Principle Of Operation
Mechanical Installation &
Installation & Operating Considerations
and Maintenance Instructions
DATA SHEET 40520
Displacement Microflowmeters are generally limited to direct measurement
usage in relatively clean, low viscosity liquid applications. If the fluid
to be metered is other than this, an alternative, inferential method utilizing
a barrier is recommended. The barrier is in the form of a fluid driven
positive displacement pump.
are two diaphragm pumps. They are selected for purposes of simplicity
and, generally, economics. Piston pumps would work as well. These pumps
are normally driven by compressed air. In the alternative recommended,
herein, hydraulic pressure replaces the compressed air as the motive force
in the primary pump. A secondary pump is employed to provide this hydraulic
pump displaces the high viscosity, unclean liquid or slurry to meet system
requirements. The secondary pump displaces a clean, low viscosity liquid,
such as, isopropyl alcohol. A DEA Microflowmeter is installed between
the secondary and primary pumps to measure the flow of the benign liquid.
Every displaced unit volume from the secondary pump will displace an equal
amount in the primary pump. Including any reasonable discrepancies due
to fluid compressibilities, elastomeric moduli, hysteresis, etc., the
accuracy of such an approach should be well within ± 3 %. Repeatability
should be substantially better than that.
can be effected by down stream process system throttling, pressure control
to the secondary pump or through a closed loop feedback control system
controlling the flow through the Microflowmeter.
of High Viscosity Fluids