One of the primary issues that can occur during the operation of an electromagnetic flowmeter is a fault within the meter itself, typically caused by damage to internal components or structural elements. Another common issue arises from external factors, such as improper installation, flow distortion, sediment buildup, and scaling. This chapter focuses on the second type of failure—those caused by external conditions.
Faults can be categorized based on when they occur: during the commissioning phase or during normal operation. Commissioning-phase failures usually happen shortly after installation and are often due to incorrect selection or improper installation of the device. Operational-phase failures occur after some time in use, typically due to the accumulation of impurities on the electrode lining or changes in environmental conditions.
From a source perspective, these faults can originate from three areas: 1) the piping system and installation, 2) environmental factors, and 3) the fluid being measured. Faults from the first category tend to appear during commissioning, while those from the second and third categories may persist throughout both the initial and operational phases.
**Commissioning Phase Failures**
These occur during the initial setup and testing of the electromagnetic flowmeter. Once resolved, they generally do not recur under similar conditions. Common causes include:
1. **Piping and Installation Issues**: Incorrect placement of the sensor, such as installing it at a high point where gas can accumulate, or placing it without sufficient back pressure, leading to an incomplete flow condition. Installing the sensor on a vertical pipe with upward flow can also cause air entrainment.
2. **Environmental Interference**: Sources include stray currents in the pipeline, electromagnetic radiation, and magnetic fields from nearby motors. While shielding and grounding can help, strong interference (e.g., from electrolysis plants) may still affect measurements.
3. **Fluid Characteristics**: The presence of small bubbles in the liquid may not impact measurements significantly, but larger bubbles can cause signal fluctuations. High solid content can generate "slurry noise," and differences in conductivity between mixed liquids can lead to erratic readings. Poor electrode material compatibility may also result in chemical reactions, forming insulating layers that hinder measurement.
**Operational Phase Failures**
After a period of normal operation, other types of faults may emerge, including:
1. **Accumulation on the Inner Wall**: Electromagnetic flowmeters are more prone to wall buildup compared to other types. If the layer's conductivity matches the fluid, it may only cause minor measurement errors. However, high-conductivity layers can short-circuit the electrodes, while insulating layers can break the circuit entirely, rendering the meter inoperable.
2. **Lightning Damage**: Lightning can induce high voltage surges through power lines, signal cables, or excitation lines, damaging the flowmeter. Most damage comes from power lines, though signal lines can also be affected. Lightning strikes often impact multiple instruments in the control room, emphasizing the need for proper surge protection.
3. **Changes in Environmental Conditions**: Some interference sources may not be present during commissioning but appear later, such as new welding near the pipeline or nearby electrical equipment. These can cause significant signal instability.
Orifice flowmeter http://
Radar level gauge http://
Input type liquid level transmitter http://://news.chinawj.com.cn
Editor: (Hardware Business Network Information Center) http://news.chinawj.com.cn
Editor: (Hardware Business Network Information Center) http://news.chinawj.com.cn
Steel Building Factory,Steel Structure Warehouse Factory,Steel Structure Workshop Factory,Steel Structure Factory Building
Guangdong Tianchen Steel Structure Engineering Co. Ltd. , https://www.tcsteeltech.com