## 各种液位计的图解符号

liquid level gauges, also known as level switches or level indicators, are essential components in industrial processes for monitoring the level of liquids in tanks, boilers, or other vessels. They provide accurate and reliable measurements of liquid levels, enabling operators to maintain optimal process conditions, prevent overflow, and ensure safety. To accurately represent these gauges in technical drawings and documentation, standardized symbols are employed. This article provides an in-depth overview of the various symbols for different types of liquid level gauges, ensuring consistent and accurate representation in engineering designs.

## Bouée-type Mechanical Float Gauge (Type L)

The Bouée-type mechanical float gauge is a common type of liquid level gauge that utilizes a float with a magnetic follower to transmit the liquid level to an external indicator. The float moves up and down with the liquid level, causing the follower magnet to rotate a gear, which in turn drives an indicator needle.

**Symbol:** ``` /-\ |L| | | |F| |_| /-\ ``` ## Displacer-type Mechanical Float Gauge (Type D)

The displacer-type mechanical float gauge employs a displacer element that is submerged in the liquid and attached to a spring. As the liquid level changes, the buoyancy force acting on the displacer varies, causing the spring to extend or compress. This movement is mechanically transmitted to an external indicator, typically a pointer or scale.

**Symbol:** ``` == |---\ / 1 \ | 0 L | |---| ``` ## Capacitance-type Liquid Level Gauge (Type C)

Capacitance-type liquid level gauges measure the capacitance between a probe and the vessel wall. The probe is inserted into the liquid, and as the liquid level changes, the capacitance between the probe and the vessel changes. This change in capacitance is detected and converted to a liquid level signal.

**Symbol:** ``` +---o---+ | + | | | | | | | | | | |_| | | | | | | | | | | | | | | |/ / | `----|-' |_ ___ '-..-' ``` ## Ultrasonic Liquid Level Gauge (Type U)

Ultrasonic liquid level gauges utilize ultrasonic waves to measure the distance between the probe and the liquid surface. Ultrasonic pulses are transmitted from the probe, and the time taken for the pulses to reflect off the surface and return to the probe is measured. This time is proportional to the distance between the probe and the surface, allowing for the determination of the liquid level.

**Symbol:** ``` ____ .-' '-. / \ | | \ ~ ~ / |_ _| |/`'''`\| _/_____\_ ``` ## Vibrating Fork Level Switch (Type V)

Vibrating fork level switches rely on a tuning fork that vibrates at a specific frequency when submerged in liquid. When the fork is not in contact with liquid, the vibrations continue at a constant frequency. However, when the fork comes into contact with liquid, the damping effect of the liquid causes the vibrations to decrease. This change in vibration is detected and used to indicate the liquid level.

**Symbol:** ``` (-=-) | | | | | | ___| |___ ``` ## Optical Level Switch (Type O)

Optical level switches utilize a light source and a light detector to detect the level of liquid. When the liquid level is low, the light beam is blocked by the liquid, preventing it from reaching the detector. As the liquid level rises, the light beam passes through the liquid and reaches the detector, indicating the presence of liquid.

**Symbol:** ``` [_] |.| |.| |.| |.| |.| ---|.__|--- ``` ## Piezoresistive Liquid Level Gauge (Type P)

Piezoresistive liquid level gauges employ a piezoresistive sensor element that is mounted at the bottom of the tank or vessel. When liquid is present, the hydrostatic pressure acting on the sensor causes it to deform. This deformation is detected by the sensor and converted into a liquid level signal.

**Symbol:** ``` . . . |.-.|.-.|-.|.-.| |-.-|.-.|-.-|-.-| |-.-|.-.|-.-|-.-| |-.-|.-.|-.-|-.-| |.-.'.-.|-.-'.'.-| '-._.-._.-._.-._.-_' ``` ## Hydrostatic Level Transmitter (Type H)

Hydrostatic level transmitters measure the liquid level based on the hydrostatic pressure exerted by the liquid. A pressure sensor is installed at the bottom of the tank or vessel, and the pressure exerted by the liquid column above it is measured. This pressure signal is converted into a liquid level signal.

**Symbol:** ``` + / \ \ / /.| / | | | | | | | | |. `---.| | | | | | | | _|_ .' '. '. |_|_|_|_| ' ' ' ' ``` ## Magnetic Level Gauge (Type M)

Magnetic level gauges consist of a float with magnets and a display unit that houses a flapper indicator. The float is positioned inside a transparent measuring chamber, and as the liquid level changes, the flapper indicator follows the movement of the float magnetically, indicating the liquid level.

**Symbol:** ``` + .-' / \ / \ | |. | |. | |. | |. | |. | |. | |. ' | `------' | | | | | | | ``` ## Selection Criteria for Liquid Level Gauges

The choice of the appropriate liquid level gauge depends on several factors, including the application, process conditions, accuracy requirements, and available technology. The following criteria should be considered:

Liquid properties (e.g., density, viscosity, corrosiveness) Process conditions (e.g., temperature, pressure, vibration) Accuracy and reliability requirements Compatibility with the process Maintenance and calibration requirements ## Conclusion

Liquid level gauges play a vital role in industrial processes by providing accurate and reliable measurements of liquid levels. The various symbols presented in this article provide a standardized representation of different types of liquid level gauges, ensuring consistent and precise communication in technical drawings and documentation. Understanding and utilizing these symbols enables engineers and technicians to effectively design and implement liquid level monitoring systems for optimal process performance and safety.