Fig 1.0 EESIFLO’s water sensor installed On a ship purifier system

Changing the oil in an engine regularly protects the system and pays off in the long run. But it also involves throwing out a lot of serviceable oil from ships that see less strenuous use, and a schedule can't predict when oil will break down ahead of time. That's why a number of efforts are aimed at developing on-board systems to measure oil quality in real time or, at least, to base predictions on specific, observable conditions. A reliable means of monitoring the condition of engine oil will permit a new kind of just-in-time maintenance, and that, according to some forecasters, could save millions of quarts of oil a year. Although ships schedule oil changes along conservative time frames, this does not solve the problems of premature lubrication failure. Industry-wide minimum standards exist for acceptable engine oil quality, engine oil performance can vary widely according to individual conditions including usage times , filtrations systems and engine design. The bottom line when scheduling oil changes is to achieve the full design service life of the engine

This means it is important to analyze the oil condition for water content and particles.Many factors affect engine oil performance in different ways. One of them could be the temperature differentials observed. Common sense tells us that an oil can hold more dissolved water at higher temperatures. Once the temperature drops , it is possible to get free water formation and eventually contamination which can create problems such as lower performance, lower life expectancy of an engine and corrosion.

Fig 1.2 Saving oil is now a global campaign

Fig 1.3 The worst that could happen when engines fail

All ship maintenance personnel must follow a recommend scheduled oil change along very conservative timeframes and usage has to be taken into account although in some parts of the world this has been neglected somewhat. An effective schedule has to call for maintenance before signs of engine wear occur. "If you see signs of wear occurring, it's too late!

EESIFLO’s Water in Oil Sensor – A dual purpose!

Sometimes schedule-based maintenance can have several disadvantages. One disadvantage is that it can be wasteful, requiring oil changes before they actually become necessary . EESIFLO’s EASZ-1 on-board oil monitoring device is now commercially available . The sensor has been designed to measure water content in oil but can also be used to measure aging of oil (or a change in its state )by monitoring the dielectric constant, which correlates to the acidity, an indicator of oil degradation. The monitor has been designed to accurately measure the water content in oil .

Fig 1.4 Unscheduled ship engine maintenance

Newly supplied oil can be used as a reference as a “dry good oil” and the capacitance of that oil can be noted and changes in capacitance can be logged and monitored over time, even compared with spot samples sent to the laboratory to ascertain how the oil has changed and what reference capacitance this might correlate to.

The important factor for the EASZ-1 is not only its ability to measure the water content in oil but also is something has changed in the oil itself. Since we can establish that both water and aged oil have a direct effect on the capacitance it is possible to have an older oil with known amounts of water (from samples taken to the laboratory) reset to the lab report values.

If logs are kept on capacitance values over time, it will be possible to see trends or changes in capacitance that may not necessarily be linked to water content increase and hence we will have more of an idea when an oil has aged. What this all means for companies who research and take great interest in monitoring is that they can move from schedule-based maintenance to condition-based maintenance, which reduces waste that occurs when oil replacement is based on a schedule.

Replacing oil at the correct time has enormous economic savings and is also bettering our environnment. A combination of measurements will present a truer picture of oil degradation than just one measurement.

Fig 1.5 Ships should be accountable for water in oil

Measuring oil quality is usually done with a complex chemical laboratory benchmark procedure that measures several parameters indicating oil degradation. These factors include viscosity, total acid number, and particle concentration. The sensor developed by EESIFLO measures the dielectric constant of oil, which increases as molecules break down and the additives in the oil deplete with use. The dielectric constant correlates well with a total acid number and is easier to measure than other properties, making it suitable as the basis of an on-board sensing system. The dielectric constant of oil depends on the length of the service period and the composition of the molecules. As friction and temperature cause the molecules to break down and as additives are depleted, the dielectric constant increases, measured by increased voltage. The sensor is similar to a variable capacitor that consists of two parallel (co-axis pipes) electrodes separated by a gap filled with oil. It consists of a sensing cell that is in direct contact with oil- an electronic circuit that converts the signal from the sensing element to output current. The sensor weighs just over 1kg and can be connected to 1” standard NPT pipe connections.

Temperature Sensitivity

One difficulty in measuring the dielectric constant is its sensitivity to temperature. As temperature rises, the dielectric constant also rises. To cancel out this temperature dependency, the sensor signal conditioner is designed with compensation circuitry. The temperature sensing element is mounted as near to the process media as possible.

In addition to measuring oil degradation by monitoring molecular breakdown, the sensor also can be used to detect the presence of contaminants such as, each of which has a different dielectric,water has a much higher dielectric constant than oil, so relatively small amounts can be detected.

The sensor can be installed on some large diesel engines. A great is to detect seawater contamination in marine engines. Other places where the system could be useful would be hydraulic systems and compressors, stern tube seal lubricant monitoring and any larger hydraulic system where water contamination is a threat.

Current specifications for standard EESIFLO EASZ-1 water in oil sensors: Contact EESIFLO International for more information at http://www.eesiflo.com