The purchase price only states what one machine costs at the moment of delivery, but an oil purifier spends most of its time on site not treating oil. While the next batch has not arrived, while the previous batch has not left the tank, while a batch that did not meet its indicators has to go round again, while the maintenance window is already occupied, the machine produces nothing and still holds floor space, manpower and a window that could have been used for production. Put these into the same set of accounts and it becomes clear why two machines with similar parameters behave so differently on site.
Waiting for oil: the machine arrives before the oil does
The most common waiting happens before the job starts. The machine is in position, the power is connected, the filter elements are fitted, but the oil has not entered the tank yet, or it has entered and is still in the heating-up phase; during that time the machine stands in a waiting state. Whether that waiting lasts long depends on one figure only: whether the size of a batch matches the rated flow.
The flow rate of the ZYD-100 is 6000 L/h, the ZYD-200 is 12000 L/h and the ZYD-300 is 18000 L/h. The rated flow determines how much oil the machine can treat per hour when it runs continuously, while what arrives on site comes tank by tank. When those two figures do not match, waiting turns from a period into a normal state: for most of the time the machine uses only a small part of its capacity, and the rest of the time is spent waiting for the next batch.
Rework: the same batch goes round a second time
The other state that produces nothing is rework. The oil has already been through the machine once, sampling and re-testing shows that one item has not reached the target, and the batch has to go into the tank again. What is spent on top is not only time and electricity, but also the filter element life, the vacuum pump oil and the heating time already used up in the first pass. So the first question about a rework is not how long a second pass takes, but why the first pass did not meet the target.
There are two common drivers. One is a batch smaller than the capability of the machine: when the ZYD-100 treats a batch continuously at 6000 L/h and the quantity delivered does not fill that time, degassing and filtration are incomplete and the indicators tend to stop outside the target line. The other is that the condition of the incoming oil is far from the target, since both the water and the gas need enough residence time under vacuum to be driven out.
The outage window: the time the machine takes up
The third account falls in the maintenance window. The machine stands in one position, no oil enters and nothing moves, but that position, the manpower and the matching electrical capacity are all held. The window is limited, and once the machine has finished the work in it, the remaining time is wasted. The value of that time depends on something that is often overlooked: how many machines there are.
The dimensions of the ZYD-100 are 1200×1400×1800 mm and the weight is approx. 720 kg; the ZYD-200 is 1800×1600×2100 mm and 1950 kg; the ZYD-300 is 2200×1800×2200 mm and approx. 1400 kg. Three machines mean three times positioning, three times heating up and three times finishing, and when the previous one has not finished, the next one can only wait.
Turn these three accounts into your own figures
None of these three costs needs an external quotation; they can be worked out from the batch data the site already holds. The method is to cut the time up first, then match each period against the quantity processed, and only then discuss which model comes out better value. The order cannot be reversed, otherwise what comes out is still a comparison of machine parameters and not an account of your own site.
| Category of cost | When it occurs | The real driver | What should be recorded on site |
|---|---|---|---|
| Waiting time | After the machine is in position and before processing starts | How well the batch size matches the rated flow | The moment the oil enters and the moment processing starts |
| Rework hours | The indicators are not met after one pass | The gap between the target indicators and the condition of the incoming oil | The number of re-tests and the items re-tested |
| Outage window | The machine occupies a position but is not producing | The number of machines and the length of the window | The quantity actually processed within the window |
- Record three moments for each batch: the oil entering, the start of processing and the oil leaving. The gaps between them are the waiting, and the stretch from the oil leaving to the re-test passing is the rework.
- Then divide the quantity processed by that time; that gives the actual performance of this machine on your own batches instead of the rated flow from the data sheet.
- When comparing models, put these three accounts onto the same day and compare them: the quantity completed in that day, the shift time and the window occupied, and see whose account is shorter.
- Match the batch size as far as possible to the quantity the rated flow can treat in one continuous run, so that the machine completes a batch in one pass instead of splitting the same oil into two passes through the machine.
The purchase price is written into the contract; the waiting, the rework and the outage window are written into the operating record, and it is the second set of figures that decides how much oil the machine actually produces in a year.
