Electrode rod for detecting water-level, method of detecting water-level, method of controlling water-level in a boiler, and method of controlling water-level in a steam separator

摘要

An insulating coating (6) formed of engineering plastic with high heat resistance, high-pressure resistance, and chemical resistance is formed on a surface of a water-level detecting electrode part (3) of an electrode rod for detecting water-level (1) attached to penetrate a metal container (5) communicating with a boiler (7) and including an external power supply connecting terminal part (2) projecting outside the container (5) and the water-level detecting electrode part (3) projecting inside the container (5). One side of a power supply (27) is connected to the external power supply connecting terminal part (2), and another side of the power supply (27) is connected to the container (5) for energization. An electrostatic capacity between the water-level detecting electrode part (3) and the container (5) is measured by using the insulating coating (6) formed on the surface of the water-level detecting electrode part (3) as a dielectric. The water-level of water to be brought into contact with the water-level detecting electrode part (3) in the container (5) can be detected from the electrostatic capacity. Proportional target water-level in the boiler (7) is set based on at least one of the burning capacity, vapor pressure, supply water temperature, and electrical conductivity of boiler water, and at least one of the burning capacity, vapor pressure, supply water temperature, and electrical conductivity of boiler water during operation of the boiler (7) is detected. A difference between the proportional target water-level to be specified by the detected values and actual water-level in the boiler (7) detected by the electrode rod for detecting water-level (1) is constantly calculated. A supply water amount is controlled such that water supply is stopped when the actual water-level exceeds the specified proportional target water-level and the water is supplied until the actual water-level reaches the specified proportional target water-level when the actual water-level falls short of the specified proportional target water-level. In this way, a good quality vapor with high dryness can stably be obtained, and a safe operation of the boiler can be conducted.