Technical Guide
August 2007
RANGEABILITY OF LIQUID TURBINE FLOW METERS
The flow ranges indicated in the previous tables show a nominal flow range
Where liquids with properties outside of the range described by these liquids are to be measured, the meter flow range will be affected.
Extended flow rates on intermittent duty cycles are permitted and shown in the flow meter design features table on page 12. It should also be noted that the use of the meter in the extended flow 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 specific gravities of
0.7or less, the minimum flow rate of the meter must be increased to maintain the linearity of the meter within the required limits. In this application, the maximum flow 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 flashing and cavitation, which will cause over ranging of, and damage to, the meter. Liquids with low specific gravities generally have high vapor pressures and high coefficients 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.
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