Water in Hydraulic Oil
Water in hydraulic oil is one of the most common causes of contamination in a hydraulic system…
Water in hydraulic oil can find its way into the fluid in a number of ways including worn seals, breathers or condensation. It may also enter the hydraulic oil through leaking heat exchangers or coolers from the water used during operation of the equipment. To prevent water getting into the oil, your equipment must have high quality design and regular maintenance, however it can be costly and time-consuming to prevent all sources of water from getting into the oil.
Water in hydraulic oil can have hugely damaging effects to your hydraulic components. Corrosion of the surfaces in the system is the most prominent effect and is caused by free water. Bearings can be directly affected by this corrosion through metal surface wear and may still be affected even if the water is the fluid has dissolved.
Not only does water wear the components of the system, but it can also have an impact on the oil itself, changing its physical and chemical properties. Physical properties include:
- lubrication and load-carrying;
- compression in hydraulic systems.
The absolute content and the relative content are two different approaches to measure how water is in your hydraulic oil and system. Absolute content measures how much water is in the oil in parts per million (ppm), whilst relative content allows you to see what the fluid water content is in relation to its saturation at certain temperatures. This method warns you of the imminent creation of free water.
The following steps can be taken to remove water in hydraulic oil:
- Draining – the separation of contaminants usually happens in the hydraulic reservoirs; the air rises to the surface, whilst the water falls to the bottom. Draining should be a regular occurrence, as it is cheap and if you have automatic drain valves installed, this reduces time-consuming maintenance.
- Free and emulsified water can be removed by using absorbent filters. The filters contain absorbent polymers which can be found in the filter matrix. This method isn’t recommended if large amounts of water exist in the oil. They also won’t remove dissolved or strongly emulsified water.
- Vacuum dehydration purifiers are able to dry water in hydraulic oil by exposing it to a partial vacuum. Flash distillation vacuum dehydration and mass transfer vacuum dehydration are the two common ways of achieving this. Flash distillation applies heat to boil as much water as it can and produces a stronger vacuum. This makes this particular method more effective, because it is removing more water from the oils than the mass transfer vacuum. The only disadvantage to this technique is the fact that the combination of the high temperature and strong vacuum has a consequence of thermo-oxidative fluid degradation as a result of the loss of volatile additives.