After a vacuum oil purifier is started, the oil in the chamber has to be heated, the chamber has to be drawn down to the working vacuum and the pipework has to be filled with flowing oil. All three happen at the same time, but the time each of them needs differs a great deal. A lot of people reach a conclusion about the machine less than ten minutes after pressing start, based on the pressure gauge, the oil temperature display and the first bucket of oil that comes out, and at that point the readings describe the building process and not the capability of the machine.
There are actually three stages after startup
The first stage is the temperature build-up. Far-infrared carbon fibre heating pulls the oil temperature in the chamber up from the ambient temperature towards the set value; the temperature control range of the TYA series is 45~80 °C, with the upper limit pulled down to 70 °C when the water content of the oil is high. The larger the thermal capacity, the slower the rise, and during this period the temperature display is moving all the time while degassing efficiency is not yet something that can be discussed. The second stage is the vacuum build-up, where the X-100 vacuum pump and the JRP-500 roots blower start in sequence and pull the pressure in the chamber down to the working range of -0.08 ~ -0.0999 MPa; the ultimate vacuum of ≤5 Pa can only be discussed once the vacuum has settled. The third stage is the flow build-up, where the oil circulates in the chamber, the oil standing in the pipework is pushed towards the filter elements, and only then does the pressure indication move from a static value to a running value.
| Stage | What the machine is doing | Can the readings be treated as a result |
|---|---|---|
| Temperature build-up | The heating circuit pulls the oil temperature towards the set value | No. The oil temperature is still changing and degassing has not yet taken place under the set conditions |
| Vacuum build-up | The two vacuum pumps extract in sequence | No. The reading is on its way up and has not settled |
| Flow build-up | The oil circulates in the chamber and the standing oil in the pipework is pushed out | No. The first batches do not represent the oil produced under steady conditions |
| Steady running | Temperature, vacuum and flow are all near their set values | Yes. Only in this stage do the readings carry a comparison |
The three things that are judged wrongly most often
The first is judging the degassing result from the oil temperature shortly after startup. While the oil has not reached the set value the conditions for flashing do not exist, so a high gas content in the oil coming out is normal and not a shortage of machine capability. The second is judging the vacuum system from the vacuum reading shortly after startup. While the front stage and the rear stage have not yet worked together, the reading sits at an intermediate value; only after the sequence has run through once does it continue to rise.
The third is judging the filtration result from the first few batches of oil. Just after startup the pipework and the housings still hold oil and particles from the previous job, and the oil pushed out with them carries those residues and does not represent the filtration result of the elements.
- To assess the degassing capability, wait until the oil temperature is inside the set range and has settled before taking a sample.
- To assess the vacuum system, wait until the two pumps have run through the sequence once before reading the gauge.
- To assess the filtration result, keep the first few batches separate and do not merge them into a qualified batch.
- Season and site conditions change the heat-up time, and in winter this period has to be extended in particular.
Leave the machine time to settle
The most direct approach is to write "entered steady running" into the site form as the point at which sampling may start, rather than taking the moment the start button is pressed as the starting point. The ambient temperature range is -20~45 °C, and the time needed to settle with the same quantity of oil differs between seasons, so that point should not be written as a fixed value.
One more point is worth making: before the machine settles it is still heating and the power has not come down. A machine with a total power of 72 + 5 kW works at full load during the build-up phase, and the energy used in that period is higher than during steady running.
In the first ten minutes the machine is preparing itself; the readings taken in that period belong to the process and not to the result.
