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Technical Guide
DAN-LIQ-Turbine Meter-TG-0807
August 2007
Page 16
METER PERFORMANCE IN HIGH VISCOSITY LIQUIDS
Increases in viscosity of the measured liquid will reduce the rangeability of the ow meter. Generally, the
minimum ow rate of the meter will have to be increased to maintain the linearity rating of the meter.
The increased ow rate may be determined according to the following ratio:
Sizing ratio = Liquid Viscosity (Centistokes)
Nominal Line Sizes
Sizing Ratio Minimum Flow (% of Normal Maximum Flow Rate)
1 Use Normal Minimum Flow Rate
1.5 20%
2 25%
2.5 30%
3 35%
4 40%
5 45%
6 50%
7 55%
8 60%
Example:
The sizing ratio of a 4-inch turbine meter measuring a liquid of 8 cSt is 8/4, or 2. The normal maximum ow
rate of this size of meter is 1450 GPM. The new minimum ow rate is 25% of 1450, or 362.5 GPM. The ow
rate for this application is now 362-1450 GPM, with standard linearity (+/-0.15%) and repeatability of (+/-0.02%)
maintained.
Note: Use of the turbine meter on high viscosity liquids at the maximum extended ow range is allowable, but
may increase the wear rate of the turbine.
The pressure drop through the meter may be estimated (for low to medium viscosities) according to the following
formula:
DP = (PD) x (μ)
1/4
x (SG)
3/4
or
DP = (PD) x (v)
1/4
x (SG)
Where:
DP = Estimated pressure drop
PD = Pressure drop for water at expected ow rate
μ = Absolute viscosity in centipoises
v = Kinematic viscosity in centistokes
SG = Specic gravity
Note: μ = (v) x (SG)