Master of Business Administration-MBA Semester 4OM0015 – Maintenance Management

Assignment Set- 2

Q1. What are the maintenance planning principles? How they contribute to the success of planning?

Ans: Maintenance Planning Principles

The principles or paradigms that are evolved over the maintenance mission will profoundly affect planning. These principles must be understood by all concerned to have effective planning process. The principles of having planning as a separate department in order to focus on the future work and consequent use of planner‟s expertise to create estimates, recognizing skill of the craftsman and measuring performance must be understood by every one concerned with production. There is a methodology of work measurement what is commonly known as wrench time and this frequently misunderstood principle and hence must be made clear to everyone concerned. Each principle identifies important crossroads. Decisions making at each crossroads on the alternative ways to conduct planning and execute is essential and ultimate success of planning depends on this situational oriented decision.

Planning Principles

There are six principles of planning and these are:

1. Organising planning functions with separate responsibility and identity.

2. Making planners to concentrate on future works as one of their primary tasks.

3. Asking planners to maintain simple base files as part of their work systems.

4. Training planners to expertise their job and dictate the job requirements through their dedicated work plans.

5. Helping planners to recognise the skill of the crafts required and arrange.

6. Organising planners to work sample their tasks while execution and hence measure the planning effectiveness.

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Let us look into each of these in detail:

1. Organising planning functions with separate responsibility and identity

In this principle, the planning function is organised as a separate function. Personnel who are most experienced and having expertise as craft maintenance crew are selected and assigned to the planning section. This type of selecting within the department and assigning a separate function will further facilitate specialisation not only in planning processes, but also focuses on the future works to be executed.

It is better that these identified Planners report to a different supervisor who will be responsible to providing direction and has an obligation to complete the assigned work in an expeditious manner, with a minimal interruptions.

The planners should engage in preparatory works. Planning activities must flow smoothly across the maintenance department. Planners need to work closely with the maintenance crew for proper execution of work with consistency. The crew members will focus exclusively on executing assigned work, and gain advantageous position as all the preparatory works involved is accomplished by concerned planner.

Planning contributes to scheduling also. This scheduling is done in such a manner that the maintenance department will utilise all their resources optimally. The lack of planning effort may decrease the number of work assignments to crew members.

2. Making planners to concentrate on future works as one of their primary tasks

Principle of planning is forward thinking with a foresight. By preparing jobs in advance, the planning facilitates improvement in labor productivity and allows the maintenance crew to start their assigned job without waiting for any resources or with blockages.

After assigned job is completed, the lead technicians or the supervisor gives feedback to the Planning section. The feedback consists of any problems the crew faced while executing the work, any changes they did in the original plan during the execution, and any other information for the planner to use in preparing future plans and schedules. The planners ensure that they will use this feedback in their future planning to improve the overall effectiveness. This valid feedback information as a record is filed separately for their future reference and use.

3. Asking planners to maintain simple base files as part of their work systems

Planning maintains a simple and secured file system, with the file code numbers indicated on it. A separate file is created for each equipment or machinery that is available in production shops and those within the purview of the planning section. Each file will have proper indications of the specific tag number of such machines. This type of file system enables planners to utilise the equipment data and the experience of the previous

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work. It also helps planners to prepare and improve the future work plans. The cost incurred for each of the previous tasks is also recorded in these equipment files.

In case any decision was taken to replace the equipment or its costly parts, the same is also recorded. As the majority of the maintenance tasks are repetitive in nature over a period of time, this type of maintaining exclusive files with information of work plans, cost and so on, will help assists planners or plant engineers to take suitable decisions on the repair or replacement. All concerned are duly trained on how to use the information from these file for decision making.

4. Training planners to expertise their job and dictate job requirements through their dedicated work plans

Planners use their personal experience and the information available in the file system, as explained above, to develop work plans. Primary responsibility of planners is to avoid anticipated work delays through their plans that include the requirements of quality and safety. To prepare such job plans, which improves the overall productivity, planners will rely greatly on their personal skills and experience, apart from using the existing data or information in the equipment files. In case of any unusual maintenance tasks must be carried out and earlier such issues have not propped up, the planners will then consult and take necessary help from Plant Engineering or Production departments.

