The training given on the day the equipment is delivered usually lasts only two or three hours, and the people who attend are the operators on shift and the shift supervisor. Not much of what is explained is actually remembered afterwards and put to use, and it comes down to three things: how to run through the checks before start-up in the right order, which readings to watch during operation, and in what order to shut down and change the element. All three are about actions, not about principles.
The first thing: the check sequence before start-up and the safety confirmation
Most site accidents are not caused by not knowing the principle but by omitting a step or carrying out the steps in the wrong order. This part of the training therefore does not introduce the functions; it walks the operators through the steps that have to be taken before start-up: confirming that the previous shift shut down normally, that the oil level in the tank is within the permitted range, that the filter element has not reached the end of its replacement cycle, and that someone has confirmed which position the valves are in. The safety confirmation is a separate section and covers whether the guardrails and the cabinet doors are in place, whether the earthing is reliable, whether no tools have been left in the maintenance area, and whether no one is within the working area.
Only after these are confirmed is the start-up sequence covered: first switch on the heating to bring the oil temperature up to the set range, then start the pump set to establish the vacuum, and then admit the oil. The reason for that order is explained as well: if oil is admitted before the temperature has come up, the higher viscosity puts the load straight onto the pump, the vacuum level will not come up while the flow reading still looks normal, and the operator will assume that everything is in order. The temperature control range of the TYA series is 45–80 °C, and where the water content is high the upper limit is brought down to 70 °C; that upper limit is not a recommendation, and above it the oxidation and the emulsification of the oil both accelerate.
The second thing: which readings to watch during operation
The readings to watch during operation are a fixed few, not every indication on the panel. The vacuum level is watched for stability in the -0.08 ~ -0.0999 MPa range; if it drops out of that range, the pumping capability or the sealing has a problem. The oil temperature is watched for stability at the set value; a temperature that will not come up and a temperature that runs high both have to be investigated. The flow is watched to see whether it matches the rated value; the ZYD-100 has a flow rate of 6000 L/h, and if the reading is clearly low the differential pressure across the filter element and the running condition of the pump set are the first things to look at. The pressure is watched to see whether it rises within the permitted range; an overpressure triggers the audible and visual alarm and stops the machine.
Besides the readings, the indicator lamps and the alarm sound have to be recognised as well. During the training these correspondences are written out beside the panel instead of being left to memory. The operating records are also covered in this part: the time of every start-up and shutdown, how much oil was processed, and whether anything abnormal occurred in between, are all recorded. When the condition of the machine has to be assessed later, this record becomes the most useful material of all. The record does not need a complicated table; a paper register serves just as well. What matters is that it is continuous and that there are no gaps.
The third thing: the correct order for shutting down and changing the element
The shutdown order is the reverse of the start-up: first stop the oil feed, then stop the heating, let the oil temperature come down and hold the vacuum for a while before stopping the pump, and finally close the valves and disconnect the power. Stopping the pump while it is hot makes the pump oil temperature too high and leaves the vacuum unreleased, so that the pump set has to re-establish the negative pressure at the next start-up, which amounts to adding a fault to every shutdown. For a prolonged shutdown the oil in the tank must also be drained off or retained as the process requires; the oil should not be left standing in the tank for long periods.
Changing the element is the one of the three that is easiest to get wrong, and during the training it is carried out in practice on the machine: release the pressure, cool down, open the filter housing, take out the old element, clean the housing, fit the new element and confirm its direction, tighten up and reset. The TYA series manual contains one explicit requirement: when the pressure exceeds 0.3 MPa the element has to be cleaned and changed. The two mistakes common on site are opening the filter housing before releasing the pressure, and fitting the element the wrong way round and running it under pressure regardless; both of these damage the sealing face of the filter housing directly.
| The three items | What it looks like when it is done properly | The common deviations |
|---|---|---|
| Checks before start-up | Each item confirmed in a fixed order, with the safety confirmation as a separate section | Skipping the oil level, the valve positions and the element cycle checks on the basis of experience |
| Readings during operation | The four items, vacuum level, oil temperature, flow and pressure, together with the alarm indications | Watching only the flow and ignoring the vacuum level and the temperature |
| Shutdown and element change | On shutdown stop the oil feed before the heating; on an element change release the pressure and cool down before opening the housing | Opening the housing before releasing the pressure, and fitting the element the wrong way round |
Why the training concentrates on actions rather than on principles
If the principles are explained once, then six months later, when an abnormality occurs, the operator is likely to recall only one of the conclusions and will not remember which step comes first. An action that has been fixed as a sequence needs no judgement in the moment: the hand moves first and the sequence follows. What actually takes the most time in the three hours is letting the operators go through the start-up sequence themselves at the panel and change an element themselves on the machine. Explaining less and doing more is the only form of this training that works.
The training does not aim at explaining the principles thoroughly; it aims at fixing the order of the three actions so that the operator does not have to think again about which step comes first when something abnormal happens.