Tank Level Sensing is very important in the process of oil and gas storage and transportation. We will analyze and introduce the automatic level measurement here. Hope to help you!
The necessity of tank level measurement
-In the process of oil and gas storage and transportation, accurately measure the height of the liquid level in the large oil storage tank. This is an important measure to correctly calculate oil storage, determine inventory, and calculate transportation.
-In oil and gas production, especially in oil and gas gathering, transportation, storage and transportation systems, oil, natural gas and associated sewage must be separated, stored and processed in various production equipment and tanks. The measurement and control of the level is essential to ensure normal production and equipment safety. Otherwise, a major accident will occur.
-For example, if the oil tank level measurement is not well controlled, there will be evacuated or oil spill “roofing” accidents. If the liquid level of the oil-air separator is too high or too low, “oil running” and “gas blow-by” accidents will occur. Seriously affect the production and safety of subsequent equipment;
-The high oil-water interface in the electric dehydrator will destroy the electric field. If it is low, it will carry oil in the water and affect production.
The basic concept of level
- Level—refers to the general term of the liquid level of the liquid medium, the level of solids or the level of particles in the container and the interface between two different liquid media.
- Liquid level-the height of the liquid medium in the container
- Material level-the accumulation height of solid or granular substances in the container
- Interface level – the level of the interface of two immiscible liquids medium
Classification of Tank Level Sensing
According to the measurement method, it can be divided into continuous measurement and fixed-point measurement.
According to its working principle, it can be divided into the following types:
- Direct reading type It measures the liquid level based on the principle of fluid connectivity.
- Buoyancy type It measures the liquid level according to the principle that the height of the float changes with the height of the liquid or the buoyancy of the liquid to the float (or sinker) immersed in the liquid changes with the height of the liquid. The former is called constant buoyancy, and the latter is called variable buoyancy.
- Differential pressure type (static pressure type) It measures the level according to the principle of the change in the static (differential) pressure generated at a certain point by the change in the height of the liquid column or the material accumulation.
- Electrically, it measures the level based on the principle of converting level changes into various changes in electricity.
- Nuclear radiation type It measures the liquid level based on the principle that when the nuclear radiation of the isotope rays penetrates the material, its intensity changes with the thickness of the material layer.
- Acoustic It measures the level according to the changes in acoustic impedance and reflection distance caused by changes in level
Direct measurement for Tank Level Sensing
Direct measurement is one of the simplest and most intuitive measurement methods. It uses the principle of communicating devices. The liquid in the container is introduced into an observation tube with a ruler. Read the height of the liquid level by the ruler
Such as: glass tube level gauge.
Manual Tank Level Sensing
Manual gauge level measurement is a basic method for measuring the volume and quality of liquids in various storage tanks.
It has the characteristics of simple operation, accurate measurement and no auxiliary equipment. It is still a main measurement method in the crude oil gathering and transportation process of various oil fields.
When measuring with a gauge, first measure the height of the liquid level in the tank, and then calculate the volume and mass of the liquid in the tank according to the cross-sectional area of the tank or the large tank volume table.
The tool used by the gauge to measure is a steel tape with a copper weight on the lower end. In order to facilitate the oil measuring operation, an oil measuring port is provided on the top of the tank. An oil measuring pipe is installed under the oil measuring port, and a hole is drilled at the bottom end of the pipe to communicate with the liquid. The purpose of setting the oil measuring pipe is to reduce the influence of the liquid level fluctuation in the tank on the oil measuring.
Magnetic flip level gauge for Tank Level Sensing
The magnetic flip level gauge has a firm structure, reliable work, and eye-catching display.
Since the measured liquid is completely sealed and magnetic coupling transmission is used, it can measure high temperature, high pressure and opaque viscous liquids, such as crude oil, sewage, etc.
The disadvantage is that after long-term use, the magnetism of the magnetic steel is degraded. Wear of the flap shaft can easily cause wrong indication
Therefore, it should be checked and corrected regularly.
Buoyancy Method for Tank Level Sensing
The buoyancy method to measure the liquid level is based on the principle of force balance, usually with the help of floats. The float is made into a hollow rigid body so that it can float on the liquid surface when it is balanced. When the liquid level changes, the float will move up and down with the liquid level. Therefore, by measuring the displacement of the float, the amount of liquid level change can be known.
