During boiler operation, we monitor and control the steam drum liquid level through a liquid level measurement system. When the steam drum level exceeds the normal operating range, the alarm system will issue an alarm signal, and the protection system will immediately take necessary protective measures to ensure the safety of the boiler and turbine. Therefore, the boiler drum level measurement system is an extremely important system for the safe operation of the unit.

Schematic diagram of boiler drum liquid level measurement system

Factors affecting changes in steam drum liquid level

The liquid level of the boiler often changes during operation. The main causes of changes in liquid level are external and internal disturbances of the boiler. When external and internal disturbances occur, it will disrupt the material balance relationship of the evaporation equipment (i.e. the balance relationship between evaporation capacity and water supply), or cause a change in the working fluid state (when the boiler pressure changes, the specific volume of water and steam changes), resulting in a change in the liquid level of the steam drum. The severity of changes in the liquid level of the steam drum is not only related to the magnitude of the disturbance, but also to the disturbance velocity.

Basic requirements for boiler drum liquid level measurement system

According to the importance of measuring the level of boiler steam drum and the characteristics of measurement technology, the boiler steam drum level measurement system should at least meet the following basic requirements:

1. Good accuracy

As is well known, the liquid level of the boiler drum is not a parameter that requires precise control compared to parameters such as main steam pressure and temperature. Generally, a deviation of less than 30mm between the two drum liquid level measurements is acceptable. It is not very difficult to maintain such accuracy under normal conditions. However, due to the complexity of the measurement object for steam drum water level and the use of connected pipe or differential pressure measurement principles, changes in steam drum pressure and measurement reference conditions can cause significant errors that far exceed the above requirements. So for a long time, ensuring the accuracy of steam drum water level measurement has always been a difficult and key issue in front of us. Guangzhou Xisen Automation Control Equipment Co., Ltd. has solved this difficulty through differential pressure measurement principle!

2. Good maintainability

The maintenance of the boiler steam drum liquid level measurement system should be simple, with minimal maintenance workload, and should be convenient for conducting online protection linkage tests of actual water level signals.