When the steam pressure is too high, if the safety valve fails and does not operate, it may lead to overpressure at its mildest, and in severe cases, an explosion accident could occur. Overpressure can cause excessive mechanical stress on the pressure-bearing components, threatening the safe operation of the equipment; explosions will force the boiler to shut down. When the safety valve operates, a large amount of steam is discharged, causing economic losses; if the safety valve operates too many times, high-pressure steam impacts the valve flap and wears the contact surface, making it easy for leaks to occur after reseating, increasing steam leakage loss. Sometimes, the safety valve may even fail to reseat, forcing the furnace to stop.
A decrease in steam pressure will reduce the enthalpy drop of steam work in the turbine, increasing steam consumption and coal consumption. Data shows that when the steam pressure is 5% lower than the rated value, the steam consumption of the turbine will increase by 1%. For direct steam boilers with double-sided water-cooled walls, when the steam pressure drops too much, it may cause the working medium at the outlet of the double-sided water-cooled wall to vaporize, affecting the stability of the water dynamics of the membrane-type water-cooled wall. The normal fluctuation range of steam pressure is ±(0.1~0.2)MPa for high-pressure boilers and ultra-high-pressure boilers.
Effect on steam temperature: Generally, when the steam pressure increases, the superheated steam temperature also rises. This is because when the steam pressure increases, the saturated temperature also rises, so more heat is needed to change water into steam (the water-cooled wall metal also absorbs more heat). Under the condition where the fuel quantity remains unchanged, the evaporation rate of the boiler will instantly decrease (because part of the steam in the boiler water condenses), meaning the amount of steam passing through the superheater decreases, while the relative absorption of steam increases, leading to a rise in the temperature of the superheated steam.
Effect on water level: When the steam pressure decreases, due to the lowering of the saturated temperature, part of the boiler water evaporates, causing the volume of the boiler water to expand, hence the water level rises; conversely, when the steam pressure increases, due to the rising saturated temperature, part of the steam in the boiler water condenses, causing the volume of the boiler water to contract, hence the water level drops.
If changes in steam pressure are caused by load changes, then the above-mentioned changes in water level are temporary phenomena, followed by changes in the opposite direction. Misjudgment or improper adjustment can easily lead to water level accidents.
Yima Wall-Hung Boiler Repair Information: What impact does steam pressure change have on boilers?
Data Source: Beijing Yima Wall-Hung Boiler Repair Phone http://blog.sina.com.cn/yimabigualu01.