Application and Maintenance of Insertion-Type Flow Meters

The insertion-type flow meter is an instrument designed based on Faraday’s law of electromagnetic induction to measure the flow of conductive liquids. Due to its simple structure, lightweight design, easy installation, and minimal maintenance requirements, it is widely used in petrochemical installations for measuring the volumetric flow of non-corrosive (water supply and drainage) conductive liquids in closed pipelines.

Features and Applications of Insertion-Type Flow Meters

The insertion-type electromagnetic flow meter consists of two main parts: the sensor and the transmitter. The transmitter and sensor can be configured as either an integral or a remote (separate) type.

The applicable range of the insertion-type electromagnetic flow meter is similar to that of standard electromagnetic flow meters.

Key Technical Features and Applications:

1. High Accuracy – Measurement results are not affected by changes in flow profile, fluid pressure, viscosity, temperature, density, or conductivity.

2. Wide Pipe Size Compatibility – Suitable for use with metal pipelines ranging from DN25 to DN3000.

3. Wide Measuring Range – Offers a wide turndown ratio, up to 100:1.

4. Corrosion and Wear Resistance – Only the electrode and liner are in contact with the measured fluid; by selecting appropriate materials, it can resist corrosion and wear.

5. Advanced Transmitter Design – Uses a high-performance 16-bit microprocessor, features a 3-line 128×64 LCD dot-matrix display (Chinese characters), supports easy parameter configuration, and offers reliable programming.

6. Low Straight Pipe Requirements – Requires only 5D of straight pipe upstream and 3D downstream (D = nominal diameter of the pipe).

Installation of Insertion-Type Flow Meters

Installation of the Remote (Separated) Transmitter

The remote transmitter should be installed as close to the sensor as possible and can be mounted on a wall or a pole. For outdoor installations, it should be placed inside an instrument enclosure to avoid prolonged exposure to direct sunlight and rain.

Installation of the Sensor (or Integral Type Unit)

To install the sensor (or integral type unit) on a pipeline, a hole must be cut in the pipe and a mounting fitting (or pipe coupling) welded onto it. The sensor (or integral unit) is then secured to this fitting.

1. Technical Requirements for Pipeline Installation

• Choose a location with minimal vibration and avoid direct sunlight.

• To ensure the sensor's measuring tube remains filled with liquid, install the sensor at the lowest point of a U-shaped pipe.

• For vertical or inclined installations, the fluid must flow from bottom to top.

• The measured fluid must completely fill the pipe.

• The sensor can be installed either horizontally or vertically, as long as the geometric line between the two electrodes is perpendicular to the pipe axis.

• To further reduce the effect of air bubbles on measurement accuracy, avoid installing the meter at the highest point of the pipeline.

• Select a location that allows for easy wiring and convenient reading.

2. Installation of the Remote Sensor (or Integral Unit) Using a Flanged Ball Valve

• Drain the liquid from the selected section of the pipeline.

• Use a gas torch to cut a circular hole (Φ40–Φ50 mm) at the selected position on the pipe, and smooth the edges as much as possible.

• Remove the mounting base from the bottom of the ball valve and place it over the hole.

• Mount the sensor (or integral unit) onto the mounting base, place a gasket between the flanges of the mounting base and the ball valve, and ensure that the flow direction arrow on the sensor points in the confirmed flow direction.

Common Issues During the Use of Insertion-Type Flow Meters

1. Improper installation position of the flow sensor may result in the measuring tube not being fully filled with liquid, triggering an “excitation” alarm.

2. The straight pipe section before the flow meter should be ≥5D, and the straight section after the meter should be ≥3D (D = nominal diameter of the pipe).

3. When the liquid contains powder or particles, sediment buildup may occur, causing wear to the liner.

4. If the liquid conductivity is near the lower limit, measurement fluctuation or instability may occur.

5. The resistance of the sensor excitation coil (between EXT+ and EXT–) should be less than 60Ω.

Despite these potential issues, the insertion-type flow meter offers numerous advantages such as simple installation, wide application, reliable measurement performance, and ease of retrofitting older systems. It is widely used in the measurement of various water-based media (such as fresh water, circulating water, and wastewater) where flow rates are variable. These meters play an effective role in water usage balance and metering within industrial systems.

Therefore, understanding the working principle, structure, characteristics, and troubleshooting methods of insertion-type flow meters will help ensure better operation and maintenance.