The discussion about connecting industrial equipment to a network tends to run to two extremes: one view is that fitting sensors makes unattended operation possible, the other is that the data is meaningless. In fact the operating data of oil filtration equipment can be used; it simply has a more specific and more limited use than it is advertised for. Put it to the judgements it really supports and it brings a real improvement.
The data that can really be collected now
Take a two-stage vacuum oil purifier as an example. With most configurations of the machine today, four kinds of operating data can be taken directly, and none of them requires any additional sensor work. These four come from the instruments and the electrical components the machine already has, so they are read directly rather than estimated by an algorithm, and the values collected are the same as the readings seen on site.
| Data that can be collected | Source | What the reading reflects |
|---|---|---|
| Running current | The motor circuit of the main circuit | The actual load on the pump and the change in the resistance of the element |
| Working vacuum | The pressure gauge or the transmitter of the vacuum system | Whether the degassing is progressing and whether the system leaks |
| Cumulative flow | The flow meter | The progress of the processing and the calculation of the energy consumption per unit |
| Running time | The timing of the control system | The maintenance interval and the baseline life of the consumables |
What these data can support
The running current tells the most through the shape of its curve. As a filter element blocks up gradually, the load on the circulation pump rises slowly and the current curve climbs slowly. If a bypass valve has opened by mistake or the pipework has been connected wrongly, the current jumps suddenly to a high value and is accompanied by a deviation in the flow. The two shapes are different and the actions are completely different, and they cannot be told apart from a single instantaneous reading.
The vacuum level, on the other hand, is suited to looking at the trend. The working vacuum is the -0.08 ~ -0.0999 MPa range; if it stays near -0.08 MPa for a long time without changing, the pumping speed of the pump or the leakage of the system has probably changed. If the vacuum curve falls gradually during the treatment while the amount of condensate drained off increases, that is usually the normal degassing process. What distinguishes the two is the shape over time and not the absolute value.
The combination of the cumulative flow and the running time gives the energy consumption per unit of oil processed, and it also establishes a baseline for the life of the consumables specific to this machine. This part of the data is particularly useful for spare parts management: counting the flow over a period and the number of element changes gives the real rate of consumption, instead of applying a general life figure and multiplying it by the number of machines.
Which promises cannot be kept at present
The statements below usually cannot be delivered at the present stage, and the expectations have to be matched at the proposal stage. A capability that cannot be delivered, written into the proposal, ends up as a source of dispute between the supplier and the user. Setting out the limits in advance is what makes the project proceed more smoothly, and it gives the later acceptance criteria a basis that both sides accept, so that the question of how the indicators are to be calculated does not have to be argued over again at the acceptance stage.
- They do not replace oil analysis. The current and the vacuum level do not show the depletion of the additives, the formation of the oxidation products or a change of oil type; these can only be established by sampling and analysis.
- They do not decide automatically whether the oil is within limits. The water content, the gas content, the cleanliness and the breakdown voltage each have their own test basis, and the operating data cannot take their place.
- They do not commission the machine automatically. The steps that involve safety and sealing still have to be confirmed on site, and a remote command cannot take their place.
- They do not reach back to older machines that have neither power nor a data interface. Missing history is missing.
- They do not replace the site inspection. Condensation inside the cabinet, ageing hoses and the condition of the elements can only be seen by a person.
How to put the data to work in practice
If the site does not yet have a complete digital system, the most economical starting point is manual recording, but the items recorded have to be fixed: for each job, record the vacuum level, the running current, the difference in the cumulative flow and the running time at the start and at the end, and attach the oil sample results from that job. After six months these records will support the kinds of judgement described above, and they depend on no network work at all.
Where a network connection is possible, the point is not to move the data to a cloud, but to bring the data back into the decisions: whether an abnormal current raises an automatic reminder, and whether the element change is triggered by the flow and the running time rather than by a calendar reminder. The test of whether an automation rule is useful is simple: when the reminder appears, does the site really need to do something? If not, it only adds noise.
The operating data tells you how the machine is working; only the oil data tells you what the oil has become, and neither one is enough on its own.