Vaisala MMT330 - Manual (Page 143)

Chapter 6 ____________________________________________________________ ppm Conversion
VAISALA _______________________________________________________________________ 141
Using Display/Keypad
1. Press any of the arrow buttons to open the Main Menu.
2. Select Measuring
by pressing the ► arrow button.
3. Select Oil coefficients
by pressing the ► arrow button.
4. Press SET
. Set the upper value A by using the ▲▼buttons.
Confirm by pressing OK.
5.
Use the ▼ button to choose B. Press SET. Set the lower value B by
using the ▲▼buttons. Confirm by pressing OK.
6. Press EXIT to return to the basic display.
Determination of Oil-Specific Coefficients
The equation of the Ppm calculation is:
ppm = aw*10
(B+A/T)
With the following procedure the coefficients A and B can be defined for
the equation:
LOG(PPM
sat
)= B + A/T
Equipment needed:
- Apparatus for determining water content ( for example, coulometric
titrator and e.g. magnetic stirrer.)
- Oil test station:
- a temperature test chamber
- for example, a conical flask (1L) sealed by PTFE stopper with
an inlet for a moisture probe
- MMT330 by Vaisala
- magnetic stirrer.
Procedure:
1. Define the water content of the oil sample with the titration. Use
the oil moisture level that is close to real conditions in the process.
2. Measure the water activity of this sample with MMT330 at two
temperatures that differ at least 20 °C. Follow the measurement
stabilization illustrated by the graph.
NOTE The sample has to be sealed very carefully. If the sample is in contact
with ambient air, its water content will be affected.