| Printer
Friendly |
Saturated Relative
Humidity (SRH) vs. Parts Per Million (PPM)
Most analysis of the amount of moisture in oil
is based on Parts Per Million or PPM. The issue with this
form of measurement is the variance of the saturation limit
of the oil from the basic PPM reading. There are several issues
that will cause the PPM saturation limit to vary from oil
to oil. They are type of oil (synthetic versus mineral), type
of additives, and the temperature of the oil when the equipment
is running or is on stand-by. Another issue with this method
of measurement is that the user does not know the saturation
level of the moisture in the oil. The reporting of the PPM
only gives a raw number. It is important to know the saturation
limit of an oil at a given temperature in order to determine
a set point for effective lubrication maintenance before free
water is present. Sponges provide a simple way to illustrate
this. Sponges of different densities hold varying amounts
of water. A dense-cell sponge can hold more water than an
open-cell sponge, even though both occupy the same cubic volume.
Trico has developed the Hydrolert Family of
products using a patented monitoring system based on the moisture
absorption capacity of the oil, Saturated Relative Humidity
(SRH). The Hydrolert monitors the moisture level in the oil
and accounts for the temperature and type of oil.
Every type of oil has a different moisture saturation level.
What the Hydrolert products do is measure the actual level
of moisture content and monitors that level against the saturation
limit. In order to understand this concept, think of it as
you would atmospheric air. We are able to measure relative
humidity levels in the air regardless of the temperature of
the air and the quality of the air. The Hydrolert does similar
monitoring for moisture content in oil.
Because the Hydrolert family of products measures the moisture
content based on saturated relative humidity; temperature
and oil type are both relative. This means there is no correction
factors to be done to the unit in order for it to function
on different oils. The unit senses that the temperature and
the saturation limit is always 100%. Because at saturation
the oil can hold no more than 100% of moisture (the sponge
is full). Monitoring as a percentage of the saturation limit
is a constant. Above 100%, free moisture is present in the
oil, ready to damage components in the housing.
The Hydrolert family of products are preset to give a warning
when oil reaches 70% of its saturation limit.