The standard configuration of the ZYD-100 is 5 × 150-500-5 fine filter elements in parallel, and the question that is often asked is whether the accuracy becomes finer once they are in parallel. The answer is the opposite: what parallel connection improves is the service life and the throughput, not the accuracy rating.
What parallel connection changes first is the filtration area
A single 150-500-5 element has a filtration accuracy of 1~5 μm and uses a deep-bed medium, in which the dirt is held by deep filtration inside the pores of the medium. With five elements in parallel the total filtration area is five times that of a single element, and the same throughput is shared between them, so each element carries only one fifth of the flow of the single-element arrangement and the dirt loading rate per unit area falls accordingly. What this looks like in practice is a much slower rise in differential pressure: a single-element arrangement may approach the alarm within a few hours, while five in parallel carry the same duty over a longer running cycle, and the number of consumable replacements falls accordingly.
Why the accuracy rating does not improve as a result
The filtration accuracy is determined by the pore structure and the retention mechanism of the medium itself, not by the filtration area. After the elements are put in parallel, each path still runs through the same element of the same specification, and no extra layers have been added to the path, so the particle size distribution passing through the oil has no essential difference from the single-element arrangement. The machine as a whole reaches a filtration accuracy of ≤1 μm and a cleanliness of NAS 1638 class 5 through the staged interception of the final fine element combined with the coarse filtration upstream, not through the number of elements.
- Filtration area increased: five in parallel, the total filtration area is five times that of a single element.
- Throughput increased: the same throughput is shared by five elements, so each one carries a lighter load.
- Service life extended: the differential pressure rises more slowly and there are fewer replacements.
- Accuracy unchanged: it is still set by the specification of the medium and does not improve with the number of elements.
The risks that a parallel arrangement carries with it
Parallel connection also means that the failure of any one branch affects the outlet oil directly. If an element is damaged on a branch, a seal ring is not seated properly or a bypass valve is opened by mistake, the particles that are not intercepted pass straight through to the downstream side. Such problems are also harder to see in a parallel arrangement: while the other four elements are still working, the overall performance at the outlet can still look acceptable, and only the test data exposes it. That is why the overpressure alarm with its audible and visual signal and the shutdown protection of the machine have to judge on the differential pressure of the whole group of elements, rather than watching only one branch.
There is another operating detail: whether the flow is shared evenly between the five elements in parallel depends on whether the resistance of the branches is the same. If one element is older than the others, or if it was sealed badly during fitting, its resistance is higher and its actual flow is lower. Over a long run the degree of contamination of the individual elements drifts apart, so when the elements are changed it is not enough to change only the one with the highest differential pressure; the whole set should be considered on the basis of its accumulated running hours.
| Indicator | Single element | 5 in parallel |
|---|---|---|
| Filtration accuracy | 1~5 μm (150-500-5) | 1~5 μm, still set by the medium |
| Total filtration area | Area of a single element | Five times the area of a single element |
| Flow carried by each element | The whole throughput | One fifth of the throughput |
| Rate of rise in differential pressure | Fast | Markedly slower |
| Failure risk | A single point of failure affects the outlet | A failed element still contaminates the downstream side, so the differential pressure has to be judged for the whole group |
Parallel connection buys service life with area, not accuracy with quantity; the accuracy has to be calculated back from the specification of the medium.