1. Reasons for instrument selection
(1) Due to improper diameter selection of the instrument, the actual flow rate after installation and use is far from the range of the instrument, mainly manifested as large pipe diameter, small flow rate, low flow velocity, actual flow rate at or below the lower limit of the instrument, and the instrument cannot operate normally, resulting in significant measurement errors.
(2) When selecting a meter, the working condition parameters provided are inaccurate and far from the actual working conditions, resulting in improper meter selection. After the instrument is installed and put into operation, it cannot operate normally, especially for gas flow measurement. The large deviation in operating pressure has a particularly significant impact on the measurement.
2. Reasons for improper installation
(1) The length of the straight pipe section upstream and downstream of the instrument is insufficient, the sealing gasket protrudes into the pipe, and the sudden contraction and expansion of the pipeline's flow resistance components cause serious disturbances to the flow field.
(2) Poor installation of liquid measuring tubes containing trace gases or gas measuring tubes containing trace liquids can cause the retention of heterogeneous fluids in the measuring tubes of vortex flowmeters, which can interfere with the measurement.
(3) When measuring liquids, installing a vortex flowmeter on a pipeline that flows vertically from top to bottom or slopes downwards, or installing a vortex flowmeter at the outlet of a pipeline object without back pressure, may cause the liquid to not fill the pipe.
(4) The installation position of the vortex flowmeter is too close to the power source (fan or pump), without a sufficiently long upstream straight pipe section and effective vibration reduction measures.
(5) When measuring high-temperature media, the vortex flowmeter is installed horizontally and forward. The converter is located directly above the pipeline, and the insulation measures for the pipeline are not in place, resulting in direct baking of the converter components by the high temperature of the pipeline and damage to electronic devices.
3. Fluid related reasons
(1) The measured fluid is not a homogeneous single-phase fluid, it may be a pulsating flow or a mixed phase flow, resulting in unstable vortex separation and large fluctuations in the output signal.
(2) The fluid is mixed with blocky solids, long fibers, or bands. A block shaped solid object moving at high speed may collide with the object and detection element, and in severe cases, it may damage the object and detection element; The entanglement of long fibers and strip like objects around the generator and detection element disrupts the stable separation of the Karman vortex street and interferes with the stable operation of the detection element.
After long-term work, the adhesion and deposition of dirt inside the fluid on the inner wall of the measuring tube and the surface of the detection element have changed the geometric size parameters of the measuring tube and the generating body, increased the measurement error of the instrument, reduced the sensitivity of the detection element, decreased the signal amplitude, and thus caused the failure of the detection element.
4. Environmental reasons
The long-term erosion of corrosive gases and moisture in the environment can cause a decrease in the insulation resistance of detection components, as well as corrosion of some electronic components, wiring terminals, and grounding terminals, resulting in an increase in contact resistance of connectors and attenuation of transmitted signals.