Unit 5: Maintenance System

🛠️ Maintenance System

A maintenance system is a structured approach used to ensure that machines, equipment, and facilities operate efficiently, safely, and without unexpected breakdowns.

Maintenance Strategies

Maintenance Planning

Maintenance planning involves organizing resources, tasks, tools, and schedules to carry out maintenance efficiently.

🔹 Key Steps

• Identify Maintenance Needs – Based on equipment manuals, failure history, or sensors.
• Set Objectives – Minimize downtime, reduce costs, improve equipment life.
• Create a Schedule – Daily, weekly, monthly plans for inspections or servicing.
• Assign Resources – Right people, tools, and spare parts in place.
• Track & Record – Document each maintenance activity for analysis.
• Continuous Improvement – Analyze failures, update maintenance schedules.

🧩 Conclusion

Effective maintenance strategies and planning help reduce unexpected breakdowns, lower costs, extend equipment life, and improve overall operational efficiency.

💰 Maintenance Economics

Maintenance economics involves evaluating the cost-effectiveness of different maintenance decisions and strategies to maximize equipment availability while minimizing total costs.

Quantitative Analysis in Maintenance

Quantitative analysis involves using numerical data and mathematical models to:

 Example Formula:

Total Cost=Maintenance Cost+Downtime Cost+Replacement Cost

Goal: Minimize Total Cost while maintaining productivity.

Optimal Number of Machines

📌 Why It Matters:

Having too few machines leads to capacity shortages and overuse (increasing breakdowns), while too many machines increase idle time and maintenance cost.

✅ Factors to Consider:

Basic Formula (Approximate):

Where:

Effective Capacity = Rated Capacity × Utilization × Efficiency

📊 Example:

If:

• Demand = 10,000 units/month
• One machine produces = 1,500 units/month
• Efficiency = 85%
• Utilization = 90%

Then:

Conclusion:

• Maintenance economics helps reduce unnecessary costs by using data-driven decisions.
• Finding the optimal number of machines ensures a balance between production needs and maintenance costs, improving overall productivity.

Replacement Strategies and Policies

Replacement strategies involve deciding when and how to replace machines or equipment that become inefficient, outdated, or too costly to maintain.

✅ Types of Replacement Strategies:

Economic Service Life

The economic service life of an asset is the period during which it is cost-effective to use, before maintenance and operational costs exceed the benefits.

How to Determine:

• Compare total cost of ownership over time (purchase cost + maintenance + downtime)
• Identify the point where average cost per year is lowest

📊 Example: If a machine becomes more expensive to maintain after 5 years, its economic life is 5 years, even if it can still run for 8 years.

Opportunity Cost

Opportunity cost is the cost of choosing one alternative over another—what you miss out on when using funds or resources for one purpose instead of a more profitable one.

🔹 In Maintenance

• Using a machine beyond its economic life might block investment in newer, more efficient machines
• Opportunity cost includes lost productivity, increased downtime, and higher energy usage

Replacement Analysis Using Specific Time Period

📌 Purpose

To compare old vs. new equipment over a specific time period (e.g., 5 years) to decide whether replacing is cost-effective.

🔢 Steps

• Estimate maintenance & operating cost of old machine over 5 years
• Estimate cost of new machine, including initial investment
• Compare using Net Present Value (NPV) or Equivalent Annual Cost (EAC)

✅ Decision Rule

If the total cost of using the new machine over a specific period is less than the old one, replacement is recommended.

Spares Management

Spares management refers to the planning, stocking, and control of spare parts required for the maintenance of equipment.

✅ Key Objectives

• Ensure availability of critical parts
• Avoid excess inventory
• Reduce downtime during equipment failure
• Control storage costs and obsolescence

📋 Categories of Spares:

Techniques in Spares Management:

• ABC Analysis (based on cost value)
• VED Analysis (based on criticality: Vital, Essential, Desirable)
• Just-in-Time (JIT) for frequently used spares
• Inventory tracking software for reordering and cost control

✅ Summary Table

Maintenance Records

Maintenance records are systematic logs or documentation of all maintenance activities performed on machines, equipment, or facilities over time.

These records help track performance, schedule future maintenance, reduce breakdowns, and support audits or quality certifications.

🧾 Key Contents of Maintenance Records

Objectives of Maintaining Maintenance Records

• Ensure equipment reliability and operational continuity
• Track frequency and cost of repairs
• Schedule preventive maintenance effectively
• Provide data for decision-making (e.g., replace vs. repair)
• Meet legal, safety, and audit requirements
• Improve asset life cycle management

🧠 Benefits of Effective Maintenance Records

Tools Used

• CMMS (Computerized Maintenance Management System) – Digital software for managing maintenance tasks and storing records.
• Manual Logs – Paper-based registers (used in small organizations).
• Spreadsheets – Common in medium-sized businesses for simple record-keeping.

✅ Conclusion

Maintenance records are essential for efficient operations, cost control, and equipment longevity. They support data-driven decisions and play a vital role in maintaining quality and safety standards in any organization.