5. Helping planners to recognise skills of the crafts required and arrange

The Planning section should recognise skills of the crafts required when firming up the scope of the maintenance work. Planners obtain clarifications from the indenting section as to what skills they propose to have in the person for such maintenance jobs. They also ask the intending sections for suggestions, which will help in having a better coordination. The planners then evolve the general strategy for the work to be done such as repair or replace, preventive or breakdown policy. In case procedures for carrying out a job are not specified in the system file, the planners must also evolve a strategy to lay out the procedures for carrying out that job.

This principle dictates that planners calls for a minimum craft skill in the job plan and hence, it depends on the available workforce being sufficiently skilled to execute the job. Accordingly, the craft technicians will use their expertise to make the specified repair or replacement.

Here again the planners and technicians work together over repeated jobs to develop better procedures and checklists. Supervisors must train technicians, wherever applicable and give proper support and guidance. Technicians must execute the job as planned without much deviation. Any deviations from the job plan is required, there must be an approval from the planner before proceeding.

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Planners give information required for supervisor to schedule the job and control required while executing. Skilled technicians give the feedback on the executed job plans, thus contributing additional information for future plans.

6. Organising planners to work sample their tasks while execution and hence measure the planning effectiveness

Wrench time is the measure of workforce efficiency and also Planning and Scheduling effectiveness. Wrench time is the proportion of available time -to- work time, when craft technicians are working on a job as planned. Any delay such as waiting for specific job plan, clearance or approvals, machine parts, tools, issue of instruction sheets, traveling to work spot, coordination required with other crafts, or equipment non availability to start the work and so on are all discounted from the wrench time before deciding on the effectiveness.

This principle dictates measurement of how much of time craft technicians have actually spent on their job site versus non productive activities, which determines the effectiveness of the planning program.

Intermediate work sampling of the wrench time gives the measure of how much the planning is helping in the process. Actual wrench time of all the technicians put together is the actual productive time. The deductions made in the wrench time due to delays are non productive time. A detail analysis is done by the planners on the non productive time. Any reduction in the non productive time will help improve the productivity and hence, planners analysis and action is desired.

Measuring wrench time will also summarise as to how well the other principles are utilised in the process of completing the jobs assigned. Accordingly, the wrench time analysis is an indicator of the effectiveness of the plan, system, and the processes adopted by the maintenance department. As this measurement is critical, it must be as accurate as possible and recorded data can be statistically analysed, which may help in decision making.

Q2. Explain briefly the ABC classification and reasons behind recommending ABC and VED classifications for managing inventory of spare parts for maintenance?

Ans: Inventory of production items, components, and aggregates are classified into groups based on their relative importance with respect to availability, the economy or the lead time for procurement. Inventory items are classified and controlled based on some criterions.

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The following are some of the inventory classifications used for production items:

• ABC Analysis Always Better Control of values.• HML Analysis High, Medium and Low unit prices of items.• VED Analysis Vital, Essential and Desirable items.• SDE Analysis Scarce, Difficult and easily available items.• FSN Analysis Fast, Slow and Non-Moving items.

While there are many classifications like the ones indicated above, the method used for classification for inventory control of spare parts are:

• ABC.• VED.

ABC analysis

The inventory of spare parts which are required to cater many machines and equipment in production units usually consists of thousands of items with varying prices, usage rates, and the lead time to supply after ordering. Hence, it is neither desirable nor possible to pay equal attention to all items.

ABC analysis is a basic analytical tool, which enables the maintenance management to concentrate its efforts where results are always greater. ABC analysis suggest the classifying of all inventory parts into three categories A, B, and C on the basis of the annual movement of spare parts for maintenance activities. Given below are the brief explanations of each.

A class items

These items constitute about 10% of the total number of parts and account for about 70% of the total money spent on inventories. In costly equipments, like, air compressors and diesel generators set, the costly items are the rotor shafts and engine block respectively. In each of these, the requirement for the department may be one in number and in two to three years time for replacement action. Here, the cost of replacement of such an item will be very high. Similarly, replacement of a transmission or gear box, chassis in the truck and wheels, form the A class spares that may be stocked for emergency break down maintenance, as they are not going to move regularly.

B class items

These items generally constitute about 20% of the total number of items and about 20% of the total cost of inventory. These are generally intermediate items. B class items in the equipment generally include the axle rods, differential gears, spindles and head stocks.

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C class items

These items constitute about 70% in numbers but account for only 10% of the total cost or purchase in the inventory. In machinery, the items like bearings, gaskets, filters, pins, bolts, nuts, washers, springs, plastic parts, belts, chains, and pulley block come under the C class items.

The above mentioned percentages versus the values have been represented as a graph in as shown below for a better understanding of the same.

Percentages Vs Values of A, B and C items

Features of A, B, C items

Now that we have read about the ABC analysis and the distinguishing factor that classify the entire inventory parts into three categories A, B, and C; let us look into the features of each of these items. The features have been provided in a tabular format for easy understanding as shown in table

Table :Features of A, B, and C items

A Class Items B Class Items C Class ItemsFew in number Moderate in number High in numberHigh in value Moderate in value Low in valueRigid control required Moderate control Least controlLow safety stock Medium safety stock Large safety stockOrdered frequently Ordered less frequently Bulk ordersContinuous check required Occasional checks Hardly any check

Multiple sources developed

A few sources developed Two of three reliable sources developed for each category

C class items of production are of low value and of less consumption and hence planned with low service levels, because the non availability of such items may not stall the entire production. Moreover, since most of them are available off the shelf, the immediate requirements could be purchased.

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As compared to the C class item in production management, C class for maintenance may be vital for the proper functioning of the equipment. This implies that it may prevent the entire equipment from running and hence bring the entire system into a grinding halt. This is especially common when such equipment is in the continuous flow process industry.

Similar alternative classification scheme relevant in the maintenance context is the VED [Vital, Essential and Desirable]. It may be beneficial if both ABC and VED classification with certain inventory levels is fixed for maintenance consumables.

The inventory service levels can be higher for C class items compared to A and B class items. By carrying additional units of inventory, the investment does not go up significantly in C class. By a similar logic, the inventory for B class items could be higher than A class items.

Q3. Explain briefly how the principles of scheduling, when followed, will improve the effectiveness and efficiency of the maintenance management?

Ans: Maintenance Scheduling Principles

Scheduling follows the vision, the principles, the paradigms, and the fact that an effective scheduling will come through effective planning process. The principles used in scheduling are the ones that enable us to achieve the objectives of forecasted skill levels for each task. This can be attained by working with job priorities and allowing the crew to handle day to day jobs and then measure the compliances.

Routine maintenance needs the use of these laid out principles, as they create a framework for successful scheduling of planned work. Each principle sets the guidelines on how the maintenance should handle different scheduling processes.

Six principles that have greatly contributed to the overall success of scheduling are:

1. Scheduler or the planners plan the jobs for lowest required skill levels, to the extent possible.

2. The entire production unit should honour and respect the importance of schedules and the given job priorities.

3. The crew, inclusive of the supervisors forecasts the available work hours of the highest skills, at least a week ahead and indicate to scheduler.

4. Schedule assigns the planned task to cover available forecasted work hours.

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5. Crew supervisor matches personnel skills and tasks while allocating the work as scheduled.

6. Schedule compliance of wrench time provides the measure of scheduling effectiveness and hence must be followed by all concerned.

Principle 1

Scheduler or the planners plan the jobs for lowest required skill levels, to the extent possible. Principle 1 specifies that the job planners should, as far as possible, be able to identify the lowest skill necessary to complete the scheduled work. The conflict here is that the supervisor, who is supervising the task, has the higher skill capability and expertise needed to guide the lowest skills while executing the job effectively.

If required the supervisor can change the skill level, based on its availability while allocating the job as scheduled. In case this change is made, the same should be recorded for future reference by supervisor, as well as, the planner or the scheduler.

Job plans should provide information about the number of persons required, lowest craft skill level, work hours or wrench time per level, and the job duration of the scheduled task. While evolving these, previous data available will be referred too.

Additional support required, if any, is also specified. Questions like-Does the job require mechanics or machinists? Does the job require three helpers to assist a certified electrician, when some urgent priorities are specified?

Principle 2

The entire production unit should respect the importance of schedules and job priorities. Schedules prepared by the scheduler may be weekly, monthly or for the full year. These schedules when released must be adhered to by the maintenance crew members without any deviations. They should also work as per the priorities mentioned in the work orders and as far as possible, should prevent undue interruption in schedules. They should know that the priority for the work is fixed by either the planner or the scheduler and is based on certain decisions taken at higher levels and as per the established plant guidelines

The scheduler may review the schedule periodically and adjust, but of course this is done in coordination with crew members, planners, and the plant manager. Plant priority should be given importance while the schedule for work and all involved should treat the priority fixed as the primary consideration.

Advance scheduling of enough work for the entire week may set the goal for maximum utilisation of the available craft hours. Through this, they can achieve effectiveness in their scheduled work. This type of scheduling will also ensure that sufficient and right work is assigned to the crew.

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Inefficiency of the entire task force peeps in if there are any interruptions by lower priority jobs coming in the way of urgent jobs that are in progress. This swapping of a running job and taking an urgent one should be resorted to, only when a true emergency arises. This swapping of the job and taking a new lower priority job must have agreement from the scheduler. In such cases, it is found that it may be better to delay the identified job in full rather than completing half.

Principle 3

Develop a weeks schedule for each crew and craft hours required. First two principles form the base for working on principle 3. Most of the production divisions prefer the scheduler to work on weekly schedules, so that the maintenance crew could be fully occupied and the continuous work on maintenance activities goes ahead. Accordingly, the scheduler develops a weeks schedule for each crew based on the available craft hours against the actual hours required. They also forecast the highest skill required, firms up job priorities, and give details of the information available for such job plans.

Scheduler selects among the works in the waiting list and analyses the backlogs if any, before firming up the weeks schedule. This exercise is done to ensure that he selects the most optimum work of that weeks worth by combining both fresh and backlog works.

The scheduler also needs to forecast the minimum and maximum capabilities of the present crew members and thus allocate them accordingly for the day or week or monthly work allocations. In this process they will also get to know whether work force from outside is warranted or not. Fixing up priorities also gives an indication whether simultaneous attack of the maintenance work is required and if so how many wrench hours the department has to borrow either from outside or within by booking overtime work.

Scheduling and preparing a plan is to ensure that the crew will perform all the works available and those assigned in the total system. This may require proactive approach and hence supervisors should safeguard the work progress in a systematic way.

Certain equipment and machineries require multiple tasks to be done simultaneously, within the lead time available for completion. In such cases, the thinking and processing will change and thus, will require a process of precedence of activities and thereby determining a critical path.

This type of work is often taken up as a project to complete the work where lead time and slack time are calculated and accordingly work is progressed. Here, both proactive and reactive approach is required by the supervisor and the crew members.

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Principle 4

A weeks schedule will assign work for all the available work hour. Principle 4 tries to bring all the previous three principle together in order to achieve 100% of the total wrench time available in the department. All the works on hand are first prioritised and rated as per the emergency, urgency, periodical, day to day work, some special variety of work, and so on.

A weeks schedule that is prepared and work assigned will cover the total available wrench hours of the department and caters to all types of priorities mentioned above. The tasks being accomplished will consume the total available hours. Accomplishing this will reflect upon the effectiveness and thus, the efficiency of the entire department.

For practicing the above type of 100% scheduling, there must be enough work load, in other words, it is possible if more and more equipments or machineries come under the gamut of maintenance.

The scheduler also prepares and assigns work plans for the following week. This helps the crew to plan their work in a systematic way by not duplicating the activities. But however, the crew will give preference in completing the higher priority work by utilising whatever skills available, than working on lower priority work. Over assigning and under assigning of work is common in industries. It is better that scheduler avoids such cases as these may cause unique problems.

Principle 5

The crew supervisor matches personnel skills and tasks. Any schedule evolved by the scheduler must be issued with all authorisations at least few days earlier to the commencement of the work. This is because; the work order released must be studied by the supervisor and crew members. Also, they have to draw the required materials, tools, and other requirements to start the work as scheduled.

In case the scheduler is not given enough time to evolve the schedule as the work coming is of utmost priority, then a meeting is conducted. This meeting involves the presence of the scheduler with the maintenance chief and the crew men to adjust the emergency work, without disturbing the ongoing works.

It is the job of the scheduler and the crew supervisor to assign the tasks after matching the personnel skills that are available for use. This will help the supervisor in handling the current day's work and any other problems that may arise due to emergency. The crew supervisor needs to ensure that each technician receives assignments totalling to a full days work.

It is the job of the crew supervisor to balance the variances between the planned and actual times, if any, in the days work. Of course such variations are expected to prop up in such activities. If there is a wide variation, then crew supervisor should consult the

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scheduler before adjustments are made. Although individual jobs show a wide variance between planned and actual times, it gets relatively balanced by the week end.

Principle 6

Wrench time is the primary measure of Planning efficiency and effective Scheduling.

The concept of wrench time is used for measuring the effectiveness of both the planning and the performance of the crew men with respect to the planned hours for each task. In other words, the wrench time is the measure of workforce efficiency and effectiveness of planning and scheduling.

Since this wrench time measurement for each of the maintenance task is important, it is essential that schedules have good compliance by the crew and thus, achieve the results as planned. It is the job of the crew supervisor to track this compliance.

In order to ensure compliance of wrench time continuously, it is advisable for the crew supervisor to keep records of all the measures and tasks date wise.

Planning individual jobs will reduce the time delays such as waiting for parts and tools. As compared to planning, scheduling tries to reduce the delays and hence, adhering to and complying with both becomes priority to all concerned with the job.

When the task is being accomplished, the work sampling of the actual wrench time in between maintenance activities will show the present status and the completion time.

Q4. Explain briefly the five levels of data developed in UMS.?

Ans: Five levels of data in UMS

The figure illustrated below tells us how the data collected from all the standardisation processes are organised at five levels in the building block fashion.

Five Levels of Data in UMS

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We shall now discuss the above mentioned five levels of organising the collected data.

Basic motions

UMS data, which is organised at five levels, as explained above, is the predetermined time system for basic motions. Analysing and classifying the data into basic motions, establishing a relationship between the motions and the time taken to perform the operations is a universal practice. Two widely used practices are:

Predetermined Time Systems, which details the methods and time measurement

Operation Sequence Technique, where work measures are made on basic motions such as reach, grasp, move, position and release operations in a process.

Data on each of these motions are recorded to establish the actual time taken for each of these. This data is then used for standardisation purposes.

Basic operations

Basic motions are grouped together as individual operations. For each process, the planner can fix up the suitable craft and skills. While standardising the process, the variables like weight of the part, distance that moves in that process and how to clamp the part during operation are tabulated and issued as standards. This data is to be followed by both the production as well as the maintenance department. Use of certain processes and its standards is also a universally adopted practice.

Craft operations

Some operations and their operating times are unique to a particular craft. For instance, we cannot start comparing processes and standards used for welding operation with say carpentry, as both are two different entities. All the data and the time taken for the craft operations in production or maintenance processes like manual handling of items, body motions, machine settings, tools and fixture setting, welding joints and the arc striking time, are all pooled and standardised. This data and process is then issued for practice.

Similar craft data for other skilled operations such as painting, carpentry, electrical, pipefitting, can also be made available to the maintenance crew

Bench marks

By incorporating the use of UMS, the maintenance supervisor can typically apply the above discussed set standards to their work. Bench marking the best standards for each of the crafts are selected and applied in their work practices to improve the overall effectiveness.

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Spread sheets

Planners need to establish planning times for large number of jobs using sample data of the benchmark jobs by using spread sheets. They help to publicise the data along with a step-by-step process. Spread sheets help us to quickly find the appropriate data and information to select the right bench mark for comparison. Certain allowances for job preparation time, area, travel time, job site time and rest and minor unavoidable delays could be applied to these bench marked times to UMS time, before allotting the job to the crew members.

For example: Benchmarking a task can be easily done in areas of work performed on electrical lighting, diesel generators, in mechanical fields like belt drives, gear boxes and material handling equipment like clutches and brakes. This has been made possible as most of the companies follow standard methods of operation and maintenance activities, which can be taken for benchmarking in your organisation for comparison of work.

Q5. Explain briefly the importance of ‘Depreciation’ and its disposition while calculating the capital expenditure of the equipment to be replaced. What are the depreciation methods that are normally used in an organisation?

Ans: Depreciation is an accounting process where the cost of the asset is spread the cost over a period of its useful economic life. An annual depreciation charge is included as an expense in the Profit and Loss account. Additionally, the value of the asset in the balance sheet is proportionately reduced by each years charge.

For example, if an asset is purchased for Rs.100000, kept in use for 10 years, and then sold for Rs.10000, it has the business cost of Rs.90000. Depreciation apply the accruals in the depreciation account to the extent of Rs.90000 within the income that asset has generated over those ten years.

The two most commonly used methods are straight line method and reducing balance method.

1. Straight line method

A fixed percentage on cost each year.

Equal monetary amount each year.

2. Reducing balance method

Reducing a fixed percentage on net book value each year.

Deducting a reducing monetary amount each year.

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Let us consider the following example:

A machine is purchased for Rs.300000. It is expected that this machine will be used for 10 years, at the end of which it will be sold for Rs.15000. Calculate the depreciation to be charged for each of the first 3 years of the machines life, using: (i) The straight line method (ii) The reducing balance method at 20% pa

Solution:

i) Straight line method

Under the straight line method, the net cost is simply divided by the expected life., that is, (Rs.300000 Rs.15000) / 10 = Rs. 2850)

So, the annual charge for every year of the machines life of 10 years is Rs.2850. [Note: for plant and machinery, the normal life expectation is around 10 to 12 years. Hence the depreciation is calculated over 10 or 12 years time period in the balance sheet]

ii) Reducing balance method (the charge for depreciation reduces per year)

Year 1 Rs.300000 x 20%= Rs. 60000

Year 2 (Rs.300000 Rs.60000) x 20% = Rs.48000

Year 3 (Rs.300000 Rs.60000 Rs.48000) x 20% = Rs.38400 and so on, until book value becomes zero.

Calculation of profit or loss

The depreciation charged per year is based on estimated useful life. On disposal, even though depreciated fully, there is some residual value of the equipment, which will be known when the equipment is disposed. This residual value has to be shown in the book of accounts.

Let us consider the following example to understand how the calculation is carried out.

An asset is purchased on 1 January 2007 for Rs.400000, and is depreciated using the reducing balance method at 20% pa. The asset is sold on 1 April 2010 for Rs.230000. Calculate the profit or loss arising on this disposal.

Solution:

Original cost = 400000

Depreciation y/e 31.03.2007 (20%) = 80000

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Net book value at 31.03.2007 = 320000

Depreciation y/e 31.03.2008 (20%) = 64000

Net book value at 31.03.2008 = 256000

Depreciation y/e 31.03.2009 (20%) = 51200

Net book value at 31.03.2010 = 204800

Thus, there is a profit on disposal of price, that is,

[Sale price of Rs. 230000 204800 (book value) = Rs. 25200

Accounting for depreciation and disposals

In the above example, the disposal occurred after three years of use. Accounting can be done even in the middle of the accounting year. In such cases, proportional depreciation for that period elapsed during the year may be considered while calculating the loss or profit. Certain times full year depreciation is also allowed.

Q6. What are the ranges that we can normally expect for each of the OCE factors? Explain how an improvement in 10 % of wrench time will offer 25% improvement in utilisation of the crew and hence the OCE.

Ans: Range of OCE factors

A brief summarisation of the ranges of the OCE factors.

OCE Elements Range      Lower Medium Higher1) Craft Utilisation 30% 50 % 70 %2) Craft Performance > 80 % 90 % 95 %3) Craft service level > 90% 95 % 98%Total OCE factor 22 % 43% 65 %

Let us take a problem to explain an improvement in 10 % of wrench time will offer 25% improvement in utilisation of the crew and hence the OCE.

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Problem

Find out the value of the craft utilisation improvement factor when a maintenance crew of 20 members are working on 5 days a week and 8 hours of work per day. The rate per hours including all incidentals works out to Rs. 700. In case the maintenance crew works with a higher craft utilisation of 10%, what benefits will accrue to the department.

Solution:

Total Craft hours and the annual craft labour cost for a crew of 20 persons are:

· Total craft hours available

· = [20 x (5 days per week x 8 hours per day) x 52 weeks per year]

· = 41600.

· Craft labour cost

· = [41600 x 700]

· = Rs.29120000 per year.

· Following table indicates the level of craft utilisation, wrench hours versus the actual cost. The list gives the values at every 10%, stating from 30% and also at 85%, which is the maximum possible craft utilisation (refer above).

Craft utilisation Level (A)

in %

Total Wrench time in hours (B)= (A) x (41600)

Actual hands on cost per hour (C) = [Rs.700 x (100%) / % at (A)]

Average wrench hours per craft positioned (D) = [(B) / 20 crew]

30 12480 2333 62440 16640 1750 83250 20800 1400 104060 24960 1667 124870 29120 1000 145680 33280 875 166485 35360 824 176890 37440 111 1872100 41600 100 2080

What if the total wrench improves by 10% say from 40% to 50%?

We can easily calculate the benefit gained in the average wrench hours form the above table:

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· Total hours gained in the wrench hours is 10% means 10% of 41600 total hours = 4160 hours.

· At 40% craft utilisation efficiency the average wrench hours in the above table is = 832.

· The number of crew who can give 41600 hours as additional 10% output works out to 5, that is, [4160/832] = 5

Therefore the 10% gain in wrench hours from the crew will result in an extra output of another 5 crew persons. In other words the improvement in the work output is 25% when only 10% extra efforts are put in by the same crew of 20, which is really significant. Hence the 10% improvement will accord an additional wrench time of 41600 hours and the total added value generated out of this service will obviously also go up.

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