Insertion magnetic inductive flowmeter insertion depth requirements and adjustments

Project Overview

• (1)To ensure sufficient straight section of the fluid in the direction, pipe diameter and valve opening changes, will produce eddy currents and flow field distortion, which will have an impact on the measurement of the sensor electrode, thus affecting the accuracy of the instrument. Therefore, it is necessary to leave the elbow, hand valves, regulating valves and other components at a certain distance as far as possible;
• (2)Avoid sources of interference as much as possible, in order to guarantee the measurement accuracy, the sensor should avoid installing in places that are prone to generating vacuum, gas, eddy current and so on. The communication cable between the sensor and the smart transmitter should avoid strong electrical equipment such as electric motors;
• (3)Ensure the perpendicularity of the fluid and the sensor magnetic field in the pipeline opening to install the pressure-taking short pipe, welding the pressure-taking short pipe should pay attention to the perpendicular direction, the requirements of the welding of the short pipe axis and the pipeline axis of the angle of 90, and the flange of the short pipe connection of the extension of the line perpendicular to the centre of a circle through the pipeline cross-section, so as to ensure that the fluid and the perpendicularity of the magnetic field;
• (4)Insertion magnetic inductive flowmeter general insertion depth has 3 cases: 1/2, 1/4, 1/8, according to the actual product parameters;
• (5)Insertion type magnetic inductive flowmeter to ensure good grounding sensor output signal ground point should be electrically connected to the measured medium.

When the fluid cuts the magnetic lines of force to generate a flow signal, the fluid itself is used as the 0 potential, and a positive potential is generated on one electrode and a negative potential is generated on the other electrode, alternating constantly. Therefore, the midpoint of the converter input (signal cable shield) must be at a common 0-potential with the fluid and conductive in order to form a symmetrical input loop. The midpoint of the converter input is electrically connected to the measured fluid via the sensor output signal's ground point. Since the sensor output signal is very small, only a few millivolts, in order to improve the instrument's immunity to interference, the 0 potential in the input loop must be grounded.

As a result of the general metal pipeline are connected to the earth flow medium through the metal pipeline and the earth electrical connection so does not require magnetic inductive flowmeter separate set of grounding devices, especially small diameter electromagnetic flow sensor. If non-metallic piping, it must be connected to a separate earth wire.

How to adjust the insertion depth of the insertion type magnetic inductive flowmeter

• 1. When selecting the electrode inserted into the average flow velocity, according to the pipeline turbulent flow conditions in the average flow velocity point about from the pipe wall H1 = 0.25D (D: pipe inner diameter) hand pressure handle to make the insertion of the rod and then into the pipe H1 deep. (At this time L2 = original L2 - H1).
• 2. After confirming that the insertion depth is correct, turn the handle so that its connection line is parallel to the centre line of the pipe, at which time the connection line of the two electrodes will be perpendicular to the centre line of the pipe, i.e. the connection line of the electrodes is perpendicular to the flow rate.
• 3. After adjusting, tighten the locking nut and then tighten the three locking screws respectively. Their role is to ensure that the insertion rod is not pushed out by the pressure inside the tube, and secondly, to ensure that the insertion rod will not vibrate. (Note: Screwing the first two screws as long as the contact with the insertion of the rod, do not force, only to screw the third screw tighten as tight as possible.)
• 4. When the selection electrode is inserted into the centre of the pipe (here is the maximum flow rate!) ), the downward pressure depth at this point H = 0.5 D. Otherwise work as above.
• 5. Loosen the set screw under the junction box, rotate the junction box to your satisfaction and tighten the set screw. Adjustment is complete.