| Abstract [eng] |
The Master's thesis examines the equipment used in steam boiler rooms and control systems of water level in steam boilers. As the modern steam boilers are of relatively small volume and high pressure, the water level tends to rise with an increase of load in the steam boiler. A sudden removal of steam may cause the water level to fall sharply in the steam boiler. Low water level in a steam boiler can lead to pipe rupture, and thereby damage it. Therefore, water level in steam boilers is a critical element of system management. In order to ensure a reliable, safe and efficient operation of a steam boiler, the present paper analyses and proposes the strategies of water level control. Modelling has shown that the water level in the steam boilers without the disturbance compensation system is maintained with large fluctuations. The simulation results showed that the most appropriate strategy is the three measuring elements' strategy with the disturbance compensation system. This system maintains the water level within the given limits and reduces the volatility of water in the steam boiler. For steam boilers modernization, the Siemens 1200 programmable logic controller which is designed for the control of technological processes of a steam boiler has been chosen. The logic controller maintains a constant water level in the steam boiler by regulating the actuator according to an outgoing steam flow from the boiler, incoming feed water stream and the existing water level in the steam boiler. |
