Application of Liquid Level Switch in the Level Measurement of Crude Oil Tank

As an important storage unit, crude oil storage tanks are widely used in petrochemical industry. According to national regulatory requirements, continuous level measuring instruments such as radar level meter, differential pressure transmitter, and liquid level switch should be installed to ensure the function of high and low liquid level alarm.

I. Requirements for liquid level measurement of crude oil storage tanks

Flammability, explosion and adhesion are the typical characteristics of crude oil. Therefore, the liquid level switch should be qualified with the requirements of explosion-proof and with high anti-hanging ability. In order to avoid the occurrence of the liquid level switch has no action or misoperation when alarm point is reached thus increasing the risk of leakage or collapse of crude oil storage tank, the high reliability of instrument is crucial.

II. Comparison of various liquid level switches.

Based on the above comparisons, liquid level switch is the most optimal instrument for the level measurement in crude oil storage tank, because liquid level switch adopts integrated structure design, has no moving parts, and not affected by the fluctuation of the liquid level or medium dielectric constant. Besides, liquid level switch no need additional calibration and can be installed immediately.

III. Selection and application of liquid level switch

Through communication with users, it is confirmed that the liquid level switches they are currently using is a kind of solid-liquid two-way liquid level switch, which also commonly used by most manufacturers in China, its fork length is generally about 100 mm, driven entirely by piezoelectric ceramics and without precise tuning. On the one hand, it consumes high power and with low safe level. On the other hand, it cannot restart again under light-hanging condition, and outputs a wrong alarm signal.

Unlike most liquid level switches in China, the fork body of Jiwei Ring-11 liquid level switch is only 40 mm long. The vibration characteristics of the two forks are completely symmetrical and can achieve complete resonance. Ring-11 liquid level switch is able to realize the level measurement of ultra-low density medium (0.5g/cm³) with strong anti-hanging techniques. In addition, Ring-11 meets the explosion-proof certification requirements (flame-proof: Ex d IIC T6, Intrinsically safe: Ex ia IIC T6), which is optimal for the application in petrochemical industry. Currently, a batch of Ring-11 liquid level switches are applying in a Xinjiang petrochemical factory for the 1stphase project of technical renovation.