Spare parts in stock: the optimal list
Which conveyor spares to always keep on the shelf and which to order on demand: unit criticality, lead time and stock-holding logic.
The failure of a small part can stop a line for a week — if that part is not in stock. But keeping “everything just in case” is also unwise: money is frozen, rubber and grease age on the shelf. In this article we break down how to build an optimal spare-parts list for a conveyor line.
Why a spares store is a balance
A spares stock is always a compromise between two risks. Too small a store means long downtime: a part is awaited for weeks, the line is idle, no product is made. Too large a store freezes working capital and accumulates clutter — rubber and polymer parts have a shelf life and spoil unused.
The task is not to “buy a lot” but to buy the right thing. A spares list is built not from the conveyor catalogue but on two criteria: how critical a part is and how long it takes to supply.
Another factor is replacement frequency. Consumable parts, such as scrapers or grease, are used up predictably and regularly — their stock is calculated simply, by a consumption norm. It is harder with parts that fail rarely but suddenly: here stock is determined not by consumption statistics but by the cost of downtime.
Criticality and supply matrix
We assess each part on two axes. Criticality — whether failure stops the line. Supply — in how many days the part can realistically be delivered. The logic is simple: we keep in stock what is both critical and slow to arrive.
| Criticality / Supply | Fast (1–3 days) | Slow (from 2 weeks) |
|---|---|---|
| Stops the line | Preferably in stock | Mandatory in stock |
| Does not stop the line | Order on demand | Small stock |
Drum bearings, for example, are both critical and often on-order — they belong in the mandatory stock. Standard fasteners have low criticality and are bought quickly — there is no point stockpiling them.
Basic conveyor spares list
From maintenance experience, a basic stock set for a conveyor line looks like this:
- Drum bearings — at least one set for each size on the line.
- Cleaning scrapers and brushes — fast-wearing, needed regularly.
- Drive and toothed belts — if there is a belt drive.
- Support rollers — a few of each size.
- Seals and oil seals — cheap, but a repair cannot be finished without them.
- Lubricant — in quantity for 1–2 service cycles, with shelf-life control.
The conveyor belt is usually not included in the basic stock — it is expensive, has a storage life and is often made to size. It is ordered in advance, guided by the forecast belt service life.
The stock volume also depends on the number of identical conveyors. If a workshop has five lines of the same size, one set of bearings covers them all — the probability of simultaneous failure is low. A unique non-standard unit that exists nowhere else, however, needs its own stock: there is nothing to substitute it with, and a make-to-order takes weeks.
Engineer’s tip. The cheapest and most important store item is a set of bearings for each drum. A bearing costs little, while its absence at the moment of failure turns a 4-hour repair into a week of downtime. This is a classic hidden TCO item: a saving on the shelf turns into losses on the line.
Spares storage conditions
A spare part in the store must wait for its moment in usable condition — otherwise the stock becomes an illusion. Rubber and polymer parts are especially sensitive to storage conditions. A few rules we pass to customers together with the list:
- Bearings — in the factory preservation packaging, in a dry room; unseal only before installation, because the grease absorbs moisture and dust.
- Rubber belts and drive belts — horizontally or on a wide drum, away from direct sun, ozone and heaters; temperature 5–25 °C. Ozone and UV destroy rubber faster than mechanical load.
- Lubricant — in a tightly closed container, with mandatory control of the production date; most greases have a guaranteed life of 3–5 years.
- Fasteners and rollers — standard conditions, but with corrosion protection.
Once a year a store audit compares the actual condition of parts with these norms. A bearing with a rusty race or a belt with cracks on the bend is written off, even if it is “new on paper”.
How to keep spares records
A store without records quickly becomes chaos. We recommend a simple system: for each item — a card with the name, size, minimum balance and date of the last replenishment. When stock falls to the minimum, an order is formed. Once a year the store is audited: rubber and grease shelf lives are checked, obsolete items written off. Spares records are logical to keep alongside the planned maintenance log — this shows which parts are really consumed and which lie for years.
A useful habit is to review the spares list after every serious breakdown. If the line stood idle because a part was missing, that part is added to the mandatory stock. This way the list does not “freeze” but evolves together with real operating experience — and becomes more accurate every year.
Conclusion
An optimal spares store is not “many parts” but the right parts: critical units with a long lead time are always kept on the shelf, cheap and quickly available ones are ordered on demand. The criticality and supply matrix helps build a list without guesswork. Need help defining the spares for your line? Get in touch — we will compile a list for your equipment.
