Vaisala INTERCAP HMDW80 SERIES Specifikace stáhnout pdf (Strana 112)

110

Moisture in Oil

/ TECHNOLOGY DESCRIPTION

Vaisala HUMICAP® Sensor for Measuring

Moisture in Oil

Water is a common contaminant in

industrial oils. Water contamination

deteriorates the performance of the

oil, be it used for lubrication, cooling,

insulation or other purposes. High

moisture content increases the risk

of corrosion, overheating, machine

malfunction and other problems

and can ultimately lead to costly

failure and unscheduled downtime.

Monitoring the oil for moisture

is a simple way of improving the

reliability of industrial machinery and

equipment. With time, substantial

savings in maintenance costs can be

achieved.

Free Water Formation –

the Critical Point

Water can dissolve in oil. When the

water content of the oil increases,

it eventually reaches the saturation

point of the oil. Once the fluid has

reached its saturation point, any

additional water introduced will

separate out as free water by forming

a distinct layer. Alternatively, the

oil can form dispersion with water,

which turns the oil cloudy. Since

most oils are less dense than water,

the water layer will usually settle

below the oil with time.

Unique Benefits of HUMICAP

in Oil Moisture Measurements

▪

Fast. Online, real-time

detection of moisture in oil

without sampling

▪

Reliable. Tells the true margin

to water saturation point in all

changing conditions, taking

into account e.g. temperature

changes and aging of oil

▪

Highly stable. Excellent

pressure and temperature

tolerance

▪

Easy to install through ball

valve – no need to shut down

the process

▪

Enables predictive

maintenance work. Trends can

be quickly identified.

Free water formation is critical in

terms of problems related to water in

oil. When water is no longer dissolved

in the oil, corrosion and wearing

of equipment increase rapidly.

Therefore it is important to keep the

moisture content safely below the

saturation point.

The ability of oil to hold dissolved

water depends on the type and age

of the oil as well as its additives.

Two major factors have an effect

on the saturation point as the oil

ages: temperature fluctuations and

changes in the chemical make-up due

to the formation of new substances

as by-products of the chemical

reactions.

Water Activity (a

w

) –

a Direct Measure of

Oil Quality

The conventional measure for

water content in oil is ppm (parts

per million), which describes the

absolute amount of water in the oil.

Ppm measurement has, however,

a major limitation. It does not

account for any variations in the oil’s

saturation point. In other words, ppm

measurement provides no indication

of how close the moisture level is to

the saturation point in a dynamic

system with fluctuating saturation

point. By measuring water activity

instead of ppm, the risk of actually

exceeding the saturation point can

be avoided.

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