Every maintenance store has two problems at once. The bearing you need at 2 a.m. isn't on the shelf, yet the racks are full of parts nobody has touched in years.
Buying more doesn't fix the first problem, and it makes the second one worse. Spare parts inventory management software helps, but only when it's built on a clear method. This guide walks through that method, from classifying spares to the numbers worth checking every month.
How a Store Ends Up Short and Overstocked at Once
Take a cement plant in Rajasthan. Its store holds thousands of items, from grease and V-belts to a spare girth gear pinion for the kiln. On a bad week, the raw mill stops for a missing coupling while the store holds three gearboxes for a machine scrapped years ago.
This happens for a few common reasons:
Parts are bought by habit or fear, not by actual usage.
The same part sits under two or three different names and codes.
Spares are issued without a work order, so nobody knows where they went.
When a machine is retired, its spares stay on the shelf.
Nobody has marked which parts are truly critical.
Each of these is fixable. The fix starts with sorting spares into groups that get different rules.
Sorting Spares by Value and Criticality
Two simple methods work well together. ABC analysis groups items by yearly spending: A items are the few that take most of the budget, and C items are the many cheap ones. VED analysis groups them by how much a shortage hurts: Vital, Essential or Desirable.
Neither method works well alone. ABC treats a cheap but vital seal like scrap, and VED ignores cost. Combine them in a 3 × 3 matrix:
Yearly spend ↓ / Criticality → | Vital | Essential | Desirable |
A (high spend) | Stock, tight control, monthly review | Low stock, firm vendor tie-up | Don't stock; buy when needed |
B (medium spend) | Stock, normal control | Moderate stock | Minimal stock |
C (low spend) | Stock generously; it's cheap insurance | Simple min-max | Buy in bulk or on demand |
At the cement plant, a mill drive coupling is B-Vital, so it's always stocked. Common bearings for conveyor idlers are C-Vital, so the store keeps plenty. Fancy paint for guard rails is C-Desirable and doesn't need shelf space at all.
Critical, consumable and insurance spares
From the matrix, three practical groups emerge. Consumables are used regularly, such as filters, belts, grease and common bearings. Critical spares are vital parts used now and then, such as a specific seal kit or coupling.
Insurance spares are the group most stores mishandle. These are costly, vital parts with long lead times that you may never use, such as the kiln girth gear pinion or a spare crusher shaft. They show zero usage, so ABC rules flag them as dead stock, but losing one could stop the plant for months. Track them as their own category, with their own rules.
Setting Min and Max Levels From What You Actually Use
Most min-max levels in Indian plant stores were set years ago by someone who has since moved on. Reset them using real issue data from the last 12 to 24 months, not purchase records.
The basic logic is simple:
Minimum = (average daily usage × supplier lead time in days) + safety stock
Maximum = minimum + normal order quantity
Say a conveyor bearing is issued about four times a month, roughly 0.13 a day. If the supplier takes 45 days, you'll use about 6 during the wait. Add a safety stock of 2, and the minimum is 8. With a normal order of 6, the maximum is 14.
Leave out one-off issues, like a project that used 20 bearings in one month. Review levels every quarter for A and B items, and every six months for C items. Insurance spares don't follow min-max at all; usually you keep one, and review the decision once a year.
Tying Every Spare to a Machine and a Job
Usage data is only reliable if every part leaves the store against a work order. "General maintenance" as an issue reason tells you nothing.
Start by building a simple parts list for each critical machine, showing which spares fit it. When a technician raises a job, the right parts show up on the screen, and the store can check stock before the work is planned. For PM jobs, parts can be reserved days ahead, so they aren't issued to someone else.
Good spare parts inventory management software makes this link automatic. It also shows where each part is used, which helps in two ways. You can standardise on common parts across machines, and you can spot spares that no longer fit anything still running.
Clearing Out Slow-Moving and Obsolete Parts
Dead stock doesn't just take up space. It hides real shortages, ties up money and makes stock counts slower.
Define the groups clearly
Call an item slow-moving if it hasn't been issued in 12 months, and non-moving after 24 months. An item is obsolete when the machine it fits has been retired, or the part has been replaced by a newer version. Keep insurance spares out of these rules, or they'll be scrapped by mistake.
Clear the backlog in steps
Check each slow item against the machines it fits. If a machine is still running, it may be a hidden insurance spare that needs reclassifying. If not, try returning it to the vendor, transferring it to a sister plant, or selling it, and agree on a write-off with finance for what's left.
Stop it building up again
Make retiring a machine trigger a review of its spares. Also, stop the habit of "ordering a few extra while we're at it", which is how most dead stock starts.
Five Numbers to Review at Month End
A short monthly review with maintenance, stores and finance keeps the balance from slipping. Track these five numbers.
Critical stockouts
Count the work orders delayed because a vital spare wasn't available. This is the number production feels most, so even one is worth discussing.
Stock value against usage
Compare total stock value with the value issued over the year. If stock keeps rising while issues stay flat, the store is filling with parts nobody uses.
Slow and non-moving stock
Track the value of items not issued in 12 and 24 months. It should fall steadily as you clear the backlog.
Stock accuracy
Count a small set of items every week and compare them with system records. If counts don't match, every other number on this list is unreliable.
Spares-related downtime
Record downtime hours where waiting for a part was the cause. This links the store directly to plant output, which is how you justify stocking the right insurance spares.
Balance Comes From Data, Not Bigger Shelves
Classify every spare, set levels from real usage, issue parts only against work orders, and clear dead stock regularly. Do that, and shortages and excess both shrink together.
PlantOps360 offers spare parts inventory management software that keeps spares linked to machines and work orders, alongside a central asset register with full lifecycle history.
Frequently Asked Questions
What is MRO inventory?
MRO stands for maintenance, repair and operations. It covers spares, tools and consumables used to keep a plant running, as opposed to raw materials or finished goods that go into the product.
What is the difference between ABC and VED analysis?
ABC analysis ranks items by how much money they consume each year. VED analysis ranks them by how critical they are to keeping the plant running. Used together, they help decide which spares to stock and how tightly to control them.
Can insurance spares be capitalised?
In India, under Ind AS 16, spare parts and standby equipment that meet the definition of property, plant and equipment can be capitalised, which often applies to major insurance spares. Check the treatment with your auditor or finance team.
