When selecting oil filtration equipment, the most common mistake is to compare only how many litres are processed per hour. What actually determines the form of the equipment is what is in the oil. The three types of oil all look like oil, but their contaminant spectra, their damage mechanisms and their acceptance indicators have almost nothing in common.
Insulating oil: the core problem is dehydration and degassing
Transformer oil, instrument transformer oil, capacitor oil and cable oil belong to the same class of problem oil. The goal is to bring the water, the gas and the fine particles down to a level at which the oil can be returned to service. For this class of oil the answer is clear: a two-stage vacuum oil purifier. The ZYD-100 uses low-temperature vacuum under negative pressure together with three-dimensional film flash evaporation, with a flow rate of 6000 L/h, a working vacuum of -0.08 ~ -0.0999 MPa, an ultimate vacuum of ≤5 Pa and a constant temperature range of 20–80 °C. The acceptance indicators after treatment and the typical configuration are set out in the table at the end of this article; the core is that water content, gas content, cleanliness and breakdown voltage all have to be met at the same time.
Hydraulic oil and machine oil: the volatile substances have to go out as well
The problems with hydraulic oil, machine oil and lubricating oil are not only water and particles, but also volatile substances such as alcohol, gasoline and ammonia dissolved in the oil. They carry away the light fractions of the oil, which shows up directly as a drop in viscosity, a lower flash point and poorer lubricating performance. The TYA series is built for exactly this kind of duty: three-dimensional evaporation works together with multi-stage oil-water separation, a medium heat-absorbing condensing system recovers the vaporised oil, and pressure protection, automatic temperature-controlled heating and automatic separation of the condensate complete the online draining; the filter supports automatic backwashing.
Do not skip the stage in front
Whatever the type of oil, the same precondition applies: oil that is too dirty must not go straight into the vacuum system. The site practice with the TYA series is to start the vacuum pump first, watch the vacuum level reach -0.06, then stop the pump and check for leak points before the oil is admitted; where the water content is high, bring the upper temperature limit down to 70 °C so that the oil does not stay in the high-temperature zone for a long time. Where the oil is heavily contaminated, pre-filter it first with a JL series portable filtering and filling machine, filtration accuracy 10~25 μm, which one person can push, and this often settles most of the problems at the front end.
| Oil type | Main contaminants | Suggested equipment | Acceptance focus |
|---|---|---|---|
| Insulating oil | Water, gas, particles | Two-stage vacuum oil purifier (ZYD series) | Water content ≤3 ppm, gas content ≤0.01%, NAS 1638 class 5 |
| Hydraulic oil, machine oil | Water, particles, volatiles | Vacuum oil purifier (TYA series) | Viscosity and flash point recovered, particle count within limit |
| Lubricating oil | Metal swarf, oxidation products, water | Plate and frame filter press, centrifugal oil purifier | Improvement in particle count and colour value |
| General pre-treatment stage | Large particles | Portable filtering and filling machine (JL series) | 10~25 μm pre-filtration in place |
The order of judgement is simple: first ask what is in the oil, then ask what indicators have to be reached, and only then decide which machine to use.