The most common order of work in selecting a machine is to look at a model first and then ask what that model can handle. Working the other way round is steadier, because the flow rate is calculated from the conditions on site and the model is only the result of matching against that calculation. Three of the site conditions decide the number.
The first calculation: how much oil is in the batch
The volume of oil to be treated is the most basic input. The quantity involved in one maintenance job on a transformer, a consignment of insulating oil, the stock in a storage tank that has to be treated; these figures are clear on site, and they are first converted into the flow rate needed: the required flow rate equals the volume of oil divided by the available treatment time.
The easy mistake here is to use all of the time. The time that is really available has to allow for feeding the oil, heating up, switching over to the outlet and draining off before stopping, so the time the oil spends in a state of effective degassing is shorter than the time on the clock. Estimate that too generously and the flow rate that comes out is below what is needed.
The second calculation: how long the window is
The outage window is a hard constraint. A short window compresses the time available for one batch and pushes the required flow rate up; at that point the question is not only whether to choose a larger machine, but also whether several batches can be treated in parallel or whether a mobile unit can bring the treatment capacity to the site.
The TYG-100 is a mobile vacuum oil purifier with a flow rate of 6000 L/h, the same level as the ZYD-100. It does not solve a short window. It solves the situation where the machine cannot go into a fixed plant room, or where several locations are served in turn. The two situations have to be judged separately.
The third calculation: how many passes are needed
How many passes a batch of oil needs depends on its starting state and on the target state. Where degassing is the main task and filtration supports it, one pass of vacuum degassing with fine filtration is often enough; where the water content is high and the particle load is heavy, coarse filtration usually has to come first and degassing after, which means the same batch goes through two sections or more. Every extra pass adds to the total treatment time required.
This is also why the number of machines and the way they are arranged have to be worked out together with the flow rate. Two machines in parallel solve the question of total throughput; one machine with its sections in series solves the question of running the same batch through several operations. The answer to those two questions is not the same.
The rated flow rates of the models
| Model | Rated flow rate | Situation it fits |
|---|---|---|
| ZYD-100 | 6000 L/h | Medium batch, fixed installation |
| ZYD-200 | 12000 L/h | Larger batch, tight window |
| ZYD-300 | 18000 L/h | Large batch or continuous treatment |
| TYG-100 | 6000 L/h | Mobile work, several locations in turn |
| TYA-50 | 2000 L/h | Small batch, continuous temperature control |
| TYA-100 | 4000 L/h | Small to medium batch, continuous temperature control |
| LY-200 | 4800 L/h | Large batch work led by filtration |
The figures in the table are rated values, that is, the capability under the specified working conditions. The actual rate on site is also affected by the initial state of the oil, the way it is fed in, the oil temperature and the configuration of the filtration section, and it is usually below the rated figure. Leaving some margin at the point of selection is steadier than buying right up against the rated value.
Where the budget is easily spent in the wrong place
The first is looking only at the flow rate and ignoring the accuracy and the vacuum level. At the same flow rate, what filtration accuracy can be reached and whether the working vacuum of -0.08 ~ -0.0999 MPa can be held steadily decide whether the treated oil is usable. The second is leaving out the supporting equipment: the inlet pipework, the storage tank, the supply capacity and the spare parts sometimes cost more than the machine itself. The third is calculating on the most optimistic window time and ignoring that the number of people available on site is limited.
Once these three calculations are done, the model is matched against them, and the machine that comes out is usually more suitable than one chosen first and made to fit afterwards, because every figure then corresponds to a specific condition on site.
The flow rate is calculated from the oil volume, the window and the number of passes; the model is matched afterwards.
