Questions regarding the setting of the boiler drum liquid level
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Regarding the issue of liquid level setting: Generally, the migration is set on the transmitter (for example, for a liquid level range of 600 mm, it is set to -6 KPa to 0), and on the DCS it is set correspondingly to 4 mA to 20 mA. I was wondering if the same principle applies to the liquid level setting in boilers as well; whether temperature and pressure compensation is necessary for the drum liquid level due to differences in pressure and temperature.
It is necessary; the range of a differential pressure transmitter is determined by three factors: the measurement range of the drum water level, the 0-water-level position of the container, and the compensation start point of the compensation system.
I also need a super-detailed explanation of the changes in the boiler drum water level difference, from start to finish! I’m almost going crazy because of the drum liquid level – this has always been something I didn’t know anything about!
Using a two-chamber balance vessel to measure the boiler level already provides the necessary compensation
Could an expert compare a two-chamber balanced container with a regular constant-pressure sampler to see which one is better?
Level gauges are also relatively high-end instruments; I attended a training session on them at the beginning of the year, and they seem to be quite sophisticated
To be honest, I wouldn’t know either; I forget it right after reading it. It’s extremely complicated. Look at this – this is what I read at the time: http://wenku.baidu.com/link?url=uQkyPdEDD3xtfcD7BD03gqgu7XMKhlX8yQZtayjjbVVkZJWFH1DY4wJX8K17lyVXKsb8TRhiyJK25anMro8A0DqouF1e58M9QnDZLOsnBLu
The boiler has basically never been maintained
After checking the link from above, the principle behind a two-chamber balanced container and those used for measuring liquid level based on differential pressure is roughly the same; the only difference lies in the way the differential pressure is set. In chemical processing, the gas phase is usually set at negative pressure while the liquid phase is at positive pressure. The side under negative pressure is filled with liquid in a condensing container, which results in a negative value for the differential pressure. In a two-chamber equilibrium vessel, the gas phase is on the positive-pressure side while the liquid phase is on the negative-pressure side; this seems different. The article also doesn’t explain the advantages of a two-chamber balanced container; I can’t see any difference between it and ordinary flange sampling.
As the original poster can see, the Baidu link refers to the double-chamber balance vessel used in power plants. As you mentioned, the sampling for positive and negative pressures is the opposite in power plants and the chemical industry; this is a common issue, but the measurement principle remains the same. The two-chamber balance vessel used in the chemical industry consists of an inner and an outer chamber. The outer chamber of the balancer is connected to the steam in the boiler drum and filled with condensate water ； The inner chamber is connected to the water in the boiler drum through a pressure guide tube located on the lower side of the balancer; the principle of a communicating vessel is applied here, which means that the water level in the inner chamber changes in accordance with the water level in the drum. The double-layer container of this design ensures that the water temperature in the outer chamber and the inner chamber is essentially equal, thereby reducing measurement errors caused by temperature differences.