On a ZYD-100 the first thing to be seen on the nameplate is the processing flow rate of 6000 L/h, the working vacuum of -0.08 ~ -0.0999 MPa and the filtration accuracy of ≤1 μm. These figures are not a set of independent lines of data: they are a set of results that hold simultaneously under specific conditions. What actually troubles people on site is treating the nameplate figures as figures that can be obtained at any time; they do not match at acceptance, and the machine itself is then suspected.
Sorting the nameplate data into three classes gives everything that follows a fixed point of reference. The first class is the rated values, such as the processing flow rate of 6000 L/h, which hold on the condition that the viscosity of the oil is in the usual range, that the inlet has been coarse filtered and that the oil temperature is in a suitable range. The second class is the structural limits, such as the ultimate vacuum of ≤5 Pa and the filtration accuracy of ≤1 μm; these two are determined by the selection of the pump set, the sealing arrangement and the filter element material, and they do not change however many machines are built. The third class is the duty-dependent figures, such as a water content of ≤3 ppm in the treated oil, a gas content of ≤0.01%, a cleanliness of NAS 1638 class 5 and a breakdown voltage of ≥65 kV; these depend on how dirty the incoming oil is and on how much the machine can remove within the given time.
Why a rated value cannot be treated as a guaranteed minimum
The conditions for the rated flow rate of 6000 L/h normally include: the incoming oil has passed the coarse filter element 150-250-50 or 110-250-50 before it enters, the oil temperature is held inside the set range, and the negative pressure at the pump inlet has not collapsed. If any one of these three is not met, the actual throughput drops. When the viscosity rises the flow falls for the same pump power; when the water content is high part of the heat goes into vaporisation instead of holding the temperature; and once the inlet element is saturated, much of the pumping speed is spent on pushing the oil through the resistance. These three cases look different on site, but the result is the same: the figure on the flow meter is below the nameplate.
There is one more case that is easier to overlook: when the vacuum level falls out of the -0.08 ~ -0.0999 MPa range the degassing efficiency drops, and the oil that comes out still meets the gas content requirement but has a high water content; the operator sees oil out of specification, while the actual cause lies in the pumping capacity and not in the heating. The same applies to a fall in the processing flow rate appearing ahead of the other indicators: it usually points to the pump set and the pipework rather than to the filtration accuracy.
Which figures are hard limits and which move with the duty
With the three classes separated, there is one further point to make: even between rated values, the different indicators move in different directions. The working vacuum is a range, and in normal running it should sit steady inside that range; a value close to the ultimate vacuum means that the system leaks little, but it is not a target that can be held under continuous pressure, because that is overpressure operation. The ultimate vacuum of ≤5 Pa is a structural capability of the machine and belongs to the hard indicators. The filtration accuracy of ≤1 μm is guaranteed by 5 × 150-500-5 fine filter elements in parallel and is also a hard indicator; change to the coarse filter element 150-250-50 or the second-stage element 110-400-20 and the accuracy immediately becomes a different order of magnitude.
- Rated values: the processing flow rate of 6000 L/h, valid on the condition that the oil is coarse filtered before it enters, the oil temperature is inside the range and the negative pressure at the pump inlet is normal.
- Structural limits: the ultimate vacuum of ≤5 Pa and the filtration accuracy of ≤1 μm, determined by the selection of the pump set and the element configuration and not improved by the duty.
- Duty-dependent figures: water content ≤3 ppm, gas content ≤0.01%, cleanliness NAS 1638 class 5 and breakdown voltage ≥65 kV, which vary with the state of the incoming oil.
Why acceptance should be discussed against the least favourable duty
Many acceptance disputes are not caused by poor workmanship; they come from the two sides assuming different conditions. The supplier tests with new oil or well-conditioned oil, the buyer tests with the dirtiest oil on site, at the lowest oil temperature and with the highest water content, and the two sets of figures naturally do not match. The effective practice is to fix the conditions in the contract or on the acceptance sheet: the oil type and the viscosity range of the incoming oil, the upper water content, the degree of inlet contamination, the continuous running time, and the sampling position and the sample volume.
| Nameplate parameter | Class | Varies with the duty | How it is checked at acceptance |
|---|---|---|---|
| Processing flow rate 6000 L/h | Rated value | Varies with the viscosity, the water content and the inlet contamination | The average after continuous feeding and stable running |
| Working vacuum -0.08 ~ -0.0999 MPa | Operating range | Varies with the feed rate and the sealing condition of the system | The steady reading under load |
| Ultimate vacuum ≤5 Pa | Structural limit | Does not vary with the duty | Read while drawing the ultimate vacuum at no load |
| Filtration accuracy ≤1 μm | Structural limit | Varies with the element configuration | Check the 5 × 150-500-5 in parallel |
| Water content ≤3 ppm, gas content ≤0.01% | Duty-dependent figure | Varies with the water content and the gas content of the incoming oil | Sample and test to GB/T 7600 and GB/T 423 |
| Cleanliness NAS 1638 class 5, breakdown voltage ≥65 kV | Duty-dependent figure | Varies with the degree of contamination of the incoming oil | Sample and test to NAS 1638 and GB/T 507 |
Once it is written down, acceptance becomes a reproducible test rather than an impression: the conditions are stated first and the readings second, and when the two do not match both sides know which end to look at. The limits of the machine do not narrow because they have been written down, but the disputes clearly reduce, because both sides are talking about the same figures under the same set of premises.
The figures on the nameplate have to be read in three classes: for the rated values look at the preconditions, for the structural limits look at the bottom line, and for the duty-dependent figures look at the incoming oil. Write the preconditions down first, then talk about the readings.