When a number of oil purifiers stand idle at the same time, the difference in their energy use is not obvious, but it adds up over a long period. Holding the heat, idling and a full shutdown are three states with completely different electricity behaviour, and which one to choose depends on whether the machine has to start working again straight away. This article sets the three out, and shows where the standby energy goes and how to account for it.
The electricity behaviour of the three standby states
A full shutdown is the cheapest of the three. The heaters, the vacuum pump, the oil pump and the control circuits all stop, and the machine returns to a state where it simply exchanges heat with the surroundings. The price is that the machine has to be heated up and drawn down again when it is started, and the oil itself has been cooled by the environment in the meantime, so the heat load has to be gone through once more.
Holding the heat means keeping the heating on and holding the temperature near a set point. Far infrared carbon fibre heating is the heating method used on this kind of equipment, and the temperature control range of the TYA series is 45~80 ℃, with the upper limit pulled down to 70 ℃ when the water content is high. In this state the heating element keeps drawing power, but far less than during the heating stage, and the running cost follows the holding temperature directly.
Idling means keeping the pumps and part of the circuit running so that the oil circulates inside the system. This is the most expensive of the three, but it gives the best readiness to produce oil at any moment, and it is what a maintenance window normally calls for. It solves the problem of the start-up time, not the problem of the cost.
What the standby energy consists of
Once the electricity is split into heating, vacuum and pumping, and the control circuits, the table below becomes easy to read, and the difference between the standby states comes mainly from these three blocks.
| Standby state | Main part of the electricity use | How it behaves | When it fits |
|---|---|---|---|
| Full shutdown | None | The longest preparation time before the next start | Out of use for a long time and not due back soon |
| Holding the heat | The heating element and the temperature control circuit | The consumption follows the ambient temperature | The machine may be started again within a few hours |
| Idling | Heating, vacuum pump, oil pump and control circuits | The highest consumption of the three | Oil is needed at any moment, before and after a maintenance window |
| Intermittent holding | The heating element switched on and off in cycles | Less than continuous holding | Long intervals, but the time of the next start is not known |
Turning the idle time into a choice
- First establish the real working rhythm of the machine, and separate the case of being stopped for a few days from the case of small jobs every day.
- Arrange the work on one batch of oil as far together as possible, so that the heating and the vacuum are established fewer times.
- Switch to a full shutdown after a certain period out of use, and keep the holding window for the machines that may have to start at any moment.
- Adjust the holding temperature to what is actually needed; there is no reason to sit at the upper limit all the time.
- Record the idle hours and the number of starts for each machine, and use that as the basis for the production plan.
- Before a machine is switched off for a longer period, check the inlet valve and drain the machine, so that no oil is left standing for a long time.
Accounting for the whole of it
Standby energy is not only electricity. Holding the heat means the machine stays at a high temperature, and the sealing parts and the insulation are held in conditions less favourable than room temperature. A full shutdown means every start includes a heating stage again, and the energy of the heating stage is normally higher than that of the holding stage. Both of these have to be counted before it can be said which way is cheaper.
For work that involves insulating oil, the ZYD-100 has a flow rate of 6000 L/h and a total power of 72 + 5 kW; a machine of that size left on holding heat produces a noticeable energy figure. On the other hand, if the machine is certain to be started in two days, letting it come up from cold to save that electricity is not necessarily the cheaper option either. The judgement is made on the working rhythm, not on habit.
A machine on standby is not a machine that is doing nothing; it is still dealing with temperature, time and the price of electricity.
