What are the consequences of boiler water level switch control?

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What are the consequences of boiler water level switch control? Steam boilers are responsible for supplying high-quality steam to the equipment that relies on it in order to meet production requirements; they must operate safely and efficiently, while also ensuring stable outlet steam pressure and a high degree of dryness. As steam is continuously generated, the boiler water keeps evaporating, and the boiler requires timely replenishment of water to maintain its water level. In cases of severe water shortage, the boiler can suffer serious damage or even explode. The water level control of a boiler consists of on-off control and regulating control. Switch control involves starting the water pump at low water levels, with the pump remaining in operation until the water level in the furnace reaches a high level, at which point it stops. Thanks to its simple structure and low cost, switch control for boiler level is widely used. However, the many problems that arise as a result cause significant trouble for enterprises; some of these problems even affect production severely or lead to safety accidents. What are the actual hazards associated with the control of boiler water level switches? How do they arise? I’d like to share some insights on this with you all. 1. Control by the boiler water level switch can cause severe water contamination in the steam. During the heating process of the boiler, steam bubbles are formed on its heating surface; these bubbles rise through the boiler water and eventually escape from the surface of the water to enter the steam system. Since the pressure at the heating surface of the boiler is slightly higher than the pressure at the water level in the boiler, the bubbles formed at the heating surface either leave the boiler’s water surface with a slight superheat or are cooled by the boiler water to the saturated temperature corresponding to that water level during their ascent; usually, the latter happens. When making up water to the boiler, the added water enters the area between the boiler’s heating surfaces and the water level in the boiler. Although the make-up water is heated before entering the boiler, its temperature is still lower than that of the water inside the boiler, which creates a cooling layer within the boiler water. As the bubbles formed on the heating surface of the boiler rise and pass through this cooling layer, they are cooled, causing the steam inside the bubbles to condense. This process gives rise to two problems: first, bubbles leaving the liquid surface and entering the steam system carry water mist with them. When a large amount of make-up water enters the boiler, the steam space above the boiler water level becomes filled with mist; as a result, the steam exiting the boiler contains high levels of moisture and has poor quality, until the boiler water reaches an isothermal state. Especially when the steam load is very high, changes in the steam load exacerbate steam carryover, leading to greater fluctuations in water level; in severe cases, this can result in low-water-level alarms and the risk of a forced shutdown of the boiler. When steam contains water, it severely affects the lifespan of pipes, valves, and equipment, increasing safety risks. For high-speed flowing steam, the water droplets mixed within it are as rough and destructive as sand particles, causing severe erosion of pipe elbows and valve seats. The water accumulated in the pipes is pushed by high-speed steam, causing it to collide rapidly with any components downstream that prevent its forward movement, such as pipe elbows, T-joints, valves, and equipment, resulting in erosion, severe vibrations, and water hammer. Water hammer can cause pipe connections and supports to loosen and deform, and in pipes and equipment that are severely corroded over time, catastrophic accidents can occur easily. Steam carrying water increases scale formation on the heat exchange surfaces of the equipment, reduces production efficiency and product quality, and also affects the measurement accuracy of flow meters. II. Increased wear on the burner and feed water pump: When the water pump starts, the large amount of water added leads to a decrease in pressure inside the boiler, which in turn increases the combustion rate. And when the water level rises and the pump stops, the fuel combustion rate decreases again. For example, when the water replenishment temperature is 80°C, the combustion rate with the water pump running is 40% higher than that with the water pump off. Since the start and stop of the water pump are intermittent and regular, the wear on the burner control device increases, as does the wear on the feed water pump. III. Large fluctuations in steam outlet pressure: At the moment the feed water pump starts, a large amount of water is supplied, and the boiler’s combustion system is unable to provide enough heat energy to vaporize the water in the boiler, resulting in a significant drop in pressure inside the boiler. This phenomenon occurs intermittently as the feed water pump starts and stops. Therefore, when controlled by a water level switch, the steam pressure at the boiler outlet fluctuates greatly. The problem becomes more severe when the load fluctuates greatly. The boiler water level control method can effectively address the above issues, as it allows for gradual addition of water in small amounts on a continuous basis during adjustment, thereby promoting a relatively constant boiler water temperature. Boiler water level control ensures a stable steam pressure and flow rate from the boiler within its capacity limits, reduces steam carryover, and slows down the wear on burners and pumps.