Problem of failed level control

The most common cause of failure in my device is the entry of sludge from within the container into the level gauge due to operational fluctuations, which leads to malfunction of the instrument. Under normal circumstances, the treatment involves removal and drainage, after which it can be put back into use

Our factory uses the DCS operating system from Zhejiang University Zhongkong. Card failures are the most common cause of liquid level issues, and this problem can usually be resolved by simply removing and reinserting the card; if that doesn’t work, the relevant card needs to be replaced. When there is a malfunction, the liquid level display will show a straight line; in such cases, it is necessary to make judgments based on the glass panels on site. The solution involves regular inspections – operators inside the facility monitor the curves, while those outside monitor the liquid level. Once any abnormalities are detected, the instrument maintenance team should be contacted immediately. As a temporary measure, manual control using valve handles can be employed, along with constant monitoring of the liquid level on site.

The original poster’s question is quite broad, so everyone can only provide examples. Let me give some: 1. The magnetic flap level gauge with remote transmission – the float gets stuck :D 2. The safety barrier of this level gauge is damaged. 3. The corresponding input DCS channel is faulty. 4. The DCS output channel for level control is damaged. 5. The level control valve is broken. There are more details as well: L

After being used for two to three cycles, the double-flange level gauge in the gasification furnace experiences corrosion by chloride ions and hydrogen, resulting in inaccurate level readings； The insulation and heating around the double-chamber balance vessel of the drum level gauge leading to the transmitter are inadequate; in winter, the instrument freezes up, resulting in inaccurate level readings. There are too many to list!

Let’s learn from everyone’s experience:D

Replace with an external ultrasonic level gauge

There are many; in the circuit from the field instruments to the controller, issues such as instrument failures, loose connections, and damaged components can occur； The controller also has issues such as manual/automatic mode switching, and excessive offset due to improperly set parameters ； Other issues in the output circuit include loose wiring, faulty retaining components, improperly sized control valves, damaged positioners, and worn valve cores. It had to be solved one by one through searching

There are many; in the circuit from the field instruments to the controller, issues such as instrument failures, loose connections, and damaged components can occur； The controller also has issues such as manual/automatic mode switching, and excessive offset due to improperly set parameters ； Other issues in the output circuit include loose wiring, faulty retaining components, improperly sized control valves, damaged positioners, and worn valve cores. It had to be solved one by one through searching

From the input perspective, and depending on the type of gauge, there are several reasons for malfunction in level gauges: 1. For float-type and magnetostrictive gauges, large impurities in the tank can cause jamming, while excessive pressure can crush the float. 2. In float-ball type gauges, issues such as drift in strain gauges or corrosion and crystallization of levers can lead to problems. 3. For differential pressure gauges, crystallization and freezing can block the flow channels, and crystallization can also occur at the diaphragm in double-flange designs. 4. In radar and ultrasonic gauges, foam on the surface of the fluid, excessive steam in the measurement area, or improper installation locations can cause echo interference.

Regarding signal input: For 4-wire gauges that show no signal despite being operational, it might be due to loose connections, or damaged safety gates or I/O cards. For 2-wire gauges that show no signal, it’s necessary to check the condition of the I/O channels. In some cases, control failures are caused by an inappropriate selection of control valves – it’s impossible to achieve proper control if the Cv value isn’t chosen correctly; in such cases, it’s necessary to replace the valve