When the temperature control settings of the TYA series are opened up, what is usually found is not three fixed positions labelled low, medium and high, but a temperature range that can be adjusted continuously. That choice in the design decides directly whether the machine can cope with several oils of completely different character at the same time.
The temperature requirements of the oils differ in the first place
The TYA series handles industrial oils such as hydraulic oil, machine oil, coolant oil and lubricating oil, with a working vacuum of -0.08 MPa and a flow rate of 2000 L/h for the TYA-50 and 4000 L/h for the TYA-100. Different oils have different viscosity indices, different flash point ranges and different additive systems. If the same machine processes one oil today and another one tomorrow and the temperature control offers only a few fixed positions, which position it ends up on depends entirely on the experience of the operator, and two results are easy to arrive at: either the temperature is too low and the water does not vapourise sufficiently, or it is too high and the oil itself is degraded more quickly.
Why fixed positions always fall at one end or the other
- Not hot enough: the water does not vapourise sufficiently, the separation in the vacuum stage is incomplete and the water content does not come down for a long time.
- Too hot: the temperature approaches the flash point and the thermal stability limit of the oil, the additives degrade and the colour of the oil darkens, which means the treatment process itself is damaging the oil.
- Jumping between positions: the intermediate temperature that is actually needed falls in neither the low nor the high position, so there is no choice but to take one of the two.
How continuous adjustment and two hard limits work together
Continuous adjustment does not mean the temperature can be raised as far as anyone likes. The ambient temperature range of the machine is -20–45 °C, because it has to work in a switch room, in a workshop or even in an outdoor shelter. In winter the ambient temperature is low and the tank loses heat quickly, so the temperature control has to be able to bring the oil up to the set value and hold it there even at a low ambient temperature; in summer the direction of the heat loss reverses and becomes the difficulty, and then it is better to bring the set value down than to fight the ambient conditions. What the temperature setting obeys first is the site conditions, not the expectations of the operator.
Why the upper limit is brought down to 70 °C when the water content is high
When the oil carries a lot of water a higher temperature is needed to vapourise it, and the upper half of the 45–80 °C range is there for exactly that. But a high water content also means that the amount of vapour in the tank rises sharply, and if the temperature is at the same time pushed up to 80 °C, a large amount of water vapour is drawn off together and the light fractions of the oil itself are easily carried over to the vacuum pump side, which increases the loss of oil. Bringing the upper limit down to 70 °C when the water content is high is a compromise between vapourising the water out and taking less oil with it.
| Condition | Approach to the temperature setting | Basis | Readings to watch |
|---|---|---|---|
| Low water content, oil in good condition | Take the lower end of the range to reduce the energy consumption | The oil is not easily degraded | Water content at the outlet |
| High water content | Take the upper end of the range, with the upper limit brought down to 70 °C | Vapourisation is adequate and less of the light fractions is carried over | Vacuum level, quantity of condensate drained |
| Low ambient temperature | Raise the set value as required, after confirming that the tank can reach the temperature | Ambient temperature range -20–45 °C | Heating time and the actual oil temperature |
| High ambient temperature | Lower the set value rather than fighting the heat loss | Ambient temperature range -20–45 °C | The deviation between the actual oil temperature and the set value |
The point of a continuously adjustable temperature is that the choice is handed to the working condition; whether it is set right depends on the judgement of two things, the oil and the site environment.