Installation considerations for mass flow meters

A mass flow meter is an instrument that accurately measures gas flow. Its measured value will not be inaccurate due to temperature or pressure fluctuations, and does not require temperature and pressure compensation. The mass flow meter directly measures the mass flow of the medium passing through the flow meter, and can also measure the density of the medium and indirectly measure the temperature of the medium. Since the transmitter is an intelligent instrument with a single-chip microcomputer as its core, more than a dozen parameters can be derived for users based on the above three basic quantities.

Installation considerations for mass flow meters

1. The mass flow meter works based on the principle of vibration, and in the process of its operation, electromagnetic technology is used to excite vibration, detect torsion angle and process detection signals. Therefore, the installation location of the mass flow meter cannot have a large vibration source, nor can it be installed near equipment that generates strong magnetic fields such as transformers and motors to prevent external interference from affecting its normal operation.

2. There is no requirement for straight pipe section when installing mass flow meter, but stress should be avoided when connecting sensor and pipeline. If there is deviation in concentricity between sensor and pipeline centerline during installation of mass flow meter, stress will be generated in vibration tube. This stress will form pressure, tension, or shear force, which will affect pipeline alignment, cause asymmetry of detection probe, lead to zero point change, and affect measurement accuracy [3, 4]. If the concentricity deviation between pipeline and sensor is too large, it may be impossible to adjust zero point. Therefore, reinforcement measures should be taken to stabilize pipeline near instrument. When installing flow sensor, soft connection should be adopted as much as possible. Flange connection screws should be tightened evenly and symmetrically. In order to reduce the influence of residual stress, flow sensor should be calibrated for zero point after installation. To facilitate installation and zero adjustment of mass flow meter, stop valves should be installed at the front and rear ends of mass flow meter.

3. The connecting cable between the sensor and the transmitter should use the manufacturer's special cable; the transmitter receives low-level signals, so the cable should not be too long. When installing the transmitter, ensure that the partition used to separate the intrinsically safe sensor cable from the power supply and output cables is installed in place; ensure that the sensor junction box and the transmitter housing are well sealed to avoid short circuits that may cause measurement errors or flow meter failures.

4. Choose different sensor installation directions according to the different properties of the fluid. Always keep the fluid in the sensor flow tube full. The U-shaped tube of the mass flow meter for gas feed measurement should face upward to avoid accumulation of condensate in the measuring tube; the U-shaped tube of the mass flow meter for liquid feed measurement should face downward to avoid accumulation of gas in the measuring tube.