Spare parts and work orders: where does the link break?

A familiar scene: the technician goes to the store for a seal kit for the return sludge pump. The storekeeper says, “someone took the last kit just yesterday.” Who? For which pump? Nobody knows. The job slips, the pump keeps running with a leak, and an urgent purchase request starts.

Or the other way round: the seal kit arrived two weeks ago and is on the shelf, but the planner doesn’t know, and the job is still on the “waiting for parts” list.

Both scenes have one root: the store and maintenance work separately. The store knows the stock and maintenance knows the need, but there is no bridge between them.

Three places the link breaks

1. The need is seen too late. The part a job needs usually becomes clear when the technician is at the equipment and has opened the pump. At that moment it is too late to supply it. If the required part is written on the work order at planning time, you can find out before the work starts whether it is there or not.

2. Stock that is there belongs to nobody. There are two seal kits on the shelf. One is needed for this week’s job. If that kit is not set aside for that job, the first person to reach the store takes it. Stock “on hand” is not the same as stock that is “available”.

3. Consumption is not tied to the job. When a part leaves the store and all that is written is “one seal kit issued”, six months later we don’t know which pump it went to. The equipment history stays incomplete, and the maintenance cost of each asset is unknown.

Reservation: stock with an owner

The answer to the second point is reservation. When the planner prepares the work order and specifies the part it needs, that quantity is reserved for that job. A reservation does not move the part; it only takes it out of “available”.

Now if someone wants a kit for another job, the storekeeper sees only one is available. The reserved kit stays put until it is issued to that job, or the reservation is ended with a reason.

On hand is the number on the shelf. Available is the number that doesn’t have an owner yet.

Shortage: a warning that reaches supply

If, at planning time, the required part is not in stock once reservations are subtracted, this should be visible right there: on the work order, as a shortage warning. The warning should not stop planning; the job can still be prepared and released. But the planner needs to see that the part is missing and request supply from the same place.

A supply request makes the need precise and traceable: what, how many, for which job. When the part arrives and the receipt is recorded, it is linked to that request. The shortage warning on the work order clears by itself, because the part is now available.

This path solves the second scene at the start of this note: the planner no longer waits for news, because the state of the part is visible on the job itself.

Issue against the job

For the third point, every part that leaves the store should be tied to a job. “Issue: one SK-45 kit for WO-1042.” That is a line in the stock movements that is never deleted or rewritten. If a mistake is made, a new correcting line is recorded next to it.

With that:

• The reservation is fulfilled, and the kit no longer counts as “reserved”.
• The consumption is recorded on the work order.
• When the work order is closed, the part and its cost reach the equipment history.

A year later, when someone asks “how many seal kits has this pump used?”, the answer is in that pump’s history. And if the answer is “three in one year”, it is time to look for the cause.

Returns and stocktaking

Two more tasks are part of the same bridge. First, returns to stock: if a part was issued to a job but not used, it should come back with a reference to that job. Second, stocktaking: a periodic count that finds the difference between the system’s number and the shelf’s.

In stocktaking too, the same “record, don’t rewrite” logic matters. If the system says 100 litres of oil and the count shows 97, the variance should be seen and approved, and then recorded as a stock adjustment, not by erasing the old number and writing 97.

Chemicals are parts too, but different

The same logic works for process chemicals, with one difference. Polyaluminium chloride in a water plant, or hypochlorite in a wastewater plant, is not consumed by a work order; its use belongs to a process unit: rapid mixing, or disinfection.

But the same questions still apply: how much do we have in stock? What is the daily use? How many days until it runs out? When chemical withdrawals are recorded against their process unit, the stock stays accurate, and use can be compared with that unit’s readings, raw water turbidity for example.

One more practical point: give shelves codes and QR tags. When the storekeeper scans shelf B-3 and immediately sees its stock, reservations and latest movements, both counting and issuing get faster and more accurate. Differences between the system and the shelf are found sooner, not at the year-end count.

What does it take?

For this bridge to work, the store and maintenance do not need to be the same person. A few things are enough:

1. The required part is written on the work order at planning time.
2. A reservation sets stock aside for the job.
3. A shortage is visible on the work order and leads to a supply request.
4. Every issue and return is tied to a job.
5. Stock movements are only ever added, never rewritten.

With these in place, nobody finds out at an open pump that the part is missing.