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Technical Guide
DAN-LIQ-Turbine Meter-TG-0807
August 2007
Page 14
RANGEABILITY OF LIQUID TURBINE FLOW METERS
The ow ranges indicated in the previous tables show a nominal ow range -- with a turndown of 10:1 - at which
the turbine will report measurement repeatable to the indicated specication based on measurement of clean
liquids such as water (specic gravity 1, viscosity 1 cSt) and mineral spirits (specic gravity 0.78, viscosity 1.8
cSt).
Where liquids with properties outside of the range described by these liquids are to be measured, the meter ow
range will be affected.
Extended ow rates on intermittent duty cycles are permitted and shown in the ow meter design features table
on page 12. It should also be noted that the use of the meter in the extended ow range should be limited to a
20% duty cycle.
LIQUID TURBINE FLOW METER PERFORMANCE WITH DIFFERENT SPECIFIC GRAVITIES
Liquid turbine meters are affected by changes in liquid density. When measuring liquids with specic gravities of
0.7 or less, the minimum ow rate of the meter must be increased to maintain the linearity of the meter within the
required limits. In this application, the maximum ow rate may be increased to allow for greater rangeability.
It is vital that proper back pressure be maintained (refer to page 18 for the formula for determining required back
pressure). Failure to do so may result in ashing and cavitation, which will cause over ranging of, and damage to,
the meter. Liquids with low specic gravities generally have high vapor pressures and high coefcients of thermal
expansion. When measuring these liquids, it is extremely important that proper installation, measurement and
proving practice be followed to provide stable temperatures and to negate the potential for poor measurement and
possible system damage.
The data on the following page are for the Daniel Series 1500 Liquid Turbine Flow Meter, and similar effects will
be observed in all design of turbine meters.