MAINTENANCE SCHEDULE TECHNIQUES - Production and Operations Management

Different types of schedules are made suiting the respective job plans and different techniques are used for making and following those schedules. The first step of all scheduling is to break the job into small measurable elements, called activities and to arrange them in logical sequences considering the preceding, concurrent and succeeding activities so that a succeeding activity should follow preceding activities and concurrent activities can start together.

Arranging these activities in different fashion makes different types of schedules. They are as follows:

  1. Weekly general schedule is made to provide weeks worth of work for each employee in an area.
  2. Daily schedule is developed to provide a day’s work for each maintenance employee of the area.
  3. Gantt charts are used to represent the timings of tasks required to complete a project.
  4. Bar charts used for technical analysis which represents the relative magnitude of the values.
  5. PERT/CPM are used to find the time required for completion of the job and helps in the allocation of resources.

Modern Scientific Maintenance Methods
Reliability centered maintenance: Reliability centered maintenance (RCM) is defined as “a process used to determine the maintenance requirements of any physical asset in its operating context”.

Basically, RCM methodology deals with some key issues not dealt with by other maintenance programs. It recognizes that all equipment in a facility is not of equal importance to either the process or facility safety. It recognizes that equipment design and operation differs and that different equipment will have a higher probability to undergo failures from different degradation mechanisms than others. It also approaches the structuring of a maintenance program recognizing that a facility does not have unlimited financial and personnel resources and that the use of both need to be prioritized and optimized. In a nutshell, RCM is a systematic approach to evaluate a facility’s equipment and resources to best mate the two and result in a high degree of facility reliability and cost-effectiveness.

RCM is highly reliant on predictive maintenance but also recognizes that maintenance activities on equipment that is inexpensive and unimportant to facility reliability may best be left to a reactive maintenance approach. The following maintenance program breakdowns of continually top-performing facilities would echo the RCM approach to utilize all available maintenance approaches with the predominant methodology being predictive.

  • <10% Reactive
  • 25% to 35% Preventive
  • 45% to 55% Predictive.

Because RCM is so heavily weighted in utilization of predictive maintenance technologies, its program advantages and disadvantages mirror those of predictive maintenance. In addition to these advantages, RCM will allow a facility to more closely match resources to needs while improving reliability and decreasing cost.

Advantages

  1. Can be the most efficient maintenance program.
  2. Lower costs by eliminating unnecessary maintenance or overhauls.
  3. Minimize frequency of overhauls.
  4. Reduced probability of sudden equipment failures.
  5. Able to focus maintenance activities on critical components.
  6. Increased component reliability.
  7. Incorporates root cause analysis.

Disadvantages

  1. Can have significant startup cost, training, equipment, etc.
  2. Savings potential not readily seen by management.

How to Initiate Reliability Centered Maintenance?
The road from a purely reactive program to a RCM program is not an easy one. The following is a list of some basic steps that will help to get moving down this path.

  1. Develop a master equipment list identifying the equipment in your facility.
  2. Prioritize the listed components based on importance to process.
  3. Assign components into logical groupings.
  4. Determine the type and number of maintenance activities required and periodicity using:
    • Manufacturer technical manuals
    • Machinery history
    • Root cause analysis findings ,Why did it fail?
    • Good engineering judgment
  5. Assess the size of maintenance staff.
  6. Identify tasks that may be performed by operations maintenance personnel.
  7. Analyze equipment failure modes and effects.
  8. Identify effective maintenance tasks or mitigation strategies.

Six Sigma Maintenance
It is the application of six sigma principles in maintenance. Six sigma is a maintenance process that focuses on reducing the variation in business production processes. By reducing variation, a business can achieve tighter control over its operational systems, increasing their cost effectiveness and encouraging productivity breakthrough.

Six sigma is a term created at Motorola to describe the goal and process used to achieve breakthrough levels of quality improvement. Sigma is the Greek symbol used by statisticians to refer to the six standard deviations. The term six sigma refers to a measure of process variation (six standard deviations) that translates into an error or defect rate of 3.4 parts per million. To achieve quality performance of six sigma level, special sets of quality improvement methodologies and statistical tools developed. These improvement methods and statistical tools are taught to a small group of workmen known as six sigma champions who are assigned full-time responsibility to define, measure, analyze, improve and control process quality. They also facilitate the improvement process by removing the organizational roadblocks encountered. Six sigma methodologies improve any existing business process by constantly reviewing and re-tuning the process. To achieve this, six sigma uses a methodology known as DMAIC (Define opportunities, Measure performance, Analyses opportunity, Improve performance, Control performance). This six sigma process is also called DMAIC process.

