Flow sensor installation and use precautions - Solutions - Huaqiang Electronic Network

1. General requirements for flow sensor installation

Due to the difference in the shape and structure design of the dry measuring tube, the weight and size of the sensors of different sizes with the same diameter are very different. For example, the 80mm diameter is only 45 tons, and the weight is 150-200kg. Installation requirements vary widely, so it must be installed in accordance with the manufacturer's installation methods and avoidance prohibitions. For example, some models of fluid flow sensors can be directly connected to the pipeline, and some models require a support frame or foundation. In order to isolate the pipe vibration affecting the instrument, sometimes the sensor and the pipe are connected by a flexible pipe, and the flexible pipe and the sensor are connected with a rigid straight pipe with support members respectively. Before purchasing, you should obtain the installation and operation manual from the manufacturer who is planning to purchase CMF for reference comparison and selection.

The installation design is designed to have a long service life. To remove premature wear and solid objects and inclusions that cause measurement errors, protective devices such as filters or gas separators are installed upstream of the sensor in fluid and pipeline conditions. If you want to be able to calibrate the instrument online, you should consider the drain connection and the valve, as well as the corresponding space.

2, flow sensor installation posture and position

The flow sensor measures residual solids, scale, and stored gas in the tube, which will affect the measurement accuracy. Generally speaking, the vertical pipe installed in the bottom-up flow is ideal; but for the non-straight measuring tube CMF installed on the vertical pipe or the horizontal pipe, depending on the pipe vibration condition and application conditions. The installation position must be filled with liquid in the measuring tube. For example, the fluid flowing through the CMF on the horizontal pipe is directly placed in the container without back pressure, and the measuring tube is often unable to be filled, which may cause the output signal to fluctuate drastically.

3. Installation of shut-off valve and control valve

In order to make no flow when zeroing, the CMF is provided with a shut-off valve upstream and downstream, and no leakage is guaranteed. The control valve should be installed downstream of the CMF and the CMF maintains the highest possible static pressure to prevent cavitation and flashing.

4, pulsation and vibration

To prevent the CMF from occurring in the process and external mechanical vibrations, ask the manufacturer about the resonant frequency range of the supplied CMF to determine if the on-site pulsation or vibration frequency is close to the resonant frequency of the CMF. A can provide the manufacturer with on-site vibration status consultation whether to take the following measures, such as: 1) setting the pulsation attenuator, 2) setting the vibration attenuator or flexible connecting tube, 3) special flow address sensor clamping fixture, etc. Wait.

5, to prevent interaction between CMF

Two CMFs of the same model are installed in series, or multiple CMFs are installed in close parallel (or parallel). Especially when mounted on the same supporting gantry, the vibration of the measuring tube will affect each CMF, causing interference and causing abnormal vibration. Make the meter inoperable. Precautions should be taken during installation, such as: to the manufacturer to propose the value of the resonance frequency close to the instrument; to open the distance of the flow sensor, not set on the same gantry, independently set the support frame; the flow sensor is installed in the opposite direction; Methods such as isolation of anti-vibration materials.

6, pipeline stress and distortion

When the CMF flange is connected to the pipe flange, tighten the bolts evenly. Do not cause stress on the CMF (for example, the planes of the two flanges are not parallel). If the short pipe of the same length as the CMF is pre-connected when the pipe is laid, the stress formed by the poor pipe can be prevented. During the process of use, due to process pressure and temperature changes, CMF will be affected by the axial force or bending/distortion force of the pipeline, affecting the measurement performance, and the necessary fixing brackets should be made.

7, the use of strong abrasive slurry

As mentioned above, it is best to use a straight tube single tube type to measure the strong abrasive slurry and to make the measuring tube in a vertical position to avoid uneven wall wear and shorten the service life. However, thinning of the wall thickness will reduce the rigidity of the measuring tube and change the flow measurement value. Therefore, it is necessary to periodically monitor and confirm the use period in the initial stage of operation of such a place.

The scaling or deposition on the inner wall of the measuring tube also affects the measurement accuracy, so it should be cleaned regularly.

8, zero drift and zero adjustment

The zero drift comes from the flow sensor section. The main reasons are: 1) asymmetry and attenuation of mechanical vibration; 2) density viscosity change of the fluid. The factors affecting the former are: a) the influence of the fixed stress at the end of the pipe; b) the change in the stiffness of the vibrating tube; c) the inconsistency of the resonant frequency of the double tube; d) the internal attenuation of the material of the tube wall. The latter affects the zero position because of structural imbalance. Therefore, even when the empty tube is adjusted, the resonance frequency of the double tube is adjusted to be uniform. When the liquid is filled, zero drift may occur. Similarly, the vibration attenuation caused by the dryness is related to the frequency. Zero drift may also occur.

The final zero adjustment must be carried out at the installation site. The flow sensor exhausts the gas, fills the upstream and downstream valves of the sensor after filling the fluid to be tested, and zeros at a temperature close to the operating temperature. If the installation changes or the degree of change is greatly changed, it needs to be re-adjusted.