The safety inspections that drove the establishment of the equipment ledger did so because the question asked by the inspection has changed. In the past the inspection asked whether this machine was present and whether it was tagged; increasingly it asks whether the condition of this machine can be stated. The second question cannot be answered by pointing at something on site; it needs written records. This turns information that used to be scattered across personal notes, shift handovers and the heads of purchasing staff into a set of data that has to be managed centrally.
The inspection items changed, and that forces the record keeping to change
The substance of the change is that the inspection has moved from static to dynamic. Whether the machine is there is a matter of looking at it before and after start-up; whether its condition can be stated requires knowing what oil it processed last time, how much, whether there was any abnormality at the time, and whether it has been used since. The first question anyone can answer; only the records can answer the second.
There is also a practical driver: if the inspection finds that a certain class of problem has no traceable evidence behind it, a whole batch of machines has to have the documentation made up. Once the ledger exists, the inspection simply calls it up from the system, and on site there is no need to search through files, look for photographs or ask long-serving employees. Many organisations only realised after one such round that building the ledger before the inspection is a great deal less work than completing it afterwards.
The minimum set of fields the ledger has to hold
The ledger does not aim to be complete, but it has to ensure that when any single machine is pulled out, its working condition can be described. Too many fields and nobody maintains them; too few and the questions asked during the inspection cannot be answered. The five categories below are normally enough. The test for whether a field is worth keeping is whether it can answer a question that really gets asked on site, and whether that question is likely to come up within a quarter.
| Field | What is recorded | What happens if it is missing |
|---|---|---|
| Equipment number | A fixed number matching the nameplate on the machine | None of the other records can be tied to a machine |
| Installation position | Down to the workshop, the line and the numbered tank it stands beside | When there is a fault, neither the person nor the machine can be found |
| Oil type | The name of the medium processed and whether it is insulating oil | Neither the element configuration nor the basis of the tests can be settled |
| Total volume processed | The volume processed this time and the total to date | Neither the consumable life nor the capacity can be calculated |
| History of abnormalities | The abnormal phenomena that occurred and how they were handled | The same problem is investigated again and again, wasting time |
How to make the ledger actually get used
The common reason a ledger falls out of use is that the maintenance cost is higher than the benefit. A form with a dozen columns filled in by hand every day is abandoned within three months. The workable approach is to reduce the mandatory entries to a minimum and to link the remaining information from the equipment running records and the sampling records, so that filling it in can be done without effort. Once the ledger becomes an extra burden, it degenerates into an empty form.
- Use a single numbering rule and use the equipment tags the site already has for the positions; do not start a second set of names.
- Copy the oil field straight from the drum label or the sampling sheet, so that the site does not invent its own abbreviations.
- Keep the history of abnormalities as an appended record; do not overwrite the earlier entries, and leave the process of the changes on it as well.
- Put the date and the name of the person recording on every entry, so that it can be checked and traced later.
How the ledger in turn guides spare parts purchasing
The most direct by-product of the ledger is that the consumption of the consumables becomes something that can be counted. Which filter element models a machine has used, how many were fitted and how often on average they are changed: once those data are brought together, spare parts purchasing changes from ordering by feel to ordering against actual consumption. Among the common element specifications, the coarse filter elements 150-250-50 and 110-250-50 are used at the front, the secondary filter element 110-400-20 is used for the transition, and the fine filter element 150-500-5 is the standard configuration of the ZYD-100, five of them in parallel. Which one is consumed fastest shows up directly in the ledger.
The elements are not the only item. The consumption rhythm of wear parts such as the vacuum pump oil and the seals can also be read from the ledger, so that stock can be prepared in advance and a shutdown is not held up in a maintenance window for want of a part. In the other direction, if the number of one type of equipment keeps growing while the stock of the matching consumables is still bought at the old rate, the spares build up. The ledger is also the only reliable source for the number of machines in service, their positions and the distribution of the load, and the accuracy of the spare parts plan rests directly on it.
It should be added that the ledger does not replace the equipment file and the documents supplied with the machine. What it records is the condition in service and the consumption; the equipment parameters still come from the nameplate and the accompanying documentation. Keeping the two apart, each in its own place, is what allows the ledger to stay light and to be maintained over the long term. Copying the parameter tables into the ledger as well usually means they are never complete and never updated.
The value of the ledger is not in the record keeping itself, but in being able to answer on the spot during an inspection what condition this machine was actually in last time.