User`s manual
AX2200/AX2300 Instruction Manual Chapter 1 Introduction
CM2-AX2200-2001 (Rev. 4, 4/2014) 1-7
Minimum Back Pressure
A minimum back pressure is required to prevent cavitation in the vortex
flow meter when installed in liquid applications. Cavitation is a phenom-
enon wherein a liquid passing through a low pressure zone no longer can
remain in the liquid phase and therefore partially flashes (or “boils”) into
its vapor phase. The resulting two-phase flow degrades the liquid calibra-
tion accuracy. For some applications, a valve downstream of the flow me-
ter may be required to increase the pressure in the meter, thereby avoiding
cavitation. The following equation defines the minimum back pressure to
prevent cavitation.
P = 2.9 P + 1.3 P
V
Where:
P = Minimum line pressure five pipe diameters downstream of the flow
meter required to avoid cavitation (psia or bara).
P = Permanent pressure loss across the flow meter (psia or bara).
P
V
= Liquid vapor pressure at actual flowing conditions (psia or bara).
Temperature Measurement
AX2000Series Flow Meters use a 1000 ohm platinum resistance tempera-
ture detector (PRTD) to measure fluid temperature.
Pressure Measurement
AX2000Series Flow Meters incorporate a solid-state pressure transducer
isolated by a 316 stainless steel diaphragm. The transducer itself is mi-
cro-machined silicon, fabricated using integrated circuit processing tech-
nology. A nine-point pressure/temperature calibration is performed on
every sensor. Digital compensation allows these transducers to operate
within a 0.3% of full scale accuracy band within the entire ambient tem-
perature range of -40°F to 140°F (-40 to 60°C). Thermal isolation of the
pressure transducer ensures the same accuracy across the allowable pro-
cess fluid temperature range of -330°F to 750°F (-200 to 400°C).