Maintenance Plan: From Asset Inventory to Schedule

What is a maintenance plan

A maintenance plan defines, for each piece of equipment, which preventive and predictive tasks will be done, how often, by whom, in how many hours and with which parts. It starts from an asset inventory, goes through a criticality ranking and ends in a schedule that fits the crew's capacity.

Pasting the manufacturer's manual into a spreadsheet is not a plan: it produces hundreds of tasks nobody completes. A good plan is the backbone of TPM and is measured with MTBF and MTTR.

Visual map of the maintenance plan

The map shows the five-step flow from asset inventory to schedule, with the numerical example used in this article.

Step 1: asset inventory

Without an equipment list there is no plan. Walk the plant and register every asset with a unique ID (tag). Minimum fields:

• Tag and description of the equipment;
• location (line, area) and manufacturer/model;
• installation date and run hours, when there is an hour meter;
• manuals and drawings on file;
• critical spares and supplier.

Group items by system (hydraulic, electrical, pneumatic). It makes writing tasks easier and helps trace repeat failures.

Step 2: asset criticality

You cannot treat every machine the same. Rank by criticality and focus effort where a failure costs the most.

Criticality = Production impact (1 to 5) × Failure likelihood (1 to 5)

Example: a packaging plant with six assets. Likelihood comes from failure history. Class A: 15 or more; B: 8 to 14; C: below 8.

The two class A assets get more frequent inspection, spare parts and a look from FMEA. Class C assets can run on planned corrective maintenance. A Pareto chart of downtime helps calibrate the scores.

Step 3: strategy, tasks and frequencies

For each asset, pick a strategy: preventive by time or usage (lubricate, change filter), predictive by condition (vibration, temperature, oil analysis) or planned corrective (run to failure when failure cost is low). Then list short tasks with an estimated duration and frequency. Simple routines (clean, lubricate, inspect) can move to production through autonomous maintenance.

In the example, the tasks add up to 180 hours a year:

By asset: press 58 h, compressor 40 h, conveyor 20 h, sealer 30 h, forklift 24 h and fan 8 h. The two class A assets hold 98 h, or 54% of the total (98 ÷ 180).

Step 4: schedule and capacity

Compare workload with capacity. If one technician has 1,800 h available per year (an assumption for the example), the plan's 180 h take 10% of that time (180 ÷ 1,800). That leaves room for breakdowns, which is healthy; a plan above 70% to 80% of capacity would be unrealistic.

Spread tasks across the calendar so they do not pile into one week, and align them with production stops. In a month without quarterly or semiannual tasks, the load is 13 work orders (WO) and 10.5 h:

Week 4 is light on purpose: it is the buffer for slips and urgent jobs. Issue work orders ahead of time with parts and tools lists.

Step 5: track and review the plan

PM compliance = PM work orders completed ÷ PM work orders planned × 100

If 12 of the 13 WOs were completed in the month, compliance is 12 ÷ 13 = 92.3%. Also track MTBF and MTTR per asset. If the conveyor had 3 failures in 4,320 operating hours, MTBF is 4,320 ÷ 3 = 1,440 h; inspections spaced too far apart relative to that figure let failures slip through. Rule of thumb: the inspection interval should be well below the MTBF.

Review the plan at least once a year and whenever a machine changes duty. An asset that never fails may be over-maintained; one that fails often needs a new task or a root cause analysis. Also check the effect on OEE.

Common mistakes

• Copying the whole manual with no criticality priority.
• Ignoring capacity: a plan at 150% of the crew is never completed.
• Incomplete inventory or no tags, which blocks history per asset.
• Fixed frequency forever, without looking at failures and MTBF.
• No owner and no agreement with production to release the machine.
• Not recording what was done, which makes review impossible.

Frequently asked questions

What should a maintenance plan contain?

Asset inventory, criticality, tasks with frequency and duration, owners, parts and the schedule.

How do I set task frequencies?

Start from the manufacturer's manual, adjust using failure history and MTBF, then review.

What is the difference between a maintenance plan and a maintenance schedule?

The plan defines what to do and how often; the schedule says which day, who and with which resources.

How do I calculate equipment criticality?

Multiply production impact by failure likelihood, both from 1 to 5, and classify as A, B or C.

What is PM compliance?

The ratio of preventive work orders completed to those planned in the period. In the example, 12 ÷ 13 = 92.3%.

How many hours a year does the example plan require?

180 hours, about 10% of one technician with 1,800 h available.

About the author

Vagner Soares

Lean Manufacturing & Behavioral Management Specialist

Over 20 years in the automotive and metalworking industries (GM and Dana), Lean Manufacturing practitioner since 2006. SENAI instructor and mentor in Brazil’s Brasil Mais Produtivo program, delivering consulting, training and audits for 50+ companies, combining quality, productivity and people development.

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