27
15.3 PI SETTING ERRORS (FOR ADDITIONAL VISCOSITY CONTROLLER)
The heaters in the booster system are controlled by a viscosity controller.
In order to get a good working viscosity system an optimum adaptation of the control parameters (P,I)
is necessary.
P = Proportional band Pb (%)
I = integral action time Ti (min)
Problem
Possible cause
Corrective action
Oscillating temperature with
distinct initial overshot
Pb too low
Increase Pb
Set point is reached very slowly
after initial exceeding
Pb too high
Decrease Pb
The set value is reached very
slowly without overshooting
Ti too high
Decrease Ti
High initial overshot followed
by fading oscillation
Ti too low
Increase Ti
15.4 HOW TO TAKE A HFO SAMPLE FOR ANALYSIS
The HFO sample must always be taken from the circulation system as close as possible to the
viscosity sensor. Never take a sample from the bunker, settle or day tank.
The HFO sample must be collected and stored in a clean bottle or sample container. The bottle or
sample container must be sealed in order to prevent contamination with other products. The sample
quantity must be at least 200ml.
Write down the actual viscosity and temperature reading when the sample is taken. Send the sealed
bottle or sample container with actual readings to a qualified laboratory or to VAF Instruments for
analysis.
