The demand for oil treatment equipment is not spread evenly across the year. While a transformer and its oil system run normally, the volume of oil to be treated is small. During concentrated maintenance, post-commissioning treatment and the purification of new equipment, the volume can multiply within a few days. The question in those periods is not whether the equipment is good, but how the peak is going to be absorbed.
Three ways to answer the peak
The first is to own a fixed machine. The ZYD-100 has a flow rate of 6000 L/h; the ZYD-200 of the same series handles 12000 L/h and the ZYD-300 handles 18000 L/h, so the machine can be matched to the annual volume and to the peak. The advantage is that it is available at any time, without waiting for delivery or transport; what it costs is the purchase, the space, the power supply and the long periods of idle time. The power supply of the ZYD-100 is three-phase 380V / 50Hz, the total power is 72 + 5 kW, the dimensions are 1200×1400×1800 mm and the weight is approx. 720 kg, so all of these have to be provided for on site.
The second is to bring a mobile machine in. The TYG-100 is a mobile vacuum oil purifier with a flow rate of 6000 L/h as well. It arrives on site, takes no permanent floor space and can move on when the work is done, which suits peaks concentrated in a few locations. The costs to include are the time to bring it in and take it away, the transport, and cleaning and checking the condition of the machine.
The third is to have the treatment carried out on site by a service provider. In this case the equipment, the operation and the safety of the oil all sit on the side of the service provider, and the user provides only the site, the oil and the inlet and outlet conditions. It suits users who have no maintenance capability of their own, or a volume too small to justify a dedicated machine.
Three things to look at when deciding
| The fact to establish | Owning a fixed machine | Bringing in a mobile machine | Contracted on-site treatment |
|---|---|---|---|
| Is the annual volume stable | Most economical when it is stable | More economical when it is concentrated in a few periods | Nothing stands idle when the volume is small |
| Gap between the peak and the average | Utilisation is high when the gap is small | A fixed machine stays idle for long periods when the gap is large | Utilisation does not come into it |
| Does the user have maintenance capability | People, spare parts and floor space are needed | Transport and cleaning add work | The maintenance duty is handed over as a whole |
The costs that are easily left out
- The cost of maintenance capability. Owning the machine means somebody has to look after the pump oil, the filter elements and the seals, and some stock has to be held. This rarely appears in a purchase budget.
- The cost of waiting. Renting equipment for a peak means scheduling the production, waiting for the transport and then checking the condition of the machine on arrival. None of that time produces any throughput.
- The cost of the oil itself. If the same batch is processed twice, the time and the energy of the second pass are wasted. The plan has to be judged on the final result and not on the individual action.
- The cost of the site. A fixed machine takes up floor space and needs a power circuit and inlet and outlet pipework, and the site conditions are usually harder to coordinate than the machine itself.
- The cost of documentation. Owning the machine means somebody has to be able to read the specification and the test reports, and that training cost tends to be underestimated.
Breaking the peak up
In most cases two approaches are used together rather than one chosen against the other. Small routine volumes can be covered by a light machine, for example the JL series cart type oil purifier with a filtration accuracy of 10–25 μm, which is kept in the oil treatment room and used as needed; a concentrated peak is then covered by vacuum degassing equipment. Splitting the two demands in this way usually costs less than asking one machine to cover all of them.
How it works out depends on how often the peaks occur, how long they last, what power and people the site has, and those facts differ from one user to the next. What is given here is therefore a framework for the decision rather than a recommendation.
The account of a peak should cover more than whether the equipment is enough; it should cover the waiting and the upkeep that no purchase order records.
