Application of Liquid Level Switch in the Level Measurement of Crude Oil Tank
I. Requirements for Liquid Level Measurement in Crude Oil Storage Tanks
As important storage units, crude oil storage tanks are widely used in the petrochemical industry. According to national regulatory requirements, continuous level measuring instruments such as radar level meters, differential pressure transmitters, and liquid level switches should be installed to ensure proper high and low liquid level alarms.
Crude oil possesses characteristics such as flammability, explosiveness, and adhesion, making high anti-hanging ability and explosion-proof capabilities essential for liquid level switches. To avoid non-response or false alarms at alarm points, which could increase the risk of crude oil storage tank leakage or collapse, the reliability of the instrument is crucial.
II. Comparison of Various Liquid Level Switches
| Item | Pros and Cons | Explosion-proof | Price |
|---|---|---|---|
| Float Level Switch | Simple structure and easy to use, but the float may become stuck. | Flame-proof | Low |
| Capacitive Level Switch | Strong corrosion resistance but challenging calibration and low accuracy. | Flame-proof/Intrinsic-safe | Moderate |
| Liquid Level Switch | Unaffected by medium properties, easy installation with no calibration required, no wear and tear, and low maintenance. Offers some anti-adhesion protection. | Flame-proof/Intrinsic-safe | Moderate |
| External Liquid Level Switch | No need for tank cleaning, but requires high installation precision. | Flame-proof/Intrinsic-safe | High |
Based on these comparisons, the liquid level switch is the most optimal instrument for level measurement in a crude oil storage tank. Liquid level switches feature an integrated structure design, lack moving parts, and remain unaffected by liquid level fluctuations or medium dielectric constants. Additionally, they require no additional calibration and can be installed immediately.
III. Selection and Application of Liquid Level Switch
Through conversations with users, it is evident that the current liquid level switches employed are solid-liquid two-way liquid level switches, commonly used by most manufacturers in China. These switches generally have fork lengths of around 100 mm and are driven entirely by piezoelectric ceramics, lacking precise tuning. They consume high power, have low safety levels, and may not restart properly under light-hanging conditions, potentially causing false alarms.
The Jiwei Ring-11 liquid level switch differs from most other liquid level switches in China. Its fork body is only 40 mm long, and the vibration characteristics of the two forks are completely symmetrical, allowing for complete resonance. The Ring-11 liquid level switch can measure ultra-low-density mediums (0.5 g/cm³) and has strong anti-hanging capabilities. Additionally, it meets explosion-proof certification requirements (Flame-proof: Ex d IIC T6, Intrinsically Safe: Ex ia IIC T6), making it optimal for use in the petrochemical industry. Currently, a batch of Ring-11 liquid level switches is being applied in a Xinjiang petrochemical factory for the first phase of a technical renovation project.