequisites 1. Research shows that the average engineer knows 50 to 100 physical and chemical laws.85 Lakhs 8 Annual Mean Maintenance Labour Hours in a year 4675. principles and effects to solve engineering problems.5 σ 6σ 12 Leadership Position 4Th 1st (sells at premium) It is interesting to note that over a period of five years. .87 T/hr 11 Quality 3.16 hours of the jobs would be completed within this time) 6 Maintenance Manpower 126 107 7 Spares cost Rs195.5 % 4 Median Corrective Maintenance Time (i. Also note the reduction in cost as reflected in the maintenance budget (a reduction of about 58%) and the improvement in quality.66 T/hr 1. And maintenance effort is also reduced to the minimum.87 hours 9 Maintenance Budget Rs 3. quality and cost reduction (the key factors to face competition). market forces have pushed down the company’s selling price almost to the extent of 20%. 5. This has been possible through continuous improvement in reliability of equipment and productive system and subsequent rise in sustained productivity. 4. It follows that maintenance planning is reduced to the minimum. It means that investigators need to know in depth the physical and chemical laws. failures/month) failures/month) 2 MTTR (Mean Time To Repair) 4 hours 2 hours 3 Steady State Availability (Markov Analysis) 96.86 hours 7. principles and effects which can be used for solving engineering problems.4 Crores Rs 1. Advantages 1. Without market demands innovation is not possible since innovation is a response to customer demands.66 hours 3108. With design imperfections removed and functionality improved. 50% of 2. Investment made in DOFR will pay for itself.e. It needs a management team that believes in innovation and is market driven. quality is improved and the process is also made more stable. 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. 95% 10.41 Crores 10 Production rate 1. But even with lower selling price the company is making more cash gains than they did when selling prices were higher. 2.49 hours 1.10% 99. Recurring cost of maintenance is reduced to nil or minimum. 3. 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.64 hours the jobs would be completed within this time) 5 Maximum Corrective Maintenance Time (i.

7. International Journal of COMADEM. Therefore. 4. Conclusions 1. 6(3) July 2003. References 1. DOFR’s concept of redesign may be applied to all types of potential failures so that the intrinsic life (reliability) is enhanced. 6. 2. internal note of RMC 2. U. PP. 19-24 3. maintenance effort is greatly reduced and maintenance planning is simplified and optimized to the barest possible. McGraw Hill International Editions.. WM Engineering Ltd. Potentially this feature may useful to downsized companies. 2003. 8. Engineering knowledge base (a new factor of production) of the organisation is greatly improved.. Chairman.K. George E. the approach would gain a bad name if applied by less competent/untrained people. 5. This of course has been the problem that has plagued CBM and indeed maintenance improvement generally 1. DOFR is a better method when compared to the existing methods since one only needs to make the improvement once to gain ongoing benefits. observing the system as a whole and design thinking. Quality losses due to malfunctioning of equipment are minimized. However. 168 9. Thru the application of DOFR. 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. Discussion notes and comments of Prof. so are the delays and wastages. 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. 3. Engineering Design. Tim Henry. Operational cost is minimized. (2003). Dibyendu De. On continuing application organisations would become highly competent to engineer new technology as and when the need comes to gain competitive advantage. 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). . It would help an organisation to respond to competitive forces effectively within a short time. 2000. DOFR extends this to all modes of failures affecting business performance thru the understanding of the complex interrelationships between different modes of failures. 3rd Edition. Manchester. 7. Oct. PP. Minimizing Equipment ‘Failures’ To Gain Competitive Advantage. Dieter.