Hi!
How can I measure the water activity (relative rumidity) of Oil? Do I need special sensors for oil or does a sensor for air humidity also work?
Do You know/have theoretical background of that?

Thank You!
Isaak

Pall have a moisture meter that measures % saturation of oils. Handy item.

Heres the link to view an article on it that may answer all of your questions. http://www.noria.com/learning_center/category_article.asp?articleid=50&relatedbookgroup=Maintenance

Hi Isaac,

the measurement of water activity has some advantages over measuring the ppm content if

1. You don´t need information about aw > 1
2. You don´t need the absolut content of water

The main advantage of using aw is the fact that very often it is desireable to know when the risk for free water comes up.

The ability to solve water is dependent on several parameters, not only the oil type, but also the ageing, the contamination etc.

So if you receive an "absolute" value of 700 ppm water in oil content, then you normally cannot judge about the risk of getting free water.

But if you receive a value of aw=0.9 at 20 degrees celsius and you know that the oil could cool down to - 20 degrees celsius, then you should consider a dehydration or something else.

R+D produces aw-transducers (We don´t know a air-humidity transducer which can be used for aw measurment - but..... ), backflushable microfilters (and systems) and the portable oil microfiltration, degasing and dehydration unit PPS-Alpha where our water transducer is built in for example. (www.r-d-c.com)
Viele Gruesse aus Freiburg,

Wolfgang

Isaac,

In adition to the pall unit listed above, there are some other units. My previous experience is with Hydac and Vailsala.
Both units gave you the saturation percentage at a certain temperature. This allow you to monitor and trendt water activity before reach the saturation point of the oil. Every oil has a different saturation point, and of course this is directly related with the oil temperature.

Total Water Measurement
Hope I am not too late but we have a device that works as a capacitance cell. The same technology is accepted in the oil industry as an accurate custody transfer device for water content in Hydrocarbons. We have minituarized the technology and made it affordable for general industry applications. It can measure at both ppm and % levels , weighs 1kg and is loop powered.
I hope this helps
phughes@eesiflow.com