Kobold DON -2/4, Operating Instructions Manual

Page: 8 / 65

DON
page 8 DON K36/1222
5. Operating Principle
Oval gear flowmeters are categorized as positive displacement flow technology.
When liquid flows through this type of positive displacement flowmeter, two oval
geared rotors measure a constant volume per rotation within a precisely machined
measuring chamber. With each rotation, a constant volume of liquid is measured.
The rotation of the oval gears is sensed via magnets embedded within the rotors.
These magnets transmit a high-resolution pulse output. The output signal can be
process externally via a remote display controller or PLC or via a variety of
output/display options available as accessories attached to the flowmeters.
The positive displacement flow technology allows for precise flow measurement of
most clean liquids regardless of the media conductivity. Other liquid properties also
have a minimal effect on the performance of this type of meter. Flow profile
conditioning is not required as with alternative flow technology options making oval
gear installations simple to install in tight spaces and at an economical price.
6. Mechanical Connection
6.1 General
Points to verify before meter installation:
Chemical compatibility of the liquid. Be sure that all wetted parts are
identified and confirmed suitable for use with the media being measured. If
unsure, please contact a KOBOLD engineer for guidance in obtaining the
proper reference materials.
Verify that the operational pressure and temperature limits are within
capability of the fully specified meter. Verify that the operational flow rates
are within the specified flow range. Viscous liquids may limit the maximum
allowable flow based on the viscosity. The max allowable flow rate may
need to be limited to ensure the differential pressure across the flowmeter
does not exceed 1 Bar, (100 kPa, 15 PSIG).
Be sure that the flowmeter is not subject to any process temperatures and/or
pressures that can cause the measured liquid to freeze or flash inside the
meter.
OPERATION:
Liquid travels around the crescent
shaped chambers created by the
rotational movement of the rotors
liquid exits the
measuring chamber
liquid entering
measuring chamber
liquid in transit