There is more than one kind of dirt in oil
During service, oil accumulates several kinds of independent problems at the same time: water and dissolved gas, suspended solid particles, dark products of oxidation, and flocculent matter precipitated from high-viscosity oil. The means of dealing with them differ considerably. Vacuum degassing deals with gas and water, filter element filtration deals with particles, the plate and frame filter press deals with solid impurities in high-viscosity oil, decolourisation deals with colour and ageing products, while centrifugation and the portable oil cart correspond to different site conditions and working intensities.
These means cannot replace one another. Vacuum degassing brings the water content down to ≤3 ppm and the gas content down to ≤0.01%, and it has almost no effect on solid particles; filter elements retain the particles, with a filtration accuracy of ≤1 μm and a cleanliness of NAS 1638 class 5, and they are equally ineffective against water dissolved in the oil. No single machine can do everything; this is the direct reason why this equipment category exists, and also why it has to be assembled from several categories.
| Equipment category | Problem addressed | Models and figures |
|---|---|---|
| Two-stage vacuum oil purifier | Gas, water, fine particles | ZYD-100/200/300, flow rate 6000/12000/18000 L/h |
| Mobile vacuum oil purifier | Degassing and dehydration on site | TYG-100 6000 L/h |
| Temperature controlled vacuum oil purifier | Degassing that requires temperature control | TYA-50 2000 L/h, TYA-100 4000 L/h, temperature control 45–80 °C |
| Plate and frame oil filter | Solid impurities in high-viscosity oil | LY-50 1200 L/h (10 sets of 200×200 filter frames, 4 kW), LY-200 4800 L/h (40 sets of 300×300 filter frames, 11 kW) |
| Portable oil cart | Small batch, intermittent filtration | JL series, filtration accuracy 10–25 μm |
| Centrifugal oil purifier | Continuous, high-capacity separation | LX-100, LX-200 |
| Decolourisation and purification unit | Colour and ageing products | TL-50, TL-100 |
The categories classify problems, not size
Looking at this equipment together, the range of sizes is wide: a portable oil cart can be pushed up to the side of a tank, while a plate and frame oil filter needs a floor area and an electrical supply of its own. They are grouped into one category not because their appearance is similar but because they are subject to the same kind of constraint — the contaminants that enter the oil have to be separated out by physical or adsorption means, and the results have to be recorded in figures that can be checked.
Conversely, if the categories were drawn by size and power, a 4 kW LY-50 and an 11 kW LY-200 would fall into different classes, even though they face the same kind of problem: solid impurities in high-viscosity oil. The difference across the ZYD series from 6000 L/h to 18000 L/h is flow rate, not principle. When the classification is built on the problem to be solved, comparison across models is meaningful and price comparison across the industry has a common reference.
One machine is often only one section of a line
Actual duty rarely calls for a single category. A common line runs as follows: first coarse filtration to remove the large particles carried in from upstream, so that the downstream precision stages are not broken through; then vacuum degassing to bring the water and gas down; fine filtration is connected when high cleanliness is required; oil of high viscosity is treated at the front end by the plate and frame filter press; and colour and ageing products are dealt with separately by a decolourisation unit. The order in which these are connected depends on the condition of the oil and the figures to be achieved on site, not on the order of the equipment list.
Placing degassing after coarse filtration makes the degassing stage more efficient, because the oil entering the vacuum side no longer carries large amounts of solids; placing the plate and frame filter press at the very front of the line protects downstream equipment from damage by large particles; decolourisation is normally arranged as the last stage when an appearance figure has to be delivered, because it is the finishing step and not the starting one. If the order is wrong, the same combination of equipment gives different results, and the cost of rework is far higher than the cost of arranging the sequence once in advance.
Select equipment by problem, not by model
- First write down the problems to be solved: water removal, gas removal, particle removal, floc removal, or colour improvement — one per line. If it cannot be written clearly, the site objective itself has not been defined.
- For each problem, list the corresponding treatment method and equipment category, instead of choosing a model first and then seeing what it can do.
- Check whether these units can be connected in series: oil inlet and outlet connections, footprint, power supply and operating sequence. Lay them out on a drawing first, then request quotations.
- Calculate the flow rate from the maximum treatment volume on site; where rotation between areas is needed, choose a mobile type, while a fixed production line is better served by a fixed installation.
- The accuracy requirement determines the division of labour among the elements: coarse filter elements 150-250-50 and 110-250-50 and the second stage element 110-400-20 for upstream interception, and the fine filter elements 110-600-5 and 150-500-5 at the end of the line.
The measurement basis must be aligned, otherwise there is nothing to compare
The same machine can give widely different results when a different measurement method is used. Water content, gas content, cleanliness and breakdown voltage each have their own measurement basis: GB/T 7600 is used for water content, GB/T 423 for gas content, GB/T 507 for breakdown voltage, and cleanliness is graded according to NAS 1638. When comparing two units, it must first be confirmed that both use the same basis; otherwise the figures placed side by side have no comparability.
| Indicator | Measurement basis | Common expression |
|---|---|---|
| Water content | GB/T 7600 | ≤3 ppm |
| Gas content | GB/T 423 | ≤0.01% |
| Cleanliness | NAS 1638 | class 5 |
| Filtration accuracy | Check against the element specification | ≤1 μm |
| Breakdown voltage | GB/T 507 | Depends on the oil type and the application |
Once the basis is unified, selection returns to a simple question: which things does this oil need solved, which class of equipment takes each of them, and after they are connected do the flow rate, the accuracy and the footprint match the site. Writing the figures, the measurement basis and the models in three adjacent columns on the same table is what gives the differences between quotations an explanation, and what gives the acceptance inspection a common point of reference.
Oil treatment exists as an independent category because the dirt in oil falls into different kinds. List the problems clearly first, then decide how many units are needed.
