Application of Boiler Drum Level Instruments

I. Importance of Boiler Drum Level Control

A. Ensuring the Safe Operation of the Boiler

1. Preventing Dry-Boiling Accidents
   • A low boiler drum level can lead to insufficient cooling of the heating surface, resulting in a decrease in the metal's overheating strength. If the level drops to a certain extent, it may trigger a dry-boiling accident, causing the metal materials of the drum and connecting pipes to deform or even rupture at high temperatures, posing a serious threat to equipment and safety.
2. Avoiding Overfilling Accidents
   • When the boiler drum level is too high, severe steam carryover may occur. Excessive water entering the steam pipeline can impact the turbine blades, causing damage and affecting the normal operation of the turbine. Additionally, overfilling can also lead to a decline in steam quality, thereby influencing the operation efficiency and stability of the entire thermal system.

B. Guaranteeing Steam Quality

1. Maintaining the Effectiveness of Steam-Water Separation
   • Accurate measurement of the boiler drum level is crucial for maintaining good steam-water separation. If the level control is improper, the steam-water separation device cannot function properly, and a large amount of water droplets containing impurities will be carried in the steam, degrading the steam quality and further affecting the performance and lifespan of steam-consuming equipment. For example, in chemical production, it may interfere with the progress of chemical reactions.
2. Ensuring the Stability of Steam Parameters
   • The stability of the boiler drum level is vital for the stability of steam parameters such as pressure and temperature. Fluctuations in the level can cause changes in steam production, which in turn lead to fluctuations in steam pressure and temperature. This is extremely disadvantageous for equipment relying on stable steam parameters, such as in power generation, where it can affect the output power and efficiency of the generator.

II. Setting Principles of Boiler Drum Level Instruments

A. Accuracy Principle

1. Selecting High-Precision Instruments
   • Based on the operating parameters of the boiler (such as pressure, temperature, capacity, etc.), select level measuring instruments with sufficient high precision. For example, for high-pressure and large-capacity boilers, measuring devices with high accuracy and the ability to adapt to complex working conditions, such as a combination of a double-chamber balancing vessel and a high-precision differential pressure transmitter, should be chosen.
2. Eliminating Interference Factors
   • Considering the complex working environment inside the boiler drum, such as steam fluctuations and pressure changes that can interfere with level measurement, corresponding measures should be taken. For example, when using a differential pressure level instrument, by rationally designing the balancing vessel and adopting pressure compensation technology, the influence of boiler drum pressure changes on level measurement can be eliminated to ensure the accuracy of the measurement results.

B. Reliability Principle

1. Redundant Setup
   • Use multiple level instruments with different principles for redundant measurement. For example, simultaneously install differential pressure level gauges, electrode level gauges, and radar level gauges. In this way, when one level instrument fails, other instruments can still provide reliable level information to ensure the normal operation of the boiler.
2. Ensuring Instrument Quality
   • Select level instruments with reliable quality and proven long-term operation. For key components of the instruments, such as the sensors of differential pressure transmitters and the electrodes of electrode level gauges, high-reliability products should be selected. Moreover, the instruments should be regularly maintained and calibrated to ensure their long-term stable and reliable operation.

C. Principle of Easy Monitoring and Maintenance

1. Reasonable Installation Location
   • The installation location of the level instrument should be convenient for operators to observe and read data. Generally, the main level display instrument should be installed in a conspicuous position near the operating platform. At the same time, the installation location should also consider the convenience of instrument installation, disassembly, and maintenance, and sufficient space should be reserved around the boiler drum for maintenance personnel to operate.
2. Maintenance Convenience
   • Select level instruments with a simple structure and easy maintenance. For example, the electrode level gauge should be designed with a structure that facilitates the replacement of electrodes. For instruments that require regular calibration, such as differential pressure transmitters, their calibration interfaces should be convenient for connecting calibration equipment to reduce maintenance time and workload and improve the reliability and economy of boiler operation.

III. Commonly Used Level Instruments for Boiler Drums

1. Direct-Reading Level Gauges (Glass Plate/Quartz Tube/Mica Water Level Gauges)
2. Double-Chamber Balancing Vessel + Differential Pressure Transmitter/Double Flange Differential Pressure Transmitter
3. Float Level Transmitter
4. Magnetic Flip Plate Level Gauge
5. Electrode Level Gauge
6. Guided Wave Radar Level Gauge