Six sigma relies heavily on statistical techniques to reduce failures and it incorporates the basic principles and techniques used in Business, Statistics, and Engineering. Six sigma methodologies can also be used to create a brand new business process from ground up using design for six sigma principles.

SIX SIGMA MAINTENANCE PROCESS
The steps of six sigma maintenance are same as DMAIC process. To apply six sigma in maintenance, the work groups that have a good understanding of preventive maintenance techniques in addition to a strong leadership commitment. Six sigma helps in two principal inputs to the maintenance cost equation: Reduce or eliminate the need to do maintenance (reliability of equipment), and improve the effectiveness of the resources needed to accomplish maintenance. Following are the steps involved in six sigma maintenance process.

Define
This step involves determining benchmarks, determining availability and reliability requirements, getting customer commitments and mapping the flow process.

Measure
This step involves development of failure measurement techniques and tools, data collection process, compilation and display of data.

Analysis
This step involves checking and verifying the data and drawing conclusions from data. It also involves determining improvement opportunities, finding root causes and map causes.

Improve
This step involves creating model equipment and maintenance process, total maintenance plan and schedule and implementing those plans and schedule.

Control

This step involves monitoring the improved program. Monitor improves performance and assesses effectiveness and will make necessary adjustments for the deviation if exists.

Enterprise Asset Management (EAM)
Enterprise asset management is an information management system that connects all departments and disciplines within a company making them an integrated unit. EAM is also referred as computerized maintenance management system. It is the organized and systematic tracking of an organization’s physical assets i.e., its plant, equipment and facilities. EAM aims at best utilization of its physical assets. It ensures generation of quality data and timely flow of required data throughout the organization. EAM reduces paper work, improves the quality, quantity and timeliness of the information and provides information to technicians at the point of performance and gives workers access to job specific information at the work site.

Lean Maintenance
Lean maintenance is the application of lean principle in maintenance environments. Lean system recognizes seven forms of waste in maintenance. They are over production, waiting, transportation, process waste, inventory, waste motion and defects. In lean maintenance, these wastes are identified and efforts are made for the continuous improvement in process by eliminating the wastes. Thus, lean maintenance leads to maximize yield, productivity and profitability.

Lean maintenance is basically equipment reliability focused and reduces need for maintenance troubleshooting and repairs. Lean maintenance protects equipments and system from the route causes of malfunctions, failures and downtime stress. From the sources of waste uptime can be improved and cost can be lowered for maintenance.

Computer Aided Maintenance
For effective discharge of the maintenance function, a well designed information system is an essential tool. Such systems serve as effective decision support tools in the maintenance planning and execution. For optimal maintenance scheduling, large volume of data pertaining to men, money and equipment is required to be handled. This is a difficult task to be performed manually.

For a planned and advanced maintenance system use of computers is essential. Here programs are prepared to have an available inputs processed by the computer. Such a computer based system can be used as and when required for effective performance of the maintenance tasks. There are wide varieties of software package available in the market for different types of maintenance systems.

  • A computerized maintenance system includes the following aspects:
  • Development of a database
  • Analysis of past records if available
  • Development of maintenance schedules
  • Availability of maintenance materials
  • Feedback control system
  • Project management.

Following are some computer based maintenance systems which can be implemented:

Job card system: It is essential to prepare a job card for each component to record the maintenance work carried out or the work to be done. Job card shows the plant code, equipment code, the job code, the nature of the jobs, the start time and finishing time of the card, man-hour spent and etc. The use of computers facilitates the issue of job cards, recording of job history and control of manpower.

Spare part life monitoring system: Under this system, information about a spare part such as its description, anticipated life and date of its installation in equipment is recorded. As and when a particular sparepart is replaced during breakdown failures or scheduled maintenance, the updating of this information is done in their respective files stored in the computer. This helps to prepare the following reports:

  • Spares repeatability in various machines indicating the performance of such spare parts.
  • Comparisons of the actual life with the estimated life of the spare parts.

Spare parts tracking system: In most of the cases maximum time is consumed in procurement of spare parts. The total time required to rectify the breakdown is summation of the time to identify the cause of the failure, time to determine the requirements of spare parts, time to procure spare parts and the time to rectify the failure. In a computerized system, the spare part tracking system is beneficial in getting required material at the earliest. A spare part file is created that contains the information about the material code, spare part identification number, the assembly or sub-assembly number and the place where the spare part is used. This helps in knowing the current position about a particular spare part and facilitates timely requirement for future demands.


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Production and Operations Management Topics