Automatic boiler level control
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Could someone explain the automatic level control system for boilers? Our factory has two 10-ton chain boilers, and one of them often runs out of water; the automatic control system does not work properly, and the water level drops within just a second once it reaches its maximum level.
10t boilers generally use single-pulse control, that is, the boiler level signal is used for regulation; a PID regulator controls the pneumatic diaphragm control valve or electric control valve. When the control is not satisfactory, it is usually due to improper setting of the PID parameters, and these parameters need to be adjusted.
For the upstream control valve, try manual control; if the liquid level remains stable, it indicates that the PID parameters are not set properly. If there are still significant fluctuations in manual mode, then the cause needs to be investigated from a process perspective.
Is it a hot water boiler or a steam one? How is it controlled nowadays, and how did this situation arise?
It shouldn’t be a problem with level control; it’s possible that the level gauge tube is blocked or the display is inaccurate. It is recommended to check the boiler’s internal components as well as the level controller
At full water level, the water level often drops within just one second; this indicates that there is a problem with the level gauge’s display, as there is interference. The threshold voltage of the level gauge can be adjusted to eliminate the effect of noise. Additionally, for small boilers, dual-level control is sufficient, that is, cascade control: the liquid level serves as the primary control parameter, while the feedwater flow rate acts as the secondary one. By adjusting the valve controlling the feedwater flow rate, stability can be achieved.
Adjust it manually; automatic methods can be unreliable sometimes. Our 240-ton models all use manual control
1 second! It’s either a operational issue (high alkalinity of the boiler water, steam-water boiling), or a problem with the level gauge.
The water quality parameters of the feedwater and boiler water can be tested; if there are no issues with the water quality, then check whether there are any internal leaks in the drainage pipes or if their opening degree is too high. The remote transmittance level gauges also need to be calibrated.