How to Properly Use a Dual-Rod Vibrating Level Switch

Dual-Rod Vibrating Level Switch is a widely used instrument for level measurement in industrial process control. The Tube-11 is the first domestically produced vibrating level switch based on a dual-rod design and is a patented product by Jiwei.

The vibrating probe of this instrument employs an inner and outer nested dual-tube design. The resonance frequency of the inner and outer tubes is finely tuned to be identical, and a piezoelectric device is used to drive and detect the vibrations. This design ensures that the inner and outer tubes resonate at the exact same frequency. When the vibrating rod probe comes into contact with the measured material, the vibration frequency of the outer tube changes, thereby disrupting the resonance condition between the inner and outer tubes. This causes a significant reduction in the amplitude of the vibrating probe, which is detected by the piezoelectric sensor, leading to a decrease in the output signal amplitude. The intelligent circuit detects and analyzes this signal change and outputs a switch signal.

This product is primarily used for measuring granular solid material levels, with a minimum measurable density of 0.02g/cm³, which meets the requirements for most granular material level measurements. The product’s performance indicators are at the industry’s advanced level, offering high reliability.

Correct model selection is crucial for ensuring the normal operation of the Tube-11 vibrating level switch. The following are the key factors to consider when selecting the product:

1. Properties of the Measured Material: Tube-11 is primarily used for measuring granular solid material levels, with a minimum measurable density of 0.02g/cm³, capable of meeting the measurement requirements for most granular materials.

2. Working Temperature of the Measured Material: The instrument can adapt to a wide temperature range, divided into three temperature zone products: normal temperature type -50℃～150℃, high temperature type -50℃～250℃, and ultra-high temperature type -50℃～400℃. For ultra-high temperature types, on-site water/air cooling conditions are required, and only the flange connection type can be used.

3. Process Connection Type Selection During Installation: Process connections are available in common threads and flanges, including thread G11/2 “, G1 “, 11/2″NPT, 1″NPT, and flanges DN50 PN40, DN80 PN40, DN50 PN16, DN80 PN16. The flange standard is HG/T20592, and customization is available upon request.

4. Signal Output Type: The output types include relay output and two-wire output for user selection. For intrinsically safe explosion-proof requirements, two-wire output should be selected; for explosion-proof requirements, both relay and two-wire outputs can be chosen.

5. Power Supply: The power supply of the instrument should follow the requirements specified in the product manual. For explosion-proof products, the power supply must strictly adhere to the requirements of the explosion-proof certificate.

6. Insertion Depth: The insertion depth can be customized according to customer requirements. The standard type is 168mm; the extended type can be selected between 178mm and 20000mm. For insertion depths exceeding 6000mm, only the cable type can be used.

7. Explosion-Proof Requirements: The instrument has passed explosion-proof dust certification and intrinsically safe dust explosion-proof certification, allowing users to select according to design requirements.

Before installation, ensure that the instrument model meets the environmental requirements of the site, such as process pressure, process temperature, chemical properties of the medium, and explosion-proof requirements, to ensure the instrument functions properly after installation. The following are common installation methods:

a. Horizontal Installation: To ensure measurement accuracy, the Tube-11 can be installed horizontally. If measurement errors within a few centimeters are acceptable, it is recommended to install the Tube-11 with a downward tilt of about 20° to avoid measurement errors caused by material adhesion on the probe. When used to measure rapidly rising and fast-flowing materials, a protective baffle should be added to protect the probe from damage, ensuring more reliable operation of the instrument.

b. Niche Installation: When the material (high density, large particles) falls vertically and impacts the level switch probe, to ensure the lifespan and measurement effectiveness of the instrument, it should be installed in a niche to protect the probe from being bent by the material.

c. Vertical Installation: For vertical installation, to avoid measurement errors caused by the conical accumulation or wall accumulation of solid material in a cylindrical container, it is recommended to install the probe at a position d/6 away from the container wall.

d. Avoid Installation at the Inlet: The installation position of Tube-11 should avoid being located at the inlet to prevent measurement errors and to protect the instrument from damage caused by material impact.

e. Moisture-Proof Measures: When the instrument is installed outdoors or in a humid environment, such as in rain or condensation, rainwater and condensation will flow downwards. Therefore, before connecting the cable, please bend and guide the cable downward to prevent water or moisture from entering the instrument. For safety reasons, wiring should only be done with the power off, and for explosion-proof instruments, wiring must follow the relevant explosion-proof wiring requirements and be correctly connected to the cables according to the different output interfaces specified in the manual.

After installation, set the density adjustment switch and the high/low level mode switch according to the on-site testing requirements. The density adjustment switch on the control panel can change the measurement sensitivity of the Tube-11, allowing it to better adapt to the measured material. The density adjustment is set to the far-right position at the factory, with a minimum measurable density of 0.05g/cm³. When dealing with particularly light materials, the density adjustment potentiometer can be rotated to the far-left position, reducing the minimum measurable density to 0.02g/cm³, making the detection more sensitive and the measurement more reliable. For the two limit alarm functions of overflow protection and dry-run prevention, the high/low level mode switch should be adjusted according to the actual on-site requirements to achieve the desired signal output state.

During operation, professional instrument technicians should enhance maintenance and monitoring. Regularly check the instrument’s operating status, and verify that the instrument’s status indicator lights are functioning correctly. Periodically inspect the probe for material buildup, promptly clean off any residual material, and maintain the instrument in good working condition. If a fault is detected, troubleshooting should be carried out according to the fault analysis in the manual. If necessary, contact the manufacturer’s after-sales service for technical assistance.