Float type level gauges can be divided into float type, float type, etc. according to different float shapes;
According to different institutions, it can be divided into steel belt type and lever type.
Hydrostatic level gauge for Tank Level Sensing
It is measured based on the pressure generated by the weight of the liquid.
Since the static pressure generated by the liquid on the bottom surface of the container is proportional to the height of the liquid level. Therefore, the liquid level can be calculated by measuring the pressure of the liquid in the container.
Ultrasonic method for Tank Level Sensing
Ultrasonic level gauges use the propagation characteristics of waves in the medium.
Therefore, install an ultrasonic transmitter and receiver at the bottom or top of the container. The emitted ultrasonic waves are reflected at the phase interface. And it is received by the receiver. The time difference between ultrasonic wave transmission and reception is measured. The liquid level can be measured.
Electrical method for Tank Level Sensing
According to different working principles, the electrical method can be divided into resistive, inductive and capacitive.
Use electrical method to measure frictionless parts and movable parts, signal conversion and transmission are convenient. It is convenient for remote transmission, reliable work, and the output can be converted into a unified electrical signal. Used in conjunction with the electric unit combination instrument. Can easily realize automatic detection and automatic control of liquid level.
Magnetoelectric method for Tank Level Sensing
The magnetostrictive liquid level sensor that uses the principle of magnetoelectric conversion for liquid level measurement is a new product launched in recent years.
Performance characteristics and selection of common oil tank level gauges
The intermediate tank only monitors parameters such as liquid level, temperature and pressure (pressure storage tank) to prevent accidents such as roof capping and vacuuming of the oil tank. There is no need to handover monitoring and measurement;
The liquid level, temperature, density, volume, and quality of the medium in the trade tank must be monitored and measured frequently, and the accuracy is very high.
Performance comparison of Tank Level Sensing
|Level gauge||Light oil||Crude oil||Heavy oil||Asphalt||Liquefied gas||Other liquids|
|Magnetic flap level gauge||ok||ok||ok||poor||No||very good|
Tank Level Sensing instruments for different media
|Level gauge||Level measurement||Temperature deletion||Density deletion||Boundary measurement||Volume measurement||Quality deletion||Installation situation||Cost|
|Magnetic flap||High precision||Can not be measured||Can not be measured||Small error||Depends on TD||Depends on Tρ||simple||low|
|Float||High precision||Can not be measured||Can not be measured||Mistaken sheep||Depends on TD||Depends on Tρ||simple||low|
|radar||High precision||important||Unable to delete||Unable to||Small error||Depends on Tρ||simple||high|
|Hydrostatic pressure||Big error||unimportant||Small error||Unable to||Big error||Depends on Tρ||complex||Relatively high|
|Magnetically induced||High precision||important||Unable to delete||High precision||Small error||Depends on Tρ||complex||high|
|Ultrasound||High precision||unimportant||Can not be measured||Unable to||Small error||Depends on Tρ||complex||high|
Selecting Guide for Tank Level Sensing
(1) Oil tank volume
·For large tanks (10000~100000m3) and relatively large liquefied gas tanks, higher performance level gauges can be used, and general level gauges can be used for medium and small tanks;
·(2) Oil tank use
High-precision level gauges should be used for trade tanks, and general level gauges can be used for intermediate tanks;
·(3) Medium characteristics
When storing high-viscosity media (such as heavy oil), try to use a level gauge that does not or has little contact with the measured medium. Such as radar type, ultrasonic type and magneto-induced level gauge, light oil can use general level gauge;
(4) Actual needs of users
·If the user requires high measurement accuracy and low investment restrictions, a level gauge with good performance can be used. Under normal circumstances, the old tank area can be retrofitted or updated according to the use and maintenance of the original level gauge.
Featured liquid level measurement devices
Sino-Inst offers over 50 Solutions for Tank Level Sensing. About 50% of these are float liquid level meters, 40% is the level switches.
A wide variety of Solutions for Tank Level Sensing options are available to you, such as free samples, paid samples.
Sino-Inst is a globally recognized supplier and manufacturer of Solutions for Liquid Level Measurement instrumentation, located in China